bore/ ring question

[fastrthnu]

My cylinders are currently +/- .001-.004 2.578 inches. (approx. 65.5mm) My compression was around 135 -140 psi with 21cc domes. I doubt it would be a good idea to use the same rings, but the next size up is 66mm (.080 over) and I dont really need to bore though. would it be safe to just get fresh rings for 65.5mm pistons and just rune a quick hone in the cylinders to 2.578735" (65.5 exact)? Also thi is the cylinder cut, I didnt measure the pistons, becuase I got to many different numbers. I dont have a manual, so does anyone know what the correct clearanced size piston would be for this bore? thanks.

[FasterThanU90]

have u measured the Bore? is there still a little crosshatch?

 

*U want a .002" piston to cyl. hone will take .003" out of cyl.

Edited September 13, 2007 by FasterThanU90

[White06Shee]

When Yo uLook Into The Cylinder, on the walls you will see, almost scrath marks, but the cross hatchs has marks going kinda like a X. if oyu dont have the cross hatch marks, than i would just get it honed.

hope maybe this help.

[fastrthnu]

My bores are average +/- .004 2.5780" . A 65.5mm bore is 2.578735 and a 65mm bore is 2.55905". I was told when I bought the motor it was .040 over which is 65mm but its so close to 65.5 now like 65.35ish. But the guy also told me it had a hot rods crank and it didnt. Im not sure what size pistons are in it now. It does still have a cross hatch all the way down with no vertical scraping. I dont wanna punch it more if I dont have to, but I might. Im not sure. But again that is the bore size, not the piston, which is smaller by x amount that I dont know. also my left cylinder is only .001" out of round, and the other is .004 out of round.

[Bansh-eman]

if there is no reason to bore your jugs then hone them out and get a nice crosshatch back. there is nothing that says everytime you rebuild the top end you have to replace your pitons and bore it out. when most guys that race are constantly rebuilding motors they rarely have to bore a motor. they simply get new circlips and bearings as needed and re-ring the pistons.

Edited September 13, 2007 by Bansh-eman

[fastrthnu]

if there is no reason to bore your jugs then hone them out and get a nice crosshatch back. there is nothing that says everytime you rebuild the top end you have to replace your pitons and bore it out. when most guys that race are constantly rebuilding motors they rarely have to bore a motor. they simply get new circlips and bearings as needed and re-ring the pistons.

 

well yeah, I dont wanna pay for new pistons and to have em punched when they dont need it and loose life time on them on top of it all for .1 horsepower gain. What Im really after is a second opinion and a cylinder to piston clearance to make sure what I have is good and all I need are the bearing clips and rings. My problem is that I was told this motor was punched .040 over and Im reading about .007 from .060 over. Im going to reseqarch the numbers on these pistons some more so see if I can find out what the f they are.

 

 

8741C are stamped on top. thats it.

[FasterThanU90]

how did u come up with these numbers?? do u have a dial bore gauge??

[fastrthnu]

how did u come up with these numbers?? do u have a dial bore gauge??

 

calipers. my numbers are based on the largest reading. they read to 1/1000 of an inch.

[FasterThanU90]

calipers.. hmm ok. well u can probably get that out of round with a rigid hone im considering doing top end jobs

[fastrthnu]

calipers.. hmm ok. well u can probably get that out of round with a rigid hone im considering doing top end jobs

[fastrthnu]

calipers.. hmm ok. well u can probably get that out of round with a rigid hone im considering doing top end jobs

 

yea I know calipers arent the best for that, but I did several cross sectional measurements to make sure I got a concrete number.

[FasterThanU90]

yea u need to gauge it and get ur largest cyl. size check taper and out of round