Piston rings and size . Help

There would be places here but they would be ordering and bumping up the price to cover. May as well do it myself and order direct. But you make a good point, I might just ring one other engine builder Ive dealt with during this disaster and see if he comes up with something ..
I just shot off an email to get the machinist to give me the bore measurement .. I'll let you all know what it is...
 
So you should be in the .010-.020 range for the gap.
The bore is sized a bit over spec.
.0015 x 3.14 = .0047.
So if rings where at .020 + .005 your at .025 still missing a few thousands in the equation.
 
OK something is not adding up then.. looks like the bore should be as Brian has there its .030 over, great . So why when I have two different .030 over rings [Grant - Hastings ] Im getting a .030 gap when they're sitting in the bore ..??? Im going out to the machinist this arvo I'll do it with them ..
 
If the measurements are correct you machinist has finished the bore .0015 bigger then it should be that gives you an extra .005 gap.
I can try and put a ford ringset in the ring gauge and see how it measures in real life...
 
Would it be worth getting some .040" over rings and file fitting them to suit?It sounds like the .030" rings are not going to work unless you decide to just live with the overspec gap. I looked on the hastings site for guidance and as stated above 10 or 11 to 20 thou is about right. 30 thou would be all right if it was a 5" bore!

Put it together, thrash the living daylights out of it and try and wear it out quick enough so you can have another go at it at +.060!

Mart.
 
NO Mart ! I don't want to be going through this again!
I'm just putting it down to learning... I'm going back tomorrow for further investigation.
 
You need to find a friend with some micrometers and find out exactly what you have. .030 ring gap is not going to hurt as much as you might think. You can go next oversize and fit all the gaps. Make sure there is enough because if not enough the gap closes when hot and will break the ring. The 0.040 will have a bit more tension, not sure how that will affect anything
 
Talkwrench said:
OK something is not adding up then.. looks like the bore should be as Brian has there its .030 over, great . So why when I have two different .030 over rings [Grant - Hastings ] Im getting a .030 gap when they're sitting in the bore ..??? Im going out to the machinist this arvo I'll do it with them ..
Click to expand...

They ( ring companies ) use to make rings in 2 different style of rings for the same bore size . For instance , if rering they had rings that would fit sad to .009 os . I'm not sure it would apply when bore but I've seen adds on e bay that list
.030-039 .
If it was me is file fit each . You've spent a lot and want it correct . A little more time file fitting the rings is worth the alternative . Just my opinion .
 
When using pistons that have not all carbon removed the rings drag. So little more clearance would do any harm. Go faster.
Make sure the rings are in line with wrist pins.
 
You need to know the exact bore size and the bores need to be straight
If the machine shop honed the cylinders on a Sunnen machine he should know if they are straight and he should know the exact bore size.
You mentioned gapless rings but most gapless rings are two piece and still have a gap so you need a bore size to order rings
For gapless rings call Total Seal or for regular rings call Hastings or Grant but I think gapless is over kill for a low compression flathead


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Just a "thought". Have you tried any of the other bores? Maybe the one you are using is the only one that was honed too much.
 
If I was to hold a top ring and close it, measure across would I get close enough to tell what oversize size the ring is? Or do rings have a certain gap built in..
 
The gap is built in, but if you are wanting to measure it that way just use a shim the size of the gap you are wanting to use. Using the gap width shim, measure across the ring. I think if I was going to do this, I would measure with a 0.010 shim, 0.020 shim & a 0.030 shim. No idea if any of this will work, never tried it. But might be worth a try.
 
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I was hoping it would be close enough Its really just to double check as I have a box full of NOS ring sets [to old to use] and most of them are just taped and written on. I got a top ring that someone had written .035 -.040 on and sure enough when in the bore it just overlapped and I couldn't straighten it in the bore.. So was going to try measure them to confirm and also the 'supposed' to be .030 sets I have, see what they come up at ..
 
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