1966 Small Block Casting Number

[Dan S.]

Good Afternoon,

I joined the organization last summer and have been following the posts with interest!! This is my first post so I hope it makes sense.

We are looking at a 1966 Coupe with a 327/350. We have a concern about the block casting number aligning with the other engine/car information. Here's the background.

The engine stamping number matches the VIN for the car (I have read that this can be altered to make it match). Other data regarding the engine are:
1) engine build date of F0112HT (January 12th),
2) block build date of A 2 6 (January 6, 1966),
3) car's build date is E18 (January 18, 1966).

This information seems to indicate an original matching numbers motor. But we are concerned about the block casting number (3892657). We thought this block was used for "late" 1966 production and throughout 1967. Were these blocks used as early as January 1966 ???

Thanks a bunch for any insights!
Dan

[Patrick B.]

Re: 1966 Small Block Casting Number

You are right that Jan 2, 1966 seems too early for the 657 casting number used for 1967 model year 327s. Unless anyone responds with evidence that the changeover occured that early, I would suspect thet the "A" in the casting date has been doctored. Prob it with a magnet to see if it has been built up with epoxy, or remove the paint for a better look. Send some pictures of the stampings if the A seems legit.

[Jeff P.]

Re: 1966 Small Block Casting Number

Dan,
My L79 is an early (mid-September) car. The casting for my block is 3858174.

[Rob M.]

Re: 1966 Small Block Casting Number

Dan,

Welcome and good question. I think that is unusual for sure and worthy of close scrutiny. I just looked at a one owner '66 327/350 built within a few days of the one you describe and it had a 174 block. I agree with Patrick and would suggest probing a little.

Good Luck

[Robert K.]

Re: 1966 Small Block Casting Number

If the cast date has been altered then the deck would have been machined removing the broach marks. A quality picture of the pad stampings could provide a definitive answer.

[Mike M.]

Re: 1966 Small Block Casting Number

bob: modifying the cast date does not require broaching the block.mike

[Dan S.]

Re: 1966 Small Block Casting Number

Thank you to everyone for your comments. Patrick suggested testing with a magnet and then sending some photos. The magnet seemed to be attracted to the A as strongly as the surrounding metal so that was inconclusive.

I am including photos of the engine number and the casting date. The casting date numbers appear to be pretty crisp and unmolested. Do any of you see something suspicious?

Unfortunately we have no documentation that would shed on light on this.

My very naive assessment is that it would be challenging to modify the casting date but who knows.

Any other thoughts????

Many thanks!
Dan


1966 engine number.jpg1966 engine block casting date.jpg

[Jeff P.]

Re: 1966 Small Block Casting Number

Could be that the "3892657" block was decked and someone stamped the assembly date and VIN derivative onto the "fresh" engine pad.

[John H.]

Re: 1966 Small Block Casting Number

The 657 block was used from '64-'67 in passenger cars and trucks in addition to the '67-only Corvette application; it's possible (although unlikely) that one of those 1966 passenger/truck 657 blocks found its way into a '66 Corvette engine instead of a 174 block. It's not "typical", but "possible".

[Patrick B.]

Re: 1966 Small Block Casting Number

Perhaps a 657 was replacement block for pre-67 usage, but I don't think it was being cast simultanously with 174 blocks. I found a 174 block on a list of blocks I used to own and it was cast A-4-6. I don't believe a 657 block was cast on A-2-6 while 174 blocks were still being cast. The Colvin book lists the 657 block for 67 passenger cars as well as Corvettes and the 174 block for 66 passenger cars as well as Corvettes .

[Mark G.]

^ndA 2 6.jpgH 2 6.jpg

[Jeffrey R.]

Re: 1966 Small Block Casting Number

I'm no expert, but the 6 looks more suspect than the A does. They both look a little off to me.
Jeff

[Rich G.]

Re: 1966 Small Block Casting Number

My 66 built Feb 2 has a 174 block cast in Jan. I'll check the exact date later.

Rich

[Dave B.]

Re: 1966 Small Block Casting Number

My 66 L79 built March 4th has a 174 block cast L305...Dec 30, 65. Engine built Jan 7, 1966.

Dave

[Dan S.]

Re: 1966 Small Block Casting Number

A big thank you to all who responded with helpful comments and to the guys who checked out the build date/casting dates on their cars. Most informative.

As I mentioned in the first post, I am new to all this. I found this forum to be most helpful and look forward to having it as part of my regular reading. Two quick observations before signing off.....

First, the more I learn about these cars the more I feel like a British archaeologist dusting off artifacts from some ancient civilization trying to recreate the aura of long ago times.

Second, you gotta love karma. Back in the '60s when I was fortunate to own several C2s, I did every thing I could to make the cars not original. Now I find myself trying to reconcile all those bonehead things I did back in the day. If only I would have............. What a hoot!

Again, thanks to all and a big shout of appreciating to the legion of folks who have compiled all the documentation on these wonderful pieces of machinery and artistry. We are in your debt.

Dan