Hello all, let me introduce myself since I'm brand new here. My name is Dan. I'm a jet mechanic at Minot Air Force Base in North Dakota, and I just bought a '91 F150 Supercab with a "rebuilt" motor for a whopping 200.00 buckaroos.

And now for a short story:

One day a friend of mine approached me. "Hey Dan" he said. "Can I put my truck in your driveway until I figure out why my 302 motor wont turn over? I just rebuilt it but I lost my garage and I need a few more days on it" I said sure. Well those days turned into a month and my friend never did figure out his problem on the motor that had never run. So I told him to get his paperweight outta my beautiful driveway. (it's really an ugly driveway) Just then the truck fairy appeared (strangely he looked exactly like my friend) and said I could have the truck in all of it's rebuilt glory for 200 bucks! I took him up on the offer, I couldnt resist. Fresh motor, shorty headers, new tires, and all power options....how could I say no to that?

The work Begins....
So I hit the starter- CLINK and silence. I did that about 3 times over just to be sure. The motor seems like it's locked up. Or somethings not right. Test the starter. Checks good. Pulled the motor, sure enough I cant turn the flexplate, flywheel, ring gear, or whatever you like to call it. So it is locked up.

I put it up on the stand and loosen all the main bearings. It turns slowwwwwww with the help of about 100+ pounds on a 2 foot rod cocked between the flywheel bolts to turn the crank. This is not right on a fresh rebuilt-duh. Ok so I loosen up the rod caps and now things are moving smoothly. So maybe the oil clearances are not clear enough. Plastigage time. Everything checks out. .0015 or better I think was what I got. Everything gets lubed and torqued properly. The thing still wont turn. Hmm I had better have a closer look at things. I am trying to avoid taking the whole thing apart down to nothing and starting from scratch...All the caps come off and I notice the stamped numbers on the caps dont match the rods. That's probably a bad thing.
By the way this is only my 2nd motor build. So I'm in mostly unfamiliar territory. My first was a Dodge 318 that went very smoothly into my 79 ramcharger lifted 9" on 35's.

Back to the story.

The caps dont match the rods. and none of them are in numerical order (I assume they are supposed to run 1-8 in order) So I figured to avoid taking off the heads and making more work for myself I may just be able to get away with matching up the caps with the rods.

This motor was clearly not put together with much attention to detail.

So everything is back in place except for the rods not being in numerical order. And after everthing is torqued properly it still doesnt turn. At least not without the mighty muscle of me putting all my weight on the bar I have attached to the crank. (that's a whopping 178 lbs!)
HMMMMmmm.

Time to find out what's binding:

By trying combinations of loosening and tightening all of the bearings I discovered that when:

A. The rear main bearing is torqued properly (98ftlbs) the motor does not rotate freely

B. When the first connecting rod bearing (front) is torqued properly (20ftlbs) the motor does not rotate freely.

C. Same with the 2nd rod bearing.
Or any combination of the 3.

D. I also discovered that all of the stamped numbers on the rods are facing the center of the engine. I could turn the rod/piston 180 deg so that they face outward but they would still be out of order.

The crank was ground .10 and the appropiate bearings are all installed. I did notice that when I removed the rear main lower that the wear on the bearing was very strange from me checking for freedom of rotation. The wear is an 8th inch strip or less on the outermost edges of the bearing with the center mostly untouched, like the bearing is concave or something. I can take pictures if thats not descriptive enough for you. Oh, and I checked that all of the pistons move freely within the cylinders without binding so that's out.

Questions:
1.Do I really need to put the pistons/rods in numerical order with the numbers facing out? Is that why they are stamped 1-8?

2.Does the numbering run back to front or front to back?

3.Why are the 1st 2 rods and the rear main binding like they are?

4.Can I compensate with slightly undersize bearings if I cant determine any other problem?

5.Can I compensate by having the macine shop check the grind on the crank, or regrind so theres no binding?

6. Do I REALLY need to take the whole dam motor apart (heads off) and start from scratch?

If you have any questions that might help you determine what the crap is going on with this motor please ask me. And thanks in advance for any suggestions that you might have!

-Dan

 

didn't read the whole post but this is what I got from it.


I alway turn the crank over after every rod is installed.


the rods/pistons are in backwards

if you take one of the caps off and look at the edge of the cap where the bearing is you will notice one side as a chamfer in it and the other side is square the Sq side face the other rod and the side with the chamfer faces the crank...

to some it up real quik I believe the numbers on the sides of the rods should face the cam.....

 

check the back side of the bearing for std or .010 or .020

 

I would just get it a machine shop and have them put it together for you..... Might cost you a few buck but hey you only got 200 in it....

 

I got lost too on that long post. Check the numbers on the main bearing caps. Number's 1, 2 and 4 can be interchanged, but they only work in their correct location. Also check that they're installed right side forward (bearing tabs facing each other) You've guessed right on the rod caps beign mixed. Stamped numbers go together. Raduised side of the rod faces the outside of the crank journal. Pistons need to be oriented correctly, notched side faces forward (if they have notches) This shortblock needs to be completely dissassembled and put back together the right way.

 

im gonna go out tonight (i hope) and tear it all down. it's like -5 degrees out. yuck. o well.

 

Being an aircraft mech, I'm sure you can appreciate the need to assemble it correctly. The main caps also have an arrow cast in the top to point them in the right direction-----arrow points to the front of the engine. And as Hemi said, check the bearing undersize(stamped into the backside) and mic the crank to make sure they're compatable. If the crank was turned, the undersize should have been stamped into a counterweight. Oversize pistons also have the oversize stamped into the tops.

 

hey all i took it all apart and discovered that he used the thrust bearing in the rear main slot. that would explain the binding i think....

 

crank installed... smooth as butter. gotta go fix planes now so the pistons will have to wait til tomorrow. by the way, in what order do the pistons go? they're numbered 1-8 so looking from the top of the engine standing at the front do they go:

8-4
7-3
6-2
5-1

YOU

 

Firewall

4-8
3-7
2-6
1-5

Grille

 

From the front of the upright motor, #1 is first hole on the left. If the motor were upside down so you are looking at the crank then your sequence above is correct.

 

thanks a lot! im very excited for this 200 dollar truck to hit the road. my girlfriend loves chevys and now she will have to start riding in a ford that i built. mwahahaha

 

It's about time she got to ride in a real truck!

 

I'd like to have seen that trick. Only way I can think of that being accomplished is with the XBFH method.

 

I'd still get the crank checked.... your right there... I would not leave it up to the guy who put it together... maybe he never checked it and just bought bearings....might need to be ground to .010 ...never know. Hate to see you go through all this only to find out the crank or bores are bad....