want to swap 350 for 283, will 700r still bolt to it

Match the OEM starter to the size of the flexplate on the engine, which has to match the bolt pattern of the torque convertor of the 700R4.
If the 2 bolt holes are in line(along the back of the block) then it's a small diameter flexplate. If staggered bolt pattern on starter then large diameter.

 

Thanks. I checked again, this time looking under the block rather than just feeling and I actually have three threaded holes. Can I ***ume that i can use either style starter with the appropriate flex plate? Is there an issue with the flexplate connection to the crank? THere is reference to two piece main seals on most flex plate specs.

 

Yes, either starter will work then as long as it matched the flexplate. The flexplate must be for either a one piece OR two piece seal engine. The balance is different between the two engine types.

 

I am confused. I believe this 1958 engine is a one piece seal engine, so is a single seal flexplate is required? The flexplates i have seen by various vendors list 55-85 engines as two peice seal. The single seal engines are listed as 86 and later. Can you clarify?

 

The vendor info is correct...a one piece rear main seal crank is round on the flexplate end and you can see the seal with the flexplate removed.

 

A 1pc RMS flexplate is different to a 2pc RMS flexplate from memory. As stated 1pc RMS crank is round with no counterweight on flange, 2pc RMS has a cast counterweight on flange. I think you would need a dual pattern flexplate. A 1pc RMS flexplate is externally balanced. I went to an internally balanced 383 with 1pc RMS and had to get the correct neutral 153t flexplate that matched my geardrive starter. The other SBC flexplate is 168t. A dual bolt pattern flexplate accommodates 10 3/4" & 11 1/2" torque converter bolt circle patterns for Powerglides, TH350s, TH400s, and 700R4 transmissions.

 

The 1958 Chevy V8 does not have a one-piece rear main seal, it is a two-piece seal. The one-piece seal was not available until 1986. The crankshaft and the flexplate are different on the one-piece seal engines. There is no flange with weight, and the bolt circle is smaller. The weight that was on the crank flange was moved to the flexplate.

 

Thanks to all for the info!