C-3, '70 454 exhaust maifolds

[D S.]

Has anyone discovered one exhaust A.I.R. manifold and one non A.I.R. exhaust manifold on a 1970 LS-5 Corvette? Mine does and I wondered why. And recently I was assisting a friend working on his numbers matching '68 327 and I saw the same thing. Did assemblers just routinely grab what was available and put them on the cars? Or?

Thanks,
Scott #43568

[D S.]

Re: C-3, '70 454 exhaust maifolds

Manifolds

[John H.]

Re: C-3, '70 454 exhaust maifolds

Someone has messed with it since it was built - they had matching manifolds on both sides when they left the engine plant; the condition you describe would have left lots of parts hanging loose on the engine dress line at St. Louis.

[D S.]

Re: C-3, '70 454 exhaust maifolds

Thanks, John. All of the brackets are intact, i.e., alternator, A/C are all there although this block was not the original one, a later 454. Apparently someone took the parts off the original block and placed them on the one we pulled out. My mechanic and I couldn't understand why one side had AIR plugged holes and the other didn't but the date codes are matched early '70 just as my car is built early '70. I now have a correct block for it (B70, car was built C70) and I wanted the manifolds to be consistent with the block date. Sadly the left one, non AIR, was busted but pieced together when placed on the block we pulled out. Sneaky. I have been fortunate to find a replacement pair of correct non AIR manifolds but the dates are F70. Given my car was built in C70 fat chance of finding early dated 454 manifolds.

Scott

[Mark #28455]

I have a March 1970 454 car too

The date code correct manifolds that came with my car were drilled for the AIR tubes, but the holes were plugged (I still have them).
Mark

[Joe L.]

Re: C-3, '70 454 exhaust maifolds

Scott-----

I've heard of this sort of thing before on early 1970 LS-5-----either one or both exhaust manifolds had AIR fittings with plugs. It seems VERY "un-factory-like" to me, especially with non-matching manifolds. However, it's THEORETICALLY possible, especially if the manifold with the plugs is the RIGHT SIDE manifold. Here's why:

For 1968 and 1969 ALL Corvette big blocks used AIR and, consequently, all manifolds had AIR fittings. For 1970, no PRODUCTION Corvette big blocks used AIR. The left side manifold changed for 1970, so, unless there were some manifolds manufactured with fittings for the stillborn LS-7 (which would have had AIR), then there would not even have been any left side manifolds with AIR fittings at the engine plant. Even if there had been some manufactured, I would have expected that those would have been sent to GMSPO for SERVICE rather than used in PRODUCTION. Certainly, there would never have been many manufactured since I doubt that they ever planned a big PRODUCTION run of LS-7 installations.

The right side manifold remained the same casting for 1970 as used for 66-69, except that the 70 manifolds were not equipped with AIR fittings (they were, consequently, the same as 66-67 Corvette big blocks without K-19). So, theoretically, the engine plant could have plugged the manifolds with AIR fittings and installed them on 1970 engines. Once again, though, I don't understand why they would not have just shipped the AIR right side manifolds to GMSPO for SERVICE requirements. I suppose that if there were a temporary shortage of the non-AIR right side manifolds they might have used them in PRODUCTION.

By the way, the above theorization is ABSOLUTELY NOT analogous to your friend's "numbers matching" 1968 small block. In fact, if it has a plugged and non-plugged exhaust manifold, then that means that it must not have AIR installed. ALL 1968 Corvette small blocks (and, big blocks, for that matter) were equipped with AIR. For 1968 it is ABSOLUTELY NOT POSSIBLE to have an original car with a non-AIR manifold.

[Terry M.]

Re: C-3, '70 454 exhaust maifolds

I have seen a number of 1970 454s with exhaust manifolds drilled for AIR with factory plugs installed. This is a fairly narrow range of serial numbers, and the 1970-1972 TIM&JG spells out the serial number range and, IIRC the style of plugs. One of the keys to determining the authenticity of this anomaly in addition to the date on the manifolds, is the style of plugs used. They are not available from your local ACE hardware store.
My guess, and it is just that, is that there were a number of exhaust manifolds set up to supply the LS7, as Joe suggested in one scenario, and instead of trashing them Tonawanda made them function for the lower horsepower engine.

[D S.]

Re: C-3, '70 454 exhaust maifolds--Thanks, all!

I certainly appreciate the specific, detailed information all of you provided. This will probably not be my last "head scratcher" post.

Thanks,
Scott

[lyndon sharpton]

Re: C-3, '70 454 exhaust maifolds

what did the plugs look like that the plant used?