help deciphering date codes on heads
Thread Starter
Cruising
Joined: Jan 2010
Posts: 10
Likes: 0
help deciphering date codes on heads
I have a 1969 350/350. Head number codes are 3927186 on both left and right.
I was told that the 'other' coding on the heads is
- R128 (for the right side)
- J78 (for the left side)
I can't figure out how to read these numbers. I believe that they are date codes for date of manufacture.
Any ideas on what these are and what they mean?
I was told that the 'other' coding on the heads is
- R128 (for the right side)
- J78 (for the left side)
I can't figure out how to read these numbers. I believe that they are date codes for date of manufacture.
Any ideas on what these are and what they mean?
Safety Car
Joined: Sep 2007
Posts: 4,452
Likes: 327
From: Indy Indiana
my book shows that the 3927186 head is a 300 HP corvette head and also a 370 HP corvette head, although there were no 370HP corvettes in 1969.
if your valves are 1.94/1.50 then it is a 300HP head, if 2.02/1.60 then 370 HP.. so depends on your valve size what application. I am sure someone will chime in on further clarification..
you may have a 350-300 base engine, are there other clues to confirm a 350-350?
the date J78 means Oct 7th 1968,
there is no 'R' designation, i expect it really says 'K 12 8' for the other head which means nov 12 1968.. look again to clarify.
if your valves are 1.94/1.50 then it is a 300HP head, if 2.02/1.60 then 370 HP.. so depends on your valve size what application. I am sure someone will chime in on further clarification..
you may have a 350-300 base engine, are there other clues to confirm a 350-350?
the date J78 means Oct 7th 1968,
there is no 'R' designation, i expect it really says 'K 12 8' for the other head which means nov 12 1968.. look again to clarify.
Thread Starter
Cruising
Joined: Jan 2010
Posts: 10
Likes: 0
Thanks for the reply.
Here's the information I had for 68 and 69 showing the nums matching mine for a 1969. The thing i can't figure out is how I get a 1968 date stamp with a 1969 head (note that the numbers for my heads don't show up on the 1968 list).
1968 Corvette Casting Numbers
Application Block Cylinder Head
327 - 300 HP (early) Base 3914660 3917291
327 - 300 HP (late) Base 3914678 3917292
327 - 350 HP L79 3914678 3917292
1969 Corvette Casting Numbers
Application Block Cylinder Head
350 - 300 HP (early) Base 3932386 3927186
350 - 350 HP (early) L46 3932386 3927186
350 - 300 HP (mid) Base 3956618 3927186
350 - 350 HP (mid) L46 3956618 3927186
350 - 300 HP (late) Base 3970010 3947041
350 - 350 HP (late) L46 3970010 3927187
Here's the information I had for 68 and 69 showing the nums matching mine for a 1969. The thing i can't figure out is how I get a 1968 date stamp with a 1969 head (note that the numbers for my heads don't show up on the 1968 list).
1968 Corvette Casting Numbers
Application Block Cylinder Head
327 - 300 HP (early) Base 3914660 3917291
327 - 300 HP (late) Base 3914678 3917292
327 - 350 HP L79 3914678 3917292
1969 Corvette Casting Numbers
Application Block Cylinder Head
350 - 300 HP (early) Base 3932386 3927186
350 - 350 HP (early) L46 3932386 3927186
350 - 300 HP (mid) Base 3956618 3927186
350 - 350 HP (mid) L46 3956618 3927186
350 - 300 HP (late) Base 3970010 3947041
350 - 350 HP (late) L46 3970010 3927187
Team Owner
Joined: Sep 2006
Posts: 31,160
Likes: 4,241
From: Westminster Maryland
Hi CRW,
It's easy... the heads being produced in the fall of 1968 were going on the 1969 model year cars that were already in production. The date in this case doesn't refer to the model year but rather when the heads were cast.
My mid-January 1971 car has many, many, 1970 dated parts. The car has an intake manifold with an August 1970 casting date but the 1971 base engine intake casting number.
Regards,
Alan
It's easy... the heads being produced in the fall of 1968 were going on the 1969 model year cars that were already in production. The date in this case doesn't refer to the model year but rather when the heads were cast.
My mid-January 1971 car has many, many, 1970 dated parts. The car has an intake manifold with an August 1970 casting date but the 1971 base engine intake casting number.
Regards,
Alan
Last edited by Alan 71; Sep 13, 2010 at 07:11 PM.
Team Owner
Joined: Jun 2000
Posts: 38,923
Likes: 1,481
From: Southbound
Cruise-In II Veteran
CRW: you engine was assembled at Flint, Michigan, then shipped to St. Louis and was on hand in the plant before your Corvette was assembled. Any casting date you find on your engine, and the engine assembly date stamped on the pad on the block, should be earlier than the time/build code on your trim tag.
