piston/cylinder wall clearance?

[400man]

would it be a bad idea to put a new high compression piston in a stock/origional bore cylinder? mine still has the stock piston, just wondering if it would be wise to just drop a high compression 85mm piston in it as is, or maybe just hone the cylinder? the only issue I can think of is there might be a tad too much room and have excessive piston/cylinder clearance and have it rattle itself to death in there.

[rubbersdown]

As long as its in spec you can just hone it and run a high compression piston.

[CJM]

Best bet is to have the bore checked before you do it to be sure and save yourself a headache later.

[sneaky11]

Hi! Just got a CP 12.5:1 87mm piston for my 400ex... it have a sheet with the honing roughness step-thru... but i didn't see anything about the wall-to-piston clearance...

My rebuilt is on neutral, if someone know what's the spec on that clearance for that kind of piston??? .003?? .004?

[sneaky11]

up! Need info... e-mailed CP, no answer... come on gearheads, lets u're wrenchs go!!

[mattl31]

Factory Service Manual says that piston to cylinder clearance is to be .0006" to .002". The service limit (worn) is .004".

[mattl31]

Factory Service Manual says that piston to cylinder clearance is to be .0006" to .002". The service limit (worn) is .004".

[sneaky11]

Thx dude!! I got my answer from CP... i need 0.0025'' of clearance

and they told me I can run on 93... not sure about that!!

[duroc825]

Originally posted by sneaky11
Thx dude!! I got my answer from CP... i need 0.0025'' of clearance

and they told me I can run on 93... not sure about that!!
Good luck with that 93 and did you upgrade head bolts? If not be prepared for blown head gaskets and stripped head bolts.

[sneaky11]

I'm pretty sure with a good pump/race fuel mix and a setup to keep it cool I'm not gonna blow anything on an OEM studs setup!!

Just have to find the right cam to go with it for less static compression build-up!!

[togup]

Originally posted by sneaky11
I'm pretty sure with a good pump/race fuel mix and a setup to keep it cool I'm not gonna blow anything on an OEM studs setup!!

Just have to find the right cam to go with it for less static compression build-up!!

Do a search before you make a decision on head studs

[bigballz400]

i have heard of this happening, i got a 440 12:1 ported and polished head, with OEM studs, ive never had a head gasket issue and ive replaced the base gasket several times never honed the cylinder, never broke the rings loose from it, im gettin pretty good at these top ends without break the rings loose lol

[togup]

Originally posted by bigballz400
i have heard of this happening, i got a 440 12:1 ported and polished head, with OEM studs, ive never had a head gasket issue and ive replaced the base gasket several times never honed the cylinder, never broke the rings loose from it, im gettin pretty good at these top ends without break the rings loose lol

Thats great that that yours hasnt crapped on you yet ,just thought I could possibly save you from future greif. I like building motors too so I want the most durable engine I can build so problems are less likely to happen due to a smart build.