Finally got my truck back on the road last week. Had the (390) engine rebuilt and broke it in the usual way. Followed on with an oil change after 30 minutes or so of break in. The system was "supercharged" with zinc additive at break in (on top of 10w40) and then doped the new 10w30 with a "normal" amount of zinc additive.

I set timing at break in to as close to the factory 4-6 degrees of advance that I could reckon (vacuum hose not attached) and then drove her home. It sat for about a week while I got enough brake in the system to drive again. Idled it for an additional 30 minutes when I moved it into the garage.

It was cold last week (below freezing) and so I drove to work on Wednesday and Thursday and ran some errands - throwing 480lb of sand in the back, for instance - during the day. Never went much over 40 m.p.h. due to crappy weather and poor driveability, but the motor was running great - first time with that kind of engine under my foot and seemed like most of the time I was just idling around town.

So, at this point in the story, I'm about 5 hours and 80 or so miles past the rebuild. On the way back from work that evening all hell broke loose.

Weather was warm (about freezing with a lovely snow/ice mix), so I idled her for a few minutes while I cleaned off the ice and snow, then drove a couple blocks over to the highway - because it was likely to be the least slippery of available options. Got going up the on ramp (first real requirement for any power) and she starts pinging and knocking like crazy. I limp to the next exit (mine) and put her next to the curb outside of my house. Realize I'm on the wrong side of the street, so fire her back up to move her and it she can't hardly start let alone idle without substantial pedal.

*Shudder* Lots of blue smoke. Etc, etc.

It sits two days overnight, but I had to move it up into my driveway Friday night to avoid snow emergency fines, possible towing, etc. Go out about 9 p.m. Starts right up with a nice idle and goes to her current location.

So, something clearly ain't right. Between the time it worked good (Weds/Thursday day) and when it didn't (Thursday night), nothing had changed - timing, carb, etc) except the weather.

This weather stuff is wishful thinking, I know, but the scenarios that I can think of that don't include a re-rebuild might be:

1. wiring went bad (unlikely)
2. timing was too retarded for the weather conditions (easy enough to advance)
3. electric choke is off too much (more likely)
4. coil is shot because wiring was bad (don't know how to know without swapping in an OE one)
5. carbeuretor decided to readjust itself (unlikely)

Gonna get the guy who did the rebuild out tomorrow afternoon. Immediate reactions? (Prayers for my project gratefully accepted.)

 

I would adjust the timing in the 10-12 BTDC range, with vacuum advance disconnected.

Then reconnect and adjust the idle to around 700 in Drive.

Adjust the mixture screws with a vacuum gauge for highest vacuum.

Do a search for FMC400's advice on adjusting the choke. If you're using an aftermarket carb like an Edelbrock or Holley it's even easier to adjust.

Josh

 

Will do. Expecting 9-12" of precip tonight so it'll be tomorrow before I get to it.

 

Won't start. Had the guy out who rebuilt the engine. "Doesn't make sense." he says... Well, at least we can agree on that.

Motor's getting gas, spark and air. But not firing. Fiddled with the carb and distributor.

Went out two days later and bought a "new" (05) F150 XLT.

It's just way to cold to pull the plugs again, so I'm gonna have to let her sit another winter.

 

may have skipped time. did you try doing a compression test?

 

next check you gear on your distributor. pinging is a serious timing issue or you just sucked up some bad fuel maybe?? definetly look at distributor/timing.

 

Thanks for all the responses, folks.

Gas: all new - the good stuff, straight into a new(ish) tank. Torques me off that I just put $116 in the day before stuff hit fan.

Distributor gear: I assume you're referring to the gear that interfaces with the camshaft (and not something to do with the trigger mechanism)? The distributor is new (Pertronix) and everything was running fine for two days straight...

Any chance it could be a sudden loss of vacuum? And why would a motor just decide to jump timing?

 

Compression: the whole engine seems to have real good compression - since the starter has to work so hard. Even if I've lost a cylinder or two, she'd still fire...

 

is it hard to crank after it's warm?

 

Dunno. When it was running, it started about the same warm and cold - after about 1-3 secs of cranking. Doesn't get warm anymore...

 

the guy who rebuilt the engine for you what did he say it might be & what could you eliminate that is not the problem with it?