[Skip Fix]

OK guys is this average,weak or good main webbing for a 400? Looks average to me, but I didn't have another block to compare with.

[KS circutguy]

Looks to me to be the thick version.

[Brian Baker]

Looks like a great candidate for 4-bolt splayed caps. Got any pics of the lifter valley?

[Skip Fix]

I'll get some tomorrow Brian.

[mysticmissle]

what is in the lifter valley that differentiates block to block? thanks Brian

[PONTIAC DUDE]

looks to be the thin casting block. support under the main caps in the area under the cylinder bore. Pics are too far away. Need pics closer to the cap mate area under the cylinders in #2. 3 & 4.

I have found 4 basic 400 casting blocks. Need to take pics before I build and sell them all to customers and put on my website?

What's the date code by the distributor.

From what I see it would be good for a bacic 455 conversion with a mild cam or a 350/375 hp 400 combo.

[PONTIAC DUDE]

Originally Posted by mysticmissle

what is in the lifter valley that differentiates block to block? thanks Brian

That works for the 455 blocks and still have to check other ares on the 455's. But if Brian tells, I'll have to kill him. LOL.

[Skip Fix]

I'll take some closer, but you can see the #2 main cap front and back side area.

[Jeff Walker]

It has less meat in the main webbing area than a 68 block or a 72 junk block I have laying around. I you look at the first pic you posted, you can see a 'step' where the cylinder ends, toward the middle of the block. Neither of mine have that but have metal there.

[birdzz]

P-dude, I have a thin web 400 I was considering installing your stroking kit on, so I take it that it works fine? I would be looking for substantially more than 375 horses, though!

Is it possible to weld it up for more strength?

[Skip Fix]

Here's closer Ken

[Skip Fix]

Jeff can you snap a picture?

here's lifter valley on a 72 HO block

[PONTIAC DUDE]

I wouldn't recommend that block for any higher hp applications. No support under the cylinder bore to the pan rail. But for a mild rebuild as i stated above shouldn't be an issue.

birdzz:
I wouldn't do the 4.250 deal with that block. But a 455 conversion with 9.0-1 compression, under 375hp and 5200 rpm won't be a problem.

FWIW: You can run real low 13's making 350/375 hp in basically stock chassis car.

Just bottom fill the block, deburr the block, ARP studs and have the line bore checked.

[455-4+1]

Originally Posted by PONTIAC DUDE

I wouldn't recommend that block for any higher hp applications. No support under the cylinder bore to the pan rail. But for a mild rebuild as i stated above shouldn't be an issue.

Dude, you may have just solved some of my problems with the mains on my sprint boat

All centred around #2 which looks like where Skips pic was taken. My block looks the same in this area. Using factory mounts at the front (either side of #2) the mains were moving around alot and cracked the cap outboard of the dowel on this side

Can you confirm if the "thicker" blocks have more material along the pan rail (shown "A" on my marked up version of Skips pic) Mine has "bosses" for the mount holes as per the pic also which wouldnt be visible if there were more meat there. I know the 58 etc blocks have more meat here and are looking for one here for a new boat engine build as we dont need a starter mount or any factory side mounts

Also does area "B" differ ? My current block (73 YT code) appears a little thicker here ?

Any help figuring this out would be great

[SergeF]

Here are some pics from my spare 67 400 block. How is that look?

[Skip Fix]

OK to me the 67 has meat all the way to the dowel whereas this block is just to the bolt area. The rails are thicker under the bore but I would think the main cap area is the more important area. Kins of subtle differences.

[SergeF]

Skip, I also have 2 70 blocks at my dad's house. If you want I can get pics later on. To me, I really dont see much difference.

[455-4+1]

Definitly alot more meat along the pan rail below the bore in the 67 block compared to my 73 YT block (area "A")

On mine the bosses for the motor mount holes show up clearly and the rail is thinner

Hmmmmmmmmm

[LPI]

The 1967 and 1968 2 bolt main blocks are very similar in structure and strength.

In 1969 they started decreasing the material in the webbing and continued doing so each year there after. If you set up a 1967, 1968, 1969, 1970, 1971, 1972 and 1973 blocks each one will have subtle changes in the main webbing area. In all cases the webbing gets thinner as the year of the block gets newer.

Another item to watch out for is the letters stamped on the oil pan rail. If there are letters stamped by the main cap webbing on the oil pan rail you better measure twice and cut once or you will be sorry. Again another item that gets blamed for engine/bearing failures when in most cases it is a measurement error.

I have the revision list from 2/69 thru 7/72 which shows most of the changes and updates over the years on these 9799 thru 485 blocks.

The actual material used was Cast Iron - G.M. 232-M

One of the reasons why the main caps break or crack at the dowel pin hole is from switching from factory bolts to ARP/Milodon studs. Studs and 4 bolt mains are not better unless you look at all of the parts and each individual application.

Another note. GM did not use "standard" diameter dowel pins in the main caps.

[LMSRACER]

Originally Posted by LPI

I have the revision list from 2/69 thru 7/72 which shows most of the changes and updates over the years on these 9799 thru 485 blocks.

The actual material used was Cast Iron - G.M. 232-M

One of the reasons why the main caps break or crack at the dowel pin hole is from switching from factory bolts to ARP/Milodon studs. Studs and 4 bolt mains are not better unless you look at all of the parts and each individual application.

Another note. GM did not use "standard" diameter dowel pins in the main caps.

For those that don't know, He's talking about the 455 Block when he says "9799 thru 485".

Also, for those that don't know, the Pontiac Dowels are 0.3095" and NOT 0.3125" (5/16").