engine going flat

[DKUBISTARACING]

I have been trying to chase this problem with the mixture settings, I have an engine that runs great for about 15 laps and then doesnt want to pull itself into the upper power band. Engine temp is about 190 to 210 depending on tune. Just cant figure out why it all of a sudden goes flat. The engine is an OS CVR run on an asphalt track with slide carb.

Next question is, do any of you guys have any problems with fuel mileage on the 5 port turbo engines? I have been thinking about getting one, but alot of guys that run in our class have a hard time making a 4 minute race with one.

[John Binz]

Have you checked to make sure the Orings around the needles aren't bad and making the needle move by itself?

[DKUBISTARACING]

its not the needles, i actually changed carbs. Im thinking I might have it figured out, we are running latemodel bodies, and i think the crankcase of the motor is getting too hot where its loosing compression.....could this be the case? there is only about 3 fins of the head that stick out of the top of the body.

[mach51]

how hot is it getting? how much fuel is through it? the fact that it runs great for 15 laps and then you have problems usually means it might need a pinch but it doesnt look like it is flaming out just losing power. how about an air leak?

[DKUBISTARACING]

I would say there is about 3/4 of a gallon through it. It seems to run the best at 205-210. My dad and I both run the same class and the same thing is happening to him and he maybe only has a 1/2 gallon through his. We are running latemodel bodies and the straightaways are pretty long. Right now we just have a hole cut in the body for the head to stick out, and it only sticks out about a half inch. Should we cut a hole in the windshield of the car? We are just running OS CVR engines against 5 port turbos, and winning races with them, but maybe asking too much out of the little OS.

[races65]

I would cut several 1/4" diameter holes in the front window area for better engine cooling.
I don't race late model, but thats what I have seen guys do.

[mach51]

umm, 210 is NOT hot for a motor - especially not a small block. MY CVR runs best at about 250-260 degrees

[assocman]

If the rules allow you to, cut out half of the windshield.

[Night Flight]

I am not sure about what is going on but if you have the ability I would buy another CVR.12 and send the one that looses power to Hobby Services it has a 2 year warranty to the best of my knowledge. If you drop me a pm or an e-mail I would be more than happy to give you the address. The tracks I run have a 260 Ft. drive line and a 212 Ft. and I have never experienced the problem you are having. As far as the temperature. I run in the Desert South West 240 is about what mine run at.

[DKUBISTARACING]

Thanks for the ideas guys, I am going to cut a hole in the windshield and see if that works. Also, the engine came with a barrel carb, after a couple weeks of that crap with the lever coming loose i ditched that carb. But in the meantime im waiting for a 10c slide carb to come in so I have been using a 10A slide carb, and that could be my problem. The 10a slide was intended for use on the hyper engines. Come to find out, the hyper engine is just a glorified CV. The 10A carb uses differant needles and a differant slide all together. So I am going to start out with those two first, cut the hole in the windshield, and (when i get it) put the right carb on.

Thanks for the input guys.

[bulletproof]

It sounds like the engine is getting to hot.the holes should helpsome but i would also double check the temp gun you are using .i have seen them be way off.