Hot weather temp tricks....

[ugbandtulsa]

Ok guys, I need all your tips on tuning, fuel, etc, for running in 90 deg weather....I just can't seem to keep my 421b running under 300! It is new, so could it just be tight? How many tanks before it loosens up a bit?

thanks,

Mike

 

[uDi_MP7.5]

300 is way too high dude, something is wrong.

Is it blowing plenty of smoke at topend, and on takeoff, etc etc? You should see a small burst of blue out of the corners and a light trail of blue on the straight, etc.

make sure everything is tightened down, I don't imagine there's an airleak but its worth making sure I guess, and just double check everything. Don't let it run at 300, it's not normal for an engine like that - you would be aiming more towards the 240-250 mark, regardless of outside temps I guess.

Try richening up the lowend, and if there's no trail of smoke on topend, richen that too. It might be best to start at factory settings again.

What nitro percentage are you running? oil percentages?

I think you should find the problem at its cause before you keep running it that hot, and my guess is tuning.

keep us posted.
udi

 

[olds97_lss]

If it's hot and humid, you may not want to run it. I've noticed that humidity has more effect on engine temp than ambient temp. I think it messes up the air/fuel mix by adding water to it. We all know that nitro and water don't mix. The methanal absorbs the water out of the air, so you get poor performance. If you try to lean it for good normal performance, it runs way to hot.

I've dealt with this before, as recently as this week. Tuesday, I ran it. It was 80 out with low humidity and it ran great and temps were around 210. Wednesday I tried to run it. It was 80 out, but humidity was about 85%. I couldn't get good power out of it without sending the temps up around 280.

 

[HP Invent]

its more tuning than anything. Start at your stock carborator calibrations and go from there. If its a tops 421, the low end needle stock calibration is flush with one turn out, and the top end needle is 5 turns out from the bottom. As uDi pointed out, what percentage nitro are you using ? If you're using 20% use one silver shim ( this is what it come stock from the factory ); 30% add a copper shim; 40% add a silver shim. If your running 30% or higher, change out your glowplug to a colder ( R7-R9 ) rating plug. Hope this helps, goodluck.

 

[Chevy-SS]

If it's new, it will run hot if you push it even a little hard. The piston/cylinder fit is very tight when new. The friction creates heat, so that's why you need to do a "break-in" process, so that you don't wear the engine out before it even gets broken in. Take the glow plug out and try to rotate the engine by hand, you will probably feel some resistance at (or near) top dead center, that's the "pinch" (tight fit).

Take it easy, run it rich, and let it get loose. You may have cooked it already though as you are going over 300 degrees in a new engine, which ain't good.