Question: '65 Through '67 Big Blocks

[Rob V.]

Did all versions of big blocks found in 1965 through 1967 Corvettes have four (4) bolt mains?Thanks In Advance, Rob

[Mike T.]

Re: Question: '65 Through '67 Big Blocks

No. Even though all Bigblocks seem to have 'Hi-Perf' in a raised casting it's no guarantee that it's a 4-bolt block. Only the high horse engines came with 4 bolt mains and those had the oil cooler fitting above the filter canister pad.
Mike T.

[Joe L.]

Re: Question: '65 Through '67 Big Blocks

Did all versions of big blocks found in 1965 through 1967 Corvettes have four (4) bolt mains?Thanks In Advance, Rob

Rob-----


All 1965 Corvette big blocks (i.e. L-78) were 4 bolt main. For 1966, the L-36 was generally 2 bolt main and the L-72 was always 4 bolt main. For 1967, L-36 was generally 2 bolt main. L-68 could have been either but I think most were 4 bolt. L-71 and L-88 were always 4 bolt. I have heard of 4 bolt mains being found on a few original L-36's.

All 1965-67 big blocks used a forged steel crankshaft.

[Rob V.]

Re: Question: '65 Through '67 Big Blocks

Thanks Mike! So, does that mean that a 1967 Corvette that "rolled out from the factory" with a 390 HP 427 most likely had a two (2) bolt main??? I appreciate your help! Rob

[Rob V.]

Re: Question: '65 Through '67 Big Blocks

Joe and Mike--Thank you for your assistance! What prompted my question is that I just recently traded my '61 'Vette that I had contemplated "stuffing a big block in" for a 1967 Coupe that had a non-original small block and a "big block" hood. I thought that the "67 Coupe would be perfect for my big block engine swap (something I always wished to do), since the original engine was missing, and I would not be destroying a correct car. Anyway, I won't bore you with the details, but I just validated/verified that the car was delivered from the factory with a 390 HP 427 as documented by the tank sticker. As a consequence l am wrestling with what type block I should put back in the car. Since the 390 HP 427 had a two (2) bolt, and purely from the standpoint of cost, it would seem that a two (2) bolt 427 block should be more affordable than a four (4) bolt block; however, I have not been able to establish a price for either the two or four bolt blocks. Perhaps I should just try and find a 454 block since the original engine is MIA; and I do not intend to "restamp" the block. I just intend for the car to be a driver. Your thoughts/comments on this subject are truly appreciated! In a quandary in Colorado... Thanks, Rob

[Keith B.]

Re: Question: '65 Through '67 Big Blocks

For bang for buck dollar wise a new crate 454 HO from GM would be your best bet. You can use all the original 67 BB things and dress it out to look like any 60's era BB you want And comes with a warranty and it's brand new

[Mike T.]

Re: Question: '65 Through '67 Big Blocks

Rob - I'm planning on adding a 427 to my 65 Smallblock Coupe once our new house and ''Garage" is done. Years ago I came across a worn but usable 2-bolt 427 passenger car engine. It hadn't been bored and was in running condition when removed. Tossed the heads and kept the shortblock and even though I don't expect to hit the high side of 6K rpm with it when done, the well assembled 2-bolt block will fit the bill just fine. It's probably going to be a lot easier for you to find a 454 engine or just a block but if you really want to have those numbers...'427', all you need to add is the right crankshaft to that 454 block. Short of looking for that telltale oil cooler fitting I mentioned earlier, no one is going to know whether it's a 2 or 4-bolt once it's in your Corvette.Mike T.

[Joe L.]

Re: Question: '65 Through '67 Big Blocks

For bang for buck dollar wise a new crate 454 HO from GM would be your best bet. You can use all the original 67 BB things and dress it out to look like any 60's era BB you want And comes with a warranty and it's brand new

Keith------


Yes, a GM crate 454 would be a good way to go. However, it's not going to appear correct. All of the current GM 454 engines are Gen VI. These differ in considerable ways from original Mark IV big blocks originally installed in all Corvettes.

As long as dates and casting numbers are not an issue, it's very possible to obtain good cores for both block and cylinder heads for a Mark IV engine and build a good "replica" of a 1966 L-36.

[Rob V.]

Re: Question: '65 Through '67 Big Blocks

Keith and Mike--Thank you for the responses! Keith, my local Corvette dealer/repair shop advised just what you did. They told me to sell the big block parts that I accumulated; get a crate engine; and be on the road in short order with a new, warranted big block. I have to admit, that is probably a very practical approach. Mike T, that is also great information that you provided! If I do build my own engine as opposed to buying a crate engine, it is good to know that it would not be necessary to "refinance the house" to buy an acceptable block to go into this car. Therefore, a 454 would do the job. I could still remount the 427 emblems in the holes that are now filled in the hood... :-) Thanks again for your thoughts! Rob

[Rob V.]

Re: Question: '65 Through '67 Big Blocks

Joe-- Thank you for your further response. Perhaps you can help with this follow-on question: Does GM still manufacture a "new" Mark IV bare big block??? (I can not locate my GM Performance Parts book). Thanks again, Rob

[Mike T.]

Re: Question: '65 Through '67 Big Blocks

Rob - A new crate engine would be the way to go to if only to avoid having to deal with a machine shop. Plenty of them around that do good work but there are enough horror stories about the 'others' to make a crate motor look like a very good decision. Plus as already mentioned, you save all that time. Keep us posted with your progress. One thing to double check on the GM crate motors is the boss for the mechanical fuel pump. Not sure about this but thought that the new Bigblocks were cast without that boss meaning you'd have to use an electric pump.

Mike T.

[Rob V.]

Re: Question: '65 Through '67 Big Blocks

Thanks Mike! I will keep you updated on the build. (By the way, the good news besides the '67 originally having a big block; my wife says she likes this particular car better than all the other ones that I have owned! :-) Guess this makes this one a "keeper") Rob

[Joe L.]

Re: Question: '65 Through '67 Big Blocks

Rob - A new crate engine would be the way to go to if only to avoid having to deal with a machine shop. Plenty of them around that do good work but there are enough horror stories about the 'others' to make a crate motor look like a very good decision. Plus as already mentioned, you save all that time. Keep us posted with your progress. One thing to double check on the GM crate motors is the boss for the mechanical fuel pump. Not sure about this but thought that the new Bigblocks were cast without that boss meaning you'd have to use an electric pump.

Mike T.

Mike------


All current GM crate big blocks now have the fuel pump boss for a mechanical fuel pump. Most previous ones did not, but the currently available ones do. Also, I believe that all now have the clutch cross shaft boss drilled and tapped.

[Keith B.]

Re: Question: '65 Through '67 Big Blocks

Joe unless I am mistaken the diffrances are very minor and only a few select people would know the difreance. The biggest thing that would tip people off would be the size of the stamp pad.

[Mike T.]

Re: Question: '65 Through '67 Big Blocks

Thanks Joe, I wasn't sure about the lack of a fuel pump boss. In the end, if Rob doesn't have a Bigblock sitting around and has to start shopping for parts here and there, the new crate motor with roller cam makes sense. I did look at the specs on the 454 HO and was surprised the compression ratio is only in the 8's but it'll still provide plenty of power.