Stalling when hard braking

[91r/t]

Just put the 70 idle air bleed jets back in it. I’ll adjust idle circuit again with a vacuum gauge and if it gets better I know I have a lean idle condition and if it’s no change or worse I know I’m chasing the wrong area and I’ll head into the vacuum issue and manual brakes possibly. I’m not going to screw around with vacuum pumps and ****. I have the parts to swap it to manual brakes and quite honestly I prefer them. Shitty weather the next few days, so won’t be able to test until Tuesday possibly.

 

[91r/t]

Ok. So I tried the 70 idle air bleeds. It’s still stalls when hitting the pedal hard which I think is a vacuum issue. Changing the float level didn’t help either. I also tried it in reverse and it does it as well which would kind of disapprove the fuel sloshing away from the jets. What I did find with the 70 air bleeds is that the idle screws have no affect on stalling the car out when turned all the way in because the car is running way too fat at idle. I’m going to go back to the 74s which seem to work way better and then readjust everything back to those air bleeds. I’m going to use the factory headlight vacuum canister that I found in a parts box that I had and use that to supplement vacuum to the booster tank. My headlights don’t currently work so I have the canister sitting around doing nothing so that will look stock and hopefully solve my problem.

 

[91r/t]

74's are 11.5% larger in area than the 70's. that's a noticeable step to the lean side. from what info I have most of those QF850's had .070" idle air bleed. you might want to check the idle jet. i'd think the idle jet should be at least .035" with the 70.

i'd also look at the timing curve in the distributor. it may need to be brought in quicker.

If I bump up to a 72-74 idle bleed and its a tad on the leaner side, can't I supplement that by adding a bit more fuel on the idle circuit adjustment screws on the 4 corners? Right now its so fat at idle with the blades open so far to keep it running....it isn't responding at all to the idle screws being turned all the way in which means its pig rich. I even choked it down to a 750 RPM idle (which is hates with the big cam) to ensure it was idling on the idle circuit and still nothing. When I had the 74's in it, it would stall out if I screwed em all the way in which is what I believe is supposed to happen. So I am thinking I am going back to 72-74 idle bleeds to clean that back up then try that vacuum can on the other issue.

 

[91r/t]

Forgot to update you all......tied into the manifold vacuum and used the canister for the headlights to store vacuum for the booster. Solved my problems. Enough vacuum for the brakes and all is well!!

 

[Mopar4Speed]

If you have power steering you can convert to a hydro-boost brake system or even simpler is to get a electric vacuum pump and connect that directly to the booster. Just my 2 cents..

 

[Stroker68]

Need a float with the provisions for the extensions.

AED jet extension will work with stock Holley floats. Always use them in rear bowl for hard launch. Should work in front also. Might consider vacuum leak/loss from brake booster.

 

[Stroker68]

Forgot to update you all......tied into the manifold vacuum and used the canister for the headlights to store vacuum for the booster. Solved my problems. Enough vacuum for the brakes and all is well!!

Nice work