Help! ST.61 w/ pipe question
 

ST.61 went from 13,800 with MA 11X7 to 16,000 with a mac's tune pipe system--wow! Only problem is keeping glow plugs from cooking. I am thinking maybe a larger prop--11X8 or 11X9 to keep rpm down. I tried running a little richer, but couldn't get it "on the pipe." I am using a Fox long reach with idle bar plug. Tried K&B 1L but couldn't keep it running. Any prop/plug combination suggestions would be appreciated (or any other suggestions for that matter as I am newbie to pipes).

Thanks.

Help! ST.61 w/ pipe question
 

Adding a .005" head shim should help. I had this same problem when I add a pipe and header to a TT40 pro. Ended up at .017" total head clearance. Although 16k doesn't seem high enough to start giving plug problems. What percent nitro are you running?

Help! ST.61 w/ pipe question
 

Thanks Painless. I am running 15% Wildcat. Where would I get a head shim? I have seen this suggested in other posts. What plug do you like?

Help! ST.61 w/ pipe question
 

I have had good luck with Fox Miracle plugs, they are about $3.50 mail order which doesn't hurt either. I think they are the best of the cheap plugs.

A cold plug like a McCoy MC9 should help also but they are pricey.

Your engine probably has a head shim in it already, so your local hobby shop could get one from the engine manufacturer / distributor, and they may offer them in different thicknesses too.

If you can't get a head shim, go with the higher pitch props to drop the rpm a little.