[enkeivette]

.011

Originally Posted by MaxFlow

I agree that 1/16, 3/16 would make the day a little easier at that clearance. This is a drysump, lateral gasport. CP piston measure .5 on the skirt. Never measured but I think that would be .011 or so at the pin boss. CP recommends .004 and I usally go .005. Wouldn't pull vaccuum very well either if any.

I'm sure the ringpack works in this combination. But if you don't have the bores right your in trouble.

.012

Originally Posted by Ed-vancedEngines

Manley and JE used to use the old TRW Forging made from if I remember correct it is 4032 low heat expansion and very heavy alloy. Those could be run at suggested .0045 to suggested .006 and I have run them at as much as .008.

The older alloys used by Forge True, Arias, and others way back in the buggy days, was a 2018 alloy and it really expanded a lot. My Aries 2018 were recommended to be at a .012. There was a saying with the circle track racers that they would work ok if the race was not loger than 250 miles. Anything longer the pistons would just keep growing as the engine got hotter. I do not know if that is true or not.

Most custom pistons now are made with blanks of 2618 and the different piston mfg do recommend different clearances becuase the finished product is not all the same. I have seen .0065 to a .012 in different engines and applications.

You need to contact Manley with the work order number if one is on the bottom of the wrist pin boss and find out from them.

Ed

.01

Originally Posted by Racerrick

Agreed I see that as a dry sump or vaccum pump ring pack. I feel 3mm oil ring are overwelmed if clearences and finish aren't just right. The trw/manley forging that is the focus of this thread has a 1/16 3/16 setup. It will live quite nicely at .008 and IMHO trw race pistons require .0065 min clearence measure at the pin so .008 is where it will be in short order due to wear.
Here a lower budget (under 10,000) real life example
(the customer provided the heads, cam, intake and carb)

A 418 drag sbc with 175hp nitrous that I machined and built 7 years ago, started with .006 clearence. 2 years ago I replaced the arias pistons due to ring land failure with 1.345 c.h. 13-1 ross pistons, the clearence is .010 at pin centerline.
This stock 2 bolt 400 block with spacer bearings has 3.845 stroke, 4.160 bore, 5.7 rod, 850 carb, comp 300 street roller and rpm heads is in a completely original but fully caged 3800 lb 69 nova with no t brake, shifted at 6000 rpm it runs 6.55 in the 1/8 at 4000 ft elevation year after year. According to et thats a +650hp motor.
I'am currently trying to get the owner to ugrade his block, install 18 deg heads and a race cam. He says no way the combination is staying the same but he will change out the block cause the caps are walking big time.