Block Casting Number Help

[Michael S.]

I just looked at an engine that has a block casting number of 3151509. I have looked on Mortec, Chevy by the Numbers and other locations and cannot find this casting number.

The date stamp is K-9-(8 or 9). The block has a spot for a fuel pump, no breather in the valley and has a long stamp pad on the front of the block. There is no stamp since the block has been decked.

Any ideas as to what this block is????

[John H.]

Re: Block Casting Number Help

Mike -

Sure it isn't 3951509? That's a '73-'80 400 block.

[Michael S.]

Re: Block Casting Number Help

Thanks John. It very well could be 39 instead of 31, it was dark in the room with the block.

I looked everywhere for a block ending in 509 and could not find one. I expected this to be a 70's block of some type.

A 400 small block is good news for this application.

Thanks so much!

Mike

[Mark #28455]

2 bolt main 400

The 2 bolt main 400 block has main caps with a wide base like the 2 bolt BB engines. The earlier 51511 4 bolt 400 block has 3 freeze plugs down the side of the block.
Mark

[Clem Z.]

just remember if you use this 400 block with

350 heads you must drill the steam escape hole in the heads to match the holes in the block. also check for cracks from the head bolt holes to the steam escape holes as these block crack there if overheated

[Joe R.]

Re: just remember if you use this 400 block with

Hi Clem:

You're just the guy to answer a question that I have long wondered about: Why isn't the 400 block more popular with hod rodders?

As I recall it was an unusual design with siamesed cylinders so that the bore size could be increased beyond what is achievable in a 350 block.

Based on the old saying, "The only substitute for displacement is cubic inches," it would seem that the 400 block might be popular with people who are trying to max out the small block configuration. I'm not sure what stroke the 400 used, but it might even be possible to stroke one to 400+ cubic inches.

Were there problems with the 400 block that made it unsuitable for hot rodders, such as cooling the siamesed cylinders?

[Mark #28455]

Re: just remember if you use this 400 block with

The original problems were associated with several issues:

Special 400 only main bearing size - no commonly available forged cranks. It wasn't till about the early 80's that Comp Cams came out with bearing spacers for $60 a set. Before that, you had to use the special Clevite thick bearings for over $100 a set to run the 350 cranks.

Trying to run the stock 400 stroke of 3.75" with a 5.7" rod required grinding of the rod bolt areas for extra cam clearance. Aftermarket rods were NOT common back then. Also required custom made pistons - again not common and took months to arrive.

This was also pre wire ring head gasket era - there wasn't a lot of sealing area between the bores.

I ran the 400 block with 350 crank in my Monza. It was a real screamer with 461X heads, but even the best heads back then were nothing like the dime a dozen racing heads today.

Mark

[Clem Z.]

Re: just remember if you use this 400 block with

they were hard to keep the cylinder walls from cracking around the bottom of the water jacket so we would pour the water jacket with expanding grout up to the bottom of the water pump holes to help stiffen up the block. they worked alright for mild hop ups for street engines but serious HP cause block problems with the main bearing webs also unless you used a 2 bolt main block and fitted it with splayed aftermarket caps. this all took time and money so they were not real popular with the racers. that is why now the 383 engine,350 block with a 400 crank is a popular setup these days. lots of torque from the 3.750 stroke but no problems from the 350 blocks.

[Joe R.]

Thanks guys! *NM*