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Carb to hood clearance question
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DRR Trophy
Picture of BTR69
posted
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.


William Kilduff
1970 Barracuda
1968 Camaro X2
1968 Caprice
1964 F100
 
Posts: 302 | Location: Wilmington NC | Registered: June 15, 2014Reply With QuoteReport This Post
DRR S/Pro
Picture of Lenny5160
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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.


Tony Leonard
 
Posts: 3379 | Location: Inver Grove Heights, MN | Registered: March 18, 2004Reply With QuoteReport This Post
DRR S/Pro
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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
 
Posts: 3524 | Location: Lakeside, Ca | Registered: February 15, 2003Reply With QuoteReport This Post
DRR S/Pro
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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.
 
Posts: 3171 | Location: 53056 | Registered: December 30, 2009Reply With QuoteReport This Post
DRR Pro
Picture of SpeierRacingHeads
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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.



Chad Speier
785-623-0963
 
Posts: 1461 | Location: Hays Kansas | Registered: January 23, 2006Reply With QuoteReport This Post
DRR Pro
Picture of Goob
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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.


"Despite the high cost of living, it remains popular."
Dave Cook
N375
 
Posts: 2174 | Location: Indy | Registered: November 21, 2008Reply With QuoteReport This Post
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