I think i may have done a mistake when i ordered my pistons.....
What's the max clearance you can use?
If JE recommends 0.0065", is it that measure all around the piston, or do i take this measurement and divide it by two? so the gap is in fact 0.00325"

Confused and really bugged by this.

 

cp recommends like .004 ish

 

To get piston to wall, you measure WHERE they say on the piston... so say its 4.030.

If they want .0065, your BORE should measure 4.030 + .0065 = 4.0365" .... providing your bore is straight, I measure a couple spots, but 1.5" down should be ducky (approx half your stroke).

No need to halve or double anything...even doing it with the "old timer" method.... put the pistons on the rod to make it easy... then slide the piston in upside down with a .006" feeler guage positioned in about the right spot on the piston (the ring area is smaller diameter, so wont get in the way). The .006" should slide, the .007" should get stuck....luckily most pistons are barral shaped, so this way works.... most of the time

 

I told them my bore was 4.030 whil in fact it is 4.033

I will talk to my engine builder about this.

I'm not to certaion on my measurement too, but at the bottom of the skirt, it had ~4.024", that leaves ~.0095".

Crossing my fingers...

 

JE pistons
http://www.jepistons.com/dept/tech/dl/piston_instrc2618.pdf

 

Theres two clearances. The built-in clearance and the extra clearance.

The built-in clearance is .0065. Thats why your piston measures 4.024 (should technically be 4.0235 or 4.030 - .0065)

The extra for blower/nitrous is .001-.003. Your bore has an extra .003. So yea, I would be concerned.

 

MAybe i'll look into having the side skirt coated...

 

the coating will only take up about .0005-.001

 

Bah, fuck it.... double check, and if its under .010", just run it... it may be a tad noisy at start up, but booo hooo, you'll be fine.

I ran my stock 5.0 pistons at .0065" in the stock bore I had to hand hone A LOT to get all the marks out... still ran 142 mph

 

Good, i have 0.007" , my bore was 4.031.
I'm glad everything is okay. JE asked for 0.0065" minimum.
Perfect.

 

THey actually advertise being able to build up skirts to get the fit right.

 

I don't know if you saw the insturctions.

0.0065 is to figure out the ring end gap.
4.030 = 0.027 - 0.028

Depending on what piston you have the piston side clearance will change.
2618 min bore clearance .0045 +

 

The sheet is asking for 0.0065" minimum piston to wall clearance. Some clearance can be added depending on application.
Too bad i dont have a scanner.

 

5-7 thousandths is about right. I have seen standard pistons in a thiry over bore! Didnt blow, raced it for two days and it started clankin.