At least this is what I hear in some circles. I've been using a decent mechanic the last couple of years. He's quite familiar with LT1s, and in his opinion, the way to go is with stock manifolds, a high-flow Y-pipe and a high-flow cat.

He attributes header leaks to the fact that the large mass of metal of the heads means they change temperatures more gradually than the header flanges, which have less mass (irrespective of the fact that one is aluminum and one is steel). With the temp of the header flange changing much more quickly than the temp of the head, the different amounts of thermal expansion are going to mean there's constantly changing pressure on the gasket (due to its being clamped between the head and the header flange). Eventually the gasket gives out. He's seen cases where the gasket has blown out in one spot, even though the locking, aftermarket exhaust manifold fasteners are still nice and tight, just like they should be.

He's also seen even mid-length headers frying heater core boxes and hoses. No amount of insulation would help... he eventually re-routed the heater core hose around the top of the wheel well to avoid problems.

Assuming the installation was done properly (good gaskets, clean mounting surfaces, proper torquing of fasteners, header flanges nice & straight, etc.) is this guy right? I have read a lot of stories about header leaks.

I'd rather not leave 20+ HP on the table, but I would prefer that over the types of problems I've read about (I don't have good frustration tolerance )

Any of you who feel you've found answers to avoiding header leaks, please share your wisdom. (And sorry for the very long post!)

 

My AS&M's have been on the car for 6 years with no leaks. They have never melted anything. Copper gaskets, ARP bolts. Check the bolts once a year. I've seen any number of LT1's without leaks and melted parts.

 

i have hooker LTs with autozone bolts, the only areas that leak are the bolts that are hard to get a good handle on and turn. there one in perticular that i can only get so tight, its the farthest back on the drivers side, there is a metal plate that blocks out any are to swing a wrench and get a good twist on the bolt. otherwise all mine are great, have been for almost a year now.

 

There are plenty of cases where headers have not leaked or caused any problems. I disagree with him on the idea of stock manifolds, high flow cat and y-pipe being the best exhaust setup. I think the main thing to keep in mind when doing a header install is to use good quality gaskets, locking header bolts, and make sure that harnesses, accessories, ect are secured safely away from the headers themselves. And as Fred noted, it is a good idea to periodically check your header bolts. I usually run a wrench over mine when changing the oil to make sure they are all still snug. I had a friend who blew out both of his header gaskets because he neglected to check the bolts and they backed out too much.

 

I think this has to be the key point. If EVERY install leaked, then no one would ever do headers. I suspect my mechanic may not be the guy to have do this... perhaps he just doesn't have the knack.

Thanks, Fred, for the suggestions on headers, gaskets and bolts.

@2000GTP, do you happen to know a shop you might recommend? I'm in Chicago's NW 'burbs...

 

My SLP LTY's ahve been on my car for two years now. Minor collector leaks here and there, but nothing bad. I also used the stock bolts in my header to head flanges. They took about 1k miles to seat themselves in there, butafter that I didn't have ANY upstream header leaks.

I replaced my trans about 3k miles ago. I had to yank the Y down w/ it. I've been dealing w/ minor cat to collector leaks. But again, nothing bad.

I had an experience over the weekend w/ a guy in the hobby shop on base w/ BAD header leak. He had a 99~ish Stang w/ BBK Mids. Apparently, those headers are garbage on Stangs and the flange dosen't sit tight with the head. So it was leaking BAD! Sounded like a farm tracktor. The flange actually sat of at an angle to the head. A couple of Stang gu-ru's there blamed the bad header design.

 

There are about three f-body specialty shops that come to mind in the area:
Street Stuff: Addison, IL
Speed Inc: Schaumburg, IL
Finish Line Performance: Naperville, IL

 

Thanks, guys. Appreciate the info.

 

T/A Bob, if youd like, i might be interested in doing the job for you if you want. i have a heated garage will all tools to do the job. i wouldnt want NEAR as much as the shops do but obviously i dont really have a rep like they do. I would go with Speed INC out of all the shops tho, they have excellent prices and always take care of their customers. just offering tho, if you would be interested in having an individual like myself do the job, i always need cash and i dont mind workin on LT1s.

 

Thanks, 69z, I am still deciding how to proceed (headers are definitely my next mod). Maybe I will PM you so I can learn a bit more about you.

As for Speed, Inc., I heard quite a few horror stories about them, but these were from several years back... I don't know yet if they'd be guys I would want to even consider... ??

 

FLP did some exhaust work on my buddies 97 Z-28 and they were the cheapest by far and did great work for him while he waited

 

Speed INC has some stories however i recently called FLP and Speed for a gear swap in my T/A. Speed wanted 250 for labor and 50 for speedo change, FLP wanted 500 and another 100 for speedo even tho ive already had my car tuned by them once before. thats what kinda got me about FLP, however i know they are in fact a good shop. Speed seems to be hit or miss but they will take care of you. just let me know if your interested, i was able to do my headers, motor mounts, OTVC wires, and complete exhaust in a little less than 2 days, so its really not a big thing. only thing i can tell you for sure, research research research. i spent months figuring out what to do for my car and i havent regretted one bit of it. good luck

 

I've heard some stories about them too, but considering some of the wild setups they have to build and tune,along with the huge volume of cars that are always coming into that shop, I can see some unhappy customers coming out of the mix. They welded in some SFCs and a cutout for me and they did a good job on it and the labor rate was very reasonable. I have heard good things about FLP as well, but they are more expensive I noticed.

 

If my headers are leaking, I am certainly unaware of it. I understand the post is repeating an old mechanic's tale, but with proper engineering, materials and fabrication, there shouldn't actually be any problem with a good seal and seating.

 

Mine have a tiny leak on the passenger side back, I couldn't get them tightened all the way down. When I yank my motor this summer im gonna replace the gaskets and install the headers with the motor out of the car.