forge piston-to-wall clearance??

[allanr5gtt]

right where do i start?
i'm running je flat top forge piston's with steel liner's. as far as i know the forge piston's as rule of thumb has some sort of piston slap until they are up to temp . but my engine still has a slight piston slap noise even when the engine is all up to temp and has been running for a good 45 mins. the noise has been there since i have had the engine and i done a a few thousand mile and hasn't got any worse.
but i going to be replacing the head in the next month and i wanted to check what sort of claerance the piston's have. so i have had a look at the je's web site but it doesn't say what temp the piston should at be when checking for claerance and i'm a bit confused how to check for the clearance ? and the web site quotes .500" is that each side of the piston or with the piston to one side?

quote from the web site

All JE and SRP Piston kits include a piston spec sheet with a piston to wall clearance recommendation. Always measure JE and SRP Pistons at the recommended gauge point, usually .500" up from the bottom of the skirt or where otherwise indicated on the spec sheet. Subtract this dimension from your finished bore size to determine your .

thanks allan

[Scoff]

theres a big old difference between 45 mins of road driving warm and race track hot, so normal to slap while warm.

I don't think you ment 0.500" clearence, thats quite a lot :D

they are saying you need to measure the piston 0.5" up from the bottom of the skirt, then measure your liner bore and the difference between the 2 is the clearence. beware though, the piston skirt is not round, so measure in which ever axis JE want you to, normally at right angles to the gudgeon pin.

[allanr5gtt]

what sort of clearance should i be looking for?

[Scoff]

god knows, depends on what the piston manufacturer reccommends. it'll be around 5 thou I guess. I wouldn't worry about it, you should hear some real drag engine's, you'd think they were screwed.

[bernard]

I have the same problem as you allen, the only time I hear mine quieten down is when Ive driving hard on a track, in fact I think my pistons used to be yours originally scoff I brought them off steve. Could you give me any details of them I could see they were milled down?

[Rob@Backyardracing]

Even 5 thou is rather large for p2w.. I wouldnt even worry about it, our civic sounds like a 500,000 mile worn out taxi... if you do messure it, as said you need to messure your bore and the stated area, also you could see what the tapper is like, a good tapper would be around 4-5 thou difference for a charged lump..

[raj]

our civic sounds like a 500,000 mile worn out taxi...

oye feck off:cooter: dont knock the taxi with 500,000 miles on the clock! thats exactly what the avensis i drive is sitting at! the girls done us proud.:D :smokin:

[Scoff]

I have the same problem as you allen, the only time I hear mine quieten down is when Ive driving hard on a track, in fact I think my pistons used to be yours originally scoff I brought them off steve. Could you give me any details of them I could see they were milled down?

those ones are wossner with wossner rings, but with compression height dropped (it was actually raised compression in my engine because of my cylinder head). In an otherwise standard engine they should give something like 7.6:1 or so. I used them with hugely honed out liners, they really rattled. done a 12.1 sec SQM @ 116mph with those pistons :D

[Ashy]

Does anyone know what the internal diameter of a standard liner would be? and what sort of tolerances would be used by the manufacturer?

Just I’ve got a set of steel liners in the garage which are slightly scored, just wondered if I could open them up enough to clean the scoring up and them still be useable.

[car.crash]

mine dont seem to rattle. is this ok? as the other 2 engines i heard with forged pistons rattle when cold.

[5teve L]

What pistons are they, some rattle, some not as bad, would think they all rattle from cold a little though... Are you sure they are forgies :wasntme:

[5teve L]

those ones are wossner with wossner rings, but with compression height dropped (it was actually raised compression in my engine because of my cylinder head). In an otherwise standard engine they should give something like 7.6:1 or so. I used them with hugely honed out liners, they really rattled. done a 12.1 sec SQM @ 116mph with those pistons :D


Yeah they rattled in my engine till it was thrashed, they need the clearance for expansion @ high temps IIRC....