Hi I need some more idea,s. I dropped a 1970 455 ci "SF" code in my car. I had light head work done and had valves cleaned up. Running a Stage 1 750 cfm carb. through stock manifolds and 2.25 exhaust. With a NAPA set of points it broke bad at 5000 RPM. I put in a set of Accels and it is better but still breaks up. I would like to make it to 5200 rpm so the car can shift itself out of 1 st. to 2nd.. The motor had about 50000 miles on it and sat with the rockers unbolted. 10 intial timing and about 34 all in. o No:
I strongly advise converting to some sort of electronic ignition. There are countless ways to do this. This will easily get you to your RPM goal and provide consistent and stable timing as well. :TU:
The 750 CFM carb is a weak point. I start pulling vaccum on my 800 CFM carb at about 4800 RPM. A 950 or 1000 will serve you much better at high RPM with a cost in streetability.
Thanks , My timing does bounce a couple degrees, I am looking at a Mallory billit electonic and I have a 800 cfm off a 74 455ci being rebuilt with bigger jets in the secondarys. I want to keep streetable till I find a conv. or who knows what Old altered ,Gasser, Anglia, to put it in and I reinstall the Stage 1. Any suggestion on setting up the 800 cfm or should I go bigger now and save the rebuild money?
Dave, Take a look at the dwell as you rev the motor. Is it relatively stable? Could be a sloppy distributor (bushings). What plugs are you using, and what gap?
Larry I will check the dwell on friday after work . Plugs are AC 44 gap 35. I pulled on a 2003 mustang gt 2 lengths 20 out so something is going right.
The Q-jet is far more streetable than a Holley IMHO. The 800 will certainly run a little faster at high RPM over the 750, particularly a well setup one! It sounds like the best match for what you want :TU:
i had problems with points, i went to a (Crane Cams) modual, and its always smooth to my 6000 RPM shift point, as for carb your 750 is fine for a 5500 rpm moter, at 2500'' i run low 12's at 110 with a 800 Qjet, and stock stage 1 pump, on a SP1 intake with a 1" spacer, leaving my carb 1'' from the hood, and have reved to 6500 rpm and the moter still wanted to go, so in my opion most cars are running to much carb and fuel pump. just my 2 cents
Kelly thanks , I am going to drop in my stage one dist. tonight I have revved it to 6200 with no problem in the stage motor . Like Larry said I may have bad bushings on the original one.
