1967 heads

[Keith N.]

Dear Fellow Members:

I am a novice owner of a 1967 Corvette small block. I've had the car about 5 years. About 4 years ago I had the motor rebuilt. I was recently warned that the rebuilder 'may' have decked the block. After comparing my block number to the block number on the prior owner's 1988 Top Flight judging sheets, I found them to be identical. I also compared the font of the numbers on the block to other '67 small block casting numbers and the characters appear to match in size, style and depth, so I am optimistic that the original number is still there, albiet it faint as the pad is also painted the same as the block and the paint has filled in the characters a little bit.

More recently, I had a mechanic who just replaced the gas tank and rebuilt the carb. The car had been running rough and stalling. It ran much better, but still not 100%, so he pulled the plugs. At least 4 were fouled, which is fine, except that according to him, they are supposed to be 5/8" and they are 3/4". He is calling them "mini-plugs" and is telling me that they are newer plugs, for newer cars, and that the heads on my motor are incorrect. Could he be right? Why would an engine rebuilder throw away my original heads, and if he did, are they also numbered? Can you help me here, because I'm ready to have a freakin heart attack...again! First the fire drill about the decked block, and now the latest panic...my car has the wrong heads!?!

Any insight will be greatly appreciated. I bought this car because it was a 97 point NCRS Top Flight car. I didn't need to trust the seller. If the NCRS Top Flights the car, that's good enough for me. I didn't think it would all be undone by an engine rebuilder who claimed to have the right credentials to do the job. We discussed the fact that the car was going to be NCRS-judged again in the future and that it was important to do it right...what a drag.

Thanks and Best Regards,

Keith

[Scott Marzahl]

Re: 1967 heads

Keith this is relatively easy to figure out. What are the casting marks on the ends of the heads where they meet the block. Are they the correct two camel humps. Also, you should remove a valve cover, just 4 bolts, this is very easy to do and read what the casting numbers are to verify.

[Joe L.]

Re: 1967 heads

Keith-----

The spark plugs used for 1955-1970 small blocks were a gasketed seat plug with a 13/16" across-the-flats wrenching surface. Beginning in 1971 small blocks changed to tapered seat spark plugs with 5/8" across-the-flats wrenching surface. No Corvettes ever used spark plugs with 3/4" across-the-flats wrenching surface.

If your plugs are 13/16" across-the-flats wrench size, the heads may be original. If they use plugs with 5/8" wrench size, then they are definitely not original.

The best thing to do is as Scott suggested-----remove the valve covers and check the head casting numbers.

[Paul L.]

Re: 1967 heads

You'll be looking for #3890462. In my case (pic) with a casting date of January 24, 1967. The Judging Manual does mention that "very late" cars had #3917291.

[Joe R.]

Re: 1967 heads

Hi Keith:

If the gas tank that you had replaced was original to the car, did you check to see if it still had the tank sticker attached? That is a valuable piece of documentation for your car.

Regarding the 67 heads, the "double hump" casting mark on original heads looks like the one in the photo below (except for the "R" that a rebuilder stamped on it). If your heads do not have this casting mark on each end, they are NOT original to the car.

On the other hand, if they do have this casting mark they may not be original, since some later production heads (such as the "slant plug" heads that used the smaller spark plugs) had the same casting mark. In that case, the best way to confirm that they are original castings is to pull the valve cover and check the casting number.

[Jack H.]

Also note...

the rebuilder's 'R' emboss could have easily been filled and smoothed out with JB Weld to eliminate it as an obvious difference from factory originality. More important, you can just make out the circular swirl marks in the casting marks which are indicative of the secondary machining methods used by Flint engine on Saginaw produced cylinder heads of the era.

The 'same' number '462 head castings were also made at the Tonawanda complex (incorrect for an original Corvette engine) and the casting marks were left 'natural' being thick and 'fudgey' without the circular mill marks. So, that's another aspect of factory originality the judges look for....

[Joe M.]

Flint vs Tonowanda

Wonder if the retrofit of uncut Tonowanda heads are the reason the you see so many cracked motor mounts on C-1s. I have seen interference bewtween the head and the motor mount and could never figure why that was. Took a grinder to a few heads to make them clear the motor mount.

[Jack H.]

?????

You lost me. This thread is about '462 heads and a 1967 Corvette. The motor mounts attached to the side of the block. How do you envision a little 'flash' on the front/rear ends of the cylinder head affecting the motor mounts?

[Joe M.]

Re: ????? related to C1 motor mounts

You raised the fact that the end of the Flint head is typically machined and the Tonowanda head is not. This struck a cord due to what I have seen on some non stock headed solid axle vettes. That is a cracked motor mount plate where it might have interfered with the end of the head casting. Seems a reasoanble question as this thread was already run out.

Anyone else ever notice this interference on a solid axle vette or perhaps have seen a cracked motor mount plate and wonder why it cracked?

[Joe R.]

Re: Also note...

Hi Jack:

The photo was of the head prior to a recent rebuild. When I repainted the head prior to installation, I filled the character with a little Bondo. In hindsight, your suggestion to use JB Weld sounds like it might have been a better approach.

[Jack H.]

Re: Also note...

Either gets the job done so long as you limit the 'fill' material to the emboss and don't oblitherate the factory original circular mill marks. Sometimes that's not so easy as I've seen heads that went through a particular machine shop where they were 'wacked' with almost the encyclopedia in terms of customer job ID info!

[Joe R.]

Re: Also note...

Hi Jack:

The opposite end of each of my heads has the name of the rebuilding company stamped in it. On the other end I only had to deal with the markings "L" and "R," which presumably indicated which side of the block they came from.