Dimpled Cylinder Walls
#1
Dimpled Cylinder Walls
I'm trying to find what would cause this in the cylinder walls. The dimples are at the top and bottom of the cylinders and on both sides. Recommended wall-to-piston clearance for the pistons is .0035" but actually measure .00065" and .0009" in the dimples.
The piston skirts are scuffed on the bottom of one side and higher on the other side.
The engine is 4.185" bore x 4.125" stroke, 13:1, 7800 rpm. 3500 street miles and ~100 1/4 mile passes.
The piston skirts are scuffed on the bottom of one side and higher on the other side.
The engine is 4.185" bore x 4.125" stroke, 13:1, 7800 rpm. 3500 street miles and ~100 1/4 mile passes.
Last edited by SSSTANG#1; 06-29-2017 at 12:55 PM.
#3
No, more PTW in the dimpled areas.
The blueprint sheet says the PTW was set to .0043"-.0045 which is more than what is recommended by Wiseco (.0035"). Now, after 3500 mi, PTW is .0065" and .009" in the dimples.
My local engine builder says the cylinder walls look like they have 100k miles on them.
The blueprint sheet says the PTW was set to .0043"-.0045 which is more than what is recommended by Wiseco (.0035"). Now, after 3500 mi, PTW is .0065" and .009" in the dimples.
My local engine builder says the cylinder walls look like they have 100k miles on them.
Last edited by SSSTANG#1; 09-01-2017 at 07:20 AM.
#6
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#7
Thats a good amount of stroke, could you post what length rods you have, and what pistons you have, and is that a dry sleeved 5.3 block? Have you measured how long your sleeves are? Almost looks like the piston is being pulled out of the bottom of the bore a little too much and getting a little rocking action going on.
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#9
Thats a good amount of stroke, could you post what length rods you have, and what pistons you have, and is that a dry sleeved 5.3 block? Have you measured how long your sleeves are?
#11
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Not an expert here, my .02 both Spanks13, & Slogo are correct.
Long Stroke,Short Rod = High Side Loading +Thin Wall due to max Bore, now add perhaps
Excessive Piston to wall clearance, 7800 RPM Magnifies all of the above.
The Domino effect of stacking intolerances.
Out of Curiousity what oil brand and viscosity.
Sorry for your loss.
Long Stroke,Short Rod = High Side Loading +Thin Wall due to max Bore, now add perhaps
Excessive Piston to wall clearance, 7800 RPM Magnifies all of the above.
The Domino effect of stacking intolerances.
Out of Curiousity what oil brand and viscosity.
Sorry for your loss.
#15
You're probably right. I have a buddy that thinks a 4" stroke would help a lot (1.48-1.53) but I'm sticking with 4.125x4.185 and proper PTW clearance and loosen up the wrist pins and try again. Maybe bring the rpm down. It has never been on a dyno so that would help to see where the power is.
Last edited by SSSTANG#1; 07-12-2017 at 09:00 PM.
#17
Not an expert here, my .02 both Spanks13, & Slogo are correct.
Long Stroke,Short Rod = High Side Loading +Thin Wall due to max Bore, now add perhaps
Excessive Piston to wall clearance, 7800 RPM Magnifies all of the above.
The Domino effect of stacking intolerances.
Out of Curiousity what oil brand and viscosity.
Sorry for your loss.
Long Stroke,Short Rod = High Side Loading +Thin Wall due to max Bore, now add perhaps
Excessive Piston to wall clearance, 7800 RPM Magnifies all of the above.
The Domino effect of stacking intolerances.
Out of Curiousity what oil brand and viscosity.
Sorry for your loss.
#18
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your pistons/rings are traveling 715 linear feet PER SECOND..
A 4 inch stroke reduces that figure to 693 feet 4 inches
for reference an NHRA Pro Stock engine sees 758 feet 4 inches with a 2:1 rod to stroke ratio
#19
I've read quite a bit and never heard of a cylinder bore cracking because of RPM, nor Excessive Piston to wall clearance. The wall clearance being to much is the worst thing I see listed. Thin Walls or a bad set of sleeves sounds like the problem. Also if you have dimples sounds like debris as anything dealing with pistons and bores generally leaves scars.
Sounds like a winner! There are a few guys running that combination and revving it. Correct pistons Fix most known problems, so if the pistons weren't hurt then what? Bad set of sleeves added with to much play with the pistons & walls. Maybe, but bad sleeves is what I guess.
Call up ole uncle Steve @ RED he's post here also. To actually get some Factual based knowledge from experience. Hope you get it corrected, it sounds like your already at it!
http://www.raceenginedevelopment.com/contact-us/
I'm sticking with 4.125x4.185 and proper PTW clearance and loosen up the wrist pins and try again.
Call up ole uncle Steve @ RED he's post here also. To actually get some Factual based knowledge from experience. Hope you get it corrected, it sounds like your already at it!
http://www.raceenginedevelopment.com/contact-us/
Last edited by Patron; 07-13-2017 at 03:12 PM.
#20
SIXTY % of an engine's rotational friction is the piston rings.
your pistons/rings are traveling 715 linear feet PER SECOND..
A 4 inch stroke reduces that figure to 693 feet 4 inches
for reference an NHRA Pro Stock engine sees 758 feet 4 inches with a 2:1 rod to stroke ratio
your pistons/rings are traveling 715 linear feet PER SECOND..
A 4 inch stroke reduces that figure to 693 feet 4 inches
for reference an NHRA Pro Stock engine sees 758 feet 4 inches with a 2:1 rod to stroke ratio