i bought a balanced rotating assembly from ebay last year.. it came with everything ring bearings crank rods pistons pins. well. i had my block all machined according to what i had and it would consume ALOT of oil.. it didn't leak any and wasn't seeming to burn any. i drove the car 1600 miles in three days and it need 3 quarts of oil.. this was a consistant 75ish mph.. nothing crazy. i figured that the kit came with moly rings and the block was finished with too course of a stone.. but i am no expert. the rings look like the were broken in. it ran fine though. i took it all apart cause something needs to change to stop it using oil.. now the question is what rings should i use.. i have speed pro power forged piston p/n L2256F30. as sugggested parts it shows a ring kit on summit. but i know that the rings need to have a certain gap because of the pistons being forged and i want to use nitrous on this motor. i cant find the spec on what the gap should be or on which rings, moly or cast will be the correct ring for what i want to do? any info would be very helpful..

 

You should probably get your block lightly re-honed to remove any glazing, or if you suspect your rings did not seat properly the bore finish may still be a little uneven. This should get you back to a fresh bore for new rings.
If you are going to run nitrous, then you should use a high quality (not cheap) moly ring. I would think .022-.024" for the top ring gap, and .020-.022" for the second ring gap. However, your new rings should have instructions and gap recommendations specifically for nitrous/performance applications with higher heat and cylinder pressure.

 

Speed Pro L2256F use the old style 5/64 rings and they are all of $35.00-$50.00 from anyone (Hastings, Seal Power, Pefect Circle, Grant ect) for moly. You can buy them at Advance or Auotzone. IF you are going to run the bottle you will have to open the gap up a little, as 500hp suggested .022 on the top and .020 on the second is a safe bet but be sure to check it against what the ring mfg's instructions say.
Your block absolutely needs to be checked with a dial bore gauge, before you put it back together. It could be the machine shops fault, like the bore is way out of round or has too much taper. A lot of things can play into exessive oil useage other than just the wall finish... unless your bore looks like it was honed with a brick at which point it's still the machine shops fault. Find out what grit stone they used. 400 grit will give the best finish for a street engine IMO but some machinest still stop at 280 grit for the finish (and as long as the cyl is the right size and has no taper 280 will work for 5/64 rings but the newer metric rings won't like it).
And finally if they used a tq plate it would be nice, but its not imperative on a street car. A bore that is strait, the right size and has the right RMS finish is the most important thing to long ring life and no oil useage.
Will

 

I had an old 350 block lying around that had some machine work done about 5 years ago, it had been bored 30. I had tore it down because I originally put the pistons in back wards, which made the rods misalign on the wrist pins. The motor made a raspy sound above 4000 rpm, so tore it down and never built it back. Until recently, I decided to build a 383 out of it. So I got it up off my garage floor, went to napa and bought a ball cylinder hone. I covered the hone in transmission fluid, stuck it in my drill and went to town. I order a Speed Pro piston kit from summit that came with rings. The motor runs great and doesn't use a drop of oil and has about 10.000 miles on it. I pull my boat with it almost every other weekend

 

well the reason i think that its the finish of the cylinder is because i just put together a lt1 and a waverunner motor that both had moly rings and the final finish was much much smoother than what i on this block.. the machine shop who bored this block was a good place.. he builds motors all day for roundy round racers.. so i know he isn't a total idiot, yet i don't think he did it without thinking... i think.. and as i said.. the rings were broke in, but there is a night and day difference of the finishes and i wouldn't have had any clue if i didn't see my other block done correctly.

 

I'm not going to knock your machine shop unless I see it, measure it myself and its screwed up beyond doubt, until that happens its nothing but speculation on my (or anyone elses for that matter) part. That said, anyone can make a mistake or forget something no matter how good they are.
But I digress, I'm here to SPECULATE... umm I mean help solve your problem. If you can actually see or feel the difference in cyl wall finish from your engine (which uses oil) to another engine you recently built (which don't) I think you found the problem, provided you used the same assembly methods and ring gap spacing (ie. where you placed the ring gaps in releation to the piston wrist pin not the actual measurement) on both engines.
Will

 

2256 pistons are a low-expansion alloy. When you bore the cylinder, make sure you have propper side clearance. TRW/speed pro will tell you the recommended side clearance. if the machine shop bored the hole too big (which is a common problem, because they think they are regular forged pistons which expand rapidly) than that is part of your problem.

What were your ring end gaps? did he line the ring openings up properly?

When the cylinders were honed, did he perform the correct cross-hatch? It shouldn't be 'smooth', the rings will never break in.

For nitrous use on a 2256 i'd go with around .020" gap on top and bottom for up to a 150 shot. You can bring it all the way out to .022" if you want to hit it hard with the juice, but the thing will have some blowby when not on the juice.

The 2256 piston runs the rings really high too, and they catch a lot of heat. I used 2256 pistons in every race motor I built for about 10 years, because they are good, cheap, and weigh right around what a stock piston does (604 grams) so you can build a budget race motor with them. But they all blow up the same way, they head up, ring rips the top land off, etc.

How far are the pistons in the hole? what thickness head gasket? what chamber size head?

-- Joe