The Ford Barn

L78CHEVELLE · 07-12-2019, 06:31 PM

Here are some things I have found out about power valves and jets for the Holley 94 carburetor series 91-99 Ford used in 1940. The standard power valves Ford used with the 94 carburetor was 7.5. The standard jet size is 51. I will not go into all the details about these two pieces just to save time. One of my original 1940 cars was smooth but no acceleration. I took the carburetor off to check its condition and found the power valve to be a size 5.5 and the jet size to be 51. I ran a vacuum check on my car and it has 20 inches of vacuum. Holley says to divide the vacuum reading I get by 2 and that is the power valve size I need. I discovered the largest power valve you can put in a 94 carburetor is 8.5, unless you want to make modification to the carburetor body in the area the power valve plunger functions. I installed an 8.5 power valve with a nylon gasket made for a Holley 94 carburetor and reinstalled the carburetor. This change I made to the power valve size brought this car alive. Acceleration is much improved with the only negative being less fuel mileage. I have even taken the carburetor off again and installed a set of 53 jets, which made the car run even better. If you would like more acceleration from your Holley 94 carburetor try the vacuum test and check your power valve and jet size. Maybe what I have learned will help you get more performance out of your car. Just for the record, I did the spark plug test after I installed the 53 jets and my plugs are just a slight tan color. More power and less miles per gallon is OK by me.

L78CHEVELLE · 07-12-2019, 06:39 PM

The carburetor I just changed the power valve and jet size on was a rebuilt carburetor from Daytona Carburetor two years ago. Do not know why they put a 5.5 power valve in a single carburetor original set up. Carburetor looks like a piece of art work, but no acceleration.

aussie merc · 07-12-2019, 07:15 PM

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carburetors are funny things and need to be reset to suit your local fuel sometimes up one size sometimes down manufactures jett at sea level using test fuel with fixed temp and humidity and not the real world

07-12-2019, 06:31 PM	#1
L78CHEVELLE Senior Member Join Date: Jul 2010 Location: London Kentucky Posts: 356	40 Ford power valve & jet solution for my car Here are some things I have found out about power valves and jets for the Holley 94 carburetor series 91-99 Ford used in 1940. The standard power valves Ford used with the 94 carburetor was 7.5. The standard jet size is 51. I will not go into all the details about these two pieces just to save time. One of my original 1940 cars was smooth but no acceleration. I took the carburetor off to check its condition and found the power valve to be a size 5.5 and the jet size to be 51. I ran a vacuum check on my car and it has 20 inches of vacuum. Holley says to divide the vacuum reading I get by 2 and that is the power valve size I need. I discovered the largest power valve you can put in a 94 carburetor is 8.5, unless you want to make modification to the carburetor body in the area the power valve plunger functions. I installed an 8.5 power valve with a nylon gasket made for a Holley 94 carburetor and reinstalled the carburetor. This change I made to the power valve size brought this car alive. Acceleration is much improved with the only negative being less fuel mileage. I have even taken the carburetor off again and installed a set of 53 jets, which made the car run even better. If you would like more acceleration from your Holley 94 carburetor try the vacuum test and check your power valve and jet size. Maybe what I have learned will help you get more performance out of your car. Just for the record, I did the spark plug test after I installed the 53 jets and my plugs are just a slight tan color. More power and less miles per gallon is OK by me.

07-12-2019, 06:39 PM	#2
L78CHEVELLE Senior Member Join Date: Jul 2010 Location: London Kentucky Posts: 356	Re: 40 Ford power valve & jet solution for my car The carburetor I just changed the power valve and jet size on was a rebuilt carburetor from Daytona Carburetor two years ago. Do not know why they put a 5.5 power valve in a single carburetor original set up. Carburetor looks like a piece of art work, but no acceleration.

07-12-2019, 07:15 PM	#3
aussie merc Senior Member Join Date: Sep 2016 Location: sydney australia Posts: 1,030	Re: 40 Ford power valve & jet solution for my car Sponsored Links (Register now to hide all advertisements) carburetors are funny things and need to be reset to suit your local fuel sometimes up one size sometimes down manufactures jett at sea level using test fuel with fixed temp and humidity and not the real world