Lotus Elan

QED piston ring gaps

PostPost by: tim22 » Fri Jun 16, 2017 4:07 pm

Has anybody fitted a set of QED piston rings at the minimum manufacturer's tolerance and able to give some assurance that this isn't risking rings butting together.

The rings are +0.030 in with ring gaps as follows:
- Top 0.008" - 0.016"
- Second 0.012" - 0.020"
- Oil 0.010" -0.020"

The top ring appears to be coated steel and the second ring cast iron, which must explain the min. gap difference.

The rings currently gap in the bores at the very lowest values for each ring, No apparent variation in bore diameter top and bottom or ovalling. I'm confident in the measurements and don't want to add tolerance for possible measuring error.

I'd like to simply fit them as they are but would probably be happier adding one or two thou just for peace of mind, particularly as 8 thou is only 2.4 thou per inch of bore, but not sure if this is necessary. I won't be racing the car but would like to know there is some reserve if I do push the engine a bit. QED advise that anything within the stated tolerances is fine - but would be more confident if anybody here could verify this from their experience?


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PostPost by: vincereynard » Sat Jun 17, 2017 8:54 am

I've just done the same and my ring gaps came out in the middle of the range. Consistent top and mid bore. As my bores are honed I expect the clearances to increase a touch anyway. Time will tell.

I cannot see how stoning another couple of thou. would be a problem if it makes you feel better.

BTW I found it much easier, whilst fitting the bottom ring, to fit the internal spring first then gently stretching the ring over it.
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PostPost by: Craven » Sat Jun 17, 2017 10:04 am

No problem whatsoever, stagger the ring gaps keep toward the sides. Make sure there is no step for the top ring to touch.
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