I'm curious about how much the clearance between carb and hood may affect engine performance. I thought about it quite some time ago, but set the idea aside since the engine/car seems to run great. I assume it's the same as it was back when this car was raced by prior owners, which gives me reason to think it's not necessarily something to worry about. Thinking about it again, after a good friends pop was asking me about it at the last race. I haven't gotten an accurate measurement, but eyeballing it, there can't be more than 2 inches clearance here. Thinking about putting a block of clay up there and closing the hood to see what it shows. Any thoughts/opinions on this?

Thanks.

My flat hood was real close. I don't have a measurement. Didn't notice any performance difference when I went to a 4" cowl.

I even think there might be consistency in having less fresh air available. It's always the same hot, dirty air.

I've always heard 3 inches of clearance, which begs the question, what if you have a air cleaner with a top, it's certainly not 3 inches from the top of the carburetor.

What does help is using an air pan to trap the air into and around the carb. That resulted in a 3, almost 4 mph gain in my car.

Bob

quote:

Originally posted by Lenny5160:
My flat hood was real close. I don't have a measurement. Didn't notice any performance difference when I went to a 4" cowl.

I even think there might be consistency in having less fresh air available. It's always the same hot, dirty air.

Agreed. I have a 4” cowl and when I blocked off the rear opening with some cardboard to try it ran the same numbers. I use an air cleaner.

3 fingers is all you need.

My car ran just fine this way.

However, just spent 75 hours lowering a Victor E for more room. More so to try different spacers.

I think mine was at about 3/4" - 1" before it affected performance, installed the scoop, and use an air cleaner base sealed to the hood.
Have added an air filter after finding a big rock laying on the front float bowl, when my distributor rotor broke, and the engine died during the burnout.
I'll always believe that broken rotor saved my engine that night.

Thanks for the input. Given the history and competitiveness I know this car to have had over the decades, I didn't think it would be an issue, but it's nice to hear from others who've been there before me. I'll likely be adding an air cleaner base, similar to the one in Chad's picture. I remember doing that in the 90's with one of my cars. Don't remember any performance gains, but it seemed to be a good idea back then to shield the carb intake from heat.

1 5/8 is what our flow guys say. Chucks AA Hemi car has less….. so did his AH car .

I once cut the vent tube partially off to get the hood to close and didn't have problems.

We have about 3/4" of hood clearance on our big block truck with a flat hood. On Nickersons chassis dyno we lost 11 hp by simply closing the hood. Not sure it really means anything on the ticket, but it definitely lost power on back to back pulls.

quote:

Originally posted by HS professor:
We have about 3/4" of hood clearance on our big block truck with a flat hood. On Nickersons chassis dyno we lost 11 hp by simply closing the hood. Not sure it really means anything on the ticket, but it definitely lost power on back to back pulls.

This is what I have found on the dyno, you straighten the air going into the carburetor, you will make more power. It's not much maybe 1-2% max

Joe

quote:

Originally posted by sr4440:

quote:

Originally posted by HS professor:
We have about 3/4" of hood clearance on our big block truck with a flat hood. On Nickersons chassis dyno we lost 11 hp by simply closing the hood. Not sure it really means anything on the ticket, but it definitely lost power on back to back pulls.

This is what I have found on the dyno, you straighten the air going into the carburetor, you will make more power. It's not much maybe 1-2% max

Joe

I'm pretty surprised at how little clearance seems to affect things, based on what folks have said. I should have an old K&N stubstack from the early 90's somewhere. As I recall, it's supposed to help contour/straighten out the airflow. Never noticed a difference back then, but the car wasn't that fast either. Probably in the 450-500 HP range. If I come across it, maybe I'll try it out and see if there's any noticeable improvement. Thanks for the input.