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Connecting Rod Bearings in a 4.9 Caddy Motor. by Capt Fiero
Started on: 12-07-2013 10:04 AM
Replies: 8 (521 views)
Last post by: Arns85GT on 12-08-2013 05:02 PM
Capt Fiero
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Report this Post12-07-2013 10:04 AM Click Here to See the Profile for Capt FieroClick Here to visit Capt Fiero's HomePageClick Here to Email Capt FieroSend a Private Message to Capt FieroEdit/Delete MessageReply w/QuoteDirect Link to This Post
As many of you know my new motor installed in my 4.9 5spd Fiero was delivered to me with an engine knock. I got a partial refund and told the shop I never wanted to hear from them again. That was nearly a year ago. I paid them for the other work they did, and took my car to deal with myself.

Well its Winter here in Surrey BC and I decided to go out and do the winter prep to the stored cars. One of those tasks is draining out a gallon of coolant from each car and filling up with fresh pure antifreeze then firing up the car and letting it run until it has warmed up.

I did this with the V8 and There are a few things that can create engine knock like I am hearing, Connecting Rod bearings, Main Bearings, Piston Slap and outside chance I thought rocker supports. Well I changed all the rockers and supports to the Allante Steel ones. Didn't make a difference.

Well doing it ICE cold fire up, and letting it run for a bit, I noticed that upon reving the motor up a bit and quickly dropping the throttle it was not a steady, Bang, Bang, Bang, Bang like a main bearing, if the rpms were right it would do a quick bang, then a double bang, double bang and then back to the normal bang. Almost like at idle you hear it bang when that cylinder fires but with changing idle up and down quickly you could get it to not only bang on compression, but get a quick bang as the crank draws the connecting rod / piston down for the intake stroke.

I am thinking about dropping the pan, and checking the rods for slop, getting some plasti gauge in there and see whats going on.

Does anything think there is a chance in hell, that I could get away with unbolting the pistons pushing them up in the bores replacing all the bearings, and under/over sizing any that need it. If the bearing has not spun and chewed the living hell out of the crank..... I am thinking it might be a cheap thing to try. The bearings are 13 bucks. I'd like to try and possibly waste 13 bucks if there is even a slim chance I wont have to spend 500 on a replacement motor, 400 on new gaskets and countless ours changing out the motor AGAIN.

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857GT Part 85GT Part 87GT Part Caddy, 93 Eldorado 4.9, 5spd Dual O2 Custom Chip, Custom Exhaust. MSD Everything Now with Nitrous. Capt Fiero --- My Over View Cadero Pics For Sale $4000, Yellow 88GT 5spd Full Poly Suspension, Lowered 1/2" in front, Corner Carver.

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lou_dias
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Report this Post12-07-2013 10:20 AM Click Here to See the Profile for lou_diasClick Here to Email lou_diasSend a Private Message to lou_diasEdit/Delete MessageReply w/QuoteDirect Link to This Post
It's been done. But only do it on the one that needs it, not all the cylinders.

I had bad luck with it on one of my first 3.X builds, my brother had good luck with it on an LS1...

You could save yourself a lot of future grief and just go 3800SC. On my 4.9 swap, I'm hoping it grenades sooner than later so that I can just send it to Archie and go LS3 + F40. My 3.4 build makes more power than my 4.9 ...

[This message has been edited by lou_dias (edited 12-07-2013).]

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trotterlg
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Report this Post12-07-2013 11:52 AM Click Here to See the Profile for trotterlgClick Here to Email trotterlgSend a Private Message to trotterlgEdit/Delete MessageReply w/QuoteDirect Link to This Post
If you have a rod knock now that journel is not round any more. Odd thing about rod bearing failures is that the metal gets taken off the bottom of the journel not the top where you think it would happen. I would pull the pan and see what you have to deal with. If one is slightly bad you may get away with replacing the bearing, but any under sized bearings will be much too tight, if you do anything you could shim the bearing some, but remember that you take out .002 inch using a .001 shim. Having less than zero clearance will mean instant death to that rod as soon at it fires up. Back in the 60's there were shops that could grind one in place in the engine. Good luck. Larry
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Capt Fiero
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Report this Post12-07-2013 12:12 PM Click Here to See the Profile for Capt FieroClick Here to visit Capt Fiero's HomePageClick Here to Email Capt FieroSend a Private Message to Capt FieroEdit/Delete MessageReply w/QuoteDirect Link to This Post
Thank You Lou and trotterlg. I use to have some bearing shim material floating around. I think it was called bearing foil as frankly it was not much thicker than tin foil. I don't think the journal itself will be in too bad of shape as depending on RPM you can get the noise to dang near disappear. I'll know more when I get the pan off and take a look. The car is parked in my driveway and its currently 13 below Zero with a windchill to -23c so I might wait until next week when it warms up to a few degree's over freezing. (I have a garage it just full of Fiero and Computer and Baby stuff.

At Lou I thought about doing a 3800 when my last 4.9 packed it in. However I opted to have a custom one off 4.9 built. I think that is why the bearing let go. It might have been fine with a stock 4.9 for years, but we have a high lift cam, custom intake with HUGE plenum and a Northstar Throttle Body. Tuned for 6500rpms Shop that built it was hoping for 300hp, I was hoping for 240-260 with 320-330lbs of torque. We own a 2000 GTP with a S2 3800SC in it. I like the motor and all, but I prefer the dynamics of the 4.9. The one thing the 4.9 can do that the 3800 can't do is off idle (450rpm) instant torque. I DO NOT WANT THIS TO TURN INTO A 3800 vs 4.9 DEBATE. I just simply prefer the characteristics of a small fuel injected V8 not to mention with the really short side exit exhaust and large flowmaster in place of the cat, I really like the sound.


Ok back to bearings. I plan to pick up the Clevite Tri Metal bearings for the motor. When I do get in there, if I find that all the rod bearings are snug, what else should I be looking for. Is there anyway to check main bearings without pulling the caps off. If it is piston pin whats going to be the easiest way to verify that. Actually if its a piston issue at all, pin or otherwise, I think it will be a lost cause, as chances are it will have taken out a cylinder wall, and the 4.9 is a disposable motor when it comes to cylinder wall issues.

Basically, I know my way around engines, however I looking for the off the book information that only comes from building a dozen motors, that mystery information that's floating around in some of your heads. I hate the idea of trashing this motor as it has so much potential.

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857GT Part 85GT Part 87GT Part Caddy, 93 Eldorado 4.9, 5spd Dual O2 Custom Chip, Custom Exhaust. MSD Everything Now with Nitrous. Capt Fiero --- My Over View Cadero Pics For Sale $4000, Yellow 88GT 5spd Full Poly Suspension, Lowered 1/2" in front, Corner Carver.

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lou_dias
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Report this Post12-07-2013 02:12 PM Click Here to See the Profile for lou_diasClick Here to Email lou_diasSend a Private Message to lou_diasEdit/Delete MessageReply w/QuoteDirect Link to This Post
I understand your reasoning, however you then went on to add nitrous and try to make the motor make more power at high rpm.
If torque is all you care about, go diesel.

With my 4.9, I realized you can't squeeze blood from a stone. I attempted to do a performance rebuild and I believe I documented my issues in your build thread already. With that motor, it's boost or nothing and nothing is much easier. When it blows up, just drop another used one in there. They aren't "rebuild-friendly".
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Raydar
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Report this Post12-07-2013 03:34 PM Click Here to See the Profile for RaydarClick Here to Email RaydarSend a Private Message to RaydarEdit/Delete MessageReply w/QuoteDirect Link to This Post
The problem with just dropping in new bearings is that something is possibly egg-shaped from all the pounding.
Larry suggested the journal. I have heard it suggested that rods will get that way too.

Good luck. Stay warm.

And don't overdo it.

[This message has been edited by Raydar (edited 12-07-2013).]

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Lou6t4gto
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Report this Post12-07-2013 06:18 PM Click Here to See the Profile for Lou6t4gtoClick Here to Email Lou6t4gtoSend a Private Message to Lou6t4gtoEdit/Delete MessageReply w/QuoteDirect Link to This Post
If you already went to all that trouble and expense to "Build this thing", IF you find "anything wrong" with the bearings or Crank, Why not just put a New Crank Kit in it, rather than a "band aide" ?
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stickpony
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Report this Post12-07-2013 11:34 PM Click Here to See the Profile for stickponyClick Here to visit stickpony's HomePageSend a Private Message to stickponyEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Capt Fiero:
Does anything think there is a chance in hell, that I could get away with unbolting the pistons pushing them up in the bores replacing all the bearings, and under/over sizing any that need it. If the bearing has not spun and chewed the living hell out of the crank..... I am thinking it might be a cheap thing to try. The bearings are 13 bucks. I'd like to try and possibly waste 13 bucks if there is even a slim chance I wont have to spend 500 on a replacement motor, 400 on new gaskets and countless ours changing out the motor AGAIN.



Man, Dave, it seems like yesterday i sent you a reprogrammed chip for your first 4.9L swap! I am very sorry to hear all the terrible luck you had with that shop owned by the FOY guy who is now banned from here. I read the threads, and was appalled at the way you and others were treated and swindled. karma is real though, rest assured, he will get whats coming to him.

anyways, give me some more details on the swap... whats the specs on the cam, and what valvetrain mods were made? I suspect you are correct, probably a bearing. Maybe the engine he installed was an early 1991 engine before GM issued that TSB to install oversized main bearings to prevent the crank knock the 4.X engine were prone to after so many miles...

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Arns85GT
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Report this Post12-08-2013 05:02 PM Click Here to See the Profile for Arns85GTClick Here to Email Arns85GTSend a Private Message to Arns85GTEdit/Delete MessageReply w/QuoteDirect Link to This Post
Hi Dave,

I now have a '93 De Ville 4.9 set up as a carb'd engine.

I had some trouble with the dizzy gear prematurely wearing, (I think I have it solved) and during the discussion period, I discussed repairing the 4.9 with PBJ.

As you likely know, he is very well versed in all things Cadillac, and he is a true expert. The consensus was this. If the engine is wrong, throw it away and get another donor.

The cost of repair will be more than the new donor motor. You can use the bits off the existing motor on the new donor.

I know this is not what you want to hear, but it may save you some time and money. Good luck,

Arn

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