CFM rating for the Holley’s used on Flatheads

[Merc Cruzer]

Where can I find a chart that lists the CFM rating for the Holley’s used on the flatheads for Ford, Lincoln and Mercury’s?

[oldskool]

i mostly see 390 cfm used on flatheads

['36 5W]

I think he is referring to the o.e.m. 2 barrel models that originally came on the flatheads.
They ranged from 145-185 c.f.m. Check the Holley website for a model-specific chart, or
perhaps someone else will chime in......

[Merc Cruzer]

First of all thank you for the information. Sorry, I should have been more specific....Looking for the 1901 "Teapot" style used on the 52'-53' Mercury’s....bottom line looking for the same design of Carb with a larger venturi...possibly use for a different application (possibly a different manufacture of engine), figuring that Holley was used extensively during the mid 50's. Due to may altitude -8300 ft. that with more air, I could increase the jet size for more power….yet still use the same air cleaner.

[stromberg81]

Smaller jets at higher altitude..Adding gas doesn't give you more power..
Duane..

[jdl]

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Originally Posted by Merc Cruzer

Where can I find a chart that lists the CFM rating for the Holley’s used on the flatheads for Ford, Lincoln and Mercury’s?

May not be the chart you need, but it is for the type of carb you have.
click the link.

http://www.oldcarmanualproject.com/m...190119522.html

[Merc Cruzer]

Originally Posted by stromberg81

Smaller jets at higher altitude..Adding gas doesn't give you more power..

Originally Posted by stromberg81

Duane..

I agree that you cannot just add more fuel.....But if you add more air.... (larger Venturi's).... then you can add more gas, hence the reason I am looking for basically the same carb (design) with larger Venturi's.....it would seem to stand to reason that if you keep the 14.7 : 1 ratio, and get a carb that would provide more air....


More air+ more fuel = more power (the basis behind a turbo or supercharger)


I did find a chart that refers to 1952-1953 Model = POLICE SPEC - R-745A, -3A, -4A, -4AAS -HOLLEY 1901 , Now I need to find out more about this carb...and what the difference was.

[barnfind08]

I think I have n.o.s. ones of the above mentioned carb. Bought out the holly factory in 1975. These are 4bolt are they not.

[Merc Cruzer]

barnfind08:

You are correct they are 4 bolt...here is are a couple of pictures of what it should look like...

[jake197000]

adding a bigger carb will only help if the engine can handle it.almost always error on the small side when it comes to carbs,the engine will be more responsive and snappier.

[rotorwrench]

I'm an aircraft mechanic that deals with higher altitudes and engines. The cfm ratings are more about how much air a particular engine can pull through it with volumetric efficiency taken into account. Some aircraft carburetors have a built in automatic mixture control that leans the mixture by barometric pressure changes. Most of the rest of them have manual mixture controls so you can lean it by ear or by EGT (exhaust gas temps). These engines are taken up as high as 23,000 feet as long as they have some form of turbocharging. If no turbo, about 13,000 is it. The Mercury carbs had 54 size jets for 5000 to 10,000 ft and 56 jets for 5000 feet or less. I think the 1901 is near 185 to 200 CFM. I'm fairly sure the old Holley 885 in my 51 is about the same. The choke & outer shroud design are the biggest difference between those two models. All the 255 CID flatheads probably had the same CFM rating and they are only 16 cubic inches more than the Ford 239 CID engines.

Kerby

[Merc Cruzer]

Originally Posted by rotorwrench

I'm an aircraft mechanic that deals with higher altitudes and engines. The cfm ratings are more about how much air a particular engine can pull through it with volumetric efficiency taken into account. Some aircraft carburetors have a built in automatic mixture control that leans the mixture by barometric pressure changes. Most of the rest of them have manual mixture controls so you can lean it by ear or by EGT (exhaust gas temps). These engines are taken up as high as 23,000 feet as long as they have some form of turbocharging. If no turbo, about 13,000 is it. The Mercury carbs had 54 size jets for 5000 to 10,000 ft and 56 jets for 5000 feet or less. I think the 1901 is near 185 to 200 CFM. I'm fairly sure the old Holley 885 in my 51 is about the same. The choke & outer shroud design are the biggest difference between those two models. All the 255 CID flatheads probably had the same CFM rating and they are only 16 cubic inches more than the Ford 239 CID engines.

Kerby

This was offered up by 51 MERC-CT:

I believe the 1901 Merc. carb has a venturi size of 1.030"
The 1901 carb on the '52 heavy duty Ford truck is 1.093"
The 1901 carb on the '52 Lincoln is 1.172"
You may be better off going in that direction

[rotorwrench]

The 52/53 F7-F700 & F8-F800 trucks used the 279 cid block and the 52/53 Lincoln used the 317 cid block. I think the 54 F700 & F800 used the 317 cid block. That would be why the venturi sizes are different. They might have had a manual choke on the trucks but I don't know for sure.

It might be easier to find a Lincoln than one of those big trucks now days. The jetting would probably need to be changed for a smaller displacement engine too. The trucks would likely have that god awful looking governor on there.

Kerby

PS: Another bit to think about is that the engine you want to up cfm on is still only going to draw so much air. Bigger cfm translates into less throttle opening for a similar rpm. The jets would likely have to be even smaller to get it to work at higher altitudes.