cut off during hard braking
Thread Starter
Safety Car
Joined: Nov 2007
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From: bottom of the sea
cut off during hard braking
my vette cuts off if i have to brake hard. i have checked the bowl level and it is about 3/4 of the way to the top of the site glass. am i missing something?
Safety Car
Joined: Sep 2005
Posts: 4,226
Likes: 643
From: Orange County Ca
And, you may have to set the secondary bowl level even a little lower to keep the fuel from splashing over on heavy braking. And, I'm assuming you have a Holley, you can buy plastic extension tubes for the bowl vents that will also help.
Thread Starter
Safety Car
Joined: Nov 2007
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From: bottom of the sea
yes i have power brakes.
so your saying that my floats are to high? i thought they needed to be that high to STOP it from cutting off. i will try the lower setting and see what happens. are ther other things that could cause this?
so your saying that my floats are to high? i thought they needed to be that high to STOP it from cutting off. i will try the lower setting and see what happens. are ther other things that could cause this?
Melting Slicks
Joined: May 2007
Posts: 3,246
Likes: 4
From: Bay Area CA
I bought a 4175 Holley spread bore replacement Brand New from Summit a while ago. It did the same thing, would die on heavy braking, or in a fast U-turn, or almost die on a steep hill if you taped the brakes on the way down. Adjusted both float levels up, same thing. down- same thing. back to stock- same thing. took it off, sent it to Holley for testing and adjustment, got it back,, put it back on- same thing. Put My Rochester back on, actually increases slightly, ~50 rpm, on heavy stop braking. Now in pieces in it's box in the hall way. Couldn't find the cause. If it's a new Carb, send it back for replacement, was thinking the problem may be in the metering block.
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Safety Car
Joined: Sep 2005
Posts: 4,226
Likes: 643
From: Orange County Ca
Yes, possibly. Not sure about Demons, but aren't they simular to a Holley? When you hit the brakes hard and the nose drops, fuel from the secondary bowl could slosh into the vent, then into the carb/engine and flood it. When I bought my car, it had a spread bore holley and when I lowered the float level on the secondary side, which is towards the rear of the car, it helped the problem. The Holley Q jet replacement is different than a regular Holly, and the vent extension tubes don't fit. I went back to a Q jet and life is good.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
With a "closed" throttle and actuating the power brakes, if you have no vacuum reservoir to provide vacuum "volume", the vacuum brake servo probably changes the vacuum level of the engine and alters the timing...maybe enough to kill it.
Melting Slicks
Joined: May 2007
Posts: 3,246
Likes: 4
From: Bay Area CA
Interesting idea, but that would mean stepping on the brakes at Any Time would kill the motor. If his problem is like mine, when standing still, ideling, stomp on the brakes- not a change, only when the car is moving at idel.
Thread Starter
Safety Car
Joined: Nov 2007
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From: bottom of the sea
the brakes get their vac from under the carb, so it makes little difference if your closed or not. my vette doesnt have a vac cannister other than the big pipe thing in the front, under the lights
Thread Starter
Safety Car
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From: bottom of the sea
Team Owner
Joined: Jul 1999
Posts: 26,545
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From: Huntersville NC
Just one thing to rule out before you go tearing into the carb:
Make sure your battery connections are tight and clean!
My car was "dying" on hard braking and I learned (the hard way) that my battery connections were bad and the battery wasn't held down properly so the darn thing was shifting under hard braking. The problem became obvious when driving at night. Hit the brakes and the lights went out.
Make sure your battery connections are tight and clean!
My car was "dying" on hard braking and I learned (the hard way) that my battery connections were bad and the battery wasn't held down properly so the darn thing was shifting under hard braking. The problem became obvious when driving at night. Hit the brakes and the lights went out.
Thread Starter
Safety Car
Joined: Nov 2007
Posts: 3,570
Likes: 0
From: bottom of the sea
Just one thing to rule out before you go tearing into the carb:
Make sure your battery connections are tight and clean!
My car was "dying" on hard braking and I learned (the hard way) that my battery connections were bad and the battery wasn't held down properly so the darn thing was shifting under hard braking. The problem became obvious when driving at night. Hit the brakes and the lights went out.
Make sure your battery connections are tight and clean!
My car was "dying" on hard braking and I learned (the hard way) that my battery connections were bad and the battery wasn't held down properly so the darn thing was shifting under hard braking. The problem became obvious when driving at night. Hit the brakes and the lights went out.
Drifting
Joined: Apr 2007
Posts: 1,970
Likes: 45
From: Cameron Park CA
Holley makes these things called "Fuel Bowl Vent Baffle/Whistle" p/n 26-40. http://www.holley.com/26-40.asp
IF your problem is caused by the secondary bowl fuel sloshing out the vent and down the secondary barrels, this part might be helpful That's assuming it will fit a Demon carb too.
My 4150 has them on both primary and secondary bowls from the factory.
Hope this helps,
Pete
IF your problem is caused by the secondary bowl fuel sloshing out the vent and down the secondary barrels, this part might be helpful That's assuming it will fit a Demon carb too.
My 4150 has them on both primary and secondary bowls from the factory.
Hope this helps,
Pete