sbc V8 quits on hard braking

[Miles]

While I was road testing rear brake adjustment on my 72 240Z with a 350 sbc the engine would just quit when making a hard stop (clutch in). I am guessing that this may have something to do with carb float adjustment. Any ideas?

 

Thanks

 

Miles

[denny411]

that sounds similiar to a problem I was discussing earlier today. This guy told me he had a 72 240 that would stall out when he made a hard turn. (right or left he couldn`t remember) My suggestion was the float.

[Guest Carlissimo]

Miles,

Sounds like you are on the right track. The fuel level is probably too low. Most carbs have a screw on the side you can remove so you can check the level in the bowl. The fuel should be right at the bottom of the screw hole.

[blueovalz]

This still happens to me even with all levels correct. I have the center pivot floats, and wonder if the side pivot would be better in this case. Unfortunately, the side force handling is more important to me than this problem is. So I am interested in any responses too. My Carter AFB carbs do not do this though.

[Tim240z]

Try this:

Set the front float level (primary circuit) slightly on the high side (not too much!!), and set the rear floats a little lower than ideal. It is unlikely that you will run the secondary bowls dry, unless you are doing sustained high rpm/speed driving, which unless it is track day, is unlikely.

What may (emphasize 'may') be happening is the fuel from the secondary (rear) bowl is sloshing into the choke tower and momentarily flooding the motor, enough to stall it with the throttle closed.

If you want to see if this is the case, set the rear float level to well below normal, so that the bowl is running almost dry, then do a hard brake and see what happens. If the exercise works, then slowly increase the float level until it starts choking a little on hard breaking and leave it there.

Remember not to run to the point of opening the secondaries while the float levels are set very low 'cause you will end up running very lean.

HTH...let us know if you come right.

Tim

[Mike C]

Tim beat me to it... Another thing you can do is take a piece of rubber fule line and connect the front and rear vents. Then take a razor blade and trim the top out of the hose. This effectively extends the vents and gives extra volume before fuel sloshes into the engine. The danger of the low rear float is fuel starvation on take-off. Jet extensions should be MANDATORY if you are running the rear float low, and are not a bad idea on a hard launching car anyways.