help!! :piston ring gap: help!!

[Spector_Supra]

i need to know what i should set the gaps in #1 and #2 rings.

final cylinder bore is 3.3099
pistons are 3.3070

 

[gaboonviper85]

Cylinder bore and piston OD have little to do with ring gap....the tsrm tells you what the ring gaps should be

 

[gaboonviper85]

Here let me do the hard work for you.

http://www.cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?S=EM&P=79

 

[IJ.]

Cylinder bore and piston OD have little to do with ring gap....the tsrm tells you what the ring gaps should be

bzzzzzz wrong the bore diameter has EVERYTHING to do with the end gaps

4 thou per inch of bore top and 5 thou per inch 2nd.

If you're going to run it hard at high boost I suggest adding 2>3 thou to the total to prevent it nipping up.

 

[gaboonviper85]

bzzzzzz wrong the bore diameter has EVERYTHING to do with the end gaps

4 thou per inch of bore top and 5 thou per inch 2nd.

If you're going to run it hard at high boost I suggest adding 2>3 thou to the total to prevent it nipping up.

What? Can you go into more detail of what exactly you mean?

 

[IJ.]

3 inch bore engine will need 12 thou end gap on the top ring 15 thou on the 2nd ring. (3 x 1 inch @ 4 thou = 12 thou)

This is an age old formula that my Father taught me 35 years ago, as I said for high output engines I add a couple of thou as they can close the end gap if ran hard/hot/lean.

 

[wiseco7mgt]

Does this calculation suit both chrome moly rings and cast rings or do they both expand at a different rate? Sorry if it's a silly question.lol

 

[IJ.]

It's a near enough thing Pete and will give a "safe" end gap with either, it used to be the other way around with the larger gap on the top ring but with modern thin rings they tend to flutter as you get a cushion of gas between the rings so now you use a larger gap on the second ring so it can vent the gas that get's by the top ring.