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#1
05-04-2011, 09:24 PM
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Piston to Cylinder Wall Clearance
What is the most piston to cylinder wall clearance anyone has run using SRP pistons on a full race engine? While freshing up my 463 it looks like one of the cylinders will have
.008. Will this be too loose? |
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#2
05-04-2011, 09:33 PM
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have run more than that. you will get some scuffing but performance wont be too affected. im in at .007 now i believe. Id have to check assembly notes.
__________________
1969 carousel red firebird 455, richmond 5 speed 1964 540 gto 1971 lemans sport convertible 1972 Maverick under slow construction |
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#3
05-04-2011, 09:35 PM
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The old "California" Pistons would run at that clearance in a race engine.
With the SRP pistons, newer modern design you would normally have a tighter clearance (piston to bore) as the piston would grow less when it was at operating temp. .008" clearance will typically make noise, and will degrade ring seal around the bore on a street engine. At some point the piston will fail from the piston slap but this might take 50,000 miles or it might take 10,000 miles. Hard to tell. If the Piston was a .030" oversize there were companies who offered .040" pistons at one time, same deal with the ring packs. A buddy with a corvette had the machine shop screw up his bore job, clearance wise, and he had 2 holes like your deal. He bought two .040" pistons, had it honed to proper size, and put it together. If you can find a Piston that is the next size larger (.010" larger) that might allow a quick fix. If your deal is a Race Engine, I would not worry about it. Tom Vaught
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"Engineers do stuff for reasons" Tom Vaught Despite small distractions, there are those who will go Forward, Learning, Sharing Knowledge, Doing what they can to help others move forward. |
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#4
05-04-2011, 10:03 PM
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You will hear the pistons until the engine warms up.
You will be fine. Lots of engines that have hard block and NO2 have clearance like that. Same thing with ring end gap, hard block they want more and even more with NO2. My Ross pistons are supposed to be .004. Well I have had the block filled so you add another .002 to .006 Whittmore told me I would hear the pistons rattle a bit until it warmed up. And he said if I was setting it up for spray he would have had to add another .002 and that would have brought it up to .008. Some Venolia and Aries pistons want .007+ as is. They are made from very high grade aluminum alloy that grows more than some lesser alloys. Just more molecules in the same amount of space I guess. You can get by with a TRW forged at .003 and cast at .001/ . The less the quality the less they grow maybe?. |
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#5
05-04-2011, 10:29 PM
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To Tom V.: It is a race only engine so I believe I will be alright. I am not to concerned about piston noise during warm up as you will not hear very much of it over the open headers.
To Mystic Missle: Are you running SRP pistons with the .007 clearance? To DragnCar: The block was filled to the bottom of the freeze plugs, so that might help me or a little, or were you only referring to blocks that were completely filled? Thanks to you all for your reply. It sounds like I will be fine, but I would still love to hear what others think. |
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#6
05-04-2011, 10:42 PM
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Dan filled my block to the bottom of the water pump holes. To tell you the truth I do not know if filling them to the bottom of the freeze plugs changes it as much.
Maybe a engine builder who has done it both ways will chime in. |
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#7
05-05-2011, 06:37 AM
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The pistons are Ross. I do use nitrous but it also gets driven for short trips on the street. I believe the majority of the scuff comes from my 6.8 rod length. My next rotating Assy will use shorter rods for sure. I run an original IA block as well not sure how a filled block compares to that. I know of set ups using same piston running .011 and spray.
__________________
1969 carousel red firebird 455, richmond 5 speed 1964 540 gto 1971 lemans sport convertible 1972 Maverick under slow construction |
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#8
05-05-2011, 12:11 PM
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Quote:
__________________
540 c.i. Ultra Street Combo Tiger Heads with Tiger Intake Induction Solutions fogger with .046 jet First ultra street/ultimate street NOS car to get into the 4's! 1.079 4.559 153.23. 3100 lbs 7.77 @ 169 1/4 Mile (2015) with EHTTFMF!! T2TTFMF! Special Thanks to: Ron at Rhodes Custom Auto Butler Peformance Jim Hostler's Transmissions (HOSGTO) on here Induction Solutions BES Racing Engines. Cheeseburger VP Racing Fuels Calvert Racing |
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#9
05-05-2011, 03:26 PM
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My block is filled to the bottom of the water pump holes as well. That is what I meant. It sounds like that since I am using a stock length rod the piston scuff will not be as bad as it could be if I were running a longer rod.
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#10
05-05-2011, 06:06 PM
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Less side load with a longer rod= less piston scuff.
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#11
05-06-2011, 05:36 PM
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Yes, the longer the rod the LESS the side loading and scuffing. The more dwell on top and bottom too. The cylinders get filled a tiny bit better with long rods also.
Check out a high millage sbc 400 with its relatively long stroke and real short rod. The middle of the bores get very worn out with these engines. In stock form they are much like stock Pontiac 455s and far ratios and where the run out of breath. |
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