Hot Rods Intake question (intentional vacuum leak)

Have you milled the throttle plates or at least beveled them for better airflow plus all of the above suggestions and I have cut the 400 block numbers out on the back of the motor and put some 010 block numbers JB welded in place with just enough track dirt to hide the cuts. You also have bondo up the cut away in the balancer and put a timing tape on it. 3 time former track champion when I ran dirt track.

 

We ran into this years ago racing a class that was carb limited. The 3 most common things done I am aware of were:

1. Gun drilled carb studs at all 4 corners and angle drilling into the base of the carb stud holes.
2. Gun drilled air cleaner stud with the air cleaner stud hole in the carb drilled clear thru the base plate. We bought a very expensive 390 4V Holley that had this done to it and it wouldn't idle if you left the stud out. The small hole let it idle with the stud in place.
3. Loose base plate bolts. use nyloc nuts. It will idle normally but at full throttle it will lift the carb and let a lot more air in. Works pretty well but hard on rings.

Have you sent the carb to a really good carb guy? We tried all that crap but a well built 390 out performed all of them. We had almost $3500 in a Holley 390. Take all the specs to the limits of the gauges. Cams also make a huge difference on these engines. Work with a cam grinder for what fits your track best.

Enjoy,
SPark

 

A friend of mine said he used the thick, rigid base gasket with washers hidden under it and really fat jetting.

Gary

 

Don't tamper with the carb , That's cheating!!!

Pull the diaphragm from the brake booster [make sure the vacuum hose goes under the carb base]

 

Have you tried two PCV valves?? I did that on a 2bbl drag car. It did pick it up 5-6 hundreds.

 

I think you should try the underside air Jets in each runner. It would be better if you could pressurize the crankcase at WOT too. They will suck oil at high manifold vacuum

 

I would work the carburetor to its legal limits and then work on the distributor advance curve.