[travis g]

I am a newbie to this site, but after doing a LOT of searching, this seems to be the best source of technical assistance on the 'net for Ford stuff.

Here's the deal. I am primarily a Chevy guy but have owned a number of Fords over the years. This weekend I bought an ultra clean, low mileage '83 F-150 XLT extended cab truck that is in VERY stock condition...351w 2bbl, C-6, 3.55 posi, EEC-III (California emmision package), and single exhaust w/cat. The engine was replaced at 58K miles with a Jasper rebuilt stock replacement engine. It has excellent oil pressure and purrs like a kitten. Factory rated power output is pretty pathetic though...something like 139hp@3800 rpms and 278 lbs-ft@2000 rpms IIRC. Gas mileage is attrocious (how can it take so much fuel to make so little power?). The problem is that it idles too high (pulls against the brakes at a dead stop in gear, and tries to diesel when you shut it off), and it runs very lean (with the corresponding lean stumble on light throttle acceleration). There appears to be absolutely no adjustability on this thing for idle speed or timing. All the vacuum hoses and fittings are in perfect shape...I could find no vacuum leaks anywhere (this was my first suspicion). Any idea's on what/how I can drop the idle speed down? I haven't got a tach installed yet, but will very soon.

I'm also playing with the idea of bumping the power level up several notches. The engine is very torquey right off idle...and thats about it. The dinky factory exhaust, tiny cam, low compression, tiny valved factory heads, and 2bbl carb work pretty well together to keep this thing from breathing at anything over 3500 rpms. I've got a set of C9OE 4bbl '69 351w heads left over from a project years ago that I am interested in getting freshened up and using (fresh guides, aftermarket springs, 3 angle valve job, hardened exhaust seats). They should wake things up quite a bit (60cc versus 69cc chambers, 1.84/1.54 versus 1.78/1.46, etc, and bowls blended/short side radius work). Will these early heads bolt on to the '83 block? Many aftermarket intakes state something about a 12 or 16 bolt pattern...whats up with that? Is pretty much any aftermarket intake compatible with the earlier heads? I think these heads will get the compression up in the low 9's. I am looking at also adding a comp cams 275DEH cam, a stealth or rpm type intake, headers and 2 1/2" duals, and around a 2200-2400 rpm convertor.

What about using an earlier electronic ignition setup like the later 70's models used with a vac advance distributor? Can I just add an earlier style distributor to the existing wiring and ignition module? What exactly does the module do anyway?

I know Chevy's (particularily small blocks) inside and out, but know just enough about Fords to be dangerous. Any input would be appreciated.

[Darkwriter77]

As far as the idle, there's a lot of things that could be up with that. For one, trace allllllllll of your vacuum lines and make sure that you don't have something rotted through, collapsed, pulled off, pinched, or incorrectly routed. A prior owner may have tried to bypass something that wasn't working (rather than fixing or replacing the problem part), and it might be pulling vacuum from an inadequate source (or none at all, if it's plugged).

If you're sure that there's no vacuum leaks, you can then try setting the base idle. I'm a bit like you in that my experience with carb'ed motors is mostly GM-related. I'm honestly not sure where the connector is on an older carb'ed Ford, but at least on the 80's Rochester 4-bbls there was an electrical connector that you would disconnect first before starting the motor so that the ECM wouldn't mess with things, whereupon you could then start the motor, set the base idle by adjusting the idle set screw, shut it off, and then reconnect that electrical connector. (Pretty much the same deal as when setting the initial timing on an EFI 5.0 motor, where you pull the spout connector first, set your timing, then plug it back in.)

The dieseling when you shut the motor off is likely due to the high idle, as it's running a mechanical fuel pump and will keep dishing it out as the motor's turning - if it's idling too high when you shut it off, it has enough inertia to keep turning, the plugs (or something else) in the combustion chamber is still hot enough to ignite the fuel still being thrown in there, and it just goes on an on. Fix the high idle and you'll surely have the dieseling problem fixed.

As far as beefing the motor up, it depends on how involved you want to get with it. If you've got a stand and engine lift, you might find it easier to just find a shortblock you can clean up, throw those extra heads onto, and put a matched cam/carb/intake setup on there, swapping the whole motors out, and then selling off the old motor to recoup your costs. Gas mileage is going to suck no matter what you do, really ... especially if you go bolting on a 4-bbl and get to dipping into the throttle every now and then.

Depending on what the smog situation is like where you're at, you might be able to get away with converting to dual cats and running true duals from there on back to help with the power. I wouldn't go bigger than 2.25" on your current heads, as it would be overkill, but if you want to just do it once in anticipation of a later headswap and such, then dual 2.5" would work. If you're limited to running a single cat no matter what, you might consider one of those two-inlet/two-outlet cats that also serves as a crossover, then running the tailpipes parallel back and then out the passenger side in a pair, a-la SVT Lightning exhausts.

Just some ideas to kick around. Hope they help!

[Jenns01TA]

Thanks for chiming in Dave, the only other thing I can think of on the idle would be the timing chain. Whatcha' think, Dave? If the timing is set too many deg past TDC????

[Darkwriter77]

Dunno. Timing chain could be stretched out and throwing off the timing a bit, but I would imagine it would be running very erratically, and the timing difference would really be obvious at the higher RPM's at WOT, where the stretched-out chain would allow for more of a timing difference.

I wouldn't think that a worn/damaged timing chain would tend to cause a consistent high idle condition, though. Bumping the timing doesn't raise the idle TOO much - only about 100 RPM different in going from 10* to 14* on the 302 in my notch, at least - and I would imagine that if the timing were advanced far enough to be causing the kind of high idle he's describing, he would probably also be getting a LOT of pinging.