Piston to cylinder wall clearance help!

Technical Forums

Mechanical/Electrical

datpak (datpak) 2013-04-22 14:38:31 +0500 #21

correct me than?whats ur calculation?

jatt121 (jatt121) 2013-04-22 14:42:00 +0500 #22

hi how do i post a new thread???

Xulfiqar (Xulfiqar) 2013-04-22 16:09:29 +0500 #23

umm - how do you stuff a full 87.00mm piston into a 87.00 mm bore? - interference fit with heat?

sammad_kh (sammad_kh) 2013-04-23 17:39:18 +0500 #24

They slide right in cuz of the ptw clearance I guess lolzz:) Anyway my block was bored today and we measured it. It was wonderfully accurate to 0.004". I am a happy camper

shadab_lodhi (Lodhi Autos Rawalpindi) 2013-04-26 21:23:50 +0500 #25

Hi Dear,
The recommended Piston to cylinder clearance with diameter 86.5 is 0.06mm - 0.07mm or (0.0023in - 0.0027in), provided the piston is original.
Always check the piston to cylinder clearance at room temperature. After honing the cylinder block let it cool by itself which will take a longer period of time, or cool it under tap water. Immediately after cooling it with tap water dry it with compressed air and dry piece of cloth to prevent it from rusting. Finally check the clearance again to verify with the above mentioned values.
Regards,
Shadab Ahmad Khan Lodhi

aqibasit (aqibasit) 2013-04-27 05:22:19 +0500 #26

For competition, use a looser bore clearance then normal to fight heat build up, this way the rings will thank you, 60 - 70 percent of the heat carried out from the piston goes through the rings! So for the ring gaps, run wider then normal gaps. You should get a spec sheet with the pistons and rings to determine the right gap for each ring depending on your bore size. Good luck.

sammad_kh (sammad_kh) 2013-04-27 06:35:21 +0500 #27

Thanks. Your numbers are correct for stock bore and stock pistons. Mine are over-bore and forged So I have kept them lose.

shadab_lodhi (Lodhi Autos Rawalpindi) 2013-04-27 20:14:26 +0500 #28

Bore does not matter, but stroke matters because the figures are always taken up to the two decimal places. The formula to find the Displacement is AxSxN, where:
A is the area of a cylinder in centimeters (cm) [Pi(3.1415) x (radius in cm x radius in cm)]
S = Stroke or distance traversed by the piston from top dead center to bottom dead center or vice versa in centimeters (cm)
N = Number of the cylinders.
You will get the answer in centimeter cube or cc.
If you put the values in the above formula you would agree with my concept.

shadab_lodhi (Lodhi Autos Rawalpindi) 2013-04-27 20:46:22 +0500 #29

Calculation and conversion from millimeter to inches and vice versa:
25.4 mm = 1 inch
1 mm = 1/25.4 = 0.039 in
.039 in (39 thou) = 1mm
.001 in (1 thou = 1/0.039 = 0.256mm
To convert mm into inches multiply mm by 0.0256. Similarly to convert inches into mm divide the inches by 0.0256.
Regards,

Xulfiqar (Xulfiqar) 2013-04-28 03:53:00 +0500 #30

umm - yeah we did that in school. A long time ago.

what is being discussed was clearance.. anyway - I have always experienced that the best cleaner for honed cylinders is soapy water, the idea is that you need a surfactant to wash it away and then spray wd40 to remove the water after wiping. solvents dont remove the grit.

shadab_lodhi (Lodhi Autos Rawalpindi) 2013-04-28 18:12:29 +0500 #31

Thank you for enriching my knowledge.
Regards.

SER_GTR (SER_GTR) 2013-04-28 18:54:30 +0500 #32

So You Makes 87.1016mm Bore To Fit 87mm Pistons

A Gap Of 0.1016mm or 0.004" ..........!!

Enough For Turbo And All The HEAT Expansion???

sammad_kh (sammad_kh) 2013-04-29 04:59:05 +0500 #33

Yes according to JE and many forums that I have researched it should be enough. Anyway the pistons are in the block and the engine is ready. We will see once it starts. Ill report on piston slap and stuff here. Thanks everyone.

SER_GTR (SER_GTR) 2013-04-29 19:05:35 +0500 #34

Good Luck...Update With Results.....!

Give It A Good Starting runs on No Load.....!