Inliners International Forums General Discussion Hi Performance advice on piston-to-bore clearance?

Sorry for bringing V8 matters to this honorable forum, but internet is filled with opinionated bench racers and I prefer real-life opinions, so I thought guys could share some track earned wisdom.

I am slowly building an alky-injected SBC 400 for my FED. The measured piston-to-bore clearances are:

#1) 0.0071"
#2) 0.0064"
#3) 0.0082"
#4) 0.0072"
#5) 0.0080"
#6) 0.0081"
#7) 0.0072"
#8) 0.0072"

Is it too tight to run without radiator, just recirculating water?

I am ready for final assembly and would prefer to not send the block to machine shop, unless piston scuffing is in the forecast for my setup. Block 'tall filled' w/ HardBlok and pistons are ROSS (forged).

Thanks,
ROC

I would get in touch w/Ross tech dept. They should know what will work.
Sorry could not answer your Q.
Every piston manufacture uses different amounts of silicone,more silicone = less piston to wall clearance needed.

MBHD

Many thanks Hank. As usual, your advices are solid and sound.

I’ve contacted ROSS Pistons, which responded:

.006 to .008 should be fine with a filled block running on alcohol.

You are welcome.I did not have much to say though.
I'm glad Ross responded.

MBHD

Even though 2618 is pretty common for forged pistons, the internal shape of pin bosses, struts to the skirt, inside dome arch, etc. all affect how the piston expands so the manufacturer gets the last word (but must always have all details including fuel, cooling etc.).
The penalty for guessing wrong is pretty expensive; a piston made the wrong shape (not enough/too much cam or barrel) can't be completely fixed by adding clearance, the entire profile should be re-machined.
We just through this when a piston made to the stock contours (but CD changed for stroke length) seized on the pin axis by less than .002" (not enough cam). It can be cured better by hand with a file than honing the cylinder +.002".
We had all existing stock re-done.