Reply to "What is a must to do ?"

You can run any cam that you want to.

The issue is that if you are going to run any kind of a filter over the stacks then you need to eliminate the fuel reversion.

What will happen if you don't is that the filer elements will get soaked with fuel and WILL catch fire the next time you try to start the car.

Jim Inglese had CompCams design one, although there are a couple of other cam companies that make them also.

The key specification is that the valve overlap has to be held to under 30 degrees total.

I believe that the CompCam spec was 28 degees. Coincidentally the Ford 4v Cleveland hydraulic cam overlap is 28 degrees as well.

One of the issues with these "Weber cams" is that the overlap does two things. It provides pressure to the intake cycle in pressurizing the plenum of a conventional intake manifold with a common plenum and pushes mixture into the next opening intake valve.

It also provides an exhaust presurization, a negative one, i.e., suction that helps the exhaust headers "scavenge" (suck out) exhaust from the exhaust valve.

If you reduce overlap, you reduce scavaging of the exhaust also.

You definitely are giving horsepower away there in the exhaust as a result.


Back in the day when these Weber individual runner manifolds were run on race cars, they used the same radical overlap camshafts in the engine as they would have with a single Holley manifold.


The 69 Boss 302's also ran an individual runner manifold initially with two Holley Donimator carbs. They had reversion of fuel also.

They used a flat aluminum plate, ostensibly for keeping foreign objects out of the open stacks, but really primarily for collecting the atomized fuel vapor in one place and permitting it to drain (drip off) in a safe place.

In the Ford GT40, that is what the alumimum "cookie sheet" over the carbs is all about.

My opinion is that if you are going to worry about running open stacks and need to cover them to feel comfortable, go to fuel injection.

You will have no reversion with that since there will be no fuel held in suspension with that system, the fuel injector shoots a timed and measured quantity of fuel into the intake port.

Actually there can be a small amount of reversion with those fuel injectors depending upon where the fuel is being shot, if it is all being sucked into the intake port or if some can't be used and it is bouncing off the port wall or valve and going the wrong direction BUT that has to do with the adjustment in tuning made with the computer.

It tends to be a non-issue though.

Primarily with Webers, you just run a stainless steel screen over each stack. How you engineer that though is another subject.