Quote:
Originally Posted by Jim Brierley
.003" is not enough clearance, period!
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I totally agree with Jim! If you plan to use solid skirt pistons. (Like Snyder's and most other national vendors supply.)
Measured from actual piston size to actual bore with an accurate bore gauge, as Brent suggests in an earlier post, the clearance should be no less than .0035" from the widest portion of the piston and the rear cylinder would be better if it were a couple tenths more. If you plan to run hard occasionally, .004" clearance on all cylinders would be better. The rear cylinder is almost always the first one to seize when there is not enough clearance. The "Siamese" portion of the cylinders is the next likely area to seize as your engine exhibits. This narrow area between the cylinders is a hot spot in the walls.
The required clearance should be developed using only a rigid hone. Any hone other than a rigid hone will not give you a true cylinder and then it is important to know how to operate the hone. The dollars you plan to invest in a hone would be better spent at a competent engine shop. Let them get it right for you.
I can show you additional pistons that were installed with .003" clearance. They are stacked on a window sill where I maintain a "Bad Practices" wall of shame. If you need to see them, I will post some photos.
I know it is often hard to determine what advice you should ignore and what advice you should take from an open forum.
My advice as to determine which to follow in this case is to pay attention to the gents that build engines.
Jim Brierley has built lots of performance and general service engines.
Brent Terry has lots of experience with engines.
I have built over 180 engines in the past ten years and repaired a number of others that were not completed correct, including some with too little clearance between the pistons and cylinder walls.
Hope your project goes well. Good Day!