1968 427 390hp block

[Jimmy D.]

[Patrick B.]

Re: 1968 427 390hp block

I have seen late 1966 942 blocks with the casting numbers ground off and the 1967 351 casting number stamped on. Maybe this block is a 351 block with the original casting number ground off and the 68 321 number stamped on. What is the casting date of this block?

[Gary B.]

Re: 1968 427 390hp block

This is the fourth or fifth block I have seen this way. And I know where this block is at.
Gary B

IMG_2744.jpg

[Jimmy D.]

Re: 1968 427 390hp block

Pat, it looks like H87. Do you have any info on 4 bolt vs 2 bolts on this years 427s?

[Joe L.]

Re: 1968 427 390hp block

Pat, it looks like H87. Do you have any info on 4 bolt vs 2 bolts on this years 427s?

Jimmy-----


In general, 1968 L-36 were 2 bolt main engines but exceptions are possible. The difference between 2 bolt and 4 bolt cannot be determined by casting number as the same castings were used for both. Please post a photo of the area above the oil filter.

[Jimmy D.]

Re: 1968 427 390hp block

Thanks Joe, l was unsure what cars got 4 bolt mains with the 427. This one is a 2 bolt. So the 400 and 435 hp had 4 bolts?

[Joe L.]

Re: 1968 427 390hp block

Thanks Joe, l was unsure what cars got 4 bolt mains with the 427. This one is a 2 bolt. So the 400 and 435 hp had 4 bolts?

[Jimmy D.]

Re: 1968 427 390hp block

Ok thanks Joe. Very helpful.

[Patrick B.]

[Jimmy D.]

Re: 1968 427 390hp block

Ok,thanks Patrick. My guess is that they repaired blocks if needed in the plant. I find it interesting that only the 435 hp blocks got machined for the 4 bolt. The early year c3 350 had 4 bolts.

Thank you

[Patrick B.]

Re: 1968 427 390hp block

Yes, only the solid lifter big blocks (and perhaps the 1966 360 hp Chevelles) were designed with the 4 bolt blocks, but they could be used on other engines if there was a momentary shortage of 2 bolt blocks. August 8 is still pretty early in the 68 model year so yours could be a ground 351. I am interested in trying to see if there is a visible difference between 351 and 321 blocks to help identify yours. My 321 block was cast in September so yours is earlier than that clear 321 casting. I will check in late March when I get home.

[Ray K.]

Re: 1968 427 390hp block

In my experience, only the mechanical camshaft / lifter engines were originally supplied with 4 bolt main bearing caps.

Ray

[Joe L.]

Re: 1968 427 390hp block

In my experience, only the mechanical camshaft / lifter engines were originally supplied with 4 bolt main bearing caps.

Ray

Ray and Patrick------


That's what I always thought, too. I also realize that the L-68 is the same as an L-36 with 3X2 instead of 4BBL. However, based on some research I did awhile back I found that the L-68 was supposed to have used a 4 bolt main block.

I've never actually disassembled an L-68 to check this. However, I'd be very interested in hearing what folks that have actually disassembled an original L-68 to see what they have found. For those with an original L-68 that have not at least had the oil pan off, I'd be interested in photos of the area of the block above the oil filter.

[Ray K.]

Re: 1968 427 390hp block

Joe,

You may have a valid point. I can't recall that I personally ever dis-assembled an L-68, or that we did one at the dealership. As you say, it would be interesting to have a photo of the block oil filter area. I can say, that service replacement new short blocks ( partial engine ) were serviced by the same part #3930851 for both L-68 and L-36 options, which was a 2 bolt main block. Think it possible ( tho not likely ) that an L-68 could have had a 4 bolt main bolt.

Ray

[Jimmy D.]

Re: 1968 427 390hp block

If I remember correctly, 1 of the 3 holes above the oil filter, the one on the left is threaded for a oil cooler. That would tell us if it's a 4 bolt main block. Am I correct?