Antrim1992

Just decided to rebuild the 300 in my '91. So I've had the block bored .030, and decked. The crank has been turned. New pistons/rings, main and rod bearings, comp cams 260h set with cam, lifters, timing gears and pushrods. I've also had a trick flow job done to the head along with it being shaved down. The rebuild has went fairly well up until now. I've got all the main caps tightened down and I can manually turn the engine by the bolt in the end of the crank. Now here's the issue...I'm still able to turn the engine up until I tighten the very last rod cap. Once it gets tightened down it will not budge. This this normal?

kd3pc

not normal...there is a tightening sequence to follow, and make sure your caps are on the correct orientation...same with the pistons,

next, will be time to break out the calipers to make sure your machine work was done correctly and that the bearings are the correct ones..

Antrim1992

Do you know where I can get all that info? I can't find it in my Haynes.

qdeezie

Sounds like you need to plastigauge your bearings. Also, you did lube your bearings right?

Antrim1992

Yes I used assembly lube. What is plastigauge?

Eric Fullerton

http://www.plastigaugeusa.com/how.html

kd3pc

Measure things and "dry" fit things to make sure things are close...be very careful to NOT scratch or score machined surfaces. Measure things - get familiar with the caliper.


I do the crank main cap bolts in three steps, 1st snugs things up - still rotates easily, 2nd time is mid range of the torque spec, say 40 ft pounds or so - still rotates easily, 3rd is full torque and double check things, and still rotates easily - may need a bar to rotate it, but it should be firm and very smooth...anything else, stop here and figure out why.

The tightening pattern is to start in the middle of the crank, and then criss cross towards one end and then the other.

Then install pistons and rods with their caps.
I second the plastigauge, or similar product and be sure to do the side slack/space measurements not just the mains to the crank.

Some of the straight 6 cylinders have a crush washer system that supplies fore and aft movement once things are in place, rotating and ready - It has been a while since I did those, so read up to see if the 300 is one of those....the others just ride on the side bearings of the main caps.

hope this helps, others may chime in...

Antrim1992

It's turning now! I went ahead and took all the bearings out and cleaned em up. Then I re-greased all of em, installed, torqued all the mains to 70 lbs and the rods to 42lbs. Now it turns! One thing I noticed is that there was some slight wear in the center of the bearings running all of the way across it end to end. Is this a big deal?

kd3pc

main or rod? Usually you will see some wear, just from the manual turning on the mains, not as often on the rods, especially at that torque...

It should be consistent and not gouged out...

bests

Antrim1992

It's on the rods but I can just barely feel them.