[Vascar]

What clearance should a high compression 455 have? What can the + or - be?

[Vascar]

What clearance should a high compression 455 have? What can the + or - be?

[Bill Boyle]

Oil clearance of .0020" on mains and rods provides adequate oil flow and cushioning. Your machinist should strive for this and you should demand it. Bill Boyle

[PONTIAC DUDE]

I would also try for .015 side clearance to keep the oil flowing as most HP engines I've seen wipe rods is attributed to expansion & heat. SD pump or M54F Melling. Later

[Vascar]

Bill,
My block had clearances of .0024 in the rear and numbers 4/3 had .0017 and .0018 and 2 had .0023 and one had .0019 Needless to say I'm not happy about it. I went back to him and asked him to make the closer to .0020 on all of them. Would I have had problems with my engine with the clearances he was trying to sell me
Thanks for all your help Bill, I'll get back to you and let you know the new clearances.

[77TA]

Isn't there a factory allowed tolerence ?
+ or - something ?

[Bill Boyle]

Vascar--first of all I'm not a machinist and don't profess to be one. Nevertheless, all machined parts have tolerances. The factory engineers set there's based on testing and experience passed down over the years. If you look at the acceptable tolerances from the factory, your specs probably fall, for the most part, within those parameters. Blueprinting attempts to meet specs more closely. While there may be a range, many times the middle ground of that range is sought. The .002 is pretty much in the middle. A slight variance, that is tighter, or larger, and I'm referring to ten thousandths, won't make any noticeable difference. As Dave Bisschop (SD Performance in Abbottsford, BC) told me recently, perfection is hard to come by, or words to that effect. The .0020 (2 thousandths) is a target for the machinist. If he doesn't get centered in the bullseye, that's pretty darn good--the tighter the grouping the better, as they say. Hope this helps.

[Bill Boyle]

Vascar--Oops, one other thing. I believe those specs comply with factory tolerances. You should have no problem with oil pressure and good lubrication. Bill Boyle

[Vascar]

Thanks Bill for the info. No wonder my builder wants to kill me. I went to my builder a couple of days ago and he said the same thing you just said, but I insisted on closer tolerances, and now he's going to go back over it and bring the number closer to .0020
I'll just buy him a bottle for the New Year and hope it smooths things over a bit.

[Bob Dillon]

VASCAR, I really think you're blowing bucks to tighten up or loosen the stated clearances here. All are within tolerance.
What is it you hope to gain? I don't think that either reliability or horsepower would come into play.
Comes a time when one just has to say "close enough." You're there.

[Vascar]

Bob It's like a food you've never tasted before. Someone tells you about it and you start to drool. Then you go out and get some just to be satisfied. Bill told me about it, then I just had to have it. I guess the more you know about something the more you want. I'll try to control myself.