The spec for my pistons (Endyn RW) calls for .0022". The machinist who is boring/honing my block said that sounded a bit on the tight side. I'd like to run the clearance as tight as possible to increase ring seal life.

As a side note, on my direct drive kart engine, I ran the clearance as tight as .0005". However, that thing has no clutch and has an RPM range of 2000 to 18000 rpm.

Sonny

 

i dont have a clue what the clearence is but do you think that you could record your kart @ 18,000 rpm? That would be sweet. I dont think I've herd a engine rev over 9k.
Blaze

 

I run piston to wall clearances @ .0030" - .0035"

 

You can look here for some cool shifter kart videos. They "only" rev to about 14k though.

http://www.ekartingnews.com/media/main.html

Some of the Italian Formula A engines rev to 23,000 rpm+. That is necessary because they run without a clutch and have no gearbox.

Sonny

EDIT-The link has been changed, so I updated it.


[Modified by Sonny, 10:12 AM 7/17/2002]

 

Some RC car engines will run up to 30,000 rpm's.

 

Hey Louis:

Good to see that you're still around. The machinist was telling me generally, he shoots for about .0010" inch of clearance per 1 inch of bore size. My bore is 75.5mm = 2.97 in = about .0029 of clearance. The SR20 is an 86mm bore, no? The same logic would yield .0034" of clearance, so I guess that's about right.

With the 2 strokes, I always had the best luck with running the clearance as tight as possible. The ring (only 1 ) seal would usually last a lot longer although I did stick a few pistons by getting too crazy during break-in.

Sonny

 

I race RC cars....those little engines scream like no other.

Do you race Bryson?

 

Of course I am still here! I think Nissan and Honda specs call for .0001" - .0005" piston to wall clearance in most cases. The SR20 is an 86mm bore from the factory.

 

Looking at the suggested and the factory specs- why is there such a difference? .0001-.0005 from the factory is a bit different than .003

Thanks
Ben

 

The factory pistons are cast and a have a high silicon content. This makes them expand less, but they are more brittle. Most aftermarket pistons are forged with lower silicon content, so they are less brittle, but they expand more.

Sonny

 

my RC ingine is a .21 ci. and run at 32k rpm and makes 2.1hp. at the crank.

 

The spec sheet that came with my JE pistons says to use a .0035" for the piston to wall clearance. Then continues to state that some applications may require more clearance.

 

My JE's paperwork call for .004'' for a B20B. I have heard this is too loose though. Any suggestions?

 

I have a custom turbo piston done at JE and their specs say .0045 or MORE

 

That's what I thought, just wondering if there was some advantage (other than necessity) to running greater clearance.
What gives with the JE clearance being double that of the Endyn? That much more expansion?

Thanks
Ben

 

yes, and Arias is even more ... as you can hear fromt he piston slap ... sounds like a diesel engine.

to orig poster: stick with 0.0021" clearance ... Endyn forging process is different than most aftermarkets.


Greg

 

Endyn just uses Wiseco blanks

 

earl, what do you mean by "blanks"?

art

 

Im running .0040" on my motor with ross custom pistons, yup sounds like a diesel engine, they're much louder than srp @ warmup

 

basically, he means the general shape of the piston. Endyn designs the combustion area, Wiseco does everything else.

 

Im running 0.005 with my 85mm JEs and they rattle a little bit on idle and decel. The more boost or nitrous your gonna run leave a little more clearance, or if you plan to do endurance racing. We have run 0.003 with JEs and they were fine on 20 psi, no problems as of yet and we have logged many miles.

 

Yeah, what John said..