Piston Oil Ring Gaps

[acenewman]

I was checking the ring gaps on some hasting rings a couple nights ago and the oil ring gap was 0.024 which is way above all of the specifications I have seen. anyone else run into this? Is it ok to have oil ring gaps that big? The top two rings were right where they were supposed to be. Chris

[d.j. moordigian]

Chris,

I assume you are dealing with fresh holes? If yes, then it's normal.

Dudley

[Bob C]

Here is Hastings info http://www.hastingsmfg.com/ServiceTips/ring_gaps.htm

Bob

[acenewman]

Yes this a freshly honed block.

[d.j. moordigian]

Chris,

Is this a freshly bored block? Or are they used holes with a hone job?
It does make a difference.

[acenewman]

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freshly bored and honed for new pistions. Im setting the ring depth by using an upside down pistion inserted till the ring grooves are no longer visible.

[d.j. moordigian]

Chris,

Your OK, have at it. BTW, I use a 4" adjustable square too square the rings,
works good,.....for the last 42 years.

[acenewman]

Call me crazy but 0.024 just seems like an awful lot. I have 3 different references calling out 0.008-0.010. You have run oil ring gaps that large with no ill effects? Don't want to go to the expense of a rebuild and then have an oil consumer on my hands.

[d.j. moordigian]

Chris,

Yes, don't forget that the second ring(of a 3 ring set) is also an oil control
ring/compression ring. If you put the second ring in upside down, it will
pump oil! Also, the 2nd ring should have a chamfer on the bottom inside or
chamfer ledge on the bottom outside or a taper on the outside.

Dudley

[James Rogers]

I just got done re-checking a set of rings in a motor that wanted to dribble oil out the filler tube. Bottom gap is .025 and the second and third (middle and top) rings at .016. I was taught as a rule of thumb to always allow .004 for each inch of piston diameter.

[James Rogers]

D.J., my hastings center rings have a chamfer on the inside bottom and a dot on the top to designate direction. The top ring can be installed either way and has no taper or chamfer.

[d.j. moordigian]

Damn.....James you got me, I said the 2nd ring wrong! The chamfer is for the ring
too flex and scrap the cylinder dry.

Yes, I use the .004" per bore unless it's a file fit set or the engine has Hyperutectic
pistons or SS top ring.

[acenewman]

Spoke to the tech support folks at Hastings today. They said the oil ring gaps should fall between 0.015 and 0.055. Which is in line with SAE specifications for modern style rings. I told them mine were at 0.024 and they felt that was perfectly fine. Also called Hart Machine Service in Ohio who did the work on the block for me and they had the same feedback. There engine build guy said they have used those same rings for years with no issues. So finally I should finish assembling my short block this weekend.

[d.j. moordigian]

Hay......would James and I give you a bum steer? The only thing else I will say is,
Hastings' figures...015"-.055". The tight side doesn't bother me, but, the .055"
is getting a bit much(for me anyway).

The best part about all this is, at least your looking at the parts and checking
things and fitting them!

Dudley

[mach0415]

Originally Posted by d.j. moordigian

Hay......would James and I give you a bum steer? The only thing else I will say is,
Hastings' figures...015"-.055". The tight side doesn't bother me, but, the .055"
is getting a bit much(for me anyway).

The best part about all this is, at least your looking at the parts and checking
things and fitting them!

Dudley

Yeah. Its scary to think that there are people who do a rough measure of the bore, order rings, and install without checking ring end gap of the new rings. I just got an NOS set of rings for a Plymouth flattie and will be filing them to match fit them. Had to do it on a '29 banger also. The blind whim throw and go method can result in broken rings, scored bores, or even worse...

Its good to measure everything several times to be sure parts are correct. If done right, hopefully the inside of the engine will never see the light of day again

[acenewman]

You said it mach0415 "If done right, hopefully the inside of the engine will never see the light of day again". I love building engines and all, but I don't want to be going back into the same one if I haven't worn it out from extreme milage acumulation. I have the top and second ring gap tolerances from Hastings as well but I left my notes on my desk at work. I will post them next week when I get back to work. The only one I memorized on the spot was the oil ring. Off the top of my head I want to say they were like 0.015-0.020?

[mach0415]

I just did a '29 and got Hastings rings from Mac's. The specs they sent were within the same info as in the Mac's catalog:


Comp ring top .012" - .015"
Middle ring .010" - .012"
Bottom ring .008" - .010"

[James Rogers]

Originally Posted by mach0415

I just did a '29 and got Hastings rings from Mac's. The specs they sent were within the same info as in the Mac's catalog:


Comp ring top .012" - .015"
Middle ring .010" - .012"
Bottom ring .008" - .010"

Suppose you put a set of new hastings rings into a bore that has just been reconditioned and honed and find that the top and second ring gap is .017 and the bottom is .026? How would you rectify this out of your specified clearance problem?

[mach0415]

Originally Posted by James Rogers

Suppose you put a set of new hastings rings into a bore that has just been reconditioned and honed and find that the top and second ring gap is .017 and the bottom is .026? How would you rectify this out of your specified clearance problem?

I would stick to the .004" per inch of bore diameter rule. My assumption is that the specs are a range on the minimum, rather than a range of minimum vs. maximum, since there is a suggested maximum of .055" if what Hastings said is correct. Although, I agree that .055" seems waaaay too much. if there is too much gap, then blowby increases, causing oil to come out places it shouldn't. Therefore, does .026" fall into that range of minimum, vs max before replacement is necessary? or Do we have another issue here?

Being the fact that you do all your machine work, only you know if your machining specs are spot on with bore diameter and taper accuracy. Others have to rely on local machine shops. There is shoddy work done, as I have had to send blocks back to have re-align bored because of discrepancies, as well as boring mess-ups. Needless to say, they are not used anymore.

It might also pay to double check accuracy with another set of rings to see if there are quality differences from part lot to part lot. Not speaking of Hastings, but budget parts are budget quality as well.

One last thought...if really worried about excessive gaps, an arguable farmer fix would be to go up a .005" rings size (if it could be found) and file fit to the desired spec if it also matched the piston.

The specs I did on one recently was on a block that had been machined at one point, but at some point had low compression, due to stuck rings. The aftermarket pistons have split skirts, and the ring tension was very low with considerably sharp edges, indicating serious wear...ahem, not to mention .055" ring end gap .
The bore taper was about .003" and was still round. That's where I ended up a little over on the higher end on the top ring. After a light hone and a remeasure, new .070" rings was where it was at upon measuring diameter. I did file fit some and others were slightly above the higher end of ring gap specs.

Here is a Hastings link to checking compression rings

http://www.hastingsmfg.com/ServiceTips/ring_gaps.htm

[acenewman]

FYI, found my notes from my discussion with the folks at Hastings. They said the tolerane range for the 1st and 2nd ring should be 0.012-0.022. Same for both rings. And of course as I mentioned before 0.015-0.055 for the oil control ring.