Ring Gap for 95 incher

[admin]

What is the recommended ring gap for a street 95 inch engine?

Posted by: sleepneagle on Mar 26, 07 11:00:41 am

[admin]

That is dependant on the type of pistons and rings you are using.
Are they cast, forged, or forged hyperutectic pistons?
Are you using cast iron, standard moly or the more common reverse twist moly rings?
There is no definate answer, it is typically dependant on the piston type though.
The pistons should have come with instructions pertaining to proper ring gap.

Posted by: dls8 on Mar 26, 07 6:48:24 pm

[admin]

In other words from your prolonged discourse......you haven't a clue!

Posted by: sleepneagle on Mar 27, 07 6:48:39 am

[admin]

There is no one gap fits all. It is usually dependant on the pistons you are using.
If I tell you to use 0.007-0.020 in. gap (stock cast piston, stock bore) this would be way too much for a hyperutectic piston.
If I tell you to use 0.006-0.009 in. gap(one type of hyperutectic piston, stock bore, ((as best as I can recall)) this would be way too little for a cast piston.
Too much gap gives poor compresion and oil consumption.
Too little gap destroys the piston, rings, and cylinder.

Posted by: dls8 on Mar 27, 07 10:31:20 am

[admin]

Ok, I looked up ring specifics at work today.
According to Hastings you will need 0.004" gap per inch of cylinder diameter - minimum gap.
3 5/8 bore = 3.625 diameter
3.625 x 0.004 = 0.0145 ring gap for top and second ring.
This is just Hastings minimum specifications.
H-D has used Hastings rings for like forever...
I was all wrong about the Hypereutectic pistons.
They need as little as 0.0005 clearance between them and the cylinder. They actually need CONSIDERABLY MORE ring gap at the top ring. This is according to Keith Black piston specifications.
I am sorry for the bum steer on that!

Posted by: dls8 on Mar 27, 07 9:05:37 pm

[admin]

I have used the Bore x .004 method. HD states .020 end gap which seemed excessive. going to trust my instincts.

Posted by: sleepneagle on Mar 28, 07 10:25:06 am

[admin]

DLS8 is correct. .003 to .004 per inch of cylinder bore is a good rule of thumb, other things to concider are thickness of the ring,ring land placement,and intended use.As long as your gap isn't one extreme or the other they will work fine.A little on the big side won't hurt and is safer than being too tight causing the ends to butt and score the cylinder wall.

Posted by: PANCHO-HDRK on Mar 28, 07 5:03:44 pm

[admin]

Be careful on thinking that the specified top ring gap is excessive. If the pistons you are usind are hypereutectic, the top ring gap has to be bigger than normal.
Hypereutectic pistons do not expand as much as the other ones. That is why they operate at a much tighter clearance to the cylinder. They are made of a relatively new alloy.
Considering that the piston rings act as a heat sink for the piston, most of these pistons are designed to place the top ring land closer to the piston crown in an effort to reflect more heat back into the combustion chamber. The result of this closer ring placement is the ring operates at a higher temperature and thusly expands more. The larger gap is necessary to prevent the ring ends from butting.

Posted by: dls8 on Mar 28, 07 10:08:01 pm