The Ford Barn

Fat Fender · 09-04-2010, 08:51 PM

I'm putting dual 94's on my 59 AB in my '40 convertible. My question is, do duals effect manifold vacuum? I have the stock vacuum cylinders that work great on the bench. I'm at 6000 ft elevation and with a single carb, the vacuum system just barely does the job. Need I worry about the duals? Thanks for any advice.
Fat Fender

V8 Bob · 09-04-2010, 09:14 PM

If the carbs are identical, with equal jetting, power valves, float settings, and you spend the time to carefully adjust the air bleeds and properly sync the carbs, you should see no loss of vacuum running two 94's. Make sure the timing is set for maximum vacuum, and note the vacuum level now with your present carb. You would be wise to run each carb on the stock intake first to be sure they operate exactlly the same, and with equal vacuum levels.

Ol' Ron · 09-05-2010, 08:08 PM

The Vacuum is created in the manifold and is not dependent on carburetors. If this was a 49-53, that would be a different story.

ken ct · 09-05-2010, 08:12 PM

What are you calling vacume cylinders????? ken ct.

joel · 09-05-2010, 09:01 PM

I'm guessing the convt. top cylinders.

Fat Fender · 09-05-2010, 11:03 PM

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Thanks for the replies. Joel has it right, the vacuum cylinders mentioned were for raising and lowering the top.

09-04-2010, 08:51 PM	#1
Fat Fender Member Join Date: May 2010 Posts: 31	Dual Carb Vacuum I'm putting dual 94's on my 59 AB in my '40 convertible. My question is, do duals effect manifold vacuum? I have the stock vacuum cylinders that work great on the bench. I'm at 6000 ft elevation and with a single carb, the vacuum system just barely does the job. Need I worry about the duals? Thanks for any advice. Fat Fender

09-04-2010, 09:14 PM	#2
V8 Bob Senior Member Join Date: May 2010 Location: Granger (Northern) Indiana Posts: 1,520	Re: Dual Carb Vacuum If the carbs are identical, with equal jetting, power valves, float settings, and you spend the time to carefully adjust the air bleeds and properly sync the carbs, you should see no loss of vacuum running two 94's. Make sure the timing is set for maximum vacuum, and note the vacuum level now with your present carb. You would be wise to run each carb on the stock intake first to be sure they operate exactlly the same, and with equal vacuum levels.

09-05-2010, 08:08 PM	#3
Ol' Ron Senior Member Join Date: May 2010 Location: Chester Vt Posts: 8,862	Re: Dual Carb Vacuum The Vacuum is created in the manifold and is not dependent on carburetors. If this was a 49-53, that would be a different story.

09-05-2010, 08:12 PM	#4
ken ct BANNED Join Date: May 2010 Location: stratford,ct Posts: 5,971	Re: Dual Carb Vacuum What are you calling vacume cylinders????? ken ct.

09-05-2010, 09:01 PM	#5
joel Senior Member Join Date: May 2010 Location: Indiana Posts: 488	Re: Dual Carb Vacuum I'm guessing the convt. top cylinders.

09-05-2010, 11:03 PM	#6
Fat Fender Member Join Date: May 2010 Posts: 31	Re: Dual Carb Vacuum Sponsored Links (Register now to hide all advertisements) Thanks for the replies. Joel has it right, the vacuum cylinders mentioned were for raising and lowering the top.