[dave6911]

I have a 67 chevelle with a 355, vortec heads, 750 speed demon carb, a MSD 6AL ignition, Comp cams extreme energy 268 with 1.6 roller tip rocker arms. Edlebrock RMP airgap intake, and flat top pistons approx 10:1 compression. The problem: when I hit the gas the car basically dies out, however, if I leave off of the throttle it corrects itself. If I have the car at 3000rpm and hit the throttle hard it will die out completely. If I ease into the throttle I don't have a problem. I dont' think it's in the carb because I had a 600 Edlebrock carb and it did the same thing. Timing is set at 12deg inital and 32deg total @ 2500 rpm. Thanks ahead for any suggestion

 

[steve70malibu]

I have a 67 chevelle with a 355, vortec heads, 750 speed demon carb, a MSD 6AL ignition, Comp cams extreme energy 268 with 1.6 roller tip rocker arms. Edlebrock RMP airgap intake, and flat top pistons approx 10:1 compression. The problem: when I hit the gas the car basically dies out, however, if I leave off of the throttle it corrects itself. If I have the car at 3000rpm and hit the throttle hard it will die out completely. If I ease into the throttle I don't have a problem. I dont' think it's in the carb because I had a 600 Edlebrock carb and it did the same thing. Timing is set at 12deg inital and 32deg total @ 2500 rpm. Thanks ahead for any suggestion

Sounds like the pump shot is not strong enough or fuel pressure is too low, check all the obvious things then try squirter changes.

Steve

 

[dave6911]

Thanks.... I'll try that.

 

[SWHEATON]

Its likely a timing & carb/fuel delivery issue of some kind.

But 1st check to ensure the fuel filter is not clogged,the fuel pump hasn't gone bad,of the accel pump diaphram hasnt gone bad or isnt out of adj on the prim side of carb.

If those things check out ok then you should get the timing corrected 1st before looking into the carb any firther. .

If your running an aftermarket perf cam the 12 deg initial is not enough so its fairly retartded which results in wasted fuel,lost power,little hotter runing motor,and yes sometimes hesitation like your experiencing.

Most mild to hot aftermarket mild to hot cams need approx 17-18 deg initial so advance it and try that.

You should be looking for approx 36-38 total max all in by 2800-3k rpms.

If the total goes over 38 by only a couple deg with 18 then back off the initial to 16 deg.

But if the total is over 40 deg you need to have the mech adv in the dist limited to 20deg max in by 3k rpms.

Then 16-18 initial + 20 deg mech in the dist = 36-38 total.

You should also run a vac adv that will give you approx 12-14 deg additional advance for better throttle resp & fuel economy.

Now after you get the ign timing squared away then its time to look into the carb if you still have the stumble or hesitation problem.

You should quickly re-check check to ensure the accelorator pump is working and adj correctly so it starts to activate/squirt fuel as soon as the prim thottle blades start to move as this can often cause or collectively be part of the problem your having.

If the accell pump is ok & it still hesitates when giving it gas while crsuing at 3k rpms i would then look into the prim jets being too lean along with wrong power valve thats not starting to activate/open when the intake manifold vacuum drops as throttle is opened and load on motor increases thus requiring more fuel.

If its a vac sec carb then you should also check to see if the secondaries are not opening up too fast at too low of an rpm . This could also add to the problem but only when the thottle is almost all the way to the floor & not like when easily taking off from a stop.

Scott