Hey guys,

I'm really sorry if this has been dealt with before, I've spent quite a while searching this morning on this forum and others, and I've come up with a bunch of conflicting information, so I figured I'd ask here and see if I could get some straight answers.

My buddy and I are Midshipmen at the U.S. Naval Academy, and we've been doing some work to his '80 F100 that he's driving up here (we're both from Texas). Anyways, we've done a pretty good tune up on it, and we're looking to bolt on some more performance out of it this fall. So far, I've got a pair of EFI exhaust manifolds for it on the way. We're also looking at doing an intake and possibly a head swap. Here's where my questions begin.

Are there any benefits (considering the cost of the swap) to going with an EFI head over the factory carbed head? I've heard people say definitely yes, and I've seen others that said the EFI heads are nothing more than "an expensive paperweight". If I should choose to make this swap, are there any considerations as far as switching over the valvetrain or the alignment of the head bolts? Also, are the issues with ignition timing easily solved, or am I going to get in way over my head here?

Finally, I'm looking for some advice on intake setups. I'm really looking towards an aluminum 4-bbl setup such as that offered by Offenhauser. I have heard a lot of ppl say that the way to go is topping it off with a 390cfm holley 4-bbl. These seem to be a little hard to find, and pricey when you do. I was looking at some other options as weel, perhaps a 500 cfm Edelbrock (is this too much?), or a ~400 cfm AFB design. Or would it be cheaper to go with a 2-bbl, and which one would work (I know virtually nothing about the different 2-bbl carbs out there). With any of these carbs, how hard is it going to be to set up the throttle linkage? It's a manual trans truck, so no kickdown, but we don't really have access to any machining to make new brackets, etc. Is there a kit out there designed for this swap, or is it fairly simple?

That's basically the questions I have right now. I just need to know what works, and whats simple and not too expensive. Simplicity is a big deal right now, because we're basically doing this stuff in the parking lot with a basic tool set. I'd feel comfortable tackling just about any of this at home in the shop, but I don't want to get in over my head without the proper tools. Sorry if any of these questions are real beginner stuff, I've got a lot of experience with mechanical work, but almost all of it was on Big Block Mopars. Quite a different beast for certain.

Thanks for the help guys, I really appreciate it.

-Levi

 

The EFI head really is better, they give you higher compression, they also have what is called a 'fast burn' combustion chamber, so you need less initial timing. Valvetrain and head bolts are the same.
The offy aluminum manifold is a dual plane one, so you can only use 4bbl carbs with it, I've been told that ideally you want 1.5-2 CFM of carb for every CI of engine, so anything from 450-600 should work.

 

I run an Edelbrock 500 with an Offenhauser dual plane manifold. It was a challenge because the carburetor sits 90 degrees from the conventional mounting direction, so the throttle swings sideways instead of front to back, if you're standing in front of the truck looking at the engine. Lokar makes a bracket and throttle cable that you can make work with this, however, because of my AC box in my truck, I had no room to pull back on the throttle linkage, as is normally done. What I had to do is engineer a custom throttle bracket that actually lets the throttle cable pull from underneath, as opposted to pull from above, and because of the leverage action, it produces the same effect. Here are some shots of my setup:





Here is the bracket I made:



This all turned out great. You can see in the pictures how I have the throttle linkage pulling forward from the bottom of the throttle shaft, rather than pulling from behind on the top of the throttle shaft going the opposite direction. Unfortunately, I had to place the throttle cable ball stud on the throttle linkage where the kick-down linkage mounts. Because of this, I was not able to install automatic kickdown linkage. However, I can still manually downshift, and I have found that the motor has enough power that I haven't needed the kickdown at all. Again, this was all because of my AC box getting in the way. You mentioned you have a manual transmission, so it's a moot point.

Unfortunately, performance upgrades often entail machine work or customization. With a dual plane manifold on an inline motor, you will have to tackle the fact that the carburetor will be sitting sideways. If you have lots of room in your engine bay without an AC box, you can get away with Lokar brackets and most of the work will be bolt-on; the only real custom work you will have to do would be trimming the aftermarket throttle cable, and mating the pedal-end of the cable to the pedal linkage on the firewall. I was able to do this with a clevis and an eye-bolt.

My manifold came with a chart that tells recommended CFM and for a 300 with an assumed maximum RPM of around 3500 (just throwing that out there), the recommended carburetor size is only 304 CFM. If you go down in RPM, it goes down as well. For example, for 3000 RPM it recommends 260 CFM. I am just pulling this off the chart. You can see these are not heavily breathing motors. They are meant to pull stumps. I do run a 500 CFM carburetor and it does great, however. I ran it straight out of the box, and it runs great, but rich. This can be remedied with different jets and metering rods, however. I do not recommend anything higher than 500 CFM.

Best of luck to you and let me know if you have any questions!

 

JMO, several things come to mind.

A there isn't anything a 2v carb can do that a 4v can't do better including gas mileage.

The Offy DP is the better choice for an otherwise stock or mildly modified 300 since it is designed for low-mid range operation where 99.9% of us drive anyway.

The EFI head is fine but probably not worth obtaining unless you need a new head anyway. A modest porting and polishing job along with a port match with the manifolds and the 3 angle valve job that was recommended will get the most out of your other mods.

The 390 Holley and the 500 Edelbrock are popular. A 400 cfm AFB I think would be ideal but they are hard to come by. Same goes for the Holley 450 cfm Spread bore Economaster. A 750 cfm QuadraJet with small block calibration would be good too and they are readily available. I am a fan of the spread bore configuration...small primaries for mpg and driveability and the bigger secondaries for the "Exxon" contributions.

fmc400 did a great job on the linkage as others have also done with which ever carb they have used...not a hard task for a couple of Midshipmen

 

Guess if the motor only pulls 300 cfm I don't have to worry about putting a canister filter on mine.

Guess this thread answers more than one question out there lol. No wonder that single 3" tube works on my motor.

 

I too am a fan of the spreadbore, but I think for simplicities sake a squarebore might be a bit better application. My buddy who's truck it is hasn't ever really messed with carbs before that much, and a Q-jet is a tough beast to learn on. I've run Q-Jets on my 440, as well as my 403 olds with amazing success, but don't really want to have to deal with the adaptor and other necessaries to fit one on a 300.

I guess the question still remains if the head swap is worth it or not. Basically, will it give any noticable driveability improvement, or are we talking a difference so small here that it's only going to show up in the numbers?

The truck does have an AC box on it, so I'd imagine I'll be left to constructing a bracket for the thing. One question though, you wouldn't happen to be able to get the dimensions off of that bracket you made would you? With a diagram and the correct dimensions, I could get my dad or bro back home to fix one up for me and get it in the mail.

Thanks for the input guys, I will continue to read with interest.

-Levi

 

I'd be happy to. Click the links below. Heads up - the pictures are kind of large because I scanned them in at full resolution to get all the details. These are the drawings that I made and gave to the machine shop.

Main throttle bracket. Mounts to the Offenhauser DP intake using two 3/8" through-bolts with washers and nuts. I think the bolts are 4" UHL.
http://users.ece.utexas.edu/~jlabund...k/bracket4.jpg

Throttle return spring bracket. Mounts to main bracket.
http://users.ece.utexas.edu/~jlabund...k/bracket3.jpg

Pedal bracket adapter. Holds my Lokar cable in front of the factory pedal bracket on my '79 - not sure what other years use the same pedal bracket.
http://users.ece.utexas.edu/~jlabund...k/bracket2.jpg

 

Muchos Gracias. Now there's some diagrams that look familiar to a Mech E.

I'll send the diagrams back to the old shadetree machine shop back home and see what dad can work up.

Thanks,

-Levi

 

Dont forget your rates while working on this!

But anyways, you want more compression. Have your tried fordsix.com? devoted to hopping up ford I6 engines, and there is a section for the 300 alone. A lot of guys will tell you to find a 240 inch I6 head, but I see them going for $1000 or more. Scarcity. most of them have been converted to razor blades decades ago.

The EFI exhausts, I am also going to use, but they do not gather the exhaust in any particular manner like the double downtube headers designed for this. Since I have to maintain emissions I am gong to stagger 2 smaller cats and then run a true dual setup

 

https://www.ford-trucks.com/forums/6...aust-mani.html

Scroll down to a post by 1982f150 where links are posted for drawings and pics of a bracket for a Holley install.

http://cgi.ebay.com/ebaymotors/Edelb...=p4506.c0.m245

New Edelbrock 500...bidding at $102.50 with one day left. Do your shopping. You might be able to save quite a little on whichever carb you settle on.

 

If he puts on a 4bbl carb and intake, does he still need to recurve his distributor for the lack of an egr? And wouldnt a set of headers be more simple and cost effective than an efi manifold?

 

Duraspark_distributor_recurve_instructions_index

EFI exhaust manifolds can be had for about $50 mol and bolt right up. Headers are fine but there are sometimes fitment problems, starter access problem, cracking and/or constantly loosening, etc.

 

Levi,
"Eyes in the boat, mister"

Sorry to hijack your post, but QuadDriver had an interesting comment concerning the desireabliity of the 240 CID head. I was searching threads to get opionons on 4 barrel carb and manifold setups for my 260 I-6. QuadDriver, can you elucidate on that comment please? My head is due (probably over due) for a valve job and I was thinking of just getting a rebuilt 300 head. After reading your comment, I am curious. Thanks.

Keith L. Wagoner
CDR USN (ret)
Class of 84'

 

I have the offy intake with and edelbrock carb. If you put the carb on with the linkage towards the front all you have to do is extend the throttle cable to reach the carb, that's on my 1985 f 150.I just used an aluminum strap with a hole in each end. It is very easy to hook up and much simpler than the setup shown above. Worst case you just replace the throttle cable with the 1980's one and whip up a simple extension.