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3800 Header question by Zeak
Started on: 03-03-2015 11:31 AM
Replies: 10 (375 views)
Last post by: Darth Fiero on 03-05-2015 03:02 AM
Zeak
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Report this Post03-03-2015 11:31 AM Click Here to See the Profile for ZeakSend a Private Message to ZeakEdit/Delete MessageReply w/QuoteDirect Link to This Post
Doing some searching on things that should and should not be done for my sc3.8 & auto trans swap.
I don't like the idea of the front cylinder bank exhaust crossing over the top of the trans.
Aside from the engine movement and vibration cracking the header, is there any other reason you can't run the front bank under the engine cradle or somewhere else?
Thanks!

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Darth Fiero
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Report this Post03-03-2015 06:47 PM Click Here to See the Profile for Darth FieroClick Here to visit Darth Fiero's HomePageClick Here to Email Darth FieroSend a Private Message to Darth FieroEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Zeak:

Doing some searching on things that should and should not be done for my sc3.8 & auto trans swap.
I don't like the idea of the front cylinder bank exhaust crossing over the top of the trans.
Aside from the engine movement and vibration cracking the header, is there any other reason you can't run the front bank under the engine cradle or somewhere else?
Thanks!


What's wrong with running the exhaust crossover on top of the transmission's bell housing? The factory does that in every FWD application it put the 3800 engine in and there were never any problems doing it that way.

Would you rather run it under the oil pan so it can heat up the oil? That's what you're going to have to do if you want to run it "under" the engine/cradle because that's the only place you can run it (pretty much like it did with the stock Fiero engine).

-ryan

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DKcustoms
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Report this Post03-03-2015 07:33 PM Click Here to See the Profile for DKcustomsSend a Private Message to DKcustomsEdit/Delete MessageReply w/QuoteDirect Link to This Post
I don't particularly care for the exhaust running over the tranny either, but with transverse setups there aren't a whole lot of other options (which is why I'd like to stretch my car eventually for a longitudinal swap).

As mentioned, cooking your oil isn't good either, so your only other good option would be a side exit in front of the motor.

[This message has been edited by DKcustoms (edited 03-03-2015).]

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Zeak
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Report this Post03-04-2015 11:37 AM Click Here to See the Profile for ZeakSend a Private Message to ZeakEdit/Delete MessageReply w/QuoteDirect Link to This Post
I don't know about "heating up the oil".
My thought was from years of dealing with inline 4's on street bikes and fwd cars.
A very small amount of company's have or would run a forward facing exhaust to the side. Most ran them under because of the direct or in-direct airflow to help keep the temps down.
I know that heat can be an issue for mid-engine's and part of my build budget is for a custom exhaust.

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gen2muchwork
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Report this Post03-04-2015 12:14 PM Click Here to See the Profile for gen2muchworkClick Here to Email gen2muchworkSend a Private Message to gen2muchworkEdit/Delete MessageReply w/QuoteDirect Link to This Post
I had thought a little about this with the 4.9 which has a similar crossover but I figured heat rises and airflow is up through the vents, so it's possibly better up there.
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Gall757
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Report this Post03-04-2015 12:21 PM Click Here to See the Profile for Gall757Send a Private Message to Gall757Edit/Delete MessageReply w/QuoteDirect Link to This Post
Ground clearance is a big issue for production vehicles. Your average driver will not be careful, and if the lowest thing in the rear of the car is the exhaust pipe, it is going to be mashed up in short order. In 2015, Fiero owners are not average drivers, and they will be concerned about potholes and driveway aprons. If you want it down there...(option B)...go for it!... You will probably want to lower the car also, so you know you will have to be an observant driver.
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Report this Post03-04-2015 01:03 PM Click Here to See the Profile for dobeySend a Private Message to dobeyEdit/Delete MessageReply w/QuoteDirect Link to This Post
For what it's worth, the stock Fiero exhaust crosses under the engine on the passenger side of the cradle.

All GM transverse FWD V6/V8 engines have a crossover pipe which goes over the transmission, though. Even the stock Fiero 2.8 has this, to route the exhaust forward to the cat, and then crosses back under the engine on the passenger side, to get to the muffler and exit. This creates a longer exhaust system than routing everything off the rear side of the engine.

edit: added transverse to clarify, as I realized some FWD cars were actually longitudinal, and they wouldn't generally have the exhaust routed over top of the bell housing.

[This message has been edited by dobey (edited 03-04-2015).]

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Darth Fiero
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Report this Post03-04-2015 05:03 PM Click Here to See the Profile for Darth FieroClick Here to visit Darth Fiero's HomePageClick Here to Email Darth FieroSend a Private Message to Darth FieroEdit/Delete MessageReply w/QuoteDirect Link to This Post
If you're concerned about engine compartment heat from the exhaust pipe routed over the transmission's bell housing, you can apply header wrap to the crossover pipe. The new "titanium" header wrap is pretty nice stuff and insulates well.

I have a turbocharged 3800 in my Fiero. I put my turbo right on top of the transmission bell housing. It is fed by a custom built y-pipe that also routes both exhaust banks to on top of the transmission's bell housing. Everything but the turbo is wrapped with header wrap. I have much more heat being put into my Fiero's engine compartment than anybody without a turbo - but I've never had a problem with all this extra heat. I did add an electric extractor fan to the driver's side deck lid vent to help extract some of the extra heat, and it does help.

As others have said, the available engine compartment space gives you little alternative for exhaust routing. So leaving the crossover pipe routed on top of the transmission's bell housing shouldn't be a deal breaker. Like I said, that's the way GM does it in pretty much every FWD V6 production car.

[This message has been edited by Darth Fiero (edited 03-04-2015).]

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Zeak
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Report this Post03-04-2015 10:06 PM Click Here to See the Profile for ZeakSend a Private Message to ZeakEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Darth Fiero:

If you're concerned about engine compartment heat from the exhaust pipe routed over the transmission's bell housing, you can apply header wrap to the crossover pipe. The new "titanium" header wrap is pretty nice stuff and insulates well.


I like the idea of a wrap, but dose that not make the pipe rust faster?

Thanks for all the input guys.
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dobey
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Report this Post03-04-2015 11:35 PM Click Here to See the Profile for dobeySend a Private Message to dobeyEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Zeak:

I like the idea of a wrap, but dose that not make the pipe rust faster?

Thanks for all the input guys.


Get it ceramic coated. Use the right type of steel. Or use titanium. Titanium is inert and weighs less. So it won't corrode at all with the heat wrap.
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Darth Fiero
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Report this Post03-05-2015 03:02 AM Click Here to See the Profile for Darth FieroClick Here to visit Darth Fiero's HomePageClick Here to Email Darth FieroSend a Private Message to Darth FieroEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Zeak:

I like the idea of a wrap, but dose that not make the pipe rust faster?



Mild steel will rust no matter if it is wrapped or not. Header wrap will hold moisture, so yes, header wrapped mild steel will rust faster.

You can instead use stainless pipe and you won't have to worry about rust or corrosion.

Ceramic coating looks awesome and will help with the heat a little, but not as effectively as header wrap.

Titanium pipe is very expensive and difficult to weld.

[This message has been edited by Darth Fiero (edited 03-05-2015).]

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