Difference in engine blocks? 3999289 vs.3963512
What are the physical difference between Blocks with the following casting numbers, these are the only numbers I have ad they have been decked. 3999289 and 3963512. I have been told the the 3999289 could have been a factory replacement for 3963516 in a LS6, any input is welcomed.
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Re: Difference in engine blocks? 3999289 vs.3963512
Michael-----
The 3963512 and 3999289 are functionally equivalent and, except of course for the casting numbers, are externally virtually indistinguishable.
In PRODUCTION the 3963512 was manufactured with both 2 bolt and 4 bolt main configuration. However, in PRODUCTION, the 3999289 was manufactured in only 2 bolt configuration. I suspect, though, that in SERVICE the 3999289 was manufactured into both 2 and 4 bolt configurations.
Now that I think a little more about it, there MAY be a difference in the configuration relative to the bosses above the oil filter between the 2 blocks. I'm not sure about that, though.In Appreciation of John Hinckley -
Re: Difference in engine blocks? 3999289 vs.3963512
Joe --not to hijack the thread, but while you're at it, could you tell me what you know about a block casting that is ONE DIGIT higher than Michael's. I have a 3999290, cast L_20_71 with a pad service motor stamping of CE259248. I know mine is a 2-bolt, and I think it was the (then) current replacement for the 396/402 displacement engine. Any other info would be welcome.Comment
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Re: Difference in engine blocks? 3999289 vs.3963512
John and Wayne-----
I don't think the 3999290 block could have been originally used for any 1968-70 applications, although it could have been a later SERVICE block for those applications. I just don't think the 3999290 part number could have been around much prior to 1971.
From what I can find, it was a 402 block originally used for 1972 applications. By that time, I think the 402 had replaced the 396 for all PRODUCTION applications. I believe the 402 "died" after the 1972 model year.
Basically, I believe this block was just a smaller bore version of the 3999289 and was designed around the 4.125" bore of the 402. It's possible that it could have been used for 396 SERVICE blocks, though, and, in that case, bored to 4.094.In Appreciation of John HinckleyComment
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Re: Difference in engine blocks? 3999289 vs.3963512
Joe & John -- interesting info. Wasn't there a minor "scandal" around 396 vs. 402 in terms of engines installed in certain lines of new cars back then ? Badges proclaimed one thing, but in reality the displacement was the other ? My memory is hazy.Comment
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Re: Difference in engine blocks? 3999289 vs.3963512
Wayne-----
Yes, there was. The 396 (4.094" bore X 3.76" stroke) was last used in PRODUCTION for the 1969 model year. For the 1970 model year the bore was changed to 4.125" yielding 402 cubic inches, but they continued to badge the cars with this engine as being 396. They did usually have a footnote in advertisements which disclosed this "discrepancy", though.
I have no idea why this was done. However, I suspect that the "oddball" bore sizing of the 396 was originally conceived to keep the cid displacement below 400 cid. I can think of no other reason for such an "oddball" dimension. I think GM had some sort of corporate edict at the time that they would not install an engine of 400 cid or greater in any mid-size car and Chevrolet wanted to use this engine in the Chevelle. By 1970 I expect that the edict had gone away, so they wanted to "rationalize" the bore sizing. However, by that time the term "396" had become so popular, they didn't want to change it for advertising and badging.
There were 2 different 402 blocks. GM casting #3969854 was used for 1970, 1971, and 1972. This block was manufactured into both 2 and 4 bolt main finished blocks. Late 1969 Chevrolet applications with 396 cid also used this block, but I think the cylinder walls had been increased in thickness to accommodate the 402 displacement soon-to-arrive. So, these late 1969 396 engines had thicker cylinder walls than other 396 blocks.
Later 1972 used the 3999290. In PRODUCTION this block was manufactured only into 2 bolt main configuration. However, I strongly suspect that it replaced the 3969854 at this time and was manufactured into both 2 and 4 bolt main configurations for SERVICE.
1972 was the last year for the 402 big block.In Appreciation of John HinckleyComment
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Re: Difference in engine blocks? 3999289 vs.3963512
Joe,
This thread is very old, but thought I would clear up a thing or two for you over the 402.
The 396 was planned to be used in other model Chevrolet's going forward. They cast a large number of the 289 casting planning on them being used to build the 396 motors. For some reason the pallets were left outside long enough to rust and make the blocks no longer usable.
After sitting there for a while someone came up with the idea of boring them 0.030 over and installing them in cars.
Chevrolet still looked at it as they were using their 396 block as originally was planned. They did not think it was an issue at all.
If this was done to the occasional block, it is not an issue.
The fact that all of them were 0.030 over, the politics of whoever it was wanted them called what they were. 402's.
This is what I was told years ago and have heard the same a number of times since.
MonteComment
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