new internals in old straight 8?

Some of you may know about my 1932 speedster project. two threads tell the tale:

http://forums.aaca.org/f230/32-buick-8-50-4-su-353115.html

http://forums.aaca.org/f165/1932-speedster-custom-2012-great-race-319610.html

I pulled the engine last week and it needs some work. Do any of you know if the later small block 8's internal parts can be worked into these early blocks? I'm thinking of the full insert bearings used from 1947, and if it's safe to bore to 3.0938 for later pistons (this block is already at 3.00, up from original 2.9375). Thanks, jc

Terrill Machine in DeLeon Texas can either convert your rods to inserts or trade you outright depending on if they have the correct ones in stock.

I did this with my 47 and it has worked out well.

As far as boring, can your machine shop do a sonic test on the block and tell you what they have to work with ?

Thanks, Bill - I dunno about the sonic test. It's all apart now and will get magnafluxed next. With the waterjacket plates off, it seems to me quite easy to actually MEASURE the cylinder OD's.

jc

Hey John, I am thinking this thread may have a better response from the Pre war group. Those are the fellas who may have this actual experience.

JC,

You might want to get with Dandy Dave Brennan (while he is still in NY state) to take a look at your engine. He can measure for wear & taper in the cylinder bores and determine if you can or should bore the cylinders. He can also check to see if you really need to modify the rods for insert bearings. Inserts have the same Babbitt material as the older poured Babbitt bearings; it's just a lot thinner on the inserts, and they are made to be replaced if that is ever needed. Poured Babbitt bearings are made with removable shims to compensate for wear over time. If your bearing journals are still round and you can still remove shims, I wouldn't modify the rods. However, I do recommend upgrading to aluminum pistons with modern rings to increase power by about 10%, use less oil, and make the engine run more efficiently.

JohnD - it is in the pre-war group as well (and speedsters). I need all the help I can find!

Thanks, too, Mark Shaw. I know I have to bore these guys (or sleeve them). There's signs of water (pitting) and a step or two at the ends of stroke! The reason for considering a change from Babbitt on the rods is that the crank journal will need at least a light grind, so the existing babbitt will be too large - they're shimless already. Aluminum pistons it is! I'm thinking the ones from the 248 ci engine from about 1947...

Egge Machine can supply new aluminum pistons for just about any size at reasonable cost...

Factory manuals say .060 is max bore. The parts manuals listed .020, .040, and .060 pistons. I wouldn't trust measurements from the water jacket side. There is no assurance that The bores are concentric with the castings. Sonic testing is the only way to be sure of wall thicknesses. If you rebabbit the rods, you can have them bored to match the reground crank journals. In my mind, the only advantage to bearing inserts on the 50 series engines is that bearings can easily be changed without having to pull the rod. They don't go out the top because the rod end is larger than the bore. Yes, in theory you can pull the rod and piston out the bottom, you will do a lot of cussing to accomplish this procedure.

Bob Engle

What final compression ratio will your modified engine be running? Or at least, what compression ratio are you aiming for?

Thanks, Mark - I have scoped out both Egge and Arias for custom pistons - I confess I was hoping to save a little green by fitting standards from the slightly larger, newer engines, but this may be the way to go.

Bob, there's the number! I have the "1932 Specifications and Adjustments' book - is there another factory manual? I don't find the overbore limit in the book I have.

Riviera, I have no specific CR target, just a solid running engine!

Thanks, guys. The engine is now in the hands of J and M machine in Southborough, MA. Super shop! Also there right now is a 1915 Buick 4, a 1937 Lincoln V-12 with huge aluminum crankcase and bolt-on iron cylinder blocks; and a fancy crank from a Voisin. My block is all tanked clean and magnafluxed (only a couple small exterior cracks). This won;t be cheap, but it will be done well!

Riviera, I have no specific CR target, just a solid running engine!

Ultimately, it is your final decision. But If it were up to me, I would go ahead and install the upgraded connecting rods with the insert bearings, especially since you are doing an overhaul anyway. I would do this for any engine that will have a final compression ratio of 6.0 to 1, or higher, that will be driven harder than an "easy-as-it-goes", sometime cruiser. The upgraded rods should have new bolts and also be magnafluxed for any incipient cracks. Perhaps Terrill Machine already does this.