piston ring gap

Ronald Wendt

Registered User
I am having a ridiculous time with new piston rings having gaps within spec

I had my engine bored .030 over asking for minimal clearance from a local supposedly reputable shop. I don't have bore gauges

I ordered a set of Speedpro rings. they had a .0295 gap when we put them in the cylinders just to check before assembly. The original rings on the original pistons had a .021 gap. called Northern Auto where I bought them and they let me send them back. They called me and claimed they checked several sets they had in stock and they all had the same gap as the set I sent back. They sent me a set from a different build date. Same deal

So I called and they agreed to send some Hastings rings in exchange even though they were more money. They came and the gap was .032. Called Hastings direct to complain and they said to send them back and they would send a set guarenteed to be correct. These are .035. ~~~

I have to admit I wonder if the bores are not oversized, but still 4 sets of rings each with a different gap?

anyone else have this issue? Any ideas? What should the gap be?

I do intend to take the block back tot he machine shop and have them check each bore with a digital gauge to be absolutely sure they did not overbore

thanks

Ron
 
You'll need to find out if the shop bored the block to the # on the piston box or if they bored it based off of a measured piston. Sealed Power warns you not to measure the pistons instead just bore the hole to the size they tell you. This is critical. If they measured the pistons, then you can be pretty sure they over-honed the block. The pistons will still be in spec regarding allowable clearance, but the rings will be gapped big as you've noticed.

If I was in this situation I would simply have the top ring converted to gapless. Total Seal will do this for you (costs about $140 or so) and then you will not have any gap issues. I would not recommend overboring any further, and as far as I know there are no "file to fit" rings available for our motors. You could try filing a set of + .040" rings down but I'd be concerned about arc diameter once you go that big. Normally you'd want to build the motor to about .018 for normal use or .021 for extreme boost. The motor will run fine at .029 but it will have more blowby. Even when bored to exact specs as listed on the side of the Sealed Power box I normally see around .024" out of the box on the rings. Of course I normally always use different pistons and rings so I don't deal with this very often.
 
XR7 Dave

Curious, why would you not have it bored .040 now?

Not sure what I can get the machine shop to do for me, we sure told them what we wanted done. They assured me they use this type of piston all the time and knew what they were doing. Maybe I was one of the few who brought up ring gap too wide. We are going to take the block in and have them measure it while we look on

A set of $140 gapless rings is still less than a whole set of .040 pistons and rings

thanks again

Ron
 
Because if its too big already and you file them the gap will be even bigger. And as was previously posted no one makes a set of file to fit.
 
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