Carb to hood spacing
 

How much room is needed between the carburetor vent tubes and the underside of the hood before problems can arise? I just installed a flat style hood on my 67 Camaro to be able to comply with a local race class which does not allow me to use my cowl hood. My vent tubes are beveled 45 degrees, but the flat top of the tube is about 1/4 inch from touching the hood. Luckily, there is a small crease in the center of the hood that is beveled up giving me a little bit of room. I'm also concerned with how much space is needed between the top of the opening of the carb and the hood. I don't like the idea of not using an air cleaner, which also does not allow the hood to close when installed. I do have a 1" spacer under the carb that is custom made to the opening of the intake carb mounting surface. I know could just remove this, but not sure how much it will affect the performance of the engine. I have moved the hood hinges up to the highest position possible. Looking for some input from you Stock & Super Stock racers.

Re: Carb to hood spacing
 

I recall someone doing some dyno testing using a Stock legal Holley (in other words, choke plate and horn intact) to see how close the underside of the hood in relation to the top of the choke horn would be. They mounted a chunk of plywood over the dyno and did pulls at various heights to see at what point there was a performance drop off. The magic number turned out to be 2".

Jim Caughlin
SS 6019

Re: Carb to hood spacing
 

Space the back of the hood,tell everyone the springs are weak :eek:

Re: Carb to hood spacing
 

Someone told me to try actually lowering the front hood hinge bolt. The rear bolt hole is not adjustable, but the front one is. It might sound backwards, but try it. I guess it kind of makes sense. If you lower the front of the hinge, in theory it might push up on the rear of the hood. Going to try adjusting it today.

Re: Carb to hood spacing
 

OK here’s a scenario if you had the hood open and had an air cleaner on it say a low profile air cleaner, how much room would you have between the vents and the top of the air cleaner? probably not much. So it’s probably around the same as the hood to vent clearance now.
I would suggest making a pass as close as it is and then taking that spacer off and making another pass see if there’s any difference.
go back with which one you prefer. Forget about adjusting the hood and making that look all stupid!

Re: Carb to hood spacing
 

Thanks Keith, that's exactly what I plan on doing, making back to back passes, 1 with and 1 without the spacer. Great perspective on original clearance of vent tubes under the air cleaner.

Re: Carb to hood spacing
 

I completely agree and you can add a carriage bolt in place of the air cleaner stud. Adjust it so that it barely clears the hood when shut. This way if your hood moves or engine moves slightly the vents will not be covered.

Robert

Re: Carb to hood spacing
 

Make the tubes as short as possible and cut at an angle.

Re: Carb to hood spacing
 

You can also lower the engine by redrilling the mounts and resectioning the frame mount if you have enough oil pan clearance....

Just make sure that you reset the pinion angles

Re: Carb to hood spacing
 

It depends with the type of carburetor, choke tower/no choke tower, hood scoop/no hood scoop.

For a flat hood car, minimum 2" and if allowed, use a lower pan drop down air cleaner pan. With a big block car, if possible, a minimum of 3".

Due to the air flow path, turbulence and design, with an active air scoop, a minimum of 4" clearance.