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FOUND RB pistons

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68LAR

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I need a set of .030" over 440 pistons. The skirt diameter has to be 4.344". Stock 1.09 pin size. Prefer floating pin, but not a necessity. Flat top with valve reliefs. Most aftermarket pistons measure 4.35". They won't work. The block has just been bored to 4.35".
 
I need a set of .030" over 440 pistons. The skirt diameter has to be 4.344". Stock 1.09 pin size. Prefer floating pin, but not a necessity. Flat top with valve reliefs. Most aftermarket pistons measure 4.35". They won't work. The block has just been bored to 4.35".
I think I have a set that are press pins on good 906 rods removed from a great running engine. I’ll do some looking yet this weekend
 
I think I have a set that are press pins on good 906 rods removed from a great running engine. I’ll do some looking yet this weekend
Thanks. Please make sure that the skirt diameter meets what I am looking for.
 
Thanks. Please make sure that the skirt diameter meets what I am looking for.
The diameter of the skirt will be based on the piston material and the piston to wall clearance intended for that material and application. If you’re at 4.350, you’ll be fine with anything made to run at that finished bore. A 2618 alloy forged will probably want .0040 to .0045 clearance. A 4032 will run a little tighter. A cast or hypereutectic will be much tighter.
 
The diameter of the skirt will be based on the piston material and the piston to wall clearance intended for that material and application. If you’re at 4.350, you’ll be fine with anything made to run at that finished bore. A 2618 alloy forged will probably want .0040 to .0045 clearance. A 4032 will run a little tighter. A cast or hypereutectic will be much tighter.

You don't understand. I had a block finished bored to 4.35" to match a set of pistons that I had. I found out afterwords that one of the pistons was defective. I ordered a replacement and it was to be for a .030" over bore. The new piston skirt measured 4.35". I can't use it and had to return it.
 
You don't understand. I had a block finished bored to 4.35" to match a set of pistons that I had. I found out afterwords that one of the pistons was defective. I ordered a replacement and it was to be for a .030" over bore. The new piston skirt measured 4.35". I can't use it and had to return it.
I do understand. A +.030 over piston doesn’t (technically, shouldn’t) measure 4.350. That’s considered the nominal bore diameter. Where did you measure the skirt diameter at on the piston?
 
The set I have looks to be a cast replacement set with no valve reliefs and measures 4.347 for .003 piston to wall at your bore. You’ll have to keep looking.
 
I do understand. A +.030 over piston doesn’t (technically, shouldn’t) measure 4.350. That’s considered the nominal bore diameter. Where did you measure the skirt diameter at on the piston?
This is my dilemma.I ordered a replacement piston and the skirt measured 4.35". It was listed for a .030" over bore block? I ALWAYS thought that the pistons would be undersized for piston to wall clearance. The replacement piston was not..
 
Why can't you just hone the cylinder for the piston that's a few thousandths over? It sure won't make any difference on compression......and if it's heavier by a few grams, that's no biggie to fix.....
 
I need a set of .030" over 440 pistons. The skirt diameter has to be 4.344". Stock 1.09 pin size. Prefer floating pin, but not a necessity. Flat top with valve reliefs. Most aftermarket pistons measure 4.35". They won't work. The block has just been bored to 4.35".


Well don't I feel dumb?? The one piston that I needed as a replacement and measured 4.35 was boxed wrong. I found a replacement piston that has the correct skirt diameter. Thanks for the replies.
 
Well don't I feel dumb?? The one piston that I needed as a replacement and measured 4.35 was boxed wrong. I found a replacement piston that has the correct skirt diameter. Thanks for the replies.
Please mark your ad "found". Thanks
 
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