Late, LATE '69 427 Heads

[Jamie F.]

I've looked through the archives and haven't found a definitive answer to the late '69 427 heads question.
Reason being I have a late 11/22/69 427 L68 car in which someone "improved" it with --840 435hp heads. I have been looking for a set of correct 3931063 oval port heads with a casting date close to my block of J-22-69 (10-22-69). AND they don't seem to exist cast that late...
Seems like all the heads cast after July of 69 are 3964290 castings which is the exact head with taper seat plug threads.
Now my question... I've seen many instances of late '69 cars with this head discussed on this board. Many have stated that these heads were probably used on late '69 cars as Tonawanda ran out of 063's. Many have also speculated that they would be machined with the old flat seat plug threads if for a Corvette. Has this been documented? Has anyone seen 3964290 heads with flat seats? I would really like to find a set of correct heads for my car but 3931063 cast this late are non-existent, and 3964290 with old style plugs are just as elusive! Any comments or suggestions???
Anyone out there with a car of the same date range that could tell me what their car has would be fantastic!!!
Thanks in advance!

[Jamie F.]

Re: Late, LATE '69 427 Heads

Here is an interesting and related thread I found on the subject>>>
http://forums.corvetteforum.com/show....php?t=1491975

[Craig D.]

Re: Late, LATE '69 427 Heads

Jamie,
My august '69 built L36 coupe has the 3964290 heads with the flat plug seats. Both heads have casting dates of G-9-9. Hope this sheds some light. Craig

[Jamie F.]

Re: Late, LATE '69 427 Heads

Craig,
Great info! Thanks for your input!
What is the trim tag date for your car?
Regards,

[Dick W.]

Re: Late, LATE '69 427 Heads

Jamie, this is one of the items that we have down to research for the revision of the judging guide.

[Jamie F.]

Re: Late, LATE '69 427 Heads

Thanks Dick for your post. I have done A LOT of research on this already. A few members where also kind enough to email me with date info on their cars.
Seems to me that the ---290 heads went into use around late August. There is even one member with a August car that has one ---290 head and one ---063 head on his car! both machined with flat plug holes. So it looks like Tonowanda ran out of 063's and started using the --290 right around the normal year break for the other chevy cars.
I'm surprised that they did the different spark plug machining and didn't put some type of designation on the part number. That is kind of unusual for GM; Two basically different parts with the same part number...
Would have been easier now days to list a different spark plug number with a VIN or date start number. But they really didn't do things like that back then, it was all about the model year.

[Terry M.]

Re: Late, LATE '69 427 Heads

Allow me to suggest, Jamie, that they didn't run out of 063 heads -- they got the OLD castings out of the system so they could use the 290 heads for the new model year.

We see a lot of instances of getting the old parts out of the system so that new parts can smoothly enter production. One example that comes to mind is the 427-cylinder case being cleared out before the 1970 model year so that the 454 cranks could enter production without the risk of interference with the cylinder case without clearance for the longer stroke crank.

So some folks with a 427 had cases clearanced for the longer stroke -- just an easy way to cheat if someone wanted.

I'm sure there are other instances of the same sort of "clear out the old parts to make way for the new parts" that could be cited. This kind of scheduling was no accident, but rather required no small bit of coordination.

[Jamie F.]

Re: Late, LATE '69 427 Heads

Terry,
Good point. I would agree.
What do you think about the issue of the new --290 heads being machined for the old plugs, just for Corvettes? This is what I have been told, but have yet to actually see one this way.
To me that goes against everything GM, but it could have happened???
Makes it tought for those of us trying to find a pair!

[Craig D.]

Re: Late, LATE '69 427 Heads

Craig,
Great info! Thanks for your input!
What is the trim tag date for your car?
Regards,

Jamie,
The build date on my trim tag is August 18th...............

[Don W.]

Re: Late, LATE '69 427 Heads

All...here's my info from my November 69 build with later heads....Don

Right side head GM8T; J 25 9 (= Oct 25, 1969); 3964290; PASS

Left side head 3964290; GM10T; J 23 9 (= Oct 23, 1969); PASS

GM Canada Import Documentation
Production Plant = St. Louis, MO
Shipping Date = Nov 17, 1969
Engine = 427 CID 390 HP 4bbl Turbo Jet V8
Dealer: Stedelbauer Chev Olds Ltd. Edmonton, AB Canada

T11106LL = Engine Code = Tonawanda Plant November 06, 69;
LL = 427/390HP w/ THD 400 Tranny

[William C.]

Re: Late, LATE '69 427 Heads

With all due respect Jamie, you are confusing Casting number which is a part number for A bare casting with a part number for the machined head. The base casting could be substituted with engineering authorization into the machining process and the end result after machining would retain the original part number for the machined head. and on through final assembly. Normal business procedure in GM.

[Erik S.]

Re: Late, LATE '69 427 Heads

A friend of mine has a fairly original L36, mid July car. Below pictures of the headers of his car - he has the 290 heads with a casting F 26 9 (June 26 1969 I guess)

Erik

[Ned T.]

Re: Late, LATE '69 427 Heads

I have a July 7 1969 Build Date. No 723929. My heads are 290 with casting date of F 24 9. I asked this question a few months ago since the "Black Book" shows them on a 70 454.