Todays run raised some questions.

[militarymaxx]

I gave up on trying to find a track close by, so my local sandpit would have to do. I won't bore you with all the details, but I do need some input on the way things ran today. First, a little background. Last week everything ran fine (out in front of my house). Temps were 200 - 230. I gave it a normal cleaning and didn't touch anything until today when I headed out to the pit for some fun. In a nutshell, it ran like crap. Temps were high (300 - 320) and even after opening up the HSN, they still stayed high. I seldom was in WOT, just short burps as the pit condition was nothing but washboards, lots of bumping around. I also noticed between runs this gurgling sound coming from around the engine/tank area and I also noticed that the fuel was working its' way back into the tank. I should also mention that the humidity was very, very high. I packed things up and headed home. Later in the day I have another go at it and things are fine again, temps are around 183 - 230, probably because of the HSN adjustment earlier in the day. I ran it with the body off. The high humidity is also gone. The gurgling is also gone. So.....

1. Did the high humidity have anything to do with what happened ?
2. Does running it with the body off make a difference and how big a difference ?
3. What the heck was that gurgling sound I heard ?
4. Did the rough track conditions have anything to do with what happened ?

Sorry for the long post. Appreaciate any and all feedback.

 

[Rolex]

1. Did the high humidity have anything to do with what happened ?
Yes it did, and the engines need to be tweeked for humid conditions. Humidity slows evaporation, and cooler fuel helps keep the engine cooler.

2. Does running it with the body off make a difference and how big a difference ?
Yes it does, since there's an unrestricted air flow when they're off. You should have a good sized hole in the windshield on the same side the engine head is on to allow maximum incoming air to cool it.

3. What the heck was that gurgling sound I heard ?
Fuel boiling in the carb, since it was running so hot.

4. Did the rough track conditions have anything to do with what happened ?
Yes, for 2 reasons. 1, it's working hard to move a heavy truck at a slower speed, and also, slower speeds mean less cooling going through.

 

[Bryson]

I have had very simalar experinces like this. If your running it in front of your house with the body off chances are when you put the body on at the sad pit along with the higher humidity it made it run real lean. I know that when I run with out the body off i can get away with low temps, and the hsn about 3 hours leaner then with the body on. Usually when I go to run on a hot day ill just richen up the lsn and hsn about 2 hours, and adjust from there. Also rember with lower temps twards the evening, your motor will start to lean also. Alot of guys at my track have lost motors because they dont pay attention, and figuar they had a good temp 30 minutes ago so it should be fine now. The gurgling noise, I have never heard of this before so hopefully someone can help you out there. Hope this helps a little.

Bryson

 

[militarymaxx]

ROLEX - Thanks so much for the feedback. Everything you said makes sense.
My only concern now is, did that boiling fuel in my carb do any damage ? The engine wasn't at those high temps for very long but boiling fuel sounds bad.
I have since checked engine compression, etc. and all is fine. Just concerned about the carb now. Again, thanks to you and everyone else. It's never said enough but the most important tool in my pit box is this website.

 

[Rolex]

It's never said enough but the most important tool in my pit box is this website.

That's a real honor for all our great members to hear. That would make a great catch phrase for the site.

As far as the boiling, no problem. It's a pretty regular occurance since the nitro fuel boils at a low temp. Spill some on your hand, and your hand gets very cold, very fast. Very low evaporation/boiling point.
Always keep a close eye on engine temp on hot days. Long term high temps are what will do your engine in permanently.