Hey Guys, Was wondering if the 350 and 403 use the same block?

I found this picture of an OL4B installed on a 403 with HEI and was wondering if it would be the same fit as a 350.

There isn't much clearance without the cap so with the cap it's super tight.

 

The 350 and 403 blocks are different, but the SBO intakes will fit 307, 350 and 403 blocks. Be aware that some intakes can not accept the GM HEI distributor without some modifications.

 

Short answer. No. Not the same block. But every single part except for pistons will interchange.

 

Oh. And no, the OL4B will not take an HEI distributor nor will an Offenhaiser 360

 

Brownbomber77,


I'll have to disagree about the Offenhauser 360 dual plane not fitting with a HEI distributor. That's what I've got installed on my 350 right now, no clearance problems at all, it's close but I've got about .050inch clearance by the intake runner.
If I had to change the timing I might have a problem since the screw hump in the cap might hit the runner but other then that I'm fine.


I'm thinking more and more towards the Performer RPM.


I'm wondering if some HEI's have a bigger diameter then others?

Thanks for the info on the blocks.

 

So you're saying that the photo that the OP posted is a fake???

 

Just for completeness, the 403 uses siamesed cylinders, unlike the 350 (or any other SBO). The blocks are completely different castings.

ALL SBO blocks are externally identical, however, so any external part (manifolds, distributor, etc) that fits one SBO will fit all of them.

 

If there is interference at the HEI/Intake, you can probably remove a little of each and gain the fitment needed. Certainly a lot of the distributor / cap can be cut away with little or no ill effect.