Hey guys, just dropped a 1976 351 w in my truck (85 f-150 4-speed manual trans 2wd) but can barely get it to turn over.. It's just a ridiculously slow crank until it stops cranking all together. I had this problem before with my 302 but fixed it with a new starter, this time it is 100% not the starter. Short description of the problem, I know, but I really don't know what more to say. Haha If you guys need more just ask but I will give a list of things I've tried so far!

1) 4 new different starters from 4 different brands, first 2 were rebuilds, 3rd was new, the one I'm on now is a high torque starter

2) using a set of jumper cables to replace the battery cables. Black on the negative battery terminal and clamped on to the bottom bolt mating the starter to the bell housing, red from the solenoid to the hot post on the starter. (No change in cranking speed)

3) jumper pack hooked up to the battery (no change)

4) cleaning grounds, mating surfaces, solenoid posts, battery posts (no change)

5) jump starting it (improved cranking speed but only while the other vehicle was revved up, actually had it running once like this but stalled due to carb adjustments and timing being off a hair)
6) using a drill to turn the oil pump drive shaft and get some oil moving through the engine (nada)

Thanks ahead of time guys, y'all are always a huge help!

 

Jump starting alone is not the best option. Try taking the good battery out of the car you are using to start the truck and see how that works. If all the same, then try to manually turn the crank with a long ratchet or breaker bar on the bolt. If it feels tight that way, then I suspect something else. We will get to that if this does not help.

 

No luck with that batt either, turned the engine by hand and WOW is it stiff

 

I would be looking a bigger battery cables as this is an ongoing problem.
Have seen posts where jumpers were used and still had slow cranking but after fitting larger cables the problem was cured.
Does the ground cable go directly to the block/starter mounting bolts?


Does the battery cable go through a separate solenoid before the starter? Solenoid may have internal problems

 

Why is the engine so stiff? What is the history on this engine? Has it been sitting around? How does it crank with the coil wire off? How does it crank with the sparkplugs out. It should fly with the sparkplugs out.

 

I'll get some bigger cables for it tomorrow, the ground goes to a bolt on the intake, which, I've tried other places on the block with the same results. As for the solenoid, I jumped the terminals on the solenoid with the same results as with the key, so that is ok

 

OK, I am not familiar with your abilities so you may say "Of course I did that." Just bare with me. You said that you just installed the motor. Was thew transmission in it when you dropped it in or did you add it after? When you mated the tranny to the motor, are you sure that you rotated the torque converter and ensured that it dropped into the gear for fluid movement. If not and it is not seated correctly, the engine will not turn easily. If this is the case, remove the tranny and check the torque converter before you break that gear and you are in more trouble. Also, when you set the tranny onto the crossmember, did it fall into place easily or did you have to force it to line it up to bolt it down. If you had to force it, take it out of the cross member and let it sit where it is comfortable and try to start the engine again. Lets see how this goes.

 

That's what I would like to know, I bought this engine from a friend selling it for one of his friends, it was only 400 so I couldn't pass it up and I was in need of an engine... All I know is it has 40k miles on it since it's rebuild and it's bored out... That's why I got the high torque starter thinking he put high comp pistons in it or something... Taking out the spark plugs is a great idea! I don't know why I didn't think of that as a test earlier! I work until 3 tomorrow so after work I will give that a try and let you guys know what happens!

 

Well... I dropped the transmission, personally I think it's easier to take the tranny out, lower in the engine, then install the transmission, but it is a manual so there's no torque converter...

 

OK, lets start with pulleys. Check to see that all move freely. No cost involved. Then try to back the tranny off of the engine and try the breaker bar method to see if it is free. Even try to jump again. Just trying to see if tranny is binding for some reason or the engine has problems.

 

Ok, before I go through all the work of yanking out the transmission, taking out all the spark plugs had a positive effect on the starter speed, so what does that tell me? Engine just needs loosened up a bit, and fresh oil flowing through it?

 

It is possible that you had a compression lock and stiffness from sitting. Did you try to crank it with plugs out. I believe I saw you noted that you pulled the distributor and forced oil through by rotating the pump. Is that correct?

 

Yessir, spark plugs out, increased the speed of cranking. Tried spinning the oil drive gear but it didn't help matters at the time... Does turning the whole engine do more than just the oil drive shaft?

 

I put all the plugs back in and it was cranking normal, until it built up compression again and slowed down...

 

Loosen the dist just enough so you can move it, but it will stay where you put it. Crank the engine and twist the dist a little one way and then the other and see if that lets it crank faster. If the timing is too advanced it will make it hard to crank over.