max allowable bore

-
P

prodart340

Well-Known Member
Joined
Oct 27, 2007
Messages
668
Reaction score
2
Location
middleway,wv
just picked up a standard bore 340 and was wondering if anyone could tell me the maximum allowable bore size for standard without getting "to loose" in the cylinder
 
So are you asking the maximum piston skirt to cylinder wall clearance, measured at the bottom of the cylinder bore, before the piston starts rattling around.
 
I've seen folks run as high as .010"-.015" on dirt track motors.....and they NOT smoke and had great compression. You gotta keep in mind, though that sounds like a lot....and it is way outta spec, you ain't talkin about but .005"-.0075" on each side. ....and yeah, they can flop around some and crack skirts on a cast piston. I wouldn't think twice about reringin one at .010" wear if I was on a tight budget. Some of them loose motors are some of the best runnin ones you'll ever build.
 
after hitting the cylinders with a ridge reamer, I get a cylinder size of 4.045, so is that too loose for a 410" build?
 
StrokerScamp said:
.............. run as high as .010"-.015" on dirt track motors...... Some of them loose motors are some of the best runnin ones you'll ever build.
Click to expand...

Yeah, but I bet they won't last long on the street that way. And don't forget TAPER. A lot of taper will work the rings to death. A quick look in my old '70 shop manual shows these factory specs:

stock bore 4.040-4.0420

max out of round .005

max taper, .010

Piston land clearance .019--.027

Clearance, top of skirt .0005-.0015

These of course for stock factory pistons
 
prodart340 said:
after hitting the cylinders with a ridge reamer, I get a cylinder size of 4.045, so is that too loose for a 410" build?
Click to expand...

I'd run hell out of it if it was mine.
 
67Dart273 said:
Yeah, but I bet they won't last long on the street that way. And don't forget TAPER. A lot of taper will work the rings to death. A quick look in my old '70 shop manual shows these factory specs:

stock bore 4.040-4.0420

max out of round .005

max taper, .010

Piston land clearance .019--.027

Clearance, top of skirt .0005-.0015

These of course for stock factory pistons
Click to expand...


I wasn't puttin up a arguement....just sayin what I have seen done.
 
StrokerScamp said:
I wasn't puttin up a arguement....just sayin what I have seen done.
Click to expand...

Neither, I. I've "pushed the limits" a little here and there. Biggest things I do is ignore valve guides, just put in better seals and run 'em.
 
67Dart273 said:
Neither, I. I've "pushed the limits" a little here and there. Biggest things I do is ignore valve guides, just put in better seals and run 'em.
Click to expand...

Yeah....I've pulled that one before too. I know the "right" way to do stuff is the right way.....but sometimes you just gotta do what you gotta do. Sometimes though, I've done stuff like that and it's ended up bein some of the best engines I've ever done. The most important thing when you assemble one is doin it CLEAN. They will last surprisingly long if just that is done.
 
I told you. In "MY" personal opinion, I would run hell out of it.
 
You must log in or register to reply here.
-

Back
Top