I'm in the process of ugrading the six in my 80 F-100. I'm not trying to build a hot-rod, I simply want to be able to do more than 70 mph on the highway without having to get out and push. I'm putting on a set of headers [haven't decided which ones yet - suggestions are welcomed] I'm also going with the Offenhauser manifold. My question is which carburetor will work best for what I want? Should I go with the Holley 390cfm 4bbl or the Holley 350cfm 2bbl? I'm not upgrading the cam at this time. Thanks for the input - BUBBA

 

I would think your truck should easily do 90 unless you have an extremely high rear end ratio. I wonder if there isn't some other problem, such as an exhaust system restriction like clogged cat or something. Do a tune up and go over to make sure everything is working well and if still no power, then pursue add ons. Definitely want a better flowing exhaust for an upgrade. The split manifold from a late 80s or 90s 300 I6 would be great (assuming it bolts right on).

INLINE SIX POWER!
300 Cubic Inches of Low RPM Truck Torque! And twin-I-beams too!
"Drive a stick young man! There'll be time for automatics when you're old and unable."

 

Hello there. I just installed the Offy DP intake and the Holley 390. It was part of my rebuild project, I also used a Crane PowerMax 260 cam and the later model split manifolds. I'm impressed with most all but the dial-in on the carb, I can't get idle below 900 rpm and fast idle is at 2000. I'll be back at it this afternoon, tweaking and stuff, but I am happy overall.

Good Luck!

Les

 

Glad it worked out for you. Don't know my cam numbers much but am thinking would the cam you bought require a higher idle due to greater valve overlap? So maybe everything is OK.

 

Good thought, I'll have to check that out when I have more time. Thanks for the info, people like you make this a most valuable and enjoyable resource.

Thx again!

Les

 

A 260 cam shouldn't have any lope...

What is causing you to idle at 900? Will it just not go lower without stalling?


-=Whittey=-

 

I would like opinions also on which way to go, either Holley 350 2bbl or 390 4bbl. Stock cam, would like better gas mileage and more response up to 2500 rpm. My mechanic says the 350 would give me better low end response. Hope for some answers for me and bubba4fl. Thanks.

 

Whittey:
It just won't adjust any lower, the screw is at it's limit. When warm, it idles at 800-900, but it also goes into fast idle at times while driving, too. Fast idle can be between 1800-2400 and will not kick down until the temp gauge is in the normal range. I know that a choke adjustment is needed. Just a little hiccup in the grand scheme of things. Just need to find the time to get it into proper tune.

I just found the cam card I printed out a million years ago, it says in the "Recommended RPM Range With Matching Components" box that minimum RPM is 1500, Maximum RPM is 4500, Valve Float 6500 RPM. I understand that to be the optimum operating range for an engine with this cam installed. That should have no impact on Idle speed, should it?

I have some other little jobs to do on the truck, found a couple gaskets that are trickling a little oil, need to install a trailer brake controller before going on it's maiden camping trip, etc. We had to fab a bracket for the throttle linkage and modify slightly but it operates through it's full range of operation properly. The truck wouldn't idle under 1200 when we found and fixed the linkage problem. Is there anything else I should keep my eyes open for?

For you fellows looking for advice: I like what the 4 bbl does for my engine, but I haven't driven a 2 bbl truck so I can't compare. Fuel economy is improving every day as I break it in, and as I learn to drive it without a heavy foot. Whatever you do to wake this engine up, I think you will be pleasantly surprised!

Good Luck!

Les