Corvette big block exhaust manifolds

[Steve Antonucci]

Hello everyone,

Here are a few questions regarding any known technical differences
between 67-72 big block Corvette exhaust manifolds. I'm currently
restoring a 69 L/71 ( 427/435hp ) and I need to find the correct
exhaust manifolds.

1) With the exception of the casting numbers & dates, were any of

the BB exhaust manifolds different in terms of flow? Stated another

way, did the L/71 or L/88 exhaust manifolds flow better than the

L/36 or L/68 exhaust manifolds? Were the manifolds even different?
2) Did all Corvette big block exhaust manifolds have SMOG ports?
3) In leiu of finding an original set of BB exhaust manifolds, are

any of the reproduction manifolds worth purchasing? Also, are

the reproduction exhaust manifolds correctly designed to be used

in a L/71 restoration project?

I saw a set of ( L/88 ) Corvette BB exhaust manifolds on ebay several
weeks ago and they went for big bucks! Is that because the seller
used the "L/88" catch phrase? In the Camaro world, "Yenko" is the
catch phrase to use.

Finally, what can price range can I expect to pay for a set of used
BB manifolds?

Thanks for all the help. I love this forum !!! As a dedicated 69
SS 396 Camaro owner, I am always amazed at the level of participation
in your Corvette forum. Hope our forum grows to the same level of
participation as this!

Thanks again,
Steve

[Joe L.]

Re: Corvette big block exhaust manifolds

Steve-----

1) There were several different Corvette big block exhaust manifold castings. 1965 were unique to that year and were GM casting #3856301 and 3856302. The 1966-74 right side all used the same casting---GM #3880828. The left side casting for 66-69 was GM #3880827; the 70-74 left side casting was GM #3969869. All 3 of the castings used for 1966 to 1974 were produced in both AIR fittings and non-AIR fitting versions. The casting numbers were the same for both versions but the finished manifold part numbers (which DO NOT appear anywhere on the part except for small, yellow painted numbers on later SERVICE manifolds) were different. All of the above-referenced castings flow just about the same. The 70-74 left side casting is a small amount more restrictive than the 65-69 left side manifolds, but it's a negligible amount of difference.

2) There is no difference betwen big block exhaust manifolds used for different big block engines except for the difference involving the presence or absence of AIR fittings; the castings and finished manifolds are the same for an L-36 as for an L-88 or ZL-1.

3) Big block manifolds of the same casting number were produced with and without AIR provisions. For the 1965-only castings, no AIR-fitted manifolds were ever produced. For 1966-74, the manifolds were of the AIR-fitted type if the engine was equipped with AIR. This included 1966 L-36 with K-19; all 1967 big block with K-19; ALL 1968-69 big block, 1971 LS-6, all 72-74 LS-4 and LS-5. As a matter of fact, all L-88s, except 1967, had AIR and AIR-fitted manifolds;

4) Using the term "L-88" in the item description often increases the price that folks are willing to pay for parts on eBay. There is NO SUCH THING, though, as an "L-88-only exhaust manifold". Big Corvette block manifolds usually do sell for high prices on eBay, though; often exceeding $250/each;

The manifolds which are available in reproduction will FUNCTION perfectly and identically to the originals. Some or all of these are manufactured from nodular iron which is a better material than the gray iron which all of the original, PRODUCTION manifolds were cast from. Some GM SERVICE big block manifolds produced after about 1984 were cast from nodular iron, though. The reproduction manifolds may have different casting marks and nuances than originals, though.

By the way, the Corvette big block exhaust manifolds were unique to all Corvette big blocks as well as 65-66 Chevrolet full size passenger cars with L-78 or L-72 engine.

[Mike M.]

Re: Corvette big block exhaust manifolds

joe: FYI there is a difference between 66 and 67 BB manifolds in that there is a teat-like protrusion on each side of the 66 manifolds tyhat the 67 and up lack. these teat-like casting protrusions were also present on the 65 396 manifolds.regards, mike

[John P.]

But how much should you pay for these?

What kind of cost are you looking at for these babies?

I need to pick up a set for my 69 as well but I dont think im going the ebay way to many bidding wars for good items.