40 Olds

Ok, I have a 65 A block in a 1940 series 90 that I picked up in May 2011. I am presently rebuilding the vehicle and added some goodies to the block, ie, Edel performer intake, 650 cfm holley, unilite distrib, hot coil,and some other amenites. Engine was running smooth but had some blowby coming from breathers and pcv. Yesterday did a comp check and #2 had 180,4 had 170, 6 had 160, 8 had 160.1 had 150, 3 had 130, 5 had 0 ,7 had 120.
After head removal on odd bank i found a groove that was in #5 cyl that ran up the cyl wall about .015 deep. Now i'm thinking broken ring is the culprit. Question is how far has anyone bored a 425 block. I know .060 is claimed to be max but has anyone gone further? Is the odd bank conducive to this much wear on these engines or may there be another issue with the crank causing that wear? Any info is appreciated.

GAOldsman

First I'd like to welcome you aboard the best Oldsmobile site on the planet. Second I've personally never owned a 425 so the 425 experts will have to chime in on how much you can punch out of it. I do know you can have the one cylinder sleeved if need be by a reputable machine shop (preferably with 20+ years experience) I've heard both good and bad things about sleeving an engine, but since it isn't the original engine in your '40 and your going to need to rebuild this one or buy another to rebuild I personally would see what it would take to rebuild that one first. The machine shop should give you a free estimate on price and how far it needs to be punched out either way, if it is disassembled. Just my .02

Scot

joe_padavano

The LIFTTER bank angle has nothing to do with cylinder wear or the reciprocating assembly. The cylinders are at the same 90 degree angle as any other Olds V8. The cylinders should have enough meat to bore more than 0.060, but you need to sonic check to verify no core shift in casting.

64Rocket

If it was me, I would find a 455 block and transfer everything over. If the 425 is stock bore, use a 455 block that is in good shape and can use only a scratch hone. You will have a better choice of cams. If the piston is in great shape re use it.


Gene

40 Olds

I broke it down sent it to Mach shop and rough bore was just completed. We saved the cyl and only need .030 over on it so block is .030 over. Waiting on pistons from Mondello to finish bore and then balance everything up. Sent 400 trans to shop and had it completely redone , ready to pick up today. Now it's wait for block to get done. Went with flat top pistons with valve relief. After all is said and done should be pushing close to 540 hp. Getting antsy now,

Rickman48

Hope everything works out - since Joe sold the shop, Mondello's in California has gone pretty much down the tubes in price, quality, and customer service!
And since he passed away, haven't heard anything about the other shop.

64Rocket

In the past, the "Paso Robbles" shop had taken 455 pistons and milled the tops off. Which made the top ring land to short, and the pistons all warp on the tops after only a few miles. When you get them make sure you have at the very least .200 from the top of the piston to the top ring.

Gene