3959512 block in a 62

[Robert I.]

I have a 340 hp 62. At some point a new short block was installed. The casting number is 3959512.

Is this the correct block for the 340 hp?

Would the same block have been used for the 300 hp engine?

Thanks

[Dennis C.]

Re: 3959512 block in a 62

I have a 340 hp 62. At some point a new short block was installed. The casting number is 3959512.

Is this the correct block for the 340 hp?

Would the same block have been used for the 300 hp engine?

Thanks

519 block was used during 1961 and the 1962 used the 870 block for the entire model year. This information is in the 61-62 judging guide, which is available from the NCRS store.

[Duke W.]

Re: 3959512 block in a 62

The ...512 block was released in the late sixties and was service ONLY. It has a rear crankcase vent provision like the ...870 block. It was processed for either small or large bearings. The retention notches for both are present, and if larger bearings are desired, like for a stroker crank, it's just a matter of align boring the mains and maybe a little grinding so the rods will have clearance with 3.75" stoke cranks. The above also applies to the ....657 block that was OE in '67.

So, no it is not an original block for a '62 or any other year Corvette for that matter, but it's an excellent basis for a stroker engine that can be configured exactly as the original engine including the PCV system. Only a knowledgeable person who observes the casting number and date code would know for sure that it is not the original block or entire engine assuming all the other original engine components are in place.

Duke

[Joe R.]

Re: 3959512 block in a 62

I agree that the 3959512 casting was a service replacement block manufactured during the late 1960's and early 1970's. It was never used in production.

Some sources say it was used in production in the early 1960's, but I think this is mistaken information based on the fact that Flint blocks had a single-digit code for the year. So, a date code of A-12-2 could be January 12, 1962 or January 12, 1972.

While this casting was not used in production, it is still a desirable casting because it has the rear crankcase vent that stopped appearing in production after 1967. This makes it compatible with the un-vented valve covers that Corvettes used up trrough 1967. And, this block has provisions for either small-journal or large-journal main bearings. It is very easy to make a 383 stroker motor using this block.

[Joe L.]

Re: 3959512 block in a 62

I agree that the 3959512 casting was a service replacement block manufactured during the late 1960's and early 1970's. It was never used in production.

Some sources say it was used in production in the early 1960's, but I think this is mistaken information based on the fact that Flint blocks had a single-digit code for the year. So, a date code of A-12-2 could be January 12, 1962 or January 12, 1972.

While this casting was not used in production, it is still a desirable casting because it has the rear crankcase vent that stopped appearing in production after 1967. This makes it compatible with the un-vented valve covers that Corvettes used up trrough 1967. And, this block has provisions for either small-journal or large-journal main bearings. It is very easy to make a 383 stroker motor using this block.

Joe------


There's no way that the 3959512 block existed in the early 60's. The part number implies a very late 1968 or 1969 release. A block dated A 12 2 could only be January 12, 1972. As far as I know, the block was not still be manufactured by 1982.

[Joe R.]

Re: 3959512 block in a 62

Hi Joe:

Yes, we are in full agreement on this. The problem is that some compilations of block casting numbers that can be found on the web incorrectly list this casting number as being from the early 1960's. This misconception has become widespread.