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I have a 1971 F100 with probably a 75ish, 300ish 6 cyl. I got the truck sight unseen, PO not available. It's a really cobbled together, minimum maintenance vehicle off of a ranch. I have got it to start. It runs pretty rough. Smoke at the exhaust, not sure yet if it's oil or gas. The choke does open, mostly. There are at least two basic tuning problems.
1. Besides the carb being really old, the vacuum lines are not properly connected, and I don't know where they all should go. I do have a functioning brake booster vac line. There are two more ports under the carb, one is going into a fitting that passes through the firewall. The third might have gone to the distributor, as it's about the right diameter, but the hose is not attached to the distributor, which is missing a vac advance cannister. Also, there's a PCV valve on the valve cover with no hose and no place to go.
2. The distributor has no vac advance cannister, so not sure where to go from there. It does accelerate like the timing is pretty good, but I'd really like to get the basic tune right, then see where things stand.
I'm in a rural area, no parts stores around, no auto shops, but I've got you guys. Thanks! Here's the project. The 3 ports I know of. Vac cannister went in this slot?
Thanks! Man, that's a lot of circles and lines. This old truck seems to just have a line into the cab, one to the brake booster, and not even one to the distributor. Plus no provision for PVC valve. I'm starting to think the engine was swapped into a truck that had the booster, so they used the PCV port for the booster, just left the dist vac line loose cause there wasn't a cannister, and connected one back to the cab. It sure runs rough. The carb is a carter yf, I'll see if a rebuild will help, plus figure out how to get the PCV hooked up. I hear the Duraspark conversion is a good idea, maybe especially since this distributor is missing parts.
Can you post up a wider shot of the engine bay? Would like to see more of the engine.
I'd have to agree that the slot used to have a vacuum canister in it. The distributor looks VERY rough right now. Might need more than a new can!
Carburetor looks to be older than a '75, but then I'm not a 300 expert by any stretch.
The brake booster can be on any large fitting. The PCV valve MUST be on a common plenum area beneath the carb. Never (well, almost never) on a single runner or even single half of the manifold. Should be sucking from all cylinders.
And clean air needs to be able to get sucked back into the engine through a filter.
Distributor vacuum can come from either full, or "ported" manifold vacuum. Some engines like one over the other, with most of the ones I've worked on liking ported more. But I've run both successfully after some experimentation.
It's VERY likely that you're also dealing with vacuum leaks. Especially so on a cobbled together rig.And especially one that's older and has potentially had a hard life.
If any of those vacuum lines are open ended, or look cracked, replace 'em and plug 'em.
When you have it idling, spray some carb or brake cleaner around the intake and carb areas (carefully!) to see if you detect any change in the idle quality.
Actually, you can use anything from water to WD-40 to carb spray. Just need to get it there to find any holes letting air in.
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