keeping open flathead cool

X

Xcludedracing

Member
Building a open flathead with a 3hp finless flywheel would it run to hot on a oval track if so how would u keep it cool. And how hot should it run
 
Last edited:
Most have a fin kit u can bold on I believe , .... But u could get away with if u have a finned head, running methanol , extra ounce of oil, swoop body and don't let it sit and idle for a long time..... Now I have never done it myself... So this is just a hypothesis
 
No fins at all might be a problem. What about the bolt on fins? Nothing keeping you from trimming them down. A stock flywheel has fins meant to cool the engine at 3600 RPM, or about, so I'm thinking at the rpm you're going to be raced at you would need a lot less fin.

Comments compliments criticisms and questions always welcome.
If the data does not support the theory, get a new theory.(Al Nunley)
 
If the finless flywheel will work or not depends on your application.

Jr Drag engines run finless flywheels (and for a reason.) Keep in mind they make an 1/8 mile pass and shut it down.


Also, idling should not be an issue -- your engine should not get hot simply idling. Generally they don't build much heat at all at an idle (very rich fuel condition at idle and no load.) Even with the shroud taped completely off (no air circulating) it is difficult to get them over 200*.

Likewise, if you're on a track that is on and off the throttle, you should be alright -- Every time you back out of the throttle, the air intake is restricted, however the fuel flow is restricted much less. This creates an over-rich condition with the sudden decrease in throttle position (often accompanied by a loud crack back through the exhaust of unburnt fuel being ignited in the exhaust pipe.) This over-rich condition cools the cylinder rapidly and if repeated could easily compensate for the lack of fins on the flywheel to assist in cooling the engine.

I wouldn't recommend running a finless flywheel on a big momentum track where you're always on the hammer though -- that's a recipe for disaster.

--
Thanks and God bless,
Brian Carlson
Carlson Racing Engines
Vector Cuts
www.CarlsonMotorsports.com
Celebrating 25 years of service to the karting industry
765-339-4407
bcarlson@CarlsonMotorsports.com
 
Mr. B. Carlson is correct !!!. Use a finned flywheel, leave the blower housing open,do not cover it up, TRY TO KEEP TEMP BELOW 385 DEGREES AND TIMING BELOW 40. With a good carb, you should never have a heat issue,but adjust as needed.Keep pop off pressure high.USE A GOOD OIL.

Robert Fisher
Ridgeway ,VA.
276- 956-2036
 
Ill be runing a 1/8th mile dirt oval with about 8deg banking also I will have a hl368a tilly on the motor how hot can it get before I have to shut it down so I dont burn it up
 
As an afterthought, running richer will keep it cooler. Increasing the jet one size might help.

Comments compliments criticisms and questions always welcome.
If the data does not support the theory, get a new theory.(Al Nunley)
 
Al, he's running a Tillotson carb, needles, no jets. To answer his question, you can run over 400 without hurting anything ,but like Robert said keep it around 375 that's plenty warm enough to assure good top end. You won't have to shut it down if the temps creep higher than what you want, just open the high side needle some to bring temps down, maybe a little more on the low side too depending on how rich it is off the bottom. I'm not sure I agree that you need to keep the pop-off high , I guess it depends on what you call high. With an .875 venturi carb on an open it will have a pretty good signal so around 9 lbs would be appropriate with that somewhat depending on the drill pattern itself. Jon
 
Well it's gonna be plenty rich then, but that's what gets an open up off the bottom hard. Try to minimize the time you have to set and idle, fire it and go.
 
You must log in or register to reply here.
Back
Top