Dear Pro Mod Wad,
I recently purchased a 1967 Nova to run in the outlaw 10.5 class.
We have a 555 from Jeff Taylor Racing that was designed as a super
class motor. It has 917 HP at 7000 and about 760 torque at 4800.
Im putting an NOS fogger on now. Any ideas for a conservative
tune up to begin with? And, maybe a maximum tune up before we add
nitrous pistons and cam.
As you did not give me a lot of info on the engine, I have to believe it was not built for nitrous use. You mentioned that you still have to change the pistons and cam for that reason, so what I would advise you to do is to be careful when you run the system. A conservative tune-up would be 24 N20 jet and 22 fuel jet with 6 PSI fuel pressure and 30 degrees of timing. A max amount would be 30 / 28 with same fuel and timing settings. Try to make 2 or 3 passes that you can shut the engine down when you lift and get GOOD plug readings. This will help you achieve a safe tune up.
Remember that you will be running a colder plug with the nitrous. Take your time and you will be fine on tune-up info and thanks for writing.
Pro Mod Wad
Dear Pro Mod Wad:
I recently installed an NOS kit on my 1999 Yamaha 700 srx snowmobile. I am in the process of installing a drag racing suspension and track with front wheels instead of skis.
My question is, if I have 22-26 jets in the Fogger nozzles for
winter, do I have to change the fuel or nitrous jet for summer.
Thanks for the letter, Elizabeth. Obviously you live where it is very cold! The answer to your question is YES! Your nitrous tune-up should be taken back to a smaller pattern to start off with as you will see much higher bottle pressures in the summer heat.
Also, in the humidity of summer, your nitrous will be less potent for a given jet size due to the weight of humid air. Once you can get a handle on bottle pressures and the way the engine responds to the nitrous on hot days, you will be able to adjust your jetting to optimum performance levels.
As the engine also will run much hotter in the summer months, take care to run colder spark plugs and do whatever you can to eliminate any detonation present from summer heat. There are a few aftermarket ignition companies out there that build timing retards, etc. You might want to look into that also as much more performance is available from your nitrous system with retarded timing.
Hope I have answered your questions satisfactorily.
Pro Mod Wad
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