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 :nod:

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.:D

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

Yet Another Nova Engine Question...
 

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:nod: 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... :tire:

just let me know :cool:

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 :nod: so far it seems that way .