Holley carb
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Junior User
Joined: Jun 2001
Posts: 89
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From: Danville, AL
Holley carb
I finally got the numbers off my carb and decided to look it up to see what size carb I had. The list number on the carb was 8007. 3174 was listed below(not sure if that matters). The carb was on the truck when I purchased it. According to holley's site its a 390cfm 4-barrel. One question I had was if this carb should even be on my 390cid? Holley's site says that this carb is for small block V8's and 6cyl's. Also, there are several tubes coming from the carb with machine screws stuck in the to plug them. It doesn't look like the electric choke is connected either. I have no clue when it comes to carbs so if anyone has any suggestions I would greatly appreciate it. Below is the link on holley's site that I believe is the carb I have. Please double check me and make sure I am correct.
http://www.holley.com/0-8007.asp
1975 F150 390cid
http://www.holley.com/0-8007.asp
1975 F150 390cid
Post Fiend
Joined: Mar 2004
Posts: 6,056
Likes: 8
From: Union, Washington
Well, that carb should have unreal throttle response (because of the small throttle bores) and do real well on gas mileage on a 390 motor (again because of the small throttle bores) but the top end is gonna be lazy. If the motor is a stock truck 390, they came with a 350CFM 2 barrel. But since the 2 and 4 barrels are rated for CFM differently, that 2 barrel would be a 248CFM in 4 barrel speak so the 390CFM 4 barrel is an big improvement but with the formula numbers that 390CFM would only rev you to 3500 rpm. But then the 2 barrel runs the motor to 4500 rpms, so yeah it will work with a bunch of low end grunt, but the top end is gonna be sluggish, pretty much like the original 2 barrel was. A 500 or 600CFM vacuum secondary carb would be better for top end, but just how much time do you spend with your motor wound out to max RPM? Not very much at all, unless you race all the time. And example is my 490 came with a 600CFM 4 barrel so the 390 should be fine for a street motor.
Postmaster
Joined: Jul 2003
Posts: 3,934
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From: iowa
well it is a 390cfm 4160 based carb. It is middle of the line between 2bbl and 4bbl carb. It will make less hp than an 600cfm carb but it has more than a stock 351 or 356cfm 2bbl. The 2bbbl carbs are rated at a 3 inches of mercury vs 1.5 for the 4bbl's. Like with cylinder heads a 28.0, depression will pull more air than 10.0 inches of mercury.
Post Fiend
Joined: Mar 2004
Posts: 6,056
Likes: 8
From: Union, Washington
It will surprise you how little a trailer will change things, if you run a truck bed canopy. It's not the weight that hurts you, but the wind resistance. My camper kills my gas mileage in both my F250s, but any trailer behind them changes nothing. With a canopy on the trucks the trailers don't change my mileage. My 1999 Ranger gets better mileage when I have a quad in the bed and the other quads on the trailer than it does with nothing in the bed and all the quads on the trailer. It's about aerodynamics with trucks rather than weight.
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Joined: Nov 2005
Posts: 166
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From: Rainier, OR
390 Cfm???
I just got my 352 back from the machine shop and it was converted to a 390.
Here's what was done(per the receipts):
Parts
1. engine kit (pistons, rings, rod & main bearings, cam bearings, gaskets, oil pump, timing set, freeze plugs, comp cam '268H-10', and lifters)
2. 390 crank
3. 390 connecting rods
4. int & exh valves
5. valve springs
6. push rods
7. oil pump drive???
8. harmonic balancer seal sleeve
9. cam thrust plate (it was broke)
10. fuel pump eccentric kit (I had converted to elec pump)
11. reconditioned rocker arm shafts
12. Edelbrock Performer 390 intake
13. flywheel ring gear
I thought the time to finish was excessive and price was a bit high $2986 but I didn't break a sweat with all this work and didn't even get dirty.
P.S. Some pics in my album and all pics at my website http://www.azcyberspace.com/65ford.php
I'm looking at a 750cfm for this? Is that overkill? I tend to have a lead foot.
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Here's what was done(per the receipts):
Parts
1. engine kit (pistons, rings, rod & main bearings, cam bearings, gaskets, oil pump, timing set, freeze plugs, comp cam '268H-10', and lifters)
2. 390 crank
3. 390 connecting rods
4. int & exh valves
5. valve springs
6. push rods
7. oil pump drive???
8. harmonic balancer seal sleeve
9. cam thrust plate (it was broke)
10. fuel pump eccentric kit (I had converted to elec pump)
11. reconditioned rocker arm shafts
12. Edelbrock Performer 390 intake
13. flywheel ring gear
I thought the time to finish was excessive and price was a bit high $2986 but I didn't break a sweat with all this work and didn't even get dirty.
P.S. Some pics in my album and all pics at my website http://www.azcyberspace.com/65ford.php
I'm looking at a 750cfm for this? Is that overkill? I tend to have a lead foot.
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Thread Starter
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Junior User
Joined: Jun 2001
Posts: 89
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From: Danville, AL
I don't have a lead foot but I'm just worried that with the camper behind me the 390cfm carb will hurt me more than it helps. Any suggestions on a new carb?
Last edited by Fireman1212; Jul 31, 2006 at 10:37 PM.
Post Fiend
Joined: Mar 2004
Posts: 6,056
Likes: 8
From: Union, Washington
Go with a 600CFM with vacuum operated secondaries. I prefer the Holleys. I still have several of the first generation 600 Holley's, the list # 1850. Then again I know how to tune and mod these carbs to get them to do what I want or need for my engine, drive train and load requirements.
Hotshot
Joined: May 2003
Posts: 11,141
Likes: 25
From: south louisiana
Originally Posted by Bear 45/70
Well, that carb should have unreal throttle response (because of the small throttle bores) and do real well on gas mileage on a 390 motor (again because of the small throttle bores) but the top end is gonna be lazy. If the motor is a stock truck 390, they came with a 350CFM 2 barrel. But since the 2 and 4 barrels are rated for CFM differently, that 2 barrel would be a 248CFM in 4 barrel speak
Post Fiend
Joined: Mar 2004
Posts: 6,056
Likes: 8
From: Union, Washington
Originally Posted by baddad457
Your misleading some here. Although the 2 bbl carb is rated differently, it would still flow what it's rated at vs the 4 bbl. It's rated at a higher vac drop because it's only two bbls. It it's rated at 350 cfm, that's what it flows at that vacuum level. I terms of venturi size, yea, it's comparable to a 248 cfm carb but with a the same size cubes pulling on it, it will flow more than those two sized barrels would on a 4 bore carb with the same enigine pulling on it.
Hotshot
Joined: May 2003
Posts: 11,141
Likes: 25
From: south louisiana
That may be so but telling someone that the 2 bbl actually flows less than a similarly rated 4 bbl is misleading. The reason Holley rated the 2 bbls at a 3" drop was that's a more realistic rating level for an engine pulling a vacuum on 2 bbls vs 4. Put a 500 cfm Holley 2bbl on a 302 and it will likely flow less than it would on a 390, more cubes pulling on ANY carb changes the ACTUAL flow, not the rated cfm. That's a constant you cannot change. The 500 in terms of actual bore or venturi size is exactly half of a 750 cfm 4 bbl. BUT it will flow more than half a 750's rated cfm, simply because it will see a stronger vacuum signal on those two bbls, vs 4 of the same size. Close the secondaries on the 750 and it will flow the same cfm as a 500. Sure the actual cfm may or may not be 500, based on the engine drawing air thru it, but it will still flow more air thru those two bbls vs the same two with two more of the same size opened next to them.
Post Fiend
Joined: Mar 2004
Posts: 6,056
Likes: 8
From: Union, Washington
Your comparison is an "apple to oranges" comparison. I was just trying to make it an "apples to apples" comparison. A 500CFM rated 4 barrel will have much smaller throttle bores and venturis than a 500CFM rated 2 barrel and will have much better throttle response. As a Holley tech at the Nationals in Tulsa, OK once told me, "a lot of little holes work much better than a couple of big holes".
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Post Fiend
Joined: Dec 2003
Posts: 6,658
Likes: 4
From: "Islander"
Higher venturi velocity carbs of equal cfm numbers will have better throttle response and torque numbers vs lower venturi velocity numbers hands down due to better fuel atomization (smaller fuel particles) unless it's a drag motor that runs full throttle. I can see "I hate Holley's") due to not understanding how they work or how you can tune them. JMO's
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Last edited by "Beemer Nut"; Aug 2, 2006 at 09:25 PM.