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Author Topic: piston/cylinder clearance  (Read 2128 times)
Garrick Clark
Sr. Member
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Posts: 499


« on: January 10, 2016, 23:13:41 pm »

Hi guys.
I have a type 4 turbo motor using AA 96 mm pistons. I have had some trouble with scoring of the cylinders and the piston skirts.
I did overlook the ring end gap. Some rings only had 2 thou clearance. I have now had the cylinders honed and  got the piston skirts cleaned up. I now have 4 thou piston/cylinder clearance.
Is this enough for turbo use.
I think the pistons are hypers but not to sure as no info came with the kit.
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Air cooled Engine builder
spanners
Sr. Member
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Posts: 286



« Reply #1 on: January 11, 2016, 00:41:24 am »

.004" is acceptable provided taper, barrelling and ovality  is correct with installed torque values, the liners expand more near the top with heat and pressure, up to .008" is OK in the lower half, taper honing gets a blank stare these days, I presume you mean ring end gap, you were lucky with end gap at .002", tho they often come like that or even less from new, scoring tells me chrome rings, I like a radius on the ends to help with that, just a wet stone working.
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Best regards, spanners.
modnrod
Hero Member
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Posts: 795


Old School Volksies


« Reply #2 on: January 11, 2016, 02:11:56 am »

https://www.google.com.au/search?q=ring+end+gap+turbo&espv=2&biw=1578&bih=973&tbm=isch&tbo=u&source=univ&sa=X&ved=0ahUKEwiIu7m6yaDKAhXj3aYKHRYXAIgQsAQIJw#imgrc=E-lhbcbg2fFslM%3A
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Garrick Clark
Sr. Member
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Posts: 499


« Reply #3 on: January 11, 2016, 20:43:18 pm »

Hey thanks for the replies guys.
I did the oven test tonight. I put a piston and cylinder in the oven at 200 for 20 minutes.
My piston to cylinder clearance is 4 thou cold 2 thou hot. Skirt clearance not ring area
Am I right in thinking the hot clearance is too tight.
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Air cooled Engine builder
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