Stalls under hard braking (manual brakes)...

[Varilux]

Last year, I installed a 3x1 Offy header on my '65 inline 200 (three Autolite 1100s).

Great performance, but I'm having one issue. When I hit the clutch and brake to a stop, the RPMs drop (if I hit the brakes long and hard enough, the car just eventually flutters and dies).

I have manual brakes, so it's not a vacuum related issue- and this problem didn't occur with the old single carb setup.

The center carb has a dashpot (must have been for an automatic). I have disabled the dashpot, but the stalling issue occurred equally before and after I disconnected it.

Any tips or places to investigate?

Happy Holidays!
Pete

http://www.just-a-six.tumblr.com

 

[RichCreations]

Last year, I installed a 3x1 Offy header on my '65 inline 200 (three Autolite 1100s).

Great performance, but I'm having one issue. When I hit the clutch and brake to a stop, the RPMs drop (if I hit the brakes long and hard enough, the car just eventually flutters and dies).

I have manual brakes, so it's not a vacuum related issue- and this problem didn't occur with the old single carb setup.

The center carb has a dashpot (must have been for an automatic). I have disabled the dashpot, but the stalling issue occurred equally before and after I disconnected it.

Any tips or places to investigate?

Happy Holidays!
Pete

http://www.justasix.tumblr.com

Check your float level in your carbs... too low, it can go lean when fuel sloshes around, too high, and it can "flood" the engine when it sloshes around...

 

[MechRick]

Check your float level in your carbs

+1

Make sure the float drop is close too. It's probably fuel sloshing over into the venturis under hard braking.

 

[B RON CO]

Hi, X2 on float level, but before you pull the center carb apart, I would go over the setup. Check ignition timing first. Assuming the outer carbs are on progressive linkage, make sure they are completely closed at part throttle. Next go over the primary (center) carb mixture screw and idle adjustment screw. You may need a higher idle, especially if there are other performance modifications. I would probably keep the dashpot in place. A final thought is the secondary carbs are open a little early and closing a little late so the engine does not have enough time to transition back to the primary carb. Good luck

 

[Varilux]

Thanks for the suggestions! (I screwed up the link in my first post- my "build page" is at http://www.just-a-six.tumblr.com - fixed it now.)

Regarding the dashpot, it has caused me all kinds of problems ever since I hooked up the new carb. Primarily, the throttle would not return to idle (every time I depressed the clutch, the RPMs would zoom up to around 2500 then settle back down- really annoying). Plus, I was still getting the stalling issue. This leads me to believe I am getting too MUCH fuel (rather than too little) when braking.

I understand the float level (although I've never attempted to adjust). Basically, if I'm getting too much fuel I should move the float down (so it will close off the fuel flow quicker). What is the "float drop?" My guess is my problem is exactly as you described (i.e., fuel is sloshing into the venturis). Assuming that is the actual problem, what do I need to do when I get the carb apart?

Regarding timing, I should also point out I have a mechanical / vacuum advance HEI distributor (not the SCV Sparkomatic, or whatever the stock distributor was called). I have the idle at around 1,100 RPMs (could idle slower, but in the Summer when I kick on the A/C it brings the idle down to about 600-700 RPM).

I'd really like to get this one solved because it really impacts the drivability (not very fun to drive a car you have to fight to keep running at every stop).

Thanks again for the help, and MERRY CHRISTMAS!

 

[B RON CO]

Hi, I got the dashpot issue, but it is hard to believe there is that much lag for the dashpot to settle down. Ok, so at over 1000 RPM your idle is too high. Can you lower it to under 900 for now? I would play with that. If you warm it up and rev it and let off the gas it should snap back and idle with no problem. The throttle is open too much for the carb to transition from idle to main jet. Also I would see what happens if the secondary carbs come in a little later. I also wonder if the clutch is out of adjustment and dragging when in gear. Does it stall in neutral or only with the clutch down in gear.

 

[ledslinger29]

That's just sexy.

 

[MechRick]

"Float drop" is the amount of travel off the seat closed position. It limits float travel which limits needle movement off the seat. Too much can cause all kinds of nasty fuel problems. The float can catch the bowl, the needle can get stuck off the seat and fuel flow can occillate. It's really critical on 4x4's due to angles, but under hard acceleration or braking the same symptoms can occur in street vehicles.

 

[Varilux]

Problem solved! Thanks for all the advice...

Finally had time to get in the garage and pop open the carb. I happen to have an extra brand new Autolite 1100 on the bench, so I decided to open both my current carb and the extra one to compare. Once I did, the problem seemed pretty obvious.

On my current carb, the float was set really low, and I could see the level of fuel in the reservoir was correspondingly low as well. I'm assuming the stalling was caused by the low level of fuel sloshing to the front of the bowl- leaving the pick up tube sucking air.

Rather than trying to bend the float arm, I decided just to swap in the upper portion of the spare carb (I could see the float was set much higher in the spare carb). I buttoned everything back up and took a drive. The first thing I noticed was the idle was a bit more consistent (which allowed me to lower my idle to 900 RPMs). The even better thing I noticed was I could stand on the brakes without having the RPMs drop off at all! So, problem fixed and the car is going to be a lot more pleasant to drive!

Thanks again, and Happy New Year!

 

[chad]

try turning the screw…it should idle @ much lower (500 - 600 rpm).

 

[Varilux]

Once it's warm, it idles nicely at 600 rpm (and with the mild cam it even sounds a bit "lopey"). With the float being off, it didn't particularly idle very well at 600, but I'm sure it would idle there now- once warm.

However, I do not have a choke (so when it's cold it needs a faster idle) and in the summer it needs a faster idle when the A/C is on (kicking the A/C on usually brings the idle down about 300 rpm). So, I just let it idle a bit faster than it should. Fortunately, we don't get very many cold days here in Dallas. To be honest, if it's that cold I probably won't be driving the Mustang- although the heater in that thing will roast you if you leave it full blast... especially on the passenger side of the car!