Too Much Carb?
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Senior User
Joined: Jan 2004
Posts: 169
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From: Hesperia CA
Too Much Carb?
I've got a 65 F250 with a standard 2bbl 352 that's needin' some repairing.
The 2 bbl's leaking at the pump diaphragm which ain't a big job, but the intake manifold is also leaking oil at the rear of the block and that's one heavy sob!
An aluminum Edelbrock is an obvious choice but here's the thing on a carb, I've already got a 750 Holley. New in the box. $100. Vacuum secondary with a mechanical choke.
That'd be fine on that 410" stroker motor I'd like to build someday but whadddaya guys think on a plain ol' 352? Too much carb?
The 2 bbl's leaking at the pump diaphragm which ain't a big job, but the intake manifold is also leaking oil at the rear of the block and that's one heavy sob!
An aluminum Edelbrock is an obvious choice but here's the thing on a carb, I've already got a 750 Holley. New in the box. $100. Vacuum secondary with a mechanical choke.
That'd be fine on that 410" stroker motor I'd like to build someday but whadddaya guys think on a plain ol' 352? Too much carb?
Post Fiend
Joined: Jan 2003
Posts: 8,600
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From: Iowa
I do agree that it's probably too much carb, but you have it so give it a shot. Throw it on there and run it. It'll probably work fine. The vacuum secondaries will "size" the carb to the engine, so the thing will probably never get the opportunity to flow the full 750cfm, though.
Logistics Pro
Joined: Apr 2005
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I just got my 600CFM H*lley, here's a chart it has on the side of the box:
(For vacuum secondary carbs)
-----------------Engine Type---------------
----------------Mild Hot Wild----------------
Engine Size
300------ 390CFM 600CFM 650CFM
350------ 600CFM 650CFM 750CFM
400------ 650CFM 750CFM 750CFM
450------ 750CFM 750CFM 850CFM
500------ 750CFM 850CFM 950CFM
550------ 850CFM 950CFM 950CFM
(For vacuum secondary carbs)
-----------------Engine Type---------------
----------------Mild Hot Wild----------------
Engine Size
300------ 390CFM 600CFM 650CFM
350------ 600CFM 650CFM 750CFM
400------ 650CFM 750CFM 750CFM
450------ 750CFM 750CFM 850CFM
500------ 750CFM 850CFM 950CFM
550------ 850CFM 950CFM 950CFM
Last edited by Chevy_Eater; Jan 7, 2006 at 10:10 PM.
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Senior User
Joined: Jun 2004
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From: las vegas nv.
small block big block carb size...
some deep into the night surfing for power reading has brought me to this,unless you have a highly unusual fe a 750 carb will be way too much. A 600 to 650 or so is better, use it for trading material for what you need.It's not just the jets and such but the size of the carb also gives the correct vacuum ...when the carb gets too big you loose vacuum , you get less efficient mixture from lower volocities and less throttle response. some big time engine builders use a formula for the vacuum and volume at given rpm's.Also,as strange as it sounds a chevy 350...small block...can use a higher cfm carb than a big block because of the difference in runner length and volume in manifold design and the demand on available mixture from the manifold every time a cylinder calls for it.Check out HTTP://www.victorylibrary.com/mopar/intake-tech-c.htm
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Posting Guru
Joined: Jul 2003
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From: Colville, Washington
The 750 cfm will work fine since you already have it. I would get some smaller jets to fine tune it to the 352, but aside from that it will work as is.
Remember the cfm of the carb does NOT make it run richer only total potential airflow; the jets, secondary metering plate and power valve control the air/fuel mixture.
Remember the cfm of the carb does NOT make it run richer only total potential airflow; the jets, secondary metering plate and power valve control the air/fuel mixture.
Post Fiend
Joined: Jan 2003
Posts: 8,600
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From: Iowa
Something interesting to note here:
Holley 500cfm 2 barrel throttle bore diameter - 1 11/16"
Holley 750cfm 4 barrel throttle bore diameter - 1 11/16"
I dont think we would be complaining too much if he was putting a 500cfm 2 barrel on it. This 750 also has vacuum secondaries, so if the engine doesn't need the extra air, it doesn't get it. It's not like he's got a double-pumper. So what's the big deal here?
Holley 500cfm 2 barrel throttle bore diameter - 1 11/16"
Holley 750cfm 4 barrel throttle bore diameter - 1 11/16"
I dont think we would be complaining too much if he was putting a 500cfm 2 barrel on it. This 750 also has vacuum secondaries, so if the engine doesn't need the extra air, it doesn't get it. It's not like he's got a double-pumper. So what's the big deal here?
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Senior User
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From: Hesperia CA
Wow! Great discussion and Thank You one and all for the responses.
Based on the "I already have it" principle I'm gonna give it a shot. I've raced 2 bbl Holleys and still got the jet kit, power valves, squirters, etc. A vacuum secondary is a new deal for me but I hear there's a spring in there somewhere that controls the opening. I'll find it.
So that leads me to the next question, bearing in mind I'm not looking for high rpm work but would like to build a solid 390 or 410 with a cam and headers some day, what kinda manifold? Single plane? Dual? Aluminum Edelbrock I suppose. Maybe a decent cast iron outa the junkyard?
Based on the "I already have it" principle I'm gonna give it a shot. I've raced 2 bbl Holleys and still got the jet kit, power valves, squirters, etc. A vacuum secondary is a new deal for me but I hear there's a spring in there somewhere that controls the opening. I'll find it.
So that leads me to the next question, bearing in mind I'm not looking for high rpm work but would like to build a solid 390 or 410 with a cam and headers some day, what kinda manifold? Single plane? Dual? Aluminum Edelbrock I suppose. Maybe a decent cast iron outa the junkyard?
Senior User
Joined: Jun 2004
Posts: 264
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From: las vegas nv.
I guess I got excited about something I read,and Rusty70f100 makes a valid point and I don't know that much about Holleys. Now in moderation I have more to think about...and about the manifold...I ran a Holly street dominator for a while and flat out on the freeway it was amazing (single plane) but I felt I could do better on lower end.I found an Offenhauser dual port in a guys backyard and currently running it.So from experience the stock 4v was a step up and ran good,the Holley was crazy good on top and the Offey is strong on bottom and mid and feels like a kick in the pants when the secondaries open.But I think it lacks a little on the very top (around a 100 and up)...
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From: Evanston, WY
Originally Posted by pntrbl
Wow! Great discussion and Thank You one and all for the responses.
Based on the "I already have it" principle I'm gonna give it a shot. I've raced 2 bbl Holleys and still got the jet kit, power valves, squirters, etc. A vacuum secondary is a new deal for me but I hear there's a spring in there somewhere that controls the opening. I'll find it.
So that leads me to the next question, bearing in mind I'm not looking for high rpm work but would like to build a solid 390 or 410 with a cam and headers some day, what kinda manifold? Single plane? Dual? Aluminum Edelbrock I suppose. Maybe a decent cast iron outa the junkyard?
Based on the "I already have it" principle I'm gonna give it a shot. I've raced 2 bbl Holleys and still got the jet kit, power valves, squirters, etc. A vacuum secondary is a new deal for me but I hear there's a spring in there somewhere that controls the opening. I'll find it.
So that leads me to the next question, bearing in mind I'm not looking for high rpm work but would like to build a solid 390 or 410 with a cam and headers some day, what kinda manifold? Single plane? Dual? Aluminum Edelbrock I suppose. Maybe a decent cast iron outa the junkyard?
-Scouder