Will this hurt performance
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Mountain Pass
Joined: Jan 2005
Posts: 141
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Will this hurt performance
Ok lets get things straight first I DO NOT want to buy an aluminum intake. Ok well I have a 75 F100 4x4 with a 4 spd. THe motor is a rebuilt 74 390 out of a 2wd F100 it is bored .30 over and has about 60,000 miles on it. It is currently a two barrel and leaks oil and the front and back of the intake. I want to seal the leaks but I would like to put a four barrel intake on it at the same time. I bought a C3A intake to put on but I have learned now that might not be a good idea. I got it cheap $25 so It's no big deal not to use it. How bad will it hurt performance and fuel mileage if I use this intake I am going to use a holley 600 cfm carb. It will have headers and a 3" exhaust on it. How much should I expect to spend for a later model intake to better match the heads. thanks for all the help.
Post Fiend
Joined: Mar 2004
Posts: 6,056
Likes: 8
From: Union, Washington
That early of an intake will have large ports, 1.16" X 2.14" while the early heads were 1.34" X 2.34") where the later heads will be smaller at 1.34" X 1.93" and the step in the mismatched sizes is a preformance killer going from large to small. Going from small intake to large head is good as the step acts as a revision pulse dam.
Cargo Master
Joined: Apr 2004
Posts: 2,574
Likes: 4
From: Golden, CO
Dude, I just saw your ad on Craigslist!
I looked up your region, went to auto parts, put 390 in the search window. I don't see that much FE stuff listed here in the Denver-Metro. I'm guessing it would only be a matter of time before you have the right intake for the right price.
I looked up your region, went to auto parts, put 390 in the search window. I don't see that much FE stuff listed here in the Denver-Metro. I'm guessing it would only be a matter of time before you have the right intake for the right price.
Post Fiend
Joined: Mar 2004
Posts: 6,056
Likes: 8
From: Union, Washington
Originally Posted by kylecoyote
I know about the head mismatch but will it be worse than the two barrel intake and carb on there now that are worn out stock?
Hotshot
Joined: May 2003
Posts: 11,141
Likes: 25
From: south louisiana
The intake will work. In spite of the port mismatch at the bottom. A better solution though (Bear will dissagree here) is to simply replace the Autolite 2 bbl carb with a Holley list 4412 500 cfm 2 bbl. These carbs are simply half of a 750 double pumper Holley and will bolt on in place of the Autolite carb. The only mod here is a minor reroute of the fuel line. I've used two of these carbs on 4 different motors in th elast 30 years and all performed stellarly.
Post Fiend
Joined: Mar 2004
Posts: 6,056
Likes: 8
From: Union, Washington
Originally Posted by baddad457
The intake will work. In spite of the port mismatch at the bottom. A better solution though (Bear will dissagree here) is to simply replace the Autolite 2 bbl carb with a Holley list 4412 500 cfm 2 bbl. These carbs are simply half of a 750 double pumper Holley and will bolt on in place of the Autolite carb. The only mod here is a minor reroute of the fuel line. I've used two of these carbs on 4 different motors in th elast 30 years and all performed stellarly.
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Mountain Pass
Joined: Jan 2005
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The intake isn't worn out the carb is and all the intakes that I am being offered on craigslist are the early style I already have a new in box holley 9834 to put on the four barrel intake I have experience with the 4412 two barrel on a couple rigs and didn't like it on either one. I just want to know if putting the old style on is going to be worse with performance and gas mileage than what is on it now I dont care if I dont gain anything I just don't want it to be worse thats all that I am asking I dont need any other info thanks for the help.
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Hotshot
Joined: May 2003
Posts: 11,141
Likes: 25
From: south louisiana
The port mismatch won't keep it from running, now what difference it actually has on either performance or mileage isn't something anyone's going to be able to truthfully tell you. I ran a 428PI intake on my 68 Merc's 390 with C8AE-H heads and it had the same mismatch. I used a list 3310 750 cfm Holley on it along with a Crane 272* Energizer cam and the stock 10.25 to 1 pistons. Also used FPA headers. The output was improved over the stock 2 bbl intake and Autolite carb. It was toast anyhow. I had a 500 cfm Holley before the overhaul and it ran great with the stock cam and exhaust manifolds, far better than the Autolite did. Ford frequently used port mismatched intakes in production when the occasion called for it. The Marine 460's had the std 460 heads and a 429SCJ intake, that was one instance. Big port mismatch there, but it worked.
Fleet Mechanic
Joined: Aug 2007
Posts: 1,804
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From: Piney Woods of East Texas
The 3" exhaust will hurt the low end performance. Just way to large to create any back pressure. Normally a properly tuned 4 barrel will get the same gas millage as a 2 barrel and maybe a little better. Installing an over size carb can cause more problems and are harder to tune. 2 barrels are easier to setup and tune.
Hotshot
Joined: May 2003
Posts: 11,141
Likes: 25
From: south louisiana
Originally Posted by kylecoyote
Ok thanks for the information. DId you run it with just the different intake and carb or did you put the cam in at the same time?
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Mountain Pass
Joined: Jan 2005
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THe truck already has all the low end that I need......I dont think that the 600 with vacuum secondaries is oversized...Ill look for an intake for a little longer and if one doesn't come up Ill give the one I have a try thanks for all the help.
Junior User
Joined: Mar 2007
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I put a c4 S code intake on my 360 with d2 heads on them. All I did was grind the bottom of the intake ports on the head so it would give the airflow a smoother transition from the intake manifold. It seems to work fine and I don't notice anything. Since you have a two barrel and switched to a four barrel I think you could notice better throttle response if you have the carb tuned right with a 600 vacuum seconday carb. Since the primary venturis are smaller on the four barrel than on the two barrel the airflow will be a little quicker. But it also depends on you combination of parts on the engine. I think if you are adding headers it will be better also.