WhiteWindsor

Just wondering if anyone has a engine similiar to mine and what fuel pressure are you running? I have a RACE HP 750 that is running rich. I have tuned the carb several times. Finally was able to get 7.5 inches of vacuum. I have tried the 6.5,2.5, and 4.5 power valve. The 6.5 ran the best but smoked more. The 2.5 ran terrible. Now i have the 4.5 and it does not run right untill after 3500 rpm. I know the carb may be too much, but the only other one i have is a 670 avenger with vacuum sec. I dont think that will be enough. I am running 6.5 psi fuel with a holley blue pump. It is strong smelling and burning my eyes. I have the exhaust cut off 3 in. behind muffler now, i am getting exhaust tips to the bumper next week. That will help with the fumes but my plugs are still getting fouled. Also with 11:1 compression what is the total timing you guys are running. I know a dyno tune is the ticket and was getting one this week but my 93 F-250 is now a six cylinder. I have .5 psi in 6 and 8 cylinder, so i have tofix thatbefore i dyno tune. I cant drive the mustang for long, it only has a 8 gal. fuel cell and gas mileage is terrible. I did not build it to drive everyday.
Thanks
Keith

Indy

Hey Keith,
Fuel pressure is good at 6.5psi... However, the fuel pressure in a carbureted car does not change how rich or lean your motors running unless too much pressureis floodingthe carb(which in that case it would be rich,lol). Fuel is stored in the fuel bowls of your carb which is supplied by the pump until float level is satisfied. The fuel is drawn in be venturi effect and not by fuel pressure delivered be your pump.

Now, if you're rich at idling that's a matter of better tuning the idle mixture screws (as your powervalves are not even in effect here yet). If you feel that you are too rich at cruise (most importantly plugs indicate rich), you need to re-jet the carb as the powervalve is only active under load (when, is indicated by the number stamped on the valve). I would jet it 2 steps lean at a time ie; if you have 80's, go to 78's. To start I would make jet adjustments "square", meaning... If I change primary jets be 2 stages, I change secondary changes by 2 stages. I am pretty sure you will find better results this way, then play with powervalves. That's my opinion, which doesn't reflect those who know better. LOL, good luck and keep us posted.

Indy

WhiteWindsor

Thanks Indy,
The jets are the only thing i have not changed. I have adjusted the fuel bowls and the four corner idle several times but still not right. I will take your advice on the jets when i get time and let you know how it does.

92BOOSTED

What jets are you using now? Also it may be your throttle blade setting to your transfer slot is not set right either. If your primary and/or secondary throttle plates are set too far open then what happens is the air flow will start pulling fuel from this transfer slot and because it is too far open your mixture screws will not work properly until they are set right. You will need to make sure that the transfer slots have about .020"-.030" uncovered from under the carb.

Ryan

WhiteWindsor

thanks guys, i will be adjusting the carb per your reccomendations this weekend.
Keith

http://s194.photobucket.com/albums/z112/keithswearingen/?action=view¤t=c3a71cc9.pbw

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