Hello. I'm currently rebuilding a 425 Superrocket from a 1966 Olds Mobile Toronado.
Could someone please tell me what the typical clearance is between the Block wall and the piston, and how large is the clearance for piston rings to be at 0.020 oversize? I need these two pieces of information to make it reasonably accurate.

thanks Wojtek and greeting from Germany

 

QUOTE=Jelonek;1651145]................. 1966 Oldsmobile Toronado................the typical clearance is between the Block wall and the piston ..................... the clearance for piston rings to be at 0.020 oversize? ...........[/QUOTE]

Are you using cast or forged pistons?

 

The NEW pistons will dictate the bore size AND final finsh SIZE of HOLE and grit of stones to hone the critter
AS WILL the ring material (Cast or Moly)
And END GAP For Rings Checked and File Fit If Needed

 

Sealed Power - E243K20 - Piston Rings - Performance - 4.145 in Bore - Drop
In - 5/64 x 5/64 x 3/16 in Thick - Standard Tension - Steel - Moly

the block is bored in the garage of my engine-specialist to new cast pistons 0.020" and I cam move it with a one hand, with and without the crankshaft but with the pistons ring is this very, very tight
We have a Clearance piston to wall .003, .... is that correct?
how can I check I if I have cast or forged pistons , on the bill I have only " 425 Olds pistons 020"
Thanks

this is a wonderful and powerful engine, I won't to get it again running

 

do you have make and part #of the pistons..??
Take a picture of the top face and the underside where rod goes ANY casting numbers there..?? Top may also have numbers to ID them

With MOLY RINGS the bores need a "finer" hone done on the cylinder walls when finished

 

this picture .. only what I have

 

 

is that cast or forged ?

 

Those are cheap cast pistons.
Correct piston to wall is built into the piston. Are you honing it with Sunnen or similar machine or a rigid hand hone?

 

How are you measuring the .003 " The factory clearance is .0008 to .0012 but a little bit loose will never hurt anything. Most pistons will have the specifications on the label on the box. Is there anything there ? It is normal to be able to move the pistons in the bore without the rings.

 

Hallo everybody and thanks for help
The pistons weren't cheap; they cost a total of 700 $ , and they were selected by a specialized company like Rocket Racing Performance in Milwaukee for the crankshaft, the engine block, and everything else , pistonsrings too.
We prepare the engines here in Germany either with Simens , Bosch with instruments, with lasers and precise technology. It looks really spaced out.
As I said, I can't tell you the entire system; the problem is Not turning without pistons. Once they're in, it's almost impossible.
greeting

 

I think your pistons are probably from Egge. If so the clearance is .0025" So your .003" is fine. I would rather have a little more clearance than not enough.

https://egge.com/product/egge-piston...a_oversize=020

Did you check the end gaps on the rings ? Those rings are old school thick rings and if you are comparing them to modern engines it will seem to be very hard to turn over.

 

Depend on your definition of cheap
https://egge.com/product/egge-piston...a_oversize=020 $689.87 from Egge.

 

That are my pistonsrings
fit to file what we made …

 

Those should be the correct rings. Did you file fit them ?

 

Of course

 

What type of lubrication do you have on the cylinder walls ? I typically wipe the cylinders down with automatic transmission fluid and then put a light coat of engine oil on the pistons and rings.

 

I guess it is very hard to answer without being there Those older engines with the the thick 5/64 rings can seem very hard to rotate compared to new engines. I would imagine you would need a 1/2" drive ratchet with a fairly long handle. How did it feel with just one piston in ?

 

Yes you are right. It is a very difficult to make a decision. I hope to be in the garage in two days then I can check everything once more time now we have free pistons with rings and this is very very tight and very heavy to turn the engine

 

Agreed. But their stuff has gotten ridiculous. A DSS forged piston is only $150 more, with a better ring pack. Night and day difference. Just saying.

 

they have no pistons for my car - there is no my specification sorry

 

The pistons in the link should be correct for yours ? There must be some type of part number on your pistons somewhere or on the box. If not get in touch with the guy that sold them to you and find out.

Either way I do not think the clearance you have is the cause of the engine being hard to rotate.