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piston availability for iron block?


dynodave

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I have pulled the head off of two of my 3 engines (302431 & 326431) so far and found cracked rings along with a ridge at the top of their std bore. In trying to decide my rebore options I do not find a good availability of pistons...especially for the 13HP. Is there a secret stash of oversize pistons somewhere that are not outrageous $$ ? I guess I can get some made ...
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If the bore is good except for the ridge, how about going with a chrome ring set, no boring required as they work well on glazed walls. You should be able to clean ridge. Even chrome rings aren't cheap, about $50 a pop, but that is the least expensive way to go.
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I find that when there is a tapered bore (ridge at top) then every time the piston goes up and down the ring works in and out of the ring land on the piston, then in a much shorter time the piston and ring are worn out even more. DAMHIK I could get a set of 4 custom pistons made and maybe a few guys would buy the rest for no more than what some of these NOS prices might be but of course if they are not readily available and in the wrong size or a huge overbore just to suit the only O/S piston available... I'd rather do it right even if it takes a while longer.
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quote:
Originally posted by Chris727
I think Sears Parts Direct had an oversized piston for the 30 cube engines not too long ago but it was marked up to $163 or so.
I think I had seen that one at sears and also another one in england for 133GBP (well over $200 before mailing). Crazy money... I thinks a custom piston order of 4 minimum will get a set of +.010 pistons for a lot less each than that.
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Here`s one on ebay, you can get new for $60.00 for the 326431 (16hp). http://desc.shop.ebay.com/i.html?_nkw=briggs+390366&_sacat=0&_sop=10&_odkw=briggs+390365&_osacat=0&_trksid=p3286.c0.m270.l1313&LH_TitleDesc=1
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The 32 cube motor is the same bore as a chevy 235 straight 6 I will check into the compression height and rod legenth and ge tback to you. If you google the bore size of the 13hp you should get back some car engines that take that bore then you just need to look into compression height and rod legenth and big end diameter for a fit to the crank. I have never liked aluminum rods and would love to find an automotive cast iron replacement for them.
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32 Cube pistons are easy enough to find, unless you need .030 over, as the .010 are still made by rotary and the .020 is still made by briggs. Its the 30 cube that are a bit harder to find... I think the 30 cube blocks can be resleeved to accept the 16hp standard pistons and will give you a little more power.
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I would think you just bore out a 30 CID 3.4375" by .125" to get std 32cid 3.562". I would think no sleeve unless the the walls are super thin and you breech the fins and have to fill air with iron. This is not unlike making a 920 Norton Commando out of a 828 (nee 850). I don't know enough yet about these engines to say.... I will likely get a +010 326431 piston. I'll keep looking for a + size for the 302431. This series seems to be quite rebuildable if the + oversizes were available. This morning I will open up the 24ci in the 3410S. THis appears to be a slighty different series with a different head bolt pattern.
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quote:
Originally posted by Robert_Rainwater
I have a 12hp that has been bored and sleeved back to original size. Runs fine.
Any idea if the 12hp is the big or smaller bolt pattern? Is yours a 300421? sm06
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Boring and a new sleeves are not that expensive around here. Not many are doing it but the guys that do it are charging a fair price I think. If I remember right $30 for the boar and $25 to $35 for a new sleeve. That takes you back to a standard parts. The worst part is completely striping the block and transporting it to and from the machines shop and re-assembling. A friend of mine rebuilds old engines (large antiques) and has custom pistons made all the time. Here again one would think it would be super high. What is available is piston blanks in 6 or 8 sizes and the piston is turned down to your specks regarding your size and ring configuration. Its done on a computerize lathe. He sends them the old piston and gives them his boar sizes and in a day or two he has a new piston custom made. I'm thinking the last one he had made was not that much higher than some of the prices I have seen for the unusual/older Briggs and Kohler pistons.
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Don't know what the #'s are for my engine, it's on a 1967 B-12. My brother works for a small engine parts place so he can get a discount on parts and I don't worry about other brand after market parts. It' the original engine.
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The Briggs 3040xx pistons are no longer available; even aftermarket. As someone else mentioned, it might be worth considering over-boring it to a 15/16HP size since these PN's are still available in both O.E.M. and after-market. Tom(PK)
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My 243431 has a good, no ridge, bore sm06 only a few vertical scratches. I'm going to hone a little bit and put in new rings $14.95. I only need to find out why there are no sparks. I'm going to bore the 32CI +10 and continue the hunt for a +10 for the 30CI engine.
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