Join Date: Feb 2013
Location: Lloydminster, Alberta
Carb tuning blower engine
Looking for some feedback on a car I’ve been working on this summer. 33 ford pro street style rod with a 350, edelbrock heads, b&m 250 blower at 6-7 psi and 1850 carbs.
I had 2 1850’s set up according to a recipe given by Tuner on fuel systems forum.
The engine runs well, except for a couple issues.
I had to go from 35 squirters and white cams to green cams to eliminate a lean pop when snapping the throttle. It would pop the blow off plate. But now if you hit the throttle hard more than once the engine loads up (doesn’t rev as high or quickly the second hit). There is no black smoke when you hit the throttle to the floor from an idle.
I have the mixture screws set for highest vacuum of 11.5” at 825 rpm idle. 1 turn. Any leaner and I can get a lean pop once in a while if I snap the throttle a few times in succession. Any leaner and the idle vacuum becomes unstable.
The strange thing is that every time you blip the throttle, or hit it to the floor from an idle or revved up to 2000, the engine will rev, but when it idles back down (and quite quickly), it loads up and the idle drops to 500 or so for a split second. Then recovers and comes back up to 800-825. There is a slight puff of black out the pipes when the rpm recover. If I lean the mixture screws this rpm recovery becomes better, but then it has a lean pop once in a while. And the idle vacuum becomes unstable as mentioned earlier.
Also, when I hold it at 2000 rpm for 10 seconds or so, then let off the throttle, the rpm will drop all the way to the point that the engine quits, like it’s out of fuel?
Timing is locked at 30, BKR6E plugs gapped at .030”. MSD dist with 6al box and blaster 2 coil. 6.5 psi fuel pressure, floats set so the fuel is at the bottom of the screw holes. If I bump the car fuel will seep out of the holes.
I haven’t tuned a car with a blower before, wondering if some of this isn’t unusual? Or any suggestions?