Piston tolerance
Thread Starter
Intermediate
Joined: Apr 2011
Posts: 32
Likes: 10
Piston tolerance
Hi,
please help me a expert,
I live in germany and have a C 3, 1972, 454cui, no tuning,
I bought a kit at summit, FEM MKP613E300 Engine Rebuild Kit,
in this kit are piston Speed-Pro hypereutectic Pistons H661CP30, 4,280 "
The company wants the motor renewed to know from me how much tolerance the hole must have,
drive normal roads, no tuning,
Thx
Udo
please help me a expert,
I live in germany and have a C 3, 1972, 454cui, no tuning,
I bought a kit at summit, FEM MKP613E300 Engine Rebuild Kit,
in this kit are piston Speed-Pro hypereutectic Pistons H661CP30, 4,280 "
The company wants the motor renewed to know from me how much tolerance the hole must have,
drive normal roads, no tuning,
Thx
Udo
Race Director
Joined: May 2006
Posts: 18,734
Likes: 2,582
maybe I'm not understanding your question but the pistons are intended for a engine block bore of 4.280. The standard bore is 4.250 so you purchased .030 oversize pistons.
vielleicht bin ich nicht zu verstehen, Ihre Frage, aber die Kolben für einen Motorblock Bohrung 4,280 bestimmt. Die Standard-Bohrung ist 4,250, so dass Sie gekauft 0,030 Übermaßkolben.
vielleicht bin ich nicht zu verstehen, Ihre Frage, aber die Kolben für einen Motorblock Bohrung 4,280 bestimmt. Die Standard-Bohrung ist 4,250, so dass Sie gekauft 0,030 Übermaßkolben.
Last edited by MelWff; Jan 29, 2015 at 04:28 PM.
Thread Starter
Intermediate
Joined: Apr 2011
Posts: 32
Likes: 10
maybe I'm not understanding your question but the pistons are intended for a engine block bore of 4.280. The standard bore is 4.250 so you purchased .030 oversize pistons.
vielleicht bin ich nicht zu verstehen, Ihre Frage, aber die Kolben für einen Motorblock Bohrung 4,280 bestimmt. Die Standard-Bohrung ist 4,250, so dass Sie gekauft 0,030 Übermaßkolben.
vielleicht bin ich nicht zu verstehen, Ihre Frage, aber die Kolben für einen Motorblock Bohrung 4,280 bestimmt. Die Standard-Bohrung ist 4,250, so dass Sie gekauft 0,030 Übermaßkolben.
The question is how much larger than the bore, the piston must be
sorry for my bad english
Race Director
Joined: Jan 2000
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From: Corsicana, Tx
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The clearance is built into the piston. The piston is smaller than 4.280". So if it is bored to exactly 4.280", then the clearance "should" be correct. Hypereutectics use pretty tight clearances...just like any other cast piston..so it will likely be in the .0025" or less range.
The perfect way is to give the pistons to the machinist and let him measure them to be absolutely sure...but pistons tolerances these days are usually pretty good.
What clearance is recommended in the piston instructions? Should be something in there.
JIM
The perfect way is to give the pistons to the machinist and let him measure them to be absolutely sure...but pistons tolerances these days are usually pretty good.
What clearance is recommended in the piston instructions? Should be something in there.
JIM
Drifting
Joined: Jun 2010
Posts: 1,781
Likes: 15
From: Oxford Ohio
Have you had the engine bored to 4.280 or it that the size it was when last driven? If it has many miles on it at the 4.280 then you'll have cylinder wear. The holes won't be round any longer. I'm have the cylinders mic'ed to see how much wear there has been and maybe have the cylinders bored again. That would give you the best results.
Pro
Joined: Dec 2014
Posts: 699
Likes: 46
From: Charlotte NC
Not being a smart ***, but Speed Pro lists the piston skirt to bore clearance right there on the box. Mine was right on the end. Gives max and min. I like .002" but you can go tighter if you like. I've seen .0005".
