Dies if brakes are applied suddenly

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slowdown

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So it's done this as long as I've driven it, just wondering what the deal is I haven't found it yet. While driving around no problems at all but say if I am behind someone who stops short or the light turns red an I have to stop suddenly, I have to try an peddle it to keep it from dying not bad just a little peddle to keep it running, on a sudden stop. It's a four speed car so it's not hard to peddle a little, no power brakes. It's a small block 318 with 4 inch stroke,rhs heads,xe284 comp cam, headers 2.5 exh, 3:55 gear,750 holly dp, mp dist chrome box, small b&m supercharger still not pos of size between 162 an 177? And the 4 speed I had mentioned earlier. I've read somewhere if I had extensions on my rear jets this might help? I'm not sure.
I did adjust jets front and back but don't remember if this carb has exstentions. I do have another carb that I do know for sure has exstentions it's a quick fuel, I can pull these to try if this might be it, I just hate to rob from a good carburetor. But if it fixes it the problem I'll have to just get a set to replace them. Any thoughts would be appreciated, Thanks. Ps running 18 initial timing, 1000 rpm idle to keep plugs cleaner as its kinda choppy below that, had plug fouling in the past. Not now nice tan.
 
I know nothing of such a combo. Maybe a vacuum tank? You would want a check valve in the appropriate spot, the line to the vacuum source.
 
Check float level. Sounds like it is to low. Recheck state of tune and timing.
 
That sounds like it could be an issue where the fuel shifting in the bowls is affecting the idle mixture.

It happens.

Extensions may very well be the answer after all.

Oh, just saw the low float post. :D

Low float and fuel moving combined could very well be why it tries to die at hard stops.
 
Thanks guys. I'll keep fiddling with it. All good points, I will check them all.
 
Float level is incorrect, go to Holley's web site, it will have very good instructions on how to adjust it.
This issue has nothing to do with jets.
 
I think it is a vacuum issue caused by the blower. the transition circuit needs to be fined tuned. Its going from a positive pressure to a negative pressure.
 
Mopar Tim said:
I think it is a vacuum issue caused by the blower. the transition circuit needs to be fined tuned. Its going from a positive pressure to a negative pressure.
Click to expand...

X2 I missed the blower on the initial post, tired last night.

Did you boost reference the power valves?
I gave you a link on how to do it in another thread.
I have a whole box of 6-32 set screws if you need some, pm me so I do not forget.

http://www.motorsportsvillage.com/modifycarb.html
 
The same thing happened to me, 1967 Barracuda with a 273 & four speed.

It turned out that the thrust bearing was so worn that the crankshaft was actually sliding forward in the block. One of the crank balance weights was hitting the block webbing & it would literally make the engine grind to a stop.

It would always restart (after cranking a while, sometimes longer than others) until the engine seized & cracked the block.
 
Weathers been crappy so I haven't messed with it, I will when it warms up a bit. To reflect the car runs great, it's just if I have to slam on the brakes all of a sudden like. The carb is a blower carb with a vacuum port connected to the blower off the bottom of the carb. I did have to lower the bowls per the holly video direction, as it was syphoning fuel when I would shut off the car. And make it hard to start. I will check an recheck all of your suggestions when it warms up a bit thanks again.
 
may need jet extensions on the primary jets. extensions on the secondary side is for lack of fuel under hard acceleration
 
Does it do this if you just suddenly pull your foot off the gas and pop it out of gear, to drop quickly from a few thou RPM to idle RPM? And are you pushing in the clutch or popping it out of gear when you brake hard, casuign a quick drop in engine RPM's? Just looking for a reason to think that a sudden stop in air flow is upsetting the mixture; it will tend to go rich with any sudden stoppage in airflow, regardless of carb position and deceleration forces.
 
nm9stheham said:
Does it do this if you just suddenly pull your foot off the gas and pop it out of gear, to drop quickly from a few thou RPM to idle RPM? And are you pushing in the clutch or popping it out of gear when you brake hard, casuign a quick drop in engine RPM's? Just looking for a reason to think that a sudden stop in air flow is upsetting the mixture; it will tend to go rich with any sudden stoppage in airflow, regardless of carb position and deceleration forces.
Click to expand...
it does it under a sudden stop, but I usually have enough time peddle it a little an it stays running. If I have to slam on the brakes while stepping on the clutch also, it will die if I don't peddle it a little. I guess the fix might be not to ride people's asses. Lol.
 
I think the float level is too low, like was suggested halfway through this thread. Is it set where the fuel level (primary & secondary) is at the bottom of the sight plugs?
 
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