When do stock headers become a restriction?

[Undercover87T]

Did a search and really didn't find a definitive answer. I'm in the process of removing my wounded 3.8 and installing a 4.1. I'm on the fence about reusing my stock headers or spending the extra $$ for aftermarket headers. My question would be at what point would the stock headers become a restriction and aftermarket headers become required? Specifically would stock headers be ok for my build? Car is a street car that will see occasional strip use with the goal to eventually run low 11's.
Specs will include:
- .030 4.1 291, comp 212/212 roller cam kit, ported irons, HS 1.6 roller rockers, ported intake/plenum/tb
- pt6262e, 3in downpipe/testpipe, 2.5 ATR exhaust
- 60lb injectors/tt chip, ls1 maf
- gbody stretch slic, gn1 rad/dual fans

 

[forcefed3.8's]

IMO, any 3 bolt turbo will see no gain with headers. Low 11's isn't a problem.

 

[Ttype6]

Did a search and really didn't find a definitive answer. I'm in the process of removing my wounded 3.8 and installing a 4.1. I'm on the fence about reusing my stock headers or spending the extra $$ for aftermarket headers. My question would be at what point would the stock headers become a restriction and aftermarket headers become required? Specifically would stock headers be ok for my build? Car is a street car that will see occasional strip use with the goal to eventually run low 11's.
Specs will include:
- .030 4.1 291, comp 212/212 roller cam kit, ported irons, HS 1.6 roller rockers, ported intake/plenum/tb
- pt6262e, 3in downpipe/testpipe, 2.5 ATR exhaust
- 60lb injectors/tt chip, ls1 maf
- gbody stretch slic, gn1 rad/dual fans

The stock crossover is the restriction. The headers are a very good design.

 

[Nick Micale]

The stock crossover is the restriction. The headers are a very good design.

Sorry, but I disagree that the stock crossover is a restriction.

It is sized to maintain velocity in the exhaust stream, especially when only 3 cylinders are feeding it. A larger diameter crossover pipe with stock headers will hinder spooling, not help it.

We have done a few custom V-6 headers with 5/8" primary tubes from the heads for higher HP and RPM cars, and still use a stock size crossover.

Also the testing we did to determine the hole size at the turbo flange shows that is also a critical dimension to maintain velocity/spooling.

In response to the original post, we have found no gain replacing stock headers, if they are in GOOD shape, until mid 10's or better.

 

[blackgn1]

Stockers have been 9's

 

[Grumpy]

Sorry, but I disagree that the stock crossover is a restriction.

It is sized to maintain velocity in the exhaust stream, especially when only 3 cylinders are feeding it. A larger diameter crossover pipe with stock headers will hinder spooling, not help it.

X2 !! we tried this years ago.. car turned into a dog !! I like stock junk

 

[Undercover87T]

Good info guys thanks. Drivers side and crossover look to have been patched in the past but dont appear to leak. Guess ill clean them up and save the $$.

 

[Ttype6]

Sorry, but I disagree that the stock crossover is a restriction.

It is sized to maintain velocity in the exhaust stream, especially when only 3 cylinders are feeding it. A larger diameter crossover pipe with stock headers will hinder spooling, not help it.

We have done a few custom V-6 headers with 5/8" primary tubes from the heads for higher HP and RPM cars, and still use a stock size crossover.

Also the testing we did to determine the hole size at the turbo flange shows that is also a critical dimension to maintain velocity/spooling.

In response to the original post, we have found no gain replacing stock headers, if they are in GOOD shape, until mid 10's or better.

I can't come up with any good argument to your statements.

 

[Mr.Spool]

i went 10's on the stock headers they will do it however,i was constantly pulling them off.save yourself the aggrivation and buy the ta perf headers and dont look back.mine havent been off since i put them on,they are sweet.

 

[Ttype6]

i went 10's on the stock headers they will do it however,i was constantly pulling them off.save yourself the aggrivation and buy the ta perf headers and dont look back.mine havent been off since i put them on,they are sweet.

Why were you pulling them off so often?

 

[Mr.Spool]

constantly leaking no matter which gaskets used,had the best luck with no gaskets and orange rtv,they have to be straightened as best you can each time.the flanges just arent thick enough and constantly warp.ive also had cracks that you must weld and had the stockers ceramic coated,pretty much all a waste of time.the ta perf are the way to go,ive had my car a long time and plan on keeping it so buying good stuff is a no brainer.

 

[bison]

That's a good question. I know I made about 550whp on a stock shortblock with a 60-1@22-23psi a few weeks ago. I welded around the ex ports and opened the flanges up as large as I could so they were very close to the largest ex ports I've seen on an iron head. This engine has potted GN1's and there is slight overhang in the port from the header flanges but i really doubt I would see any hp with a different set of headers.

 

[Undercover87T]

So looks like the main reason to upgrade headers isn't for increased performance but for increased durability. I just pulled my 3.8 today and my drivers side header looks to have been welded multiple times around the typical weak point and also the flange was welded to the header. I may just upgrade them for piece of mind. So TA performance would be a good choice? Other option would be GN1's.

 

[Mr.Spool]

i put the stainless headers on and the car had a different tone and throttle response seemed better,but just the fact i have had no issues with them is worth it to me even if the car et the same.i have thrown enough parts on these cars to realize that maybe the headers feel better on the car because of the seal,or maybe they do perform better,but i know it was a good decision cause they are still on there

 

[Grumpy]

So looks like the main reason to upgrade headers isn't for increased performance but for increased durability. I just pulled my 3.8 today and my drivers side header looks to have been welded multiple times around the typical weak point and also the flange was welded to the header. I may just upgrade them for piece of mind. So TA performance would be a good choice? Other option would GN1's.

Call Nick @ Az GN... He has TA stock replacements .. Look really nice !!!

 

[Undercover87T]

I see there are two different versions of TA's headers, one called stock replacements and others are called performance headers. Whats the difference between them?

 

[turbofabricator]

I like the design of the stock replacement TA headers over their race version. On the race versions the cross over comes real close to the cross member, fuel return and vent lines. (I mean REAL close. I have to bend the lines outta the way.)

 

[trbojo]

i have a GREAT reason for replacing stock, welded 3 times headers.... it's called having a piece of slag break off and take out the exhaust wheel on a $900 f#%$%^$king dollar center section!!!!!!!!!

 

[Undercover87T]

Call Nick @ Az GN... He has TA stock replacements .. Look really nice !!!View attachment 155945

Where can I buy those jet hot coated stock replacement TA's? ArizonaGN doesn't list any options for coatings and Gbodyparts only offers the race version coated.

 

[Grumpy]

Where can I buy those jet hot coated stock replacement TA's? ArizonaGN doesn't list any options for coatings and Gbodyparts only offers the race version coated.

Call Nick ...
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