Well, I got an '85 F-250 a week ago. 300, C6, 4x4. This thing runs like it was on it's last legs a year ago. I can usually get it started fine, but it shakes, poofs, sputters, coughs, and runs rough. I warmed it up today and did a compression test. Every spark plug was carbon fouled. Not too surprising since the tailpipe will leave carbon splatter on the driveway when revved. Funny thing is every cylinder gave decent compression. I thought for sure with the engine running so crappy that valves or runs or something must be long since shot. But here are my numbers, going radiator to firewall:

127
130
132
126
130
120

which makes me happy because I don't want to tear into the engine itself if I don't have to, but I do want to make this truck a driver. Everything else on the truck is good. Steering, tranny, lights, nice flatbed. It just needs an engine.

Another thing that gets me is this truck gets pretty decent mileage, I'd guess probably around 15 mpg, when just cruising at highway speed, not so good doing stop and go. Most of the sputtering, weezing, coughing, is at idle and trying to get going, it actually runs half ok when the engine speed is up. Which I don't get why the mileage is good because it's obviously running way rich if it's splattering carbon out of the tailpipe.

So anyway, I bought a duraspark II distributor off of eBay. Someone, I don't remember who, posted a link about 'dirt cheap ignitions', and using an HEI coil with a duraspark distro. I don't believe I can use the TFI ignition that came with this feedback carb when I change the carburetor out. I have a clifford intake and efi exhaust manifolds in the garage and I plant on putting both of these on and the duraspark/HEI 'dirt cheap ingnition'. My question though is this:

I bought a four barrel motorcraft carb from a guy here in town for $30. He said it was a running carb when pulled and it does look in pretty alright shape. It's a 1973 model 4300, it's supposedly square bore even though the primaries are just a tiny bit smaller than the secondaries. Anybody ever run a motorcraft 4300 on a 300 before? With my compression what it is I imagine putting a new ignition and intake and exhaust and carb on this thing ought to fix it right up again, good as new. But I'm curious if anyone that's been there and done that has any advice about this carburetor. Thanks

 

Autolite 4100-4300 Carb Info [Archive] - Squarebirds, Rocketbirds, and Fifties/Sixties Ford Discussion Forum

http://realbig.com/detomaso/1999-07/1101.html

A little info on the 4300 there.

Dirt cheap Ignition

gofastforless.com

Ignition info there.

 

Are those 'wet' or 'dry' numbers for your compression test? If only 'dry' numbers, do a 'wet' test to check for possible problems (valve seals leaking, head gasket, etc.). Your #6 is _just_ above 10% less than the highest reading... personally, if the 'wet' compression check does not reveal any problems, I would consider at least re-ringing the pistons. I forget what the 'healthy' numbers are for the 300, but I know there is a max allowance below those numbers that are an indicator that it's time to rebuild. You could probably do a bit of tuning on the truck, maybe go one step hotter on the plugs if absolutely necessary, but eventually, you're going to have to overhaul.

 

I'm not sure what you mean by 'wet'. If by wet you mean I didn't stop the flow of gasoline through the carb, then yeah, it was a wet test. If you mean did I put a teaspoon of oil in each cylinder, then no, it was a dry test. I don't plan on opening up this engine at all. To either just do rings or a complete rebuild. They are almost the same amount of work anyway. To be honest, I only want to put a couple hundred dollars into this thing and then be able to get a couple or three years from it. Then tear it down for parts. So those compression numbers are good enough for me for that truck. Even if they are supposed to be 150 in perfect condition (that's a guess).

Thank for the links Harte3

 

Yeah, 'wet' test is squirting oil in through the spark plug holes and re-running the compression test. I would consider doing it anyhow, to see if it reveals other problems. Other than that, I was not saying that you couldn't run the engine with what you plan to do to it, but eventually it will need an overhaul. You could probably just do a rebuild on it when you do finally decide to tear it down, though - not sure of what your plans are with using it for parts.

I ran a GM 250 I-6 with more wear on it than those numbers indicate (guessing here, don't recall what the guy told me the numbers were)... until it finally sat parked not being run for far too long. The only thing that engine really needed was the ridges reamed out a quick hone and re-ring and at most new bearings and oil pump installed - but even all that was still in such good condition, I could have probably gotten by without it or just getting a new battery and doing some ignition and carb work and kept it running. I don't recall if it had previously been overbored, but worst case would have been boring the block and using oversize pistons - I still regret not getting that engine going again and finishing somewhat restoring the car it was in, but can't really go back and change it now as it was over 20 years ago.

 

Hopefully it is a problem in the choke. You seem to have good, equal compression. Is it putting out black smoke?

Black smoke = fuel, blue smoke = oil, white smoke = coolant (except on a cold morning, let's not get too technical :-P)

 

Yeah, it does put out a little black smoke. The choke opens up fine, but it's kind of moot anyway since I'm tearing off the intake carb and exhaust and TFI ignition and replacing it all. I'm just going to wait until I've got a place (soon hopefully) where I can take the engine out. I know it sounds like unnecessary work to take the engine out when I'm not technically tearing into the engine. But for one, I just can't seem to get a socket to slip over the lower manifold bolts, and two, I really don't like squeezing my guts against the fenders of a tall truck for hours at a time.

I sympathize with your lost inline project Kernel. I had a 1958 chevy apache pickup years ago with a 235 straight six in it. All original, oil bath air cleaner, cartridge type oil filter. Wood bed floor, wrap around windshield and rear window. I loved the 'clickety' sound of that engine. Sold it through eBay to a guy in california who said he was acquainted with Jesse James and was going to completely redo the thing. Maybe so, I don't know. Was an awesome truck though

 

Why not figure out what the problem is first?
Before you go replacing things.
You may have some bad seals on your Valves and they can be replaced without too much teardown.