New "396" question`

[Bill W.]

Reinforcement gussets !!!! I have 2 962 blocks
without gussets. Both were 375 HP 66 Chevelle. One with a assy.date of TI030EF. and a Hi Per. cast on the rear .The other I cant get to . These blocks are Identical to my Corvette blocks except they dont have Gussets?They have the big oil plug ,4 bolt main,etc. My Question is .I thought when there was a change in a casting the casting number changed ? Does anybody have a late "real" 396 Corvette without Gussets ?And why would they do this. The judging manual says all 962s have gussets. Also I have never seen a 961 with Gussets ,a big oil hole and 4 bolt main...Bill

[Wayne M.]

Re: New "396" question`

..... My Question is .I thought when there was a change in a casting the casting number changed ? Does anybody have a late "real" 396 Corvette without Gussets ? And why would they do this. The judging manual says all 962s have gussets. Also I have never seen a 961 with Gussets ,a big oil hole and 4 bolt main...Bill

Bill -- can't answer your direct question, but I believe that gussets were more a function of casting date, and not main journal bolting. Gussets were definitely eliminated before the end of calendar 1965; maybe those with cast months J, K or L.

Here's a 961 I have with gussets, cast E-14-5.

[Patrick B.]

Re: New "396" question`

Gussets aren't the only difference between 65 and 66 model year 962 blocks. The 65's were cast with 427 water jacket cores and can be bored out to at least 427 bore plus .060 (4.310"). You will go thru the water jacket if you try that with a 66 or later 396 block.

[Clem Z.]

Re: New "396" question`

Gussets aren't the only difference between 65 and 66 model year 962 blocks. The 65's were cast with 427 water jacket cores and can be bored out to at least 427 bore plus .060 (4.310"). You will go thru the water jacket if you try that with a 66 or later 396 block.

the original 65 corvette 396 blocks were to be 4.250,427 bore but GM managment came out with a edict that no engine would be larger than 400 cu in but i guess the blocks were all ready designed.

[Cecil L.]

Re: New "396" question`

Gussets aren't the only difference between 65 and 66 model year 962 blocks. The 65's were cast with 427 water jacket cores and can be bored out to at least 427 bore plus .060 (4.310"). You will go thru the water jacket if you try that with a 66 or later 396 block.

I have heard this before, yet have seen no documentation nor anecdotal evidence. I have an early 65 961 block and it failed the pencil test. If you've never heard of the pencil test, remove one of the freeze plugs on the side of the block that gives you a near direct view of the cylinder wall castings. Try to fit a standard #2 pencil between the cylinder walls...if it goes, it is not thick enough for 427 bore, if it doesn't go through, it may be thick enough, but the only certain way to tell is by sonic-checking.

[Clem Z.]

Re: New "396" question`

I have heard this before, yet have seen no documentation nor anecdotal evidence. I have an early 65 961 block and it failed the pencil test. If you've never heard of the pencil test, remove one of the freeze plugs on the side of the block that gives you a near direct view of the cylinder wall castings. Try to fit a standard #2 pencil between the cylinder walls...if it goes, it is not thick enough for 427 bore, if it doesn't go through, it may be thick enough, but the only certain way to tell is by sonic-checking.

back in the day i bored a 66 up 396 block to 4.250 and after running it 4 cylinders split.

[Dick W.]

Re: New "396" question`

back in the day i bored a 66 up 396 block to 4.250 and after running it 4 cylinders split.

But knowing you, it was probably overbored to 4.500"

[Bill W.]

Re: New "396" question`

Yep the 66 962 I cant get to is bored to 427 and has 2 split cylinders .Again why did they reuse the same casting number when they were not the same block ? Clem do you think all Pass . 962s had thick walls and all Hi per. had thin .Or do you think it was related to the deletion of the ribs and the 66 model year ?. Bill

[Clem Z.]

Re: New "396" question`

Yep the 66 962 I cant get to is bored to 427 and has 2 split cylinders .Again why did they reuse the same casting number when they were not the same block ? Clem do you think all Pass . 962s had thick walls and all Hi per. had thin .Or do you think it was related to the deletion of the ribs and the 66 model year ?. Bill

i think it has to do with the year as my guess would be only blocks cast for 65 396 corvettes should be bored to 4.250. back then i never paid any attention the ribs on the block.

[Carl N.]

Re: New "396" question`

i think it has to do with the year as my guess would be only blocks cast for 65 396 corvettes should be bored to 4.250. back then i never paid any attention the ribs on the block.

I have a 962 blocks from full size Chevy with "E" "5" cast dates and gussets bored to 4.25 - ran for several years a 1/4 mile at a time in a '65 Impala with no problems till a MoPar driver protested a loss and NHRA tech made us tear it down - needless to say we took it out and thats why its sits in the back of the shop today!

I believe the 4 bolt 962 blocks cast in '65 can handle the 4.25 bore as long as everthing else is ok - as stated before the original valve train was the weak link - IMO the original pushrods were prone to fail as often as keepers and inner springs.

[Wayne M.]

Re: New "396" question`

Pertinent quotes from "How to Hotrod BB Chev's" 1972 revision, pg 101.

"It's no secret that the 396 and 402 blocks can be safely bored to 427/454 size of 4.251 inches. ......we do know that some 4-bolt 396/402 blocks have been bored to as large as 4.311 inches (439 cubic inches with 3.76" stroke -- my note), but not always successfully."

(another paragraph) "Fortunately, the BB Chevy has unusually thick cylinder walls. These are nominally 0.260" (if there's no core shift) in high performance 396 blocks."

[Patrick B.]

Re: New "396" question`

It's not just a matter of no core shift. The 396 blocks made in the 65 model year are heavier than other 396s and 427s because of the 427 water jackets combined with 396 bores. You can feel the difference when you pick them up. Only those blocks (and ZL-1s) have the ribs over the timing chain cover.