Wiseco Piston/Wall Clearance

[38racing]

What would you recommend for piston to wall clearance for lightwieght Wiseco pistons. Lateral gas ports on the bottom ring only. Does the .005 per inch of bore rule apply to metric rings when gapping them? Last question, what do you recommend for clearence for rod and main journals. Both are .010 under. Use to use stock specs. and I've been told these are to tight but no one has been nice enough to suggest anything different. Thanks for the help.

[ATOYOTA]

Your machinist controls all those dimensions. anyone who builds engines knows what clearances need to be for race specs. on a crank you want on the upper end of oem spec clearance and +.0005", so you have the machine shop tell the guy running the crank grinder to go to race clearances.

When a cylinder is proplerly bored, it will come out correct for the pistons. The pistons are manufactured with the correct dimension to provide the correct clearance on a correctly bored cylinder.

Check with Wiseco on their recommendations for top ring end gap. Forged pistons can run tighter end gap then Hypereutectic.

[84Dave]

I've run WiseCo pistons in my Pro-4 Ford 4-cylinders for decades. Measure the diameter of the pistons @ the tip of the skirts. Then add .004". That number should be the finished cylinder-bore size. Rod & main-bearing clearances? On my 8500+ Fords, I use .002"-.0025" on the rods & .0025"-.003" on the mains. You indicate lateral gas ports on the BOTTOM ring?? That statement doesn't make sense to me. Lateral gas ports should be used in the top ring land only. And your ring end-gap will depend on the number of lateral ports and the top dimensions of the piston in the ring-land area. -Dave-

[38racing]

Yes Dave you are correct about the ports. Please forgive my ignorance as I got a couple of things mixed up. The pistons just have metric rings attached to stock 5.2 rods. I also forgot to mention that it is a 2.3 Ford. Thank you for the info. and I hope you're enjoying Utah!

[84Dave]

38........ if you have a decently stout race engine, you must be careful with the top ring gap using lateral gas ports. Why? With lateral ports, the top ring picks up more heat than with no ports. My personal example: 2.0L SOHC Ford, 13.5:1, dual side-draft 50DCO Webers, dry-sump oiling, 231 HP & 8500 peak rpm. Before I began using gas ports, my standard rule for ring gap was .0055"/inch-of-bore. Both top and 2nd rings. I used the same rule the first time I used lateral gas ports on a high-speed 1/2-mile paved oval. Bad ju-ju! 25 laps into a 75 lap race, the engine began to miss terribly & we shut it down. The cause? The top ring butted, lifted the top ring land, and cracked a chunk out of the piston top. Destroyed all (4) pistons in the engine. One additional point of info. I was running 5.7" rods & the ring stack was highly compressed on the pistons. PLUS...... there was only .150" of aluminum between the top of the ring land & the piston crown on the WiseCo's. So the top ring picked up a lot of additional heat, being so close to the piston crown, and using the gas ports. My gap rule was immediately modified to .007"/inch-of-bore for the top ring & remained .0055"/inch-of-bore for the 2nd ring. Problem solved! Have not experienced any problems with ring-butt since. -Dave-