[charlie66]

Is there any information out there on 350ci blocks stating their thicknesses in cylinder wall and main web thickness? Is there a better year than another? Do they run in line with the 400ci blocks or are they in a different league of their own.

Thank you

[Jay S]

76 and later 350s with the casting number starting with 500 had weak main webs. The earlier 350s have differences in cylinder scallops, on the both the intake and exh, IRC…the later post 1973 350s have just scallops on the exh only. The scallops are an easy way of identifying 350s. I don’t know of any cylinder wall thicknesses differences.

[charlie66]

Do you know if the earlier 350ci block mains are as good as the 400ci or are they weaker?

Thanks

[Formulas]

I have a 1970/350 the main webs are the same as any other 1970 V-8

[charlie66]

Originally Posted by Formulas

I have a 1970/350 the main webs are the same as any other 1970 V-8

Ok, Thank you..

[433lemans]

My memory fails me but years ago, I believe it was on the Classical Pontiac website when it was flourishing, someone was going to take a 350 block and cut thru I suppose with a big band saw in an effort to see how thick the cylinder walls are. Anyone here remember this?

[steve25]

The block casting numbers for the 350 changed significantly in mid 75 just like they did in mid 75 when the 400 went to the thin wall main web’s.
So I would conclude that post Aug 75 is the cut off for a good 350 block.

Up until then the 350 block casting number had not changed for 2.5 years.

[Formulas]

On a 3 per side freeze plug block you can measure between the 2 center cylinders in the water jacket then measure bore to bore at the deck do some math to come up with a ball park wall thickness of course this would not account for core shift and sonic testing is king if your pushing limits

[Dragncar]

If you can find a 59-60 389 block those are known for being very thick and beefy.
If you can get around the starter issue.

[hurryinhoosier62]

Originally Posted by Dragncar

If you can find a 59-60 389 block those are known for being very thick and beefy.
If you can get around the starter issue.

Wilcap transmission adapter from Speed Gems. Not cheap, but does give the ability to use Chevy bolt pattern transmissions along with mounting the starter on the ‘59-‘60 389 blocks. Butler lists an adapter as well but I haven’t researched it.

[sdbob]

Local Pontiac dealer gave me a 75 350 block out of brand new A body. Service issue leaking coolant. There was a small crack below one of the freeze plugs. Bad casting maybe , I kept it then I junked it. I thought about trying to repair it.Its the only Pontiac V8 I experienced this with.

[Dragncar]

I threw away a perfect std bore 69 350 block. I wish I had kept it.
It was a fun street engine with 48s and a 2801.

[bdk1976]

Originally Posted by 433lemans

My memory fails me but years ago, I believe it was on the Classical Pontiac website when it was flourishing, someone was going to take a 350 block and cut thru I suppose with a big band saw in an effort to see how thick the cylinder walls are. Anyone here remember this?

I remember that thread, but don't recall if it ever came to fruition?

I scraped most of that site before it's demise and put it into a database, but there were some issues with the way it was structured/delimited so never did get a 'clean' personal archive. I may be able to search it for this thread if I have some time/inclination.

You can also access a lot of the site via the internet archive - may be able to find it there somehow.