I'm going to go look at a 90 IROZ that was orginally a 305 TPI 5-spd but has been converted to a 355 carb motor. No idea where the 350 came from nor does the owner since the guy before him did all the work etc.

I found this: http://wiki.answers.com/Q/Is_there_a...it_up?#slide=2

So if it just has bolts going through the center of the valve covers it should be a 1 PC then?

Thanks for any help.

 

SHOULD be a 1 pc. It's likely since the original flywheel was probably reused. But it is not guaranteed. Centerbolt valve covers can be bolted to ANY sbc.

 

Best bet is to ck the block's casting #.

 

Thanks for the quick response. I'll see if the owner can send me the casting #. Is there a certain number past that will be all 1pc rear main?

 

The casting numbers are not really sequential like I think you're thinking. Best thing to do is google the casting number, there are many sites out there that list the block information.

You might also be able to by pulling the valve covers off and looking down the pushrod holes for the dogbones and spider arms of a roller cam setup. If it has them, it's a 95% chance it's a 1pc RMS engine, unless the builder used a retrofit kit.

 

although not a gaurantee, most 1 piece rear main seals have the oil dipstick on the passenger side. and most 2 piece are on the drivers side.

 

Checking the casting numbers would be the best bet. A date code would be a second option. A third is that all of the 1 piece rear main seal small blocks have an externally balanced flexplate, so if you popped off the inspection cover on the trans, you should be able to see the counter weight between the flexplate and the converter if you spin the crank slowly.