350 blocks
 

I have a 73 350 motor, how can i tell if it's a 4 bolt or disired block? Right now it's too greasy to touch, so where and what do I look for? Fondling around dirty things is not my favorite.

Re: 350 blocks
 

There should be a casting number on the back of the block, I believe there is one on the front by where the alternator mounts as well.

Re: 350 blocks
 

As long as you are not intending to rev it's guts out, it doesn't really matter.
A 2 bolt block will stand up to the average performance build just fine.
As long as the block is solid and not execssively worn, it's good to go.

Re: 350 blocks
 

I would say just pull the oil pan and check the mains.

Re: 350 blocks
 

Check the casting number (passenger side back of the block). If it ends in 010 it's either a 4 bolt main or heavy duty 2 bolt main. Either is a good starting point if it's not been overbored by .060 yet.

Re: 350 blocks
 

010 i beleive is the code for a 350 it wouldnt telly you main bolts or any thing there should be other castin marks and or stampings showing nickle content and main bolts and all that good stuff

Re: 350 blocks
 

Look for 010 and/or 020 under the timing chain cover, they're the better blocks, either 2 or 4 bolt. As long as it's a daily driver and not beat hard, a 2-bolt is fine. If you like driving it like you bought it at Harbor Freight, you best start with a good 4-bolt block. Gotta pull the pan, there are no single 350 castings from this time that tell if it's 2 or 4 bolt other than 400's.

Re: 350 blocks
 

my 78 jimmy isn't (stock 305) but it's supposed to be "period correct" 350 with 4 bolt mains
this is what the back looks like and the front numbers
you can usally blast back there with a pressure washer to see them