Piston Clearance Opinions
05-24-2019, 05:26 PM
#16
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The coating that was already applied to my stroke pistons was applied too thick. My shop is sending them out to be re-done properly. Same folks that coated my bearings.
Given that 100.5 piston is smaller than my 104mm pistons and from what I read the larger the piston the larger the clearance, should the .00125 be greater?
Thanks.
EDIT: According the 968 WSM the clearance looks like .020mm
Given that 100.5 piston is smaller than my 104mm pistons and from what I read the larger the piston the larger the clearance, should the .00125 be greater?
Thanks.
EDIT: According the 968 WSM the clearance looks like .020mm
Why are you coating something that was already "ready to gp", with the correct plating?
I've yet to see ANY spray on, baked on, glued on, whatever anyone can "dream on" coating that works in an Alusil bore.
The factory finish on pistons made for Alusil bores is a plating process....electrically deposited onto the surface.
968 pistins are forged from an aluminum with a slower expansion rate than the cylinder they run in.
When I have one of these engines bored, I have my machine shop "shoot for" less than .0010" of clearance. All boring and honing must be done with torque plates attached (on both sides at the same time) to achieve this clearance.
05-24-2019, 05:33 PM
#17
Rennlist Member
Kevin:
Why are you coating something that was already "ready to gp", with the correct plating?
I've yet to see ANY spray on, baked on, glued on, whatever anyone can "dream on" coating that works in an Alusil bore.
The factory finish on pistons made for Alusil bores is a plating process....electrically deposited onto the surface.
968 pistons are forged from an aluminum with a slower expansion rate than the cylinder they run in.
When I have one of these engines bored, I have my machine shop "shoot for" less than .0010" of clearance. All boring and honing must be done with torque plates attached (on both sides at the same time) to achieve this clearance.
Why are you coating something that was already "ready to gp", with the correct plating?
I've yet to see ANY spray on, baked on, glued on, whatever anyone can "dream on" coating that works in an Alusil bore.
The factory finish on pistons made for Alusil bores is a plating process....electrically deposited onto the surface.
968 pistons are forged from an aluminum with a slower expansion rate than the cylinder they run in.
When I have one of these engines bored, I have my machine shop "shoot for" less than .0010" of clearance. All boring and honing must be done with torque plates attached (on both sides at the same time) to achieve this clearance.
05-24-2019, 07:30 PM
#18
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I agree, but they came coated and coated too thick. I'm just trying to get the clearances fixed so I can move ahead with the project. Removing the S02 coating is beyond my skill set. Letting my machine shop take the lead. As you have admonished me in the past... there is a lot more to stroker engine than just assembling some parts. I need that on a plaque. I'll pass on the 0010 to my shop and we can go from there.
05-24-2019, 07:37 PM
#19
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05-25-2019, 04:20 AM
#20
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05-25-2019, 05:14 AM
#21
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05-26-2019, 09:37 AM
#22
Team Owner
I had a set of 928 pistons coated and the process was that the parts were grit blasted prior to the new coating being applied,
if this happened then the chromium coating will be damaged or lost.
To this date the pistons have not been installed AFAIK
if this happened then the chromium coating will be damaged or lost.
To this date the pistons have not been installed AFAIK
05-26-2019, 02:36 PM
#23
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Just get them "Ferroprinted", they will be fine.
05-27-2019, 12:24 PM
#24
The pistons are normally lightly air-brush blasted before application of a skirt coating. What I have found is that the iron does not get completely removed.
But taking off the coating would seem antithetical. Some of the skirt coo stings are “wear in” in that they are too thick on purpose and the piston then wears in the bore to what is needed. A “la “line to line” coatings.
But taking off the coating would seem antithetical. Some of the skirt coo stings are “wear in” in that they are too thick on purpose and the piston then wears in the bore to what is needed. A “la “line to line” coatings.
08-13-2019, 02:08 PM
#25
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Thread Starter
@Adamant1971 Epilogue to this? What was the final target clearance? What was the final measured clearance? Did the engine run?
Last edited by Adamant1971; 08-13-2019 at 02:25 PM.