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#1
03-28-2024, 01:24 PM
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Piston wall clearance and Coating skirt
I have a new engine I am putting together and it has Ross/Butler pistons. I have the piston to wall clearance set to .004 per the tech sheet that came with the pistons. Now I am considering having the piston skirts and tops coated. Problem is the thickness of the dry film coating is .001-.0015. This would reduce my clearance by .002 to .003 and I wouldn't have enough clearance after coating. I don't want to have my block honed again so I suppose I should just forget about coating the skirts.
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Tim Corcoran |
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#2
03-28-2024, 01:43 PM
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Most of the coating shops say to let the coatings wear in. Do not adjust clearance because of the coating.
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| The Following User Says Thank You to PAUL K For This Useful Post: | ||
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#3
03-28-2024, 10:46 PM
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Is that the same for rod and main bearings?
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Tim Corcoran |
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#4
03-28-2024, 11:01 PM
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No, the coating is thinner on bearings. Well at least most of the time.
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| The Following User Says Thank You to PAUL K For This Useful Post: | ||
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#5
03-29-2024, 08:20 AM
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Under extreme pressures and rubbing like the side of a piston molly coatings eventually will wear away
one may ask why bother then? the molly coating reduces galling and wear of the piston mainly during break in when the cylinder hone is most abrasive on rod and main bearings less surface abrasion and a more robust hydrodynamic oil wedge and probably less surface speeds vrs piston skirt all leading to a longer coating life on bearings
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A man who falls for everything stands for nothing. |
| The Following User Says Thank You to Formulas For This Useful Post: | ||
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#6
03-29-2024, 10:23 AM
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If a cylinder wall has been plateau honed after been final honed, or already broken in then sending pistons out to having a skirt coated will only serve to lessen the green out of your wallet.
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Wernher Von Braun warned before his retirement from NASA back in 1972, that the next world war would be against the ETs! And he was not talking about 1/8 or 1/4 mile ETs! 1) 1940s 100% silver 4 cup tea server set. Two dry rotted 14 x 10 Micky Thompson slicks. 1) un-mailed in gift coupon from a 1972 box of corn flakes. Two pairs of brown leather flip flops, never seen more then 2 mph. Education is what your left with once you forget things! |
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#7
03-29-2024, 02:28 PM
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One reason a person may want to coat the skirts on the pistons is to take up excessive clearance.
One reason a person may want to coat their bearings is to simplify the decision whether the bearing should be replaced or not. |
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#8
03-30-2024, 08:42 PM
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After listening to everyone's comments including from my machinist and Butler performance I have decided not to use any coatings. My rods are at .0025 and the mains are .0032 and piston skirt to wall is .004. I am happy with the clearances not going to mess with any coatings that would add $500.00 to this already expensive build.
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Tim Corcoran |
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#9
03-30-2024, 11:25 PM
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Are the pistons Ross 2618 or some other 4032 piston?
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1967 Firechicken, 499", Edl heads, 262/266@0.050" duration and 0.627"/0.643 lift SR cam, 3.90 gear, 28" tire, 3550#. 10.01@134.3 mph with a 1.45 60'. Still WAY under the rollbar rule. |
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#10
03-30-2024, 11:48 PM
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Quote:
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| The Following User Says Thank You to PAUL K For This Useful Post: | ||
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#11
03-31-2024, 07:25 AM
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I agree with leaving it as is, especially with the bearings !
Face the facts, if a running motor is relying in its coated bearings to stay alive then that time span of staying alive is going to be short anyway! eventually that coating gets worn thru and your done but you don’t know it until bearing clearance noises and loss of performance takes place.
__________________
Wernher Von Braun warned before his retirement from NASA back in 1972, that the next world war would be against the ETs! And he was not talking about 1/8 or 1/4 mile ETs! 1) 1940s 100% silver 4 cup tea server set. Two dry rotted 14 x 10 Micky Thompson slicks. 1) un-mailed in gift coupon from a 1972 box of corn flakes. Two pairs of brown leather flip flops, never seen more then 2 mph. Education is what your left with once you forget things! |
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#12
03-31-2024, 06:00 PM
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Steve Morris has a few videos on the a coating he has started using on his builds.
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