SMTA Firecrater Piston Trouble

wijd · Mar 3, 2009

I am rebuilding my SMTA and I pulled the pan off to find several chunks of piston in the bottom. Pistons 1 2 and 3 all have broken skirts on the side that faces the distributer. The other side looks fine on all of them. Has anyone else ever seen anything like it before? I thought it was unusal to have 3 pistons all broke in the same place on the same side.

Owen Aaland · Mar 4, 2009

That is completely normal. It is what happens when they get worn so they have too much clearance between the skirt and sleeve. I once overhauled an H that had seven of the eight skirts broken off.

Janicholson · Mar 4, 2009

Owen is correct, I would bet that if you slipped a long thin feeler up into the skirt to sleeve on the remaining "good" piston that it would measure more than .010" clearance at the top of the travel. This is plenty enough to allow the rocking of the piston to impact crack the skirt. The real miricle is that the pistons that were broken didn't wedge at an angle and seize the engine. JimN

Janicholson · Mar 4, 2009

Owen is correct, I would bet that if you slipped a long thin feeler up into the skirt to sleeve on the remaining "good" piston that it would measure more than .010" clearance at the top of the travel. This is plenty enough to allow the rocking of the piston to impact crack the skirt. The real miricle is that the pistons that were broken didn't wedge at an angle and seize the engine. JimN

Too Far Gone · Mar 4, 2009

Id say your sleeves are completely worn out allowing too much slop in there

SMTA Firecrater Piston Trouble

wijd

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Owen Aaland

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Janicholson

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Janicholson

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Too Far Gone

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