Re: Std 8 engine rebuild - 1929 or 1936?

Posted by Owen_Dyneto On 2012/8/23 15:39:42

Mal, I'm on uncertain ground here, more wild speculation than speaking from experience. I don't know what you intend to do with this engine, but babbitt bearings certainly held up well-enough in the 6th and 7th series speedsters with higher HP than the 36 Eight, so within reason, I wouldn't be concerned unless you were going to really press this thing to the limit. If you were, I suspect the 36 rods would interchange but then the problem becomes obtaining the insert bearings - they've been NLA for decades though I hear from time to time that Max has repro'd them - don't know that for a fact but it's just a phone call or email to confirm. If you browse the Service Letters from 35 and later you will find information about fitting them to earlier engines. Modifying babbitt rods for inserts has a mix of absolute horror stories and success stories - some really good reseach into which method you use would be appropriate. I have some articles on this which I've posted before and can again if you haven't seen them. The conversion that requires the rod bolts to be notched for clearance is certainly one that I'd stay away from.

Yes, most of the power increase was from the compression ratio. The other significant component was manifolding. The camshaft change in 1934 might have been a minor factor, but I doubt it, I believe the lift stayed the same and the same valves are used.

I suspect that the cylinder bore casting from a 36 might fit onto a 29 crankcase though there were lubrication systems changes that may or may not be an issue; changing the bore casting only solves the engine mount problem and would also give you downdraft carburetion and the 45-degree manifold mounts that gave larger ports for better breathing.

Keep us posted, please.