1G Piston to cylinder wall clearance?

[thejollyrancher]

Hey guys,
I grabbed a used block. PTW clearnace is about .004 per side. twice as much as their should be. But the motor ran perfectly before and theres not a sign of slap. Is this a big issue?

Thanks!

 

[bling5tatus]

It probably won't be if you don't notice any abnormal wear. What kind of pistons are they? Forged pistons usually get a larger PTW clearance because of their expansion when they're hot.

 

[thejollyrancher]

It probably won't be if you don't notice any abnormal wear. What kind of pistons are they? Forged pistons usually get a larger PTW clearance because of their expansion when they're hot.

Stock pistons. Ya theres no abnormal wear.

 

[lasthope05]

If your total ptw clearance truely is 0.008, its way too huge even for an all out drag motor. What im shocked to hear is you have no scuffing or side wall damage as its close to a 0.010 overbore on standard pistions.

Run it if you want. I wouldn't. Factory limit is 0.002 total.

 

[thejollyrancher]

If your total ptw clearance truely is 0.008, its way too huge even for an all out drag motor. What im shocked to hear is you have no scuffing or side wall damage as its close to a 0.010 overbore on standard pistions.

Run it if you want. I wouldn't. Factory limit is 0.002 total.

Sounds like if Im not having problems, Im going to. Thanks for the input!

 

[arrowhead]

How are you taking those measurements, can you slide a.008, just on one side, and how far down are you taking your readings.

 

[bastarddsm]

You need a micrometer and a dial-bore gauge. If it's .004" total ptw, then I'd run it no problems, but be warned it will have some leak down, and blowby. But it will probably run fine.

 

[donniekak]

How are you measuring? Pistons are barrel shaped, so the top of the piston is much smaller than the skirt 90* to the pin. Sticking a feeler gauge between the top of the piston and the cylinder wall is a useless measurement.

As noted above, a dial bore gauge, and micrometer are needed.

 

[thejollyrancher]

How Im measuring is Ive taken out the piston, removed the rings, and fed it in upside down. With a ribbon feeler Im measuring the clearance near the bottom of the cylinder between the wall and the skirt.

In the absence of a bore gauge and micrometer, Ive read that this is a decent way to do it.

 

[arrowhead]

OK, but are using 2 feeler gauges to take this measurement to arrive at this clearance, that is 2 of 004.

 

[thejollyrancher]

Im using a single .008 gauge on one side. Thats all that will fit. Sorry for the confusion