eileenthevette

Today, I was moving my recently rebuilt 427 around & though since it had valve covers off, I would ID the heads. Car is very late '69 VIN#329XX of 38,762 (Oct-Nov '69).

Block cast #3963512 ('69-427, '70/71-454) casting date "I 8 9" (Sep 8, '69) Assembly stamp "T 10 05 LM" (Oct 5, 427/390,QJ,4spd) VIN derivative matches. All is right with the world. Now the mystery.

Heads cast #3964290. According to Black Book these are for a '70-454. But casting date is "I 5 9" (Sep 5, '69) 3 days OLDER than my block casting date.

Is it possible that due to the overrun in the '69 year that GM used up all the heads #3931063 (correct '69 427/390 heads) and just started using the #3964290? I've heard of stranger things happening during assembly, "undocumented" L-88/89's, etc.

Is there a huge difference in these heads?

I've never been accused of being the brightest bulb in the guage cluster, but my thought would be that since a 454 is basically a stroked 427, the chambers might be taller to allow for lower compression that everyone was moving toward in early '70's. Right? Wrong?

All opinions would be appreciated. Thanks.

Dave

PS-I did a search of #3964290 and only found 1 thread back in June by 68NJConv454.

694speed350

according to a restoration book i have those castings were used on the 70 model year run of the 454 also.

eileenthevette

Right. My question is why would 454 heads be on a "correct for the car" 427 engine?

Everything else matches. Tranny, diff, carb, distributor, even the alternator matches although it is listed under "uncertain usage".

I think that since GM was dis-continuing the 3931063's, and the '69 year went long, that they started putting 3964290's on 427's. Not accusing anybody of anything here...don't care. Just want to solve the mystery.

Either that or they were replaced later. But why would someone go to the trouble to replace correct 427 heads with date matched 454 heads? What's the advantage?

Can anyone with a '69 BB (L36 or L68) later than VIN 32,967 verify that they have 3931063 or 3964290 heads?...PLEASE! Thanks!

FrankVincent

According to Corvette by the Numbers, 1955-1982 ...

3931063 - 1969 427 - 390,400hp - 2.06/1.72 - 100.967cc

3964290 - 1969 427 - 390,400hp - 2.06/1.72 - 100.967cc
1970 427 - 390

(1970, the "427" may be a missprint and should read 454 .. ??)

According to GM blueprint, 290 heads are identical to 063 heads except for a tapered spark plug seat. Blueprint revision release dated 4/21/69.

eileenthevette

Awesome! Thanks for the info Frank! I do not have Corvette by the numbers. Will have to pick that up.

Yes. 427 in 1970 is probably a misprint. My black book shows it as 454/390hp. There should be no '69 454's, and no '70 427's. But my black book is 2000 edition, could be old.

So functionally they are the same heads, and one could have replaced the other mid production. AHA!

Would still be curious on a 69 BB later than mine though...

Anyway, thanks again for the info. Beer and a giant popcorn for you!

Dave

JohnZ

I don't have the '69 JG, but the NCRS Pocket Spec Guide says the 4290 heads were '70 only; if deviations have been documented, it will say so in the JG.

eileenthevette

Thanks for the post John. I will have to get a copy of the JG as well as "Corvette by the Numbers" that Frank said had the 290's for both '69 & '70. I would like to see that in print.

I'm not doubting that it is not documented. I have heard that a lot of undocumented things rolled out the doors back then. To me, the simplest explanation is usually correct, and my theory seems simple enough.

I was a little disappointed that my thread got moved over here because I was hoping some '69 L36/L68 owners (after my VIN) could verify their head numbers for me. I don't think I'm going to get too much C3 traffic over here. Oh well, mystery continues. Thanks.

BTW, I peeked at your Vette photos. AWESOME! Is that the one I see in all the "Restorer" & "Driveline" ads?

JohnZ

I really need to edit that section - way too many images, don't know how all the dupes got there; I built that Grand Sport in 1995, and sold it in 1998.

Ironcross

If you're not the original owner, there may have been the necessity for a valve job in the Vettes earlier history and the heads were merely exchanged for some already built. I know we always use to have several sets of reconditioned heads available for immediate exchange. 35 years ago numbers didn`t mean very much.

eileenthevette

Yeah, I thought about that too. But if the block was cast on Sep 8th 1969, assembly stamped on Oct 5th 1969, and car was built around Oct 15th 1969, then count shipping, prep, pickup, etc., the owner probably didn't get his hands on the wheel until early November.

The 1970 run started mid December-July 1970? Say my car did need a valve job within this 9 month period. Shouldn't a set of heads cast dated Sep 5th 1969 already have been out the door on a 1970 454/390? They didn't use them in 1971.

In other words, what are the odds that...
1) A brand new 427 needs a valve job in less than 9 months?
2) These heads (some of the 1st made for the 1970 454 run) were shipped as parts to coincidentally the general location as my car was being driven?...and
3) The set of heads someone grabbed off the shelf were dated within three days of the matching block for the car?

And if numbers matching didn't mean anything back then, why would someone go to the trouble to track down heads dated within 3 days of the block?

I know this is not documented anywhere, but as in science...The presence of documentation definitely proves something did happen. But the absence of documentation does not prove that it did not happen.

I go back to my original point, the simplest explanation is probably the correct explanation.

Thanks for the input Ironcross.

knight37128

All the original motors I dug into; the heads are older than the block.

just my .02


P.S. If your car was built Oct 5th; someone was driving it by Oct 14th.

grantstigers

Heads cast #3964290. According to Black Book these are for a '70-454. But casting date is "I 5 9" (Sep 5, '69) 3 days OLDER than my block casting date.

The heads on your car are 100% correct. Books are not always correct but are based on what part numbers were given from GM. I had a 69 L71 late car built in Oct. When I took the engine apart I assumed it had 840 heads. But to my amazment it had 291 heads. So that is 1970 head but even better yet NCRS book says it was the 460 hp LS7 heads. The heads were dated Sept 69. I was going to buy 69 Sept 840 heads to make it correct book wise but after investigating and talking to one other original owner of a very late 69 L71 and it also had the 291 heads. So I left them and no wonder I had no problems screaming down the road at 7500 rpm.
So in a nut shell. You have the correct heads that came with your car. Grant

Easy Mike

1969 production ended on 12/19/69. The line shut down after that and remained closed through the first of the new year. 1970 production began in January, 1970 but none of the cars were available to the public until near the end of February. The new model introduction was not until February, 1970.

eileenthevette

Guys, Thanks to all for the input.

Ironcross - Sorry, I didn't mean to just shoot holes in your theory. I am an ex-engineer and deal a lot in probablilities of events, etc. I also do a lot of research and know that things just like you mentioned DID happen, as well as many other strange things at the GM plant. Plus it was past my bedtime and I was probably a little cranky. I appreciate your input.

Easy Mike - Spot on once again...you da man!

grantstigers:Thank you for verifying this. I was really hoping another '69L BB owner would chime in here. Yaaaaaay!

RPOL68

Just went through some of this with my Oct 03 1968 build date L68. I had correct heads when I bought the car in 1982. I went through the engine in 1985 and have had a pinging problem every since. This Summer I broke a valve spring and during the repair I noticed that the casting dates on the heads were '71. The machine shop must have given me the wrong heads back in '85 and I didn't notice. These heads were open chamber and tapered seat spark plugs.

GM went to the 1/2" tapered spark plugs in 1970. I was using 3/4" gasketed plugs, correct for the 1969 063 closed chamber heads. See the problem here? The threads of the plug I was using stuck 1/4" into the chamber and I'm sure they overheated quickly because of it. Ping ping.

I was able to locate some 063 heads and the performance improvement is very noticeable and no pinging. I did a lot of web research on this, I just have to locate all those printouts.

Per Mortec:

3931063....68-69...oval..CLOSED..396, 402, 427, 101cc chamber

3964290....69-70...oval..CLOSED..396, 402, 427, 454, 101cc chamber
Large or small hex spark plugs used

3964291....69-72...rect..CLOSED..396, 402, 427, 454, 109cc chamber, Large or small hex spark plugs used, crate motor usage in years after 1970.

eileenthevette

Interesting. So were the heads you replaced 4291's ?

RPOL68

The ones I pulled off were 292s

427SIXPACK

this is an interesting question:
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