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eph_kay's Build: 88 Coupe 3.4TDC by eph_kay
Started on: 03-15-2011 12:31 AM
Replies: 110
Last post by: BV MotorSports on 09-22-2011 07:15 PM
Sourmug
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Report this Post03-18-2011 11:21 AM Click Here to See the Profile for SourmugSend a Private Message to SourmugDirect Link to This Post
L67:

According to my last conversation with Joe last fall, he uses 4 mounts and no dog bone.

eph:

Enjoy your build. I will now return to lurking mode

Nolan

[This message has been edited by Sourmug (edited 03-18-2011).]

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fieroguru
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Report this Post03-18-2011 11:23 AM Click Here to See the Profile for fieroguruSend a Private Message to fieroguruDirect Link to This Post
My take on this is you shouldn't plan to mount the 3.4 TDC in the same fashion as the 2.8... which is the center engine mount/upper dog bone and two stock transmission mounts. Sure it is the easy way to mount it, but could lead to reliability issues.

I have been down the breaking/bending mounts and cracking cradle path before with my SBC/swap... and it gets old really quick. But the issue wasn't the engine/transmission combo, it was the design of the mounts for said combination. I was able to revise mine and go from "fixing" something mount related every month to not touching them for 4 years and 40K miles. It all boils down to the mount design and quality of manufacturing.

Likewise, I just got done "reworking" the mount setup on a 3800SC/Getrag car for the same reason... too much movement and was bending/braking stuff. Spreading the mounts so they have about 24" between and using mounts that are mechanically locked so they can not come apart provided a night/day difference in keeping the engine in place. No dogbone was used on this setup either.

Anymore, I perfer to use the 4 corner mount setup where the mounts are seperated by about 24" front to rear. This requires 4 custom mounts, but I enjoy fabrication work. I haven't done a 3.4TDC swap yet, but when I do would I will use my same 4 corner mount approach.
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mattwa
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Report this Post03-18-2011 03:25 PM Click Here to See the Profile for mattwaClick Here to Email mattwaSend a Private Message to mattwaDirect Link to This Post
 
quote
Originally posted by Sourmug:

No offense Matt but that's crap.

Talk to Fieroking, he has no problems with his DOHC, it's mounted rock solid without a dog bone, I know as I've driven it. Yes I know about the cam carriers I've handled them. But be honest, you are not basing your comments on your personal experience you are are only repeating what you heard from L67.

You guys don't like the 3.4 DOHC and that's fine, there's a reason that engines come in so many different flavours. However, the issues that you guys are listing are mounting problems not engine problems, the cars that they came in aren't breaking dog bones or having heads banging into the fire wall.

Not bashing, just expressing my opinion.


That's not true, I am basing my comments from my personal experience, I was in the middle of doing that swap when L67 stepped in and gave me his advice, and it makes perfect sense to me, and I saw it with my own eyes.
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Report this Post03-18-2011 04:21 PM Click Here to See the Profile for Doug85GTSend a Private Message to Doug85GTDirect Link to This Post
Broken engine mounts are not caused by tall cylinder heads. It is caused by the torque applied by the crank as the engine tries to accelerate the car. No matter what the cyclinder head configuartion, the forces are going to be applied the same way. 200 ft-lbs of torque is the same whether is is done by a 3800SC, 3.4 DOHC, 4.3, or whatever. It is still 200 ft-lbs of torque. Poor engine mount configuration or construction will break no matter the engine.
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Sourmug
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Report this Post03-18-2011 04:49 PM Click Here to See the Profile for SourmugSend a Private Message to SourmugDirect Link to This Post
 
quote
Originally posted by mattwa:

That's not true, I am basing my comments from my personal experience, I was in the middle of doing that swap when L67 stepped in and gave me his advice, and it makes perfect sense to me, and I saw it with my own eyes.


Matt:

Please allow me to clarify. Have you driven a 3.4 DOHC fiero? Did you get yours running so that you could see the way the engine reacts in the bay? Did you experience any of the failures? If not then, no you don't personal experience on how the install would have been once finished, only on the mechanics of what you had done so far.

I'm not meaning to slam you just pointing out that you are just repeating what you heard from someone else.

Anyways, enough comment from me, I don't want to see this thread trashed any further.

Nolan

[This message has been edited by Sourmug (edited 03-18-2011).]

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pmbrunelle
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Report this Post03-18-2011 07:35 PM Click Here to See the Profile for pmbrunelleClick Here to Email pmbrunelleSend a Private Message to pmbrunelleDirect Link to This Post
 
quote
Originally posted by L67:
You drive around in a stock 2.8, don't even think about lecturing me in automotive engineering.


I'm smart enough to wait until I'm done my engineering degree before tampering with these things. Or if I do tamper, and I experience a failure, I will blame my lack of knowledge rather than the components.

Is bolting/welding together random scrap without calculation considered proper dogbone design? Is guessing that the factory 2.8 bottom three mounts will be adequate considered proper engineering?

Don't blame the engine. If the engine is different, then design the mounts accordingly. You bit off more than you can chew with your 3.4.

[This message has been edited by pmbrunelle (edited 03-18-2011).]

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sspeedstreet
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Report this Post03-18-2011 08:37 PM Click Here to See the Profile for sspeedstreetClick Here to Email sspeedstreetSend a Private Message to sspeedstreetDirect Link to This Post
 
quote
Originally posted by Doug85GT:

Broken engine mounts are not caused by tall cylinder heads. It is caused by the torque applied by the crank as the engine tries to accelerate the car. No matter what the cylinder head configuration, the forces are going to be applied the same way. 200 ft-lbs of torque is the same whether is is done by a 3800SC, 3.4 DOHC, 4.3, or whatever. It is still 200 ft-lbs of torque. Poor engine mount configuration or construction will break no matter the engine.


All very true. And while I'm not crazy about the additional weight at the top of the engine, the height has at least one advantage. My dogbone mount is as high as it can possibly be without interfering with the decklid. That means I have the maximum mechanical advantage possible to resist the torque of the engine.

And the talk about the single engine mount is ridiculous. It has two engine mounts, one being the dogbone. If there is a stock front mount failure I'm betting either poly bushings are being used or the mount was not properly modified for use with the LQ1 block. Mine uses stock rubber mounts including the 1988 fluid filled engine mount. The dogbone uses poly. The engine has very little movement and transmits almost no noise or vibration up to 7000 rpm. It is so smooth under acceleration it feels like an electric motor pushing you in the back.

I love everything about it and I'm glad I did the swap.
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Report this Post03-18-2011 08:53 PM Click Here to See the Profile for L67Click Here to Email L67Send a Private Message to L67Direct Link to This Post
 
quote
Originally posted by Doug85GT:
Broken engine mounts are not caused by tall cylinder heads. It is caused by the torque applied by the crank as the engine tries to accelerate the car. No matter what the cyclinder head configuartion, the forces are going to be applied the same way. 200 ft-lbs of torque is the same whether is is done by a 3800SC, 3.4 DOHC, 4.3, or whatever. It is still 200 ft-lbs of torque.



Moment of inertia (aka Newton's second law)

F = d/dt (mv)

"The farther out the object's mass is, the more rotational inertia the object has, and the more force is required to change its rotation rate." The DOHC requires more effort to accelerate or decelerate over the axle (change its angular velocity) because its mass is distributed farther from its axis of rotation: mass that is farther out from that axis must, for a given angular velocity, move more quickly than mass closer in. Now consider how much force is applied to the engine when abruptly downshifting (engine braking) to second gear at 60 mph; it's more than 200 ft lbs, and the mounts have to decelerate the engine's velocity about the axle, which is much more than a smaller engine which is better supported and has a smaller moment of inertia.

Nutshell (TL;DR) you slept through physics 2101, try again.

 
quote
Originally posted by Sourmug:
Did you get yours running so that you could see the way the engine reacts in the bay? Did you experience any of the failures? If not then, no you don't personal experience on how the install would have been once finished, only on the mechanics of what you had done so far.


This of course applies to you also. Driving someone else's swapped vehicle isn't nearly enough information to understand or talk about longevity or design implementation. What works one day might fail the next. By the way, looking at Joe's setup, it looks as if his is mounted exactly the same way mine was - standard getrag mounts, stock middle engine mount, rear anchor. If you feel it's mounted well, have Joe get sideways with you in the car, launch the car, and engine brake at high speeds. I doubt he'd comply, I've gathered he's a rather conservative party through the tonality of conversations I've had with him.

 
quote
Originally posted by pmbrunelle:
I'm smart enough to wait until I'm done my engineering degree before tampering with these things. Or if I do tamper, and I experience a failure, I will blame my lack of qualifications rather than the components.


But not smart enough to keep your mouth shut. You have no idea who I am, my educational background, how my car was assembled or the amount of calculation that went into it. You've never built a set of mounts in your life, but automatically assume that everyone else who does does so without the fabrication and mathematical abilities to do so correctly. You go get your degree and come back and play with me when you know what you're talking about.

 
quote
Originally posted by pmbrunelle:
Don't blame the engine.


You're attaching emotional discourse to what I've said, stop reading between the lines and start reading what I type. There is scientific reasoning behind why the DOHC needs to be mounted differently than other powerplants. These are stipulations inherent of using such a large engine, and require being addressed if one expects to race their engine and not break it.

 
quote
Originally posted by pmbrunelle:
If the engine is different, then design the mounts accordingly.


I suppose I'll force feed you how the topic of mounting came up rather than expect you'll read.

 
quote
Originally posted by L67:
Yeah I know, so take care of it; don't flog it when it's cold, keep the oil topped off, and be sure its mounted as stiffly as


 
quote
Originally posted by pmbrunelle:
You bit off more than you can chew with your 3.4.


Chewing is directly proportional to the size of your stones kid, you've never chewed anything, therefor you can continue stepping off. People are driving across the state for me to work on their cars and have me install engines for them, my work speaks for itself. I don't think you have the balls to change your spark plugs.

 
quote
Originally posted by sspeedstreet:
All very true. And while I'm not crazy about the additional weight at the top of the engine, the height has at least one advantage. My dogbone mount is as high as it can possibly be without interfering with the decklid. That means I have the maximum mechanical advantage possible to resist the torque of the engine.


Actually what he said is wrong. Also understand that you have less mechanical advantage because of how tall the DOHC is; the engine tries to rotate over the dogbone mount, not against it. I had the same setup you have including an additional support mount. I was going through dogbones so your setup would not work for me if I used it again. That has a lot to do with my driving habbits, but I don't want an engine that I can't be hard on. I'm glad it works for you. OP take head.

[This message has been edited by L67 (edited 03-20-2011).]

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pmbrunelle
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Report this Post03-18-2011 09:01 PM Click Here to See the Profile for pmbrunelleClick Here to Email pmbrunelleSend a Private Message to pmbrunelleDirect Link to This Post
 
quote
Originally posted by L67:
but automatically assume that everyone else who does does so without the fabrication and mathematical abilities to do so correctly.


Your mounts broke, didn't they?
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Report this Post03-18-2011 09:08 PM Click Here to See the Profile for L67Click Here to Email L67Send a Private Message to L67Direct Link to This Post
GM and West Coast Fiero's mounts broke, my dogbone bracket is still being used by the person I sold it too. I build high quality things.
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Report this Post03-18-2011 10:14 PM Click Here to See the Profile for Doug85GTSend a Private Message to Doug85GTDirect Link to This Post
 
quote
Originally posted by L67:

Moment of inertia (aka Newton's second law)

F = d/dt (mv)

"The farther out the object's mass is, the more rotational inertia the object has, and the more force is required to change its rotation rate." The DOHC requires more effort to accelerate or decelerate over the axle (change its angular velocity) because its mass is distributed farther from its axis of rotation: mass that is farther out from that axis must, for a given angular velocity, move more quickly than mass closer in. Now consider how much force is applied to the engine when abruptly downshifting (engine braking) to second gear at 60 mph; it's more than 200 ft lbs, and the mounts have to decelerate the engine's velocity about the axle, which is much more than a smaller engine which is better supported and has a smaller moment of inertia.

Nutshell (TL;DR) you slept through physics 2101, try again.




You still don't get it do you? All of the forces that we are talking about work at the crank, not the heads.

 
quote
Originally posted by L67:
"The farther out the object's mass is, the more rotational inertia the object has, and the more force is required to change its rotation rate."


This is true but it doesn't help your argument any. Since the heads are further away from the crank "more force is required to change its rotation rate." If anything, it makes it harder to move the 3.4 DOHC than a shorter engine.

 
quote
Originally posted by L67:
F = d/dt (mv)


Did you google that or are you trying to make yourself look smart? d/dt is acceleration and (mv) is mass. In other words force = mass X acceleration.

How much force is there when acceleration is ZERO?

Here is the $64,000 question. If the engine is properly mounted, then what is the effective amount of acceleration (or movement) that the engine has in the engine bay?


What is the key here? Proper mounting. If you fail to properly mount the engine, then Newton's laws work against you.
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Report this Post03-18-2011 10:28 PM Click Here to See the Profile for sspeedstreetClick Here to Email sspeedstreetSend a Private Message to sspeedstreetDirect Link to This Post
 
quote
Originally posted by L67:


Actually what he said is wrong. Also understand that you have less mechanical advantage because of how tall the DOHC is; the engine tries to rotate over the dogbone mount, not against it. I had the same setup you have including an additional support mount. I was going through dogbones so your setup would not work for me if I used it again. That has a lot to do with my driving habbits, but I don't want an engine that I can't be hard on. I'm glad it works for you. OP take head.



What? Have you no concept of a lever? Apparently not. And this "rotating over" crap is just that, crap. My crank center distance to each end of the dogbone is within 1/2". You have no idea what you're talking about and you continue to prove it every time you post.

My apologies to the OP. Nine years on this forum and I've never felt the need to call someone ignorant. If you want to build an LQ1, there are plenty of people on the forum who love this motor and will give you a hand when you ask for it.

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Report this Post03-18-2011 10:28 PM Click Here to See the Profile for pmbrunelleClick Here to Email pmbrunelleSend a Private Message to pmbrunelleDirect Link to This Post
 
quote
Originally posted by Doug85GT:
Here is the $64,000 question. If the engine is properly mounted, then what is the effective amount of acceleration (or movement) that the engine has in the engine bay?

How much force is there when acceleration is ZERO?


Honestly, I don't think he's stupid, just confrontational, and has a personal problem with the 3.4 since he had trouble with one in the past.

Now, even if the engine doesn't move at all with respect to the engine bay, there are still forces of acceleration.

Here's a tangible example. If you floor the gas pedal, and you're pinned into the back of your seat, you're not moving with respect to the car. But you feel the forces of acceleration in your body.

The car is not an inertial frame of reference.

[This message has been edited by pmbrunelle (edited 03-18-2011).]

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Report this Post03-18-2011 10:30 PM Click Here to See the Profile for pmbrunelleClick Here to Email pmbrunelleSend a Private Message to pmbrunelleDirect Link to This Post

pmbrunelle

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quote
Originally posted by sspeedstreet:
What? Have you no concept of a lever? Apparently not. And this "rotating over" crap is just that, crap.


It's good to have the dogbone at the end of a long lever.

If you also have the mass at the end of a long lever, that sort of negates the advantages.

Now that I read again, if I understand correctly, emc also makes it sound like the axis of the dogbone in a half-assed setup (fault of the 3.4?) is far from the direction of the force you want to transmit, making an upwards reaction at the engine end of the dogbone.

But then why wouldn't one use a different dogbone geometry (change the angle) if it's so bad?

[This message has been edited by pmbrunelle (edited 03-18-2011).]

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Report this Post03-18-2011 11:01 PM Click Here to See the Profile for Doug85GTSend a Private Message to Doug85GTDirect Link to This Post
 
quote
Originally posted by pmbrunelle:


Honestly, I don't think he's stupid, just confrontational, and has a personal problem with the 3.4 since he had trouble with one in the past.

Now, even if the engine doesn't move at all with respect to the engine bay, there are still forces of acceleration.

Here's a tangible example. If you floor the gas pedal, and you're pinned into the back of your seat, you're not moving with respect to the car. But you feel the forces of acceleration in your body.

The car is not an inertial frame of reference.




You are absolutely right. There are forces at work. My whole point is that those forces don't of what kind of engine that is sitting in the engine bay. All of the acceleration and deceleration is supposed to be internal to the engine and transmission. So it doesn't matter if the heads are taller and heavier since they don't play a part in the primary forces at work. If the block or heads are moving, then you have bad mounts.

L67 has been trying to say that the LQ1 is special and breaks more engine mounts because it is top heavy. That is not true at all. That is why I said earlier that 200 ft-lbs of force is the same no matter what kind of engine it comes out of. If the engines all had the same mounting configuration then they could all use the same engine mounts for the same amount of power. It would not matter that one engine was a little more or less top heavy.

What would matter is if those forces were increased such as the engine is pushing 500 ft-lb of torque. In that case, stronger mounts would have be made regardless of the engine.
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Report this Post03-18-2011 11:13 PM Click Here to See the Profile for Doug85GTSend a Private Message to Doug85GTDirect Link to This Post
 
quote
Originally posted by pmbrunelle:


It's good to have the dogbone at the end of a long lever.

If you also have the mass at the end of a long lever, that sort of negates the advantages.

Now that I read again, if I understand correctly, emc also makes it sound like the axis of the dogbone in a half-assed setup (fault of the 3.4?) is far from the direction of the force you want to transmit, making an upwards reaction at the engine end of the dogbone.

But then why wouldn't one use a different dogbone geometry (change the angle) if it's so bad?




The mass at the end of the lever does not play a part in it.

Let's take a step back and look at the forces we are dealing with here. The pistons are moving up and down so they really don't matter. What matters is the rotational force being exerted by the crank shaft.

Think of a bank vault door. It weighs literally a ton or more yet can be opened by one man. If that man starts to move the door he can built up momentum and can easily crush something between the one ton door and the wall. But what if you put a door stop there that prevents him from moving it? Then he can't accelerate the door to build up force. Instead he can only apply the force that he can muster with his muscles.

This is the same situation with any engine. If the engine is securely mounted, then the only force you have to counter is the rotaional force of the engine as it tries to twist in place.
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Report this Post03-18-2011 11:21 PM Click Here to See the Profile for pmbrunelleClick Here to Email pmbrunelleSend a Private Message to pmbrunelleDirect Link to This Post
I understood the top-heavy thing as being important for front-rear acceleration of the entire car (but it would pale in comparison to a launch).

But yeah, for the clutch popping downshift thing, the heads are irrelevant, since the heads have nothing to do with the rotating parts.
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Report this Post03-18-2011 11:29 PM Click Here to See the Profile for L67Click Here to Email L67Send a Private Message to L67Direct Link to This Post
 
quote
Originally posted by Doug85GT:
Think of a bank vault door. It weighs literally a ton or more yet can be opened by one man. If that man starts to move the door he can built up momentum and can easily crush something between the one ton door and the wall. But what if you put a door stop there that prevents him from moving it? Then he can't accelerate the door to build up force. Instead he can only apply the force that he can muster with his muscles.


I concede to this point. However, my engine was building up enough momentum to break the mounts during deceleration of rotation under hard driving conditions and stock mounting, using the same mounting setup that most of the community was using at that time. I understand perfectly what you're saying, but I had enough tolerance in my setup so that the additional mass at the top of the engine became a problem. As I mentioned before, I would mount the engine differently knowing now what I do. I didn't of course because I decided the DOHC wasn't worth the trouble, not that I had "bitten off more than I could chew".

[This message has been edited by L67 (edited 03-18-2011).]

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Report this Post03-18-2011 11:47 PM Click Here to See the Profile for indyguyClick Here to Email indyguySend a Private Message to indyguyDirect Link to This Post
Sorry to use this term but OMFG people the guy starts a build thread is exited about HIS CHOICE TO DO THIS and you come after him like it's your mission in life to tell him he shouldn't do it cause this or that. I hope he proves you all wrong and does it like he want's and rubs it in your face. Just because you failed in your attempt does not mean everyone else will! (Sorry to hijack Chris) Hope you make the cruise in april. If you don't have a fiero to drive I got a couple that need drivers for the cruise see ya
Ryan

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Report this Post03-18-2011 11:48 PM Click Here to See the Profile for pmbrunelleClick Here to Email pmbrunelleSend a Private Message to pmbrunelleDirect Link to This Post
I'm sure you get a lot of stored energy in what, 2 degrees of movement from a halt?
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Report this Post03-18-2011 11:53 PM Click Here to See the Profile for qwikgtaClick Here to Email qwikgtaSend a Private Message to qwikgtaDirect Link to This Post
Just to chime in. I watched others fabricate engine mounts to lower the motor 1 inch. I didn't feel this was that big of a deal, maybe I just don't know what I don''t know. I used the stock GM engine bracket attached to a WCF poly mount. I had a set of WCF poly mounts on the trans side. I had a dogbone bracket located in the stock location, but it was not the stock bracket. I made one. And I connected the dogbone to the engine lift bracket near the old power steering pump. Now I understand that folks here like to tell you what they did, and some like to tell you what to do with no actual experiance. I can tell you that I never felt any issues with the motor being too high in the engine bay, and I didnt' have any issues with the dog bone location. The motor is mounted with Poly mounts and it did't move at all. The dogbone was just gravy. I can't say that I beat on the engine, but i felt that I rode it hard for almost 2K miles. Maybe 2K miles is not enough to discover problems. I don't know, but agian, I can't say I babied it all the time. Did I drop the clutch from 3-4 K Hell no!! Did it spin the tires , yes.

Custom motor mounts and trans mounts are great if thats what you want to do, but I don't think they are needed. I used the WCF ones, but I think Rodney Dickman still sells Poly mounts for the 2.8L I also had a set of them, and I would have used them over the WCF ones, its just that I got the WCF ones first. I liked Rodneys design better. There was no size differance, but I just liked them better.

And as others have stated, there are several folks on this forum who have actually built a running DOHC Fiero, and we will help you with the Facts of those builds.



picture of the dogbone bracket

Rob


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Report this Post03-19-2011 11:32 AM Click Here to See the Profile for eph_kayClick Here to Email eph_kaySend a Private Message to eph_kayDirect Link to This Post
Hey guys don't worry about bothering me with this jibber jabber, progress isn't the fastest in the garage right now and I am completely enjoying the read!

Oh, and besides there are quite a few smart people in here talking things out, I am learning some things, and the physics recap is great.

Also I will probably put a link on the first page to where I get back to making any visual progress, incase people want to skip this.

:Car Update:
I got the steering rack out and am unbolting the front suspension, I've been cleaning out the garage and have somebody coming today to get my old engine/tranmission.

Chris
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Report this Post03-19-2011 11:57 AM Click Here to See the Profile for Formula88Send a Private Message to Formula88Direct Link to This Post
 
quote
Originally posted by qwikgta:

Custom motor mounts and trans mounts are great if thats what you want to do, but I don't think they are needed. I used the WCF ones, but I think Rodney Dickman still sells Poly mounts for the 2.8L I also had a set of them, and I would have used them over the WCF ones, its just that I got the WCF ones first. I liked Rodneys design better. There was no size differance, but I just liked them better.


Thanks for adding some first hand experience.
Keep in mind, though, that you ARE using custom mounts. They just happen to bolt into the stock locations. The OEM mount setup with stronger mounts may be all you need in some cases. The four point mount setup may make a dogbone unnecessary and provide more strength still.

That's where the engineering comes in. How much stronger is needed? It's easy to overbuild something and make it 5 times stronger than it needs to be, but that adds unnecessary weight and expense. The thing about engineering that always bugged me was that, in general, you don't want to design the "best" piece to do the job. You want to design the "worst" piece that will still meet all of your design criteria. Anything more is heavier or more expensive than necessary. For personal custom work, it's not a big deal, but for mass production like an automobile assembly line, it's the difference between profit and bankruptcy, reliability and lemons.
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Report this Post03-19-2011 01:28 PM Click Here to See the Profile for crazyinkcSend a Private Message to crazyinkcDirect Link to This Post
 
quote
Originally posted by indyguy:

Sorry to use this term but OMFG people the guy starts a build thread is exited about HIS CHOICE TO DO THIS and you come after him like it's your mission in life to tell him he shouldn't do it cause this or that. I hope he proves you all wrong and does it like he want's and rubs it in your face. Just because you failed in your attempt does not mean everyone else will! (Sorry to hijack Chris) Hope you make the cruise in april. If you don't have a fiero to drive I got a couple that need drivers for the cruise see ya
Ryan



sexy. Even if you did spell excited wrong. He could always drive Betty if its not ready, or maybe Bob...

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C'mon you know my 4cylinder is Pimp. Just admit it. You'd own it.

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Turkey on Rye
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Report this Post03-19-2011 04:24 PM Click Here to See the Profile for Turkey on RyeClick Here to Email Turkey on RyeSend a Private Message to Turkey on RyeDirect Link to This Post
Hey man, you sure you want to do a TDC? :-P
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fieroguru
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Report this Post03-19-2011 08:37 PM Click Here to See the Profile for fieroguruSend a Private Message to fieroguruDirect Link to This Post
Just a point of clarification... as you design mounts for a transverse application, crankshaft torque isn't the most significant factor to be concerned with... it is the drive line torque about the differential. It is the single largest factor in a transverse application and is an order of magnitude (10 times) greater than the engine crankshaft torque.

Say your engine puts out 300 lb-ft at the flywheel. First gear and the final drive multiplies the torque seen at the axles. So if you are running a Fiero getrag 5 speed the axles see 300 lb-ft x 3.50 (1st gear) x 3.61 (final drive) = 3790 lb-ft when the engine is putting out 300 lb-ft and assuming the tires are not spinning.

For those that say the engine weight counter acts the drive line torque, it does but is still rather insignificant. Say your engine weighs 500 lbs and there is 12" between the crank center line and the differential so the engine weight only provides 500 lb-ft towards resisting the 3790 lb-ft axle torque... not going to matter much. With a Fiero getrag, it is 8" not 12" so the 500 becomes 375 which is even less.

Now the 3.4TDC likes to rev, and so some pair it with transmissions the other engine swaps tend to avoid. Running a fiero getrag with the 3.94 final drive the same 300 lb-ft engine torque becomes 4137 vs 3790. If you run the 4.10 4 speed, then you are looking at 4341.

The more mounts (dogbone included) your drive train has, the less force any single one had to withstand.
The further the mounts are from each other (front to back) the less they will have to withstand.
Improperly designed or improperly located mounts have a greater chance of failure.
Excessive engine torque and excessive gear reduction increases the loads on the drive line mounts and will increase the opportunity for failure.

Now lets see some 3.4 TDC swap progress!
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Doug85GT
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Report this Post03-19-2011 08:55 PM Click Here to See the Profile for Doug85GTSend a Private Message to Doug85GTDirect Link to This Post
 
quote
Originally posted by qwikgta:



picture of the dogbone bracket

Rob



Hey Rob,

I'm surprised that you have your dog bone anchored there. A number of other LQ1 cars broke that aluminum engine cover. Yours is still holding up fine?


Also, thanks for the explanation FieroGuru. That was very informative. When I do my LQ1 swap, I am plan to have two engine mounts plus the dog bone in addition to the transmission mounts.

[This message has been edited by Doug85GT (edited 03-19-2011).]

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qwikgta
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Report this Post03-19-2011 09:27 PM Click Here to See the Profile for qwikgtaClick Here to Email qwikgtaSend a Private Message to qwikgtaDirect Link to This Post
 
quote
Originally posted by Doug85GT:


Hey Rob,

I'm surprised that you have your dog bone anchored there. A number of other LQ1 cars broke that aluminum engine cover. Yours is still holding up fine?


Also, thanks for the explanation FieroGuru. That was very informative. When I do my LQ1 swap, I am plan to have two engine mounts plus the dog bone in addition to the transmission mounts.



After reading Guru's post above, it may not be a wise choice. I had seen only one failure and the individual said that he believed it was because he had placed the bone at an angle and not straight. I had mine located in a perfect straight angle to the bracket. The motor with the poly mounts did not move anyway, but I did the bone becuase I wanted the extra. Now to make matters worse, for me, the bone was rigid mounted, no poly, no rubber. It was a solid mount. The motor could not move at all with it attached. That would lead you to believe it would break sooner, but I had no problems with it. If you look at the pic again, I had two hiem joints with a threaded rod between them. It would not be how I would do it if I was doing another swap. I'd find a better way to do it, but time was the issue, and so I used this setup.

Rob

------------------


88 Coupe, CJB T-TOP, LS376 and a GT clip
http://www.youtube.com/watch?v=QAH9yjw6XR0

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Fieroking
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Report this Post03-21-2011 01:13 AM Click Here to See the Profile for FierokingClick Here to visit Fieroking's HomePageClick Here to Email FierokingSend a Private Message to FierokingDirect Link to This Post
My 3.4 DOHC has been running for 3 years now. I have had no problems with the mount setup that I used. I used Dodge trans mounts to help lower the engine and a poly mount under the engine I made a front mount for the engine that is under the AC compressor. The engine doesn't move around. While I don't drive it like a race car, I don't baby it either the engine does love to rev. When my son comes home to visit (in the Navy) he flogs the ever loving crap out of it and the car just loves it.
My opinion is to mount the engine the way engines have been mounted from the beginning i.e. 2 transmission mounts and 2 engine mounts.

I love my 3.4 DOHC. Build your car and enjoy it.

Joe Sokol

------------------
85 SE Daily driver with a 3.4 DOHC OBD II
88 Formula/GT 4.9 Allante Intake (My Baby)

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tesmith66
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Report this Post03-21-2011 05:14 AM Click Here to See the Profile for tesmith66Send a Private Message to tesmith66Direct Link to This Post
Pics? Do you simply replace the rubber in the Fiero mount setup with the Dodge mount?

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1986 SE 350 V8

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Doug85GT
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Report this Post03-21-2011 09:35 AM Click Here to See the Profile for Doug85GTSend a Private Message to Doug85GTDirect Link to This Post
 
quote
Originally posted by tesmith66:

Pics? Do you simply replace the rubber in the Fiero mount setup with the Dodge mount?




See this page for a good writeup with pics of the Dodge mounts.

http://www.gmtuners.com/Cus...4DOHCFiero/swap3.htm
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Custom2M4
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Report this Post03-21-2011 06:14 PM Click Here to See the Profile for Custom2M4Click Here to Email Custom2M4Send a Private Message to Custom2M4Direct Link to This Post
 
quote
Originally posted by fieroguru:

Now the 3.4TDC likes to rev, and so some pair it with transmissions the other engine swaps tend to avoid. Running a fiero getrag with the 3.94 final drive the same 300 lb-ft engine torque becomes 4137 vs 3790. If you run the 4.10 4 speed, then you are looking at 4341.

Now lets see some 3.4 TDC swap progress!


Eph_kay; your new goal in this build is to utilize all 4341 ft/lbs of torque at the wheels.
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qwikgta
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Report this Post03-21-2011 10:34 PM Click Here to See the Profile for qwikgtaClick Here to Email qwikgtaSend a Private Message to qwikgtaDirect Link to This Post
I guess the point that was missed was that you have to do a lot of cutting and modifying on the cradle, motor mounts, engine mount to lower the motor what? one inch. Why? That seems to be a lot of effort when you can just use the Poly mounts (3), in the stock location, with the stock brackets, with no mods. Add in a good Dog-Bone or a 4th mount (both great ideas). Thats all I'm saying. Unless there is some kind of serious gain to be had by lowing the motor, forget it, you will have enough issues with the wire harness, and your turbo setup to worry about all the added BS.

Rob
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Fieroking
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Report this Post03-21-2011 11:05 PM Click Here to See the Profile for FierokingClick Here to visit Fieroking's HomePageClick Here to Email FierokingSend a Private Message to FierokingDirect Link to This Post
I followed Ryan's mount method using the Dodge mounts for the trans. My aim was to get the oil pan level with the bottom of the cradle, this helped with clearance on the top of the engine. My front mount is different I used a front mount from a 3800 and used a Poly trans mount under it and installed 2 short poly end links under the AC compressor as the 4 mount. I'll look on my other computer and see if I have pictures.

Joe Sokol

------------------
85 SE Daily driver with a 3.4 DOHC OBD II
88 Formula/GT 4.9 Allante Intake (My Baby)

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engine man
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Report this Post03-22-2011 10:04 AM Click Here to See the Profile for engine manClick Here to Email engine manSend a Private Message to engine manDirect Link to This Post
glad to see a 3.4 TDC build i think this engine is way under rated for its potential . search Mat Hawkins he had or has a 3.4 TDC turbocharged in a fiero that made 417 whp i am sure it would be great to pick his brain on things

http://www.youtube.com/watch?v=-6jv_s1hUJg

[This message has been edited by engine man (edited 04-13-2011).]

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Fieroking
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Report this Post03-24-2011 10:34 PM Click Here to See the Profile for FierokingClick Here to visit Fieroking's HomePageClick Here to Email FierokingSend a Private Message to FierokingDirect Link to This Post
I looked in my photo's of my 3.4 build and could only find the poor picture of the front mount that I put on my build



As I said earlier I used the front mount off a 3800 sitting on poly trans mount

Joe Sokol

------------------
85 SE Daily driver with a 3.4 DOHC OBD II
88 Formula/GT 4.9 Allante Intake (My Baby)

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mattwa
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Report this Post03-24-2011 11:14 PM Click Here to See the Profile for mattwaClick Here to Email mattwaSend a Private Message to mattwaDirect Link to This Post
 
quote
Originally posted by Fieroking:

I looked in my photo's of my 3.4 build and could only find the poor picture of the front mount that I put on my build

As I said earlier I used the front mount off a 3800 sitting on poly trans mount

Joe Sokol




You used Sway bar end links as a mount? That's something I haven't seen before.

[This message has been edited by mattwa (edited 03-24-2011).]

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solotwo
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Report this Post03-27-2011 09:40 PM Click Here to See the Profile for solotwoSend a Private Message to solotwoDirect Link to This Post
Interesting read. I love all the engineering info. I was going to go on to engineering school after I finished Community college but life got in the way. Now my son is an engineer.

For me I would not do the DOHC engine. Why??? I saw to many broken motors in the broken motor pile at the dealerships I have worked at. It's just me. If see a lot of one engine it tells me, not to pursue this engine. It is just me. Thats all. No engineering reason. I have even seen some of the new 3.6VVT engines that cadillac uses, but not as many as I remember seeing of the 3.4 DOHC.

Just my .02 worth
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Report this Post04-07-2011 06:29 PM Click Here to See the Profile for eph_kayClick Here to Email eph_kaySend a Private Message to eph_kayDirect Link to This Post
Just a quick update, I have the car completely taken apart, I am getting ready to start cleaning and painting the chassis and components.

I am looking at doing the Toronado Hubs like BubbaJoe did on the Northstar stretched fiero.

I am also looking into a custom set up for the rear that I am still messing around with what approach to take.

I am actually working out the details of getting myself a hobby CNC mill to make me a custom intake and a few other parts for this car, should be a valuable tool to have.

Chris
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Sourmug
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Report this Post05-11-2011 11:49 PM Click Here to See the Profile for SourmugSend a Private Message to SourmugDirect Link to This Post
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