Author Topic: High performance engine parts ID (Read 7537 times)

paulages · « **on:** March 11, 2011, 06:24:22 PM »

I'm going through an engine for a customer, with some good bits in it: RC 315 cam, alu retainers, hogged out intake ports, RC ENG lightened alternator rotor... and 65mm pistons of unknown manufacturer. Can anyone identify these:

The bores look pretty clean, but the clearances are pretty large.... .003" at smallest and .0065" at largest. None of the holes are more than .0005" out of round, but all four have .001" taper. Not knowing what they are, I don't know what the spec limits are though...

Anyone?

billybobobrain · « **Reply #1 on:** March 11, 2011, 06:36:33 PM »

I don't know what brand they are but I do know that forged pistons expand more then cast and Wisco 836 pistons specify .0002 clearance. My machinist bored mine out at .00015 and I have permanent mold cast pistons, So that seems a little on the large side to me, probably a cheap bore job.

Big Jay · « **Reply #2 on:** March 11, 2011, 07:16:45 PM »

Do they say RC or RC Eng up inside? If so, they would be Arias.

paulages · « **Reply #3 on:** March 11, 2011, 07:23:13 PM »

Quote from: Big Jay on March 11, 2011, 07:16:45 PM

Do they say RC or RC Eng up inside? If so, they would be Arias.

I expected they might be RC considering the other parts, but they don't say RC anywhere. They do say "240-SS" on the bottom of the domes.

I could see .004" clearances on forged pistons, but .005" and .006"? $:-\$

mick7504 · « **Reply #4 on:** March 11, 2011, 07:25:30 PM »

They look very similar to RC pistons.
Here are a couple of photos of some RC pistons (67mm) that are top gas ported.
Mick

paulages · « **Reply #5 on:** March 11, 2011, 07:37:33 PM »

Yeah, I'd say those are RC, considering yours say 250SS on the bottom. Thanks! Any p to w specs?

mick7504 · « **Reply #6 on:** March 11, 2011, 07:56:47 PM »

Quote from: paulages on March 11, 2011, 07:37:33 PM

Yeah, I'd say those are RC, considering yours say 250SS on the bottom. Thanks! Any p to w specs?

No sorry mate.
Have no specs at all.
Frank (754) may be able to help with that.

754 · « **Reply #7 on:** March 11, 2011, 09:39:14 PM »

They look a lot like an Arais set I have.

Would not be surprised if they are RC.

Contrary to what many have said on here, including Jay, if I remember right, it was hard to get anyone around here to bore & fit a hole to a forged piston at anything less than a thou an inch.. so it would not surprise me if someone said they were setup at .003.. moreso if the owner was a known-runthe#$%*outait rider! Nowadays, this is not done..

For years, I thought I had forged slugs in my 836cc. ran the crap out of it for years.. at times it had a long rest but when it finally had to come apart it was 25 years.. and the pistons had similar clearance.. cept I then found out I was running cast slugs...

(I had just come back from a 2 K ride!)

Look at it this way, if they still have taper, and you can find rings, grab another set of cylinders and have at er.... you may like that 315...

billybobobrain · « **Reply #8 on:** March 11, 2011, 10:59:48 PM »

I think I have one to many zeros in my numbers up there.

paulages · « **Reply #9 on:** March 12, 2011, 03:48:50 PM »

Quote from: 754 on March 11, 2011, 09:39:14 PM

They look a lot like an Arais set I have.

Would not be surprised if they are RC.

Contrary to what many have said on here, including Jay, if I remember right, it was hard to get anyone around here to bore & fit a hole to a forged piston at anything less than a thou an inch.. so it would not surprise me if someone said they were setup at .003.. moreso if the owner was a known-runthe#$%*outait rider! Nowadays, this is not done..

For years, I thought I had forged slugs in my 836cc. ran the crap out of it for years.. at times it had a long rest but when it finally had to come apart it was 25 years.. and the pistons had similar clearance.. cept I then found out I was running cast slugs... (I had just come back from a 2 K ride!)

Look at it this way, if they still have taper, and you can find rings, grab another set of cylinders and have at er.... you may like that 315...

I wish this were mine, Frank. My customer instructed me to just "make it right." However, a new set of sleeves and a new bore job is a fairly pricey fix, and I want to be sure before recommending it. The pistons look good though. I'll re-measure the clearances, but there is definitely .001" taper in every hole. Doable but pushing it, especially with .005"-.006" at the bottom of a couple of them. IMO.

754 · « **Reply #10 on:** March 12, 2011, 08:11:28 PM »

Used barrel 100 or less..
Boring/fitting 200 ish..
plus rings abd gaskets 130ish

vs new pistons /boring 700 ish at least.. unless you go cast 850s

if he does go new, try to get the pistons..

paulages · « **Reply #11 on:** March 13, 2011, 12:25:27 AM »

Quote from: 754 on March 12, 2011, 08:11:28 PM

Used barrel 100 or less..
Boring/fitting 200 ish..
plus rings abd gaskets 130ish

vs new pistons /boring 700 ish at least.. unless you go cast 850s

if he does go new, try to get the pistons..

I should amend my statement... pricey, a bit. Not as bad as new pistons. I think I have barrels, if not he probably does. We'd just be looking at the cost of boring. Like I said, I just want RC specs to make sure we get it right if we have to do it again.

Should I just assume that forged pistons should run closer to .002" new, .004" max?

Big Jay · « **Reply #12 on:** March 13, 2011, 06:40:19 PM »

RC used both Venolia and Arias. I thought all of the Arias had RC under the dome.

Both of those were 2618 material and can not run the tight tolerances that the 4032 Wisecos can. You first have to measure and see how much taper is left in the pistons before determining the clearance.

MRieck · « **Reply #13 on:** March 13, 2011, 06:48:05 PM »

Cyclex has that 915 kit and the Wiseco's weigh the same as stock pistons if I remember correctly. i can weigh them as I have a set on the shelf. They are a newer design.....a decent looking pistons. If the the guy is going to spend money on new sleeves etc I'd recommend getting rid of those old, heavy clunky pistons and use some more modern stuff.

paulages · « **Reply #14 on:** March 14, 2011, 12:28:47 PM »

Quote from: Big Jay on March 13, 2011, 06:40:19 PM

RC used both Venolia and Arias. I thought all of the Arias had RC under the dome.

Both of those were 2618 material and can not run the tight tolerances that the 4032 Wisecos can. You first have to measure and see how much taper is left in the pistons before determining the clearance.

I'll measure the taper this afternoon. Thanks, guys. Mike- I certainly agree, I'm just not sure how much he's willing to spend on the project. I'm pretty sure a new set of stock barrels will be free for him, then he'd just be looking at the cost of boring. Oh, how I wish everyone would go top-of-the-line...

paulages · « **Reply #15 on:** March 15, 2011, 12:37:21 PM »

Ok...

All four pistons measure exactly the same, with .002" taper. All four holes measure .001 taper, but clearances vary from .0045"-.006". I'm going to recommend new sleeves and a re-bore. Would you guys agree that the pistons seems fine, and what clearances would you recommend the re-bore be set to? I'm thinking .002" will be fine?

Big Jay · « **Reply #16 on:** March 15, 2011, 10:51:49 PM »

I think that would be too tight for a 2618 piston. You should try for .005" under the ring, so that would be .003" at the bottom.

paulages · « **Reply #17 on:** March 15, 2011, 11:48:11 PM »

Quote from: Big Jay on March 15, 2011, 10:51:49 PM

I think that would be too tight for a 2618 piston. You should try for .005" under the ring, so that would be .003" at the bottom.

That makes me feel like these holes aren't quite as bad as I thought, but there's so much inconsistency, I'd rather go for the new block. The tightest clearances right now are .00675" at the ring and .00575" at the skirt. The loosest is .00725" at the ring.

Thanks, Jay.

Retro Rocket · « **Reply #18 on:** March 16, 2011, 12:17:49 AM »

Quote from: Big Jay on March 13, 2011, 06:40:19 PM

RC used both Venolia and Arias. I thought all of the Arias had RC under the dome.

Both of those were 2618 material and can not run the tight tolerances that the 4032 Wisecos can. You first have to measure and see how much taper is left in the pistons before determining the clearance.

My RC engine has Venolia pistons in it.....

Silverback · « **Reply #19 on:** March 16, 2011, 02:28:01 PM »

I have a set of Arias pistons that look identical. They have 240-SS under the dome.

paulages · « **Reply #20 on:** March 16, 2011, 03:50:14 PM »

Quote from: Silverback on March 16, 2011, 02:28:01 PM

I have a set of Arias pistons that look identical. They have 240-SS under the dome.

Yeah, those do look identical. You don't have any paperwork on yours, do you?

Silverback · « **Reply #21 on:** March 17, 2011, 07:13:36 AM »

Unfortunately, no! I am going to have to find rings for these eventually as they are going in my next build. I can't remember the exact measurements on them at the moment, but I seem to remember them being just under 65mm. I had a few sets of 836 cylinders around and they were just undersized for all of them.

Edit: Fixed post per Paulages keen eye.

paulages · « **Reply #22 on:** March 17, 2011, 02:19:19 PM »

Quote from: Silverback on March 17, 2011, 07:13:36 AM

Unfortunately, no! I am going to have to find rings for these eventually as they are going in my next build. I can't remember the exact measurements on them at the moment, but I seem to remember them being just under 67mm. I had a few sets of 836 cylinders around and they were just undersized for all of them.

836 pistons would be in the 65mm ballpark, not 67mm.

Silverback · « **Reply #23 on:** April 05, 2011, 05:58:31 PM »

Out of curiosity, does anyone know where to get rings for these pistons off hand? Just melted my stock set, so it's time to put these in.

Lykowsky · « **Reply #24 on:** April 06, 2011, 05:09:49 AM »

Big Jay is right about clearences if them are made of 2618:

2618 performance pistons alloy has less than 2% silicon, and the low-silicon content causing the extra heat-expansion, these pistons have their cylinders bored to a very loose cold-fit, from what is written about clearances them should be fitted with 0.005.

Lykowski

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Author Topic: High performance engine parts ID (Read 7537 times)