Need help determining casting year.

[Roger G.]

[Joe L.]

Re: Need help determining casting year.

I’m trying to figure out what year a block with casting number 3963512 was cast. I see what looks like a date code on the side of the block, near the freeze plugs. B 4 ?, can’t tell if it’s 9 or 0. The engine build code is T0225jc, not sure whether it’s JC, JQ, or JO. The block was decked, partial vin mostly erased. The suffix code may have been partially shaved.

I think this block was cast on Feb 4, engine built on Feb 25. The build code date and date code on the side of the block make sense.

The JC suffix seems to suggest a 396 though I’ve never heard of a 396 using this block.

Does the date code located on the side provide a clue? I heard the location of the casting date was moved to the rear, near the bell housing some time after this block started production. Was the 3963512 block available in Feb of 1969?

Roger------


The 3963512 block was being cast in February, 1969 and, at that time, would have had the casting date located on the side of the block as you have described.

The 3963512 block was never used for 396 cid big blocks.

[Mark F.]

Re: Need help determining casting year.

...The JC suffix seems to suggest a 396 though I’ve never heard of a 396 using this block...

Roger,

Hmmmm...FYI I know the JC engine suffix was used on 1967 427 400hp manual transmission cars...although I'm not not sure if it was used as an engine suffix before '67 or after(?). Also, the JC suffix in '67 was not associated with the block casting number you have listed.

PS - a good quality, close-up photo might help others more knowledgeable than me decipher more info for you...

[Kenneth B.]

Re: Need help determining casting year.

Pictures on the CF website

[Roger G.]

Re: Need help determining casting year.

Yes, pictures on the CF website. I didn't see a way to insert images when I posted this request.
It looks like the block was decked, may have damaged the build date/suffix, erased most of the partial VIN.
From info I have received it looks like it's a Feb 4, 1969 casting.
I don't know what to make of the suffix, suggests a 396 but the casting number and bore size suggest a 427 or 454.

[Joe L.]

Re: Need help determining casting year.

Roger,

Hmmmm...FYI I know the JC engine suffix was used on 1967 427 400hp manual transmission cars...although I'm not not sure if it was used as an engine suffix before '67 or after(?). Also, the JC suffix in '67 was not associated with the block casting number you have listed.

PS - a good quality, close-up photo might help others more knowledgeable than me decipher more info for you...

Mark-------

The suffix code "JC" had 3 Chevrolet V-8 engine usages as follows:

1965 409 cid 340 HP with K-66 and 4 speed trans in full size passenger cars

1967 427 cid 400 HP (3X2) and 4 speed trans in Corvette

1969 396 cid 350 HP and 4 speed trans in Chevelle and El Camino

[Mark F.]

Re: Need help determining casting year.

Mark------- The suffix code "JC" had 3 Chevrolet V-8 engine usages as follows:
1965 409 cid 340 HP with K-66 and 4 speed trans in full size passenger cars
1967 427 cid 400 HP (3X2) and 4 speed trans in Corvette
1969 396 cid 350 HP and 4 speed trans in Chevelle and El Camino

Thanks, Joe - I did not know about the 409 and 396 suffixes...good to know
Even if it was a decked, ground-out "JG" code (400HP w/ A.I.R. and Powerglide in 1967), the block casting number doesn't line up w/ a '67 and you also indicated that block casting number was never used for a 396...so the mystery continues

[Roy S.]

Re: Need help determining casting year.

Mark, I think by 1970 the 512 block had the date code on the bell housing flange of the block. If it is on the side I believe it has to be a 69 block.

[Terry M.]

Re: Need help determining casting year.

Mark, I think by 1970 the 512 block had the date code on the bell housing flange of the block. If it is on the side I believe it has to be a 69 block.

That has been my experience as well.

[Mark F.]

Re: Need help determining casting year.

Mark, I think by 1970 the 512 block had the date code on the bell housing flange of the block. If it is on the side I believe it has to be a 69 block.

Thanks, Roy (and Joe and Terry) - Happy Thanksgiving to all...!

Where I get tripped up in this whole thing is Alan Colvin's "Corvette by the Numbers" (1st ed. April 2002) page 106 lists Corvette Block casting #3963512 as being introduced "1969 mid-year".

Without violating his copyright (although this forum would fall under the "fair use" exclusion as far as I'm concerned), excerpts include:
"...Production of this block began in October 1968 and continued through the 1971 model year. This block was very special because it was used as a 427 and 454 block simultaneously during the 1969 and 1970 model year..."

His Chart has the following application information:
1969 (mid-year) 427 - 390 (2-bolt main) and 400, 430 and 435 (4-Bolt Mains)
1970 454 - 390 (2-bolt main)
1971 454 - 365 (2-bolt main) and 425 (4-Bolt Main)...

So, if Alan's data is correct (I have no reason to think otherwise) where does the "JC" or "JG" suffix come in on the engine assembly stamping? (there are no CORVETTE "JC" or "JG" codes [or anything even close] in '69, '70, or '71 as far as I can tell)...

I know I'm showing my ignorance here, but were block casting numbers unique (no cross-division use?) for each GM Division?
Could this block have been used in one of the other Divisions who also used either "JC" or "JG" suffixes?

It's a puzzle to me...sorry if I am missing something very basic

[Joe L.]

Re: Need help determining casting year.

Thanks, Roy (and Joe and Terry) - Happy Thanksgiving to all...!

Where I get tripped up in this whole thing is Alan Colvin's "Corvette by the Numbers" (1st ed. April 2002) page 106 lists Corvette Block casting #3963512 as being introduced "1969 mid-year".

Without violating his copyright (although this forum would fall under the "fair use" exclusion as far as I'm concerned), excerpts include:
"...Production of this block began in October 1968 and continued through the 1971 model year. This block was very special because it was used as a 427 and 454 block simultaneously during the 1969 and 1970 model year..."

His Chart has the following application information:
1969 (mid-year) 427 - 390 (2-bolt main) and 400, 430 and 435 (4-Bolt Mains)
1970 454 - 390 (2-bolt main)
1971 454 - 365 (2-bolt main) and 425 (4-Bolt Main)...

So, if Alan's data is correct (I have no reason to think otherwise) where does the "JC" or "JG" suffix come in on the engine assembly stamping? (there are no CORVETTE "JC" or "JG" codes [or anything even close] in '69, '70, or '71 as far as I can tell)...

I know I'm showing my ignorance here, but were block casting numbers unique (no cross-division use?) for each GM Division?
Could this block have been used in one of the other Divisions who also used either "JC" or "JG" suffixes?

It's a puzzle to me...sorry if I am missing something very basic

Mark------


At the time, the only other GM division that used Chevrolet casting numbers was GMC.

[Terry M.]

Re: Need help determining casting year.

Thanks, Roy (and Joe and Terry) - Happy Thanksgiving to all...!

Where I get tripped up in this whole thing is Alan Colvin's "Corvette by the Numbers" (1st ed. April 2002) page 106 lists Corvette Block casting #3963512 as being introduced "1969 mid-year".

Without violating his copyright (although this forum would fall under the "fair use" exclusion as far as I'm concerned), excerpts include:
"...Production of this block began in October 1968 and continued through the 1971 model year. This block was very special because it was used as a 427 and 454 block simultaneously during the 1969 and 1970 model year..."

His Chart has the following application information:
1969 (mid-year) 427 - 390 (2-bolt main) and 400, 430 and 435 (4-Bolt Mains)
1970 454 - 390 (2-bolt main)
1971 454 - 365 (2-bolt main) and 425 (4-Bolt Main)...

So, if Alan's data is correct (I have no reason to think otherwise) where does the "JC" or "JG" suffix come in on the engine assembly stamping? (there are no CORVETTE "JC" or "JG" codes [or anything even close] in '69, '70, or '71 as far as I can tell)...

I know I'm showing my ignorance here, but were block casting numbers unique (no cross-division use?) for each GM Division?
Could this block have been used in one of the other Divisions who also used either "JC" or "JG" suffixes?

It's a puzzle to me...sorry if I am missing something very basic

Mark
1969 was the last year to use two character suffix codes in Corvette. I can't speak for other GM models however.

Anyone with a Lime book. I think that has all the available suffix codes for all GM models.

[Richard M.]

Re: Need help determining casting year.

Mark
1969 was the last year to use two character suffix codes in Corvette. I can't speak for other GM models however.

Anyone with a Lime book. I think that has all the available suffix codes for all GM models.

Ed graciously posted it HERE.

I'll have to ask him if I could add it to our Sticky.

Rich
Edit...P.S. In that thread he said it's ok so I will at some point.

[Mark F.]

Re: Need help determining casting year.

Mark 1969 was the last year to use two character suffix codes in Corvette. I can't speak for other GM models however. Anyone with a Lime book. I think that has all the available suffix codes for all GM models.

Hi Terry…Thanks
– agreed on the lime book! What a resource that is! I had downloaded that several years ago, but forgot about it until you mentioned it. And Rich beat me to the punch …I was just typing this up when I saw Rich’s post come in about Ed’s book…”Thanks to the sharing spirit of Mr. Edward McComas (9316) back in Feb 2018, he made his lime book available to anyone on TDB who wanted it as long as they abided by his caveat “…I reserve all rights, and I do not grant permission for the use of this information for commercial or profit purposes.” …

- and yes, I knew a three-character suffix started out there sometime – just wasn’t sure of the cut-off of the two-character suffix format.

I guess what I was trying to say (or maybe ask not so clearly?) was after looking at the pad shots over on CF – could there have been a three-character engine assembly stamp suffix that definitely started with a “J” and was followed by two additional characters - the third of which had been completely decked off – and the second of which could have been a partially-decked “C”, “O”, “Q”, or “G”??

According to Ed’s Lime book the answer is no.

• Looks like there were 44 suffixes that began with a “J” (23 of which were unique). None of those were three-character suffixes; they were all two (...ooops, there is one single character "J", too...) – and many of them (21) were used in multiple years and in varying powertrain configurations.
• Years where initial “J” codes were used included ’56, ’64, ’65, ’67 and ‘69
• During those years, they applied to 265, 283, 327, 396, 409 and 427 cubic inch engines – with 155, 195, 220, 250, 265, 300, 325, 340, 350, 365, 375, 400, and 435 HP
• Vehicles listed using initial “J” codes included Camaro, Chevelle, Corvette, El Camino, Nova, Passenger Car and Truck 6000 Series (no other GM Divisions)

To quote a former Defense Secretary: “There are known knowns…things we know that we know. There are known unknowns…things that we know we don't know. But there are also unknown unknowns…things we don't know we don't know.” The mystery continues