my engine runs really great with no problems aside from this. if i brake lightly it is ok. however when i brake pretty hard, my engine will almost die, (rpms drop to 200) but then comes back. is this a vacuum leak?

 

You definitely need to utilize a vacuum gauge while the car is in gear....

It could be one of two things bro;

1) With the car idling, hold you're left foot on the brake very firmly, then with the right foot, mash the gas.... then release. If it wants to stall, then yes, you have a vacuum leak!

2) If she wants to stall ONLY after braking, as well as after you make a turn.... then it's the float in the CARB, she's probably set too low, especially if you added to the engine.

But if she's a new crate engine, then it's probably somewhere in the vacuum lines.... where's you're brake vacuum hooked up?

 

Its definately #1. i have it hooked up to the port on the back of the 650 dp carb. whats the best way to check for leaks?

 

With the car idling.... spray some CARB Cleaner around the intake manifold bolts, as well as by the CARB base. Once you hear the engine 'rev up', this is the area where you're vacuum leak will be....

If possible, if you're not utilizing the vacuum port on the intake manifold itself.... get you're hands on a fitting for it, then hook the brake line to the new fitting on the intake manifold (only if no vacuum leak is detected though.... otherwise just correct the vacuum leak, and leave the brake vacuum line where it is).

 

i will do this tomorrow, thanks

 

question. on a 650 holly dp, where does the brake booster hook up? i put it in the big posrt on the back of the carb...shouls it be there or in the intake manifold????

 

it should go onto the intake man...

 

the carb hangs over the hole in the intake where it is supposed to go, it the only place i can think to put it. is it ok to have it connected on the carb?

 

They have fittings that are angled at 90°, you'll have to remove the CARB, add some thread sealant to the fitting, then simply install it...

But, if you're brakes are working okay, and you found you're vacuum leak, then the above is optional.... however, you get a much stronger vacuum pull from the intake.

 

well, i found it. turns out that the hose by the distributor cracked a little, so it wasnt visible. i replaced it and all is well again. thanks for all your help!

 

Excellent!!