aluminum verses cast iron piston

Dennis P · Mar 4, 2017

I am setting up to bore my blocks in a UTS (4 3/8). I was told to bore/hone it & end up with 2.5 clearance for aluminum or 4.5 clearance for Cast Iron. What are others doing?

buickanddeere · Mar 4, 2017

If both light aluminum and heavy cast are properly balanced , the bottom end has less stress with the lighter pistons.

mEl · Mar 4, 2017

(reply to post at 12:45:14 03/04/17)

I do not build that brand but have not used cast pistons in many years, pistons must stop and start at top and bottom of bore and the lighter the piston the less power is robbed in the process of starting and stopping weight. There are others who will disagree but IMHO reciprocating weight is a power robber. I any brand, upgrades from stock are almost always Aluminum.

forty40 · Mar 4, 2017

(quoted from post at 09:45:14 03/04/17) I am setting up to bore my blocks in a UTS (4 3/8). I was told to bore/hone it & end up with 2.5 clearance for aluminum or 4.5 clearance for Cast Iron. What are others doing?

.0025 for any type piston material at that dia is looking for black storm clouds on the horizon. The Waukesha service manual calls for. 003 in a 3-3/4 bore using cast iron pistons. A good place to start with forged aluminum pistons is .001/in. of bore. For higher comp ratios and basically a short warm up and then full load, .00125/in. of bore is a little safer.

535353m · Mar 4, 2017

when talking clearance totals,--is it per side or total ???????????

MikeJM · Mar 5, 2017

Piston to bore clearance is always represented as total clearance.

Dennis,
Whoever told you those clearances, I'm not sure I would take any advice from them. If you put your engine together with .0025 and aluminum pistons it will lock up in short order. .0045 with aluminum would be better. What/whose piston are you using? Forged or cast? Working or pulling?

Next important thing is ring end gap, not enough and the gaps touch and you will scuff the bore.

For example I run .012" on a turbo charged diesel with 4 3/4 forged pistons. About 600-700 horse.

BushogPapa · Mar 9, 2017

Total... or 1/2 for each side...!!

aluminum verses cast iron piston

Dennis P

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buickanddeere

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mEl

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forty40

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535353m

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MikeJM

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BushogPapa

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