2v vs. 4v carb
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Elder User
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From: AL
2v vs. 4v carb
I just bought a '70 F250 with the original 390. It's been sitting for awhile and the carb needs cleaning/rebuilding. I plan to drain the tank, blow out fuel lines and change the fuel pump for good measure.
I was thinking of swapping in a new 4v and an Edelbrock manifold instead of rebuilding the existing 2V. When the engine needs a rebuild I will install a RV cam other than that it will remain stock. I will use this truck for towing a camper around 3000# for now, one day we may upgrade to something that weighs around 5000#.
Is the 4v a good upgrade? I thought I'd improve fuel milage under normal driving and increase power when I open the secondaries.
What would be a good size (cfm) carb for this application? What brand carb adapts easily to the 390?
I was thinking of swapping in a new 4v and an Edelbrock manifold instead of rebuilding the existing 2V. When the engine needs a rebuild I will install a RV cam other than that it will remain stock. I will use this truck for towing a camper around 3000# for now, one day we may upgrade to something that weighs around 5000#.
Is the 4v a good upgrade? I thought I'd improve fuel milage under normal driving and increase power when I open the secondaries.
What would be a good size (cfm) carb for this application? What brand carb adapts easily to the 390?
Logistics Pro
Joined: Jan 2011
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From: Antelope Valley ,CA
You'll get mixed opinions on this ,
personally i think it's worth it on a stock 390 stick to max 600 cfm vacuum secondary carb and a dual plane intake . adding headers will be the best mod as the stock exhaust manifolds are real constrictive .
personally i think it's worth it on a stock 390 stick to max 600 cfm vacuum secondary carb and a dual plane intake . adding headers will be the best mod as the stock exhaust manifolds are real constrictive .
FTE Leadership Emeritus
Joined: Jul 2002
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From: Long Island USA
600cfm should do just fine for mildly-built 390s. 700+ should only be done if you really WANT to spend a lot of time tuning the carb, AND are going to go very high revs. Otherwise, 600 will be just fine.
Me, I'd go Holley, but that's just me - I'm used to them.
Fleet Owner
Joined: Jun 1999
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From: Creedmoor, North Carolina
It is very likely that the 390 is really a 360 (you can measure the stroke to be sure). If that's the case rebuilding the carb might be a better option.
Get a 390 in there for sure, with at least full dual exhaust, headers better, then the 4 barrel becomes better option.
John
Get a 390 in there for sure, with at least full dual exhaust, headers better, then the 4 barrel becomes better option.
John
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From: AL
Your right about most 390's being a 360. I checked the stroke and it's a 390. In 1970 all they offered in the trucks was a 390 with a 2bbl. Same for late 60's through early 70's
The truck has dual exhaust now but stock manifolds. It sounds like I should rebuild the 2bbl and spend my money on headers now and be on the look out for a used Edelbrock 4bbl manifold.
The truck has dual exhaust now but stock manifolds. It sounds like I should rebuild the 2bbl and spend my money on headers now and be on the look out for a used Edelbrock 4bbl manifold.
FTE Leadership Emeritus
Joined: Jul 2002
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From: Long Island USA
Sounds like a plan. When I put headers on a completely stock 360, it really woke up, even with a 2bbl. I can only imagine the 390 will wake up just as much if not more.
Let us know how it works out
Let us know how it works out
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From: AL
Thanks for all the help!!
One more question. What brands are preferences for headers?
On my 55 Chevy car I've been running ceramic coated Headman headers that are ceramic coated. My car is used daily and so far they haven't given me any trouble. They have the ball & socket connection to the pipe which have proven to be leak free. I also installed Earl's gaskets for the header flange to head mount and they haven't leaked so far. This combination has around 35k miles. Now they do hang down lower than the frame rail which I don't like, they have some road scares as well.
One more question. What brands are preferences for headers?
On my 55 Chevy car I've been running ceramic coated Headman headers that are ceramic coated. My car is used daily and so far they haven't given me any trouble. They have the ball & socket connection to the pipe which have proven to be leak free. I also installed Earl's gaskets for the header flange to head mount and they haven't leaked so far. This combination has around 35k miles. Now they do hang down lower than the frame rail which I don't like, they have some road scares as well.
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Hotshot
Joined: May 2003
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From: south louisiana
Not sure where you learned that. I had a 70 F100 that supposedly had a 390, but ended up being a 410, and it had a 4 bbl from the factory. All that aside, for what you're going to do with it, I agree with the looking for a used 4 bbl(aluminum) intake, no point in spending money on a new intake. But another option would be a 500 cfm Holley 2 bbl, these are dead reliable and perfectly sized for a 390. Their only drawback is the 50 cc acellerator pump. It will however bolt right onto your 2 bbl intake and only require a minor fuel line reroute. If you do nothing else, get a set of headers on it.
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From: AL
I was going by the 1969 thru 1971 brochure on the 390/2bbl info.
The previous owner actually replaced the original Carter 2bbl. with a 500 cfm Holley 2bbl. several years ago. It's been sitting and probably only needs cleaning. I'm going to service it, blow out the fuel lines, drain the tank, install a new fuel pump and install some headers for now.
You mentioned the 500 cfm Holley's 50cc accelerator pump being a drawback. How would I correct this? Does it need something more aggressive or does it need to be smaller. Can this be changed?
Thanks again for the help. I'm brand new to FE motors.
The previous owner actually replaced the original Carter 2bbl. with a 500 cfm Holley 2bbl. several years ago. It's been sitting and probably only needs cleaning. I'm going to service it, blow out the fuel lines, drain the tank, install a new fuel pump and install some headers for now.
You mentioned the 500 cfm Holley's 50cc accelerator pump being a drawback. How would I correct this? Does it need something more aggressive or does it need to be smaller. Can this be changed?
Thanks again for the help. I'm brand new to FE motors.
Post Fiend
Joined: Dec 2007
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From: Lost
I'd bet there were more 2v 390's in F100's, than 4v. There were enough of each to warrent a different engine code for 2v vs 4v. H = 390 2v 73-76, M = 390 4v, but it only appears to have been an option for 75-76. I don't think a 4v 390 was even offered 68-74.
Fleet Owner
Joined: Jun 1999
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From: Creedmoor, North Carolina
I am aware of the 390 availability, most FEs are sold as 390s when they were 352s & 360s. Truth is of all FEs installed in trucks very few were actually factory 390s.
Don't know what you are looking for in mpg improvement, but about 1 might be all you pickup. These ol brickbats aren't able to find it anywhere. Too much wind resistance.
John
Don't know what you are looking for in mpg improvement, but about 1 might be all you pickup. These ol brickbats aren't able to find it anywhere. Too much wind resistance.
John
Hotshot
Joined: May 2003
Posts: 11,141
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From: south louisiana
I was going by the 1969 thru 1971 brochure on the 390/2bbl info.
The previous owner actually replaced the original Carter 2bbl. with a 500 cfm Holley 2bbl. several years ago. It's been sitting and probably only needs cleaning. I'm going to service it, blow out the fuel lines, drain the tank, install a new fuel pump and install some headers for now.
You mentioned the 500 cfm Holley's 50cc accelerator pump being a drawback. How would I correct this? Does it need something more aggressive or does it need to be smaller. Can this be changed?
Thanks again for the help. I'm brand new to FE motors.
The previous owner actually replaced the original Carter 2bbl. with a 500 cfm Holley 2bbl. several years ago. It's been sitting and probably only needs cleaning. I'm going to service it, blow out the fuel lines, drain the tank, install a new fuel pump and install some headers for now.
You mentioned the 500 cfm Holley's 50cc accelerator pump being a drawback. How would I correct this? Does it need something more aggressive or does it need to be smaller. Can this be changed?
Thanks again for the help. I'm brand new to FE motors.
Post Fiend
Joined: Dec 2007
Posts: 8,521
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From: Lost
Did you purchase this truck new? I have heard of others claiming the same, but have never found anyone that could *prove* the 410 4V was actually factory installed. I would love to believe these were factory installed, but I truely suspect most were salvage yard purchases swapped early in the truck's life.
Ford sales literature showed the 390 2V was the largest engine offered for a F100 until 75. The 460 4V could be had as early as 73, but only in F250/350.
I don't recall if the 390 4V was offered prior to 75 in the F250/350, but doesn't show as an option for F100's thru 74 (F150 didn't exist until 75).