Headers

[John A.]

How can I identify a factory set of headers. I have a set that came on my 68 tri-435 in 1978. Been hanging in garage since. GM stamped on flange on both ends, but no part # Is that the way they came ? I heard there where very few of them. Any info thanks

[Joe L.]

How can I identify a factory set of headers. I have a set that came on my 68 tri-435 in 1978. Been hanging in garage since. GM stamped on flange on both ends, but no part # Is that the way they came ? I heard there where very few of them. Any info thanks

John------


Headers were never installed on any PRODUCTION Corvette as delivered from the factory.

In addition, I do not recommend the installation of headers on any Corvette that is going to be street driven. Personally, I would NEVER install headers on any Corvette I owned.

[Duke W.]

Big block headers and sidepipes were manufactured By an outfit outfit called Kustom Headers for Chevrolet and were listed with part numbers in the Chevrolet Power Manuals from the seventies. These were strictly for racing. As Joe said, headers were never installed on ANY Corvette engine at the assembly plant, including L-88 and ZL-1.

I also agree with Joe regarding headers on road cars. Avoid, period!

If you post photos of the headers along with closeups of any identifying numbers or symbols, we can help you determine if these are the above headers.

Duke

[John A.]

I know they came on no cars, heard sold through parts dept.

[Duke W.]

The racing headers manufactured by Kustom Headers for Chevrolet that were cataloged in the Chevrolet Power Manuals from the seventies were set up for side exhaust, and the side pipes were included. Your headers have pretty short primary tubes and are set up for an under the car exhaust system.

So I don't think they were sold by GM. The "GM" die stamp may not mean General Motors, but I don't know what it might stand for or who the manufacturer of these headers might be.

Duke

[Owen L.]

In addition, I do not recommend the installation of headers on any Corvette that is going to be street driven. Personally, I would NEVER install headers on any Corvette I owned.

I also agree with Joe regarding headers on road cars. Avoid, period!
Duke

Just curious here... would you guys explain your reasons?

[Joe L.]

Just curious here... would you guys explain your reasons?

Owen-----


Headers cause extra heat affecting all engine compartment components. In addition, headers result in more heat in the passenger compartment.

They also result in more noise and a greater propensity for exhaust leaks.

All of the above is not a problem for race cars but is a problem for street cars.

[Owen L.]

Thank you Joe -- I've never had them or wanted them, but it's one of the first things folks recommend to better performance.

Here is the page of special exhaust components from my 3rd edition (1978) Chev. Power book. I was wondering if the 9 on John's was referencing the first xxx709, but not if it's on both headers:

IMG_1547.jpg

[Duke W.]

Adding to what Joe said, headers don't allow installation of the OE heat shields or RFI shielding so burned spark plug wires and radio interference can be an issue. Also, headers require gaskets since the header flanges are not always dead flat, and the bolts require frequent checking because they have a tendency to loosen up.

Headers need significant valve overlap in order for rarefaction waves to arrive at the exhaust valve seat late in the exhaust stroke in the mid to upper rev range, which can improve VE, but any exhaust back pressure negates this effect to varying degrees. So in addition to significant valve overlap they need zero back pressure to be most effective.

I always shake my head in amazement when guys install headers on low overlap cam engines like hydraulic lifter 283s, 250/300 HP 327s, and base 350s that have very little valve overlap. So all they do is just create all the issues that Joe and I have mentioned.

They're relatively inexpensive and easy to install compared to something like head massaging that will provide a real performance improvement in the upper rev range regardless of valve overlap and have been hyped by advertising and hot rod magazines for decades, which is why guys think they are the first "bolt-on" performance improvement to install.

Duke

[Rob V.]

Joe and Duke--

Interesting facts and points to consider regarding the use of headers on street driven cars! Thank you very much for the information!!

Best Regards,
Rob

[Joe L.]

Thank you Joe -- I've never had them or wanted them, but it's one of the first things folks recommend to better performance.

Here is the page of special exhaust components from my 3rd edition (1978) Chev. Power book. I was wondering if the 9 on John's was referencing the first xxx709, but not if it's on both headers:

IMG_1547.jpg

Owen-----


The GM #3960709 and 3960710 were actually available until July, 1983 when they were discontinued without supercession.

[Richard M.]

A few links with photos after a Google part# search...

https://www.corvetteforum.com/forums/c3-parts-for-sale-wanted/4460736-coated-gm-kustom-l-88-headers-and-tubes.html

https://www.corvetteforum.com/forums/c1-and-c2-corvettes/4084370-how-to-tell.html

This one has catalog pictures in post#2

https://www.corvetteforum.com/forums/c3-parts-for-sale-wanted/4819490-sold-kustom-headers-big-block-headers-and-sidepipes.html