What replacement pistons- HP500 EFI w/Whipple
04-19-2006, 12:16 AM
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What replacement pistons- HP500 EFI w/Whipple
Going thru my short block- previous pistons were great but not designed for blower use and top land was not happy (A lot of variables- all being checked out) Dustin says to stay at 8.75 comp. What piston is similar but with a thicker top land?
Last edited by Cattitude; 04-19-2006 at 12:27 AM.
04-19-2006, 04:36 AM
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Re: What replacement pistons- HP500 EFI w/Whipple
That piston has a 1cc dome. They work good if in good shape. I assume you are talking about the top ring lifting which usually occurs at the intake valve cut out.
A flat top will work. It has a -3cc ratio but I think you will have to bore it to a 4.500" to get one unless it is custom made. By time you add the few cubic inches and mill the heads .010 to clean up you will be close. Add .0015" clearance to the piston clearance to help with the heat of the blower.
A flat top will work. It has a -3cc ratio but I think you will have to bore it to a 4.500" to get one unless it is custom made. By time you add the few cubic inches and mill the heads .010 to clean up you will be close. Add .0015" clearance to the piston clearance to help with the heat of the blower.
04-19-2006, 07:43 AM
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Re: What replacement pistons- HP500 EFI w/Whipple
Originally Posted by Linster
That piston has a 1cc dome. They work good if in good shape. I assume you are talking about the top ring lifting which usually occurs at the intake valve cut out.
A flat top will work. It has a -3cc ratio but I think you will have to bore it to a 4.500" to get one unless it is custom made. By time you add the few cubic inches and mill the heads .010 to clean up you will be close. Add .0015" clearance to the piston clearance to help with the heat of the blower.
A flat top will work. It has a -3cc ratio but I think you will have to bore it to a 4.500" to get one unless it is custom made. By time you add the few cubic inches and mill the heads .010 to clean up you will be close. Add .0015" clearance to the piston clearance to help with the heat of the blower.
Ring lifting at the valve pocket- EXACTLY- at 5 out of 8, and the other could be bad too if I put a straight edge to them. No sense in running these again.
With the clean bores and plans for more clearance anyway, I was hoping to hone and run STD- am I SOL on finding a good std piston? a few tenths would not be that big a deal imho- the little 2.3 could use the help, I would/could bump the pulley up a size. I don't want to squeeze to close to the edge, rather be a few didgits slower and running the boat home every trip
04-19-2006, 08:24 AM
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Re: What replacement pistons- HP500 EFI w/Whipple
A custom piston set of 10 pcs in the long run would be your best bet. The piston company can lower the top ring land to combat the heat fatigue in thin areas and do yourself a favor and get coated tops.
04-19-2006, 11:47 PM
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Re: What replacement pistons- HP500 EFI w/Whipple
Originally Posted by cstraub
A custom piston set of 10 pcs in the long run would be your best bet. The piston company can lower the top ring land to combat the heat fatigue in thin areas and do yourself a favor and get coated tops.
Also I think the 5/16 rings are a lot cheaper than the metric stock 500efi's
Rob
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