if the piston/sleeve set is run in properly it should have excellent compression but pretty much lose all pinch . this is when the engine performs at its best

i have been shimming all my engine at .80mm for a while and noticing much better performance and runtimes across the board .

i am glad it is weorking out for you , if you properly shim for 20% (.60mm) then you will experience better performance but you will be better off to use 30% and properly shim for that .

to each his own

Thanks Monty. Mine has no pinch but a TON of compression. I'll shim it to .8 thanks man.

It runs good. Its new, only 1 gallon. Im just trying to find the right plug.

Comparing an S821B, a P5XS, and a 21-7, which would make the best truggy engine? What's the power output like (low/mid/top) with an S821B? Is it suitable for a truggy, or is it more suited to a buggy?

Also, is the three port BF21N Nova Limited Edition a good truggy for medium sized tracks with some big, short run-up jumps?

i have personally used all three in a truck and like the p5 for an all around engine . the 821b is a powerhouse of an engine and would not be a bad choice in a truck if you were to use for a medium to large track layout . the 21-7 is awesome and is a little smoother than the other two and would be best suited for larger tracks as well . that 821b port design really makes alot of rpm sounds wicked with the right pipe



the bf limited would be an excellent choice for smaller tracks , nice consistent running engine with just enough power . "houston tuned" is a fair amount more power .

Thanks for the info Monty. You've given me more food for thought. Leaning towards one of your Rebuilt/Houston-Tuned P5X mills...

just let me know

Carbon build up on the top of piston something normal?? Or engine running too lean/rich??

Thanks

undershimmed and a little rich

cool, thanks for the help

Houston, .80 shims. 3 Copper 1 Alum. Correct

the aluminum are .30mm and there are 3 sizes of the copper so use calipers to measure

Hey Monty, I have yet another question for you. I partially tore my +4 down last night to seal it up (left piston/sleeve alone, no need to remove) and noticed a bit of carbon on the piston, kind of a 1/4 mooncrescent shape near the exhaust port. I read a bit about shimming so I decided to see what was in the +4 and found two .30 alum and one .20 copper to hit the .80 that you like. I have not lost all mechanical pinch when cold yet, but am reeaaal close. The temps have not taken a dive yet either.

Anyway should I just leave the .80 alone or add another .10 because of the carbon? I am thinking that it is still bit rich as like I said the temps have not fallen, my HS needle is still flush with the copper barrel it is in which is roughly 3.75 turns or so. I am hoping to see that temp drop any day now, it makes great power with a lot of smoke running 230 so it is safe, maybe it is time to lean it out a bit? Thanks again

you are never gonna get an engine that burns 100% clean guys . a little build up is inevitable . as far as shimming past .80mm , i dont think it is necessary myself .

i am beginning to think that these engines they put the lapping compound in are breaking in way faster than the older stuff. kind of bypassing the dropping stage so far it seems that way .