Question on turning over 250 by hand

[Love 70 Chevys]

My recently acquired project truck has not run in four years. I want to turn the 250 motor over by hand to see if it is locked up. I’m thinking my best bet is to thread a bolt into one of the tapped holes on the harmonic balancer and then put a socket on a breaker bar and turn it that way. The threads have been gunked up with paint and I want to chase them with a tap. Does anyone know the bolt size and thread pitch? ¼-20?, 5/16-18? Something else? Is this the best way to turn over the motor, or is there a better way? Thanks in advance for any advice!http://67-72chevytrucks.com/vboard/a...1&d=1488545751

[James the III]

Originally Posted by Love 70 Chevys

My recently acquired project truck has not run in four years. I want to turn the 250 motor over by hand to see if it is locked up. I’m thinking my best bet is to thread a bolt into one of the tapped holes on the harmonic balancer and then put a socket on a breaker bar and turn it that way. The threads have been gunked up with paint and I want to chase them with a tap. Does anyone know the bolt size and thread pitch? ¼-20?, 5/16-18? Something else? Is this the best way to turn over the motor, or is there a better way? Thanks in advance for any advice!http://67-72chevytrucks.com/vboard/a...1&d=1488545751

Me.. if there is still a battery hooked up unhook it it..\\

!) pull the plugs
2) spray oil into each cylinder
3) wait.. tic toc tic toc.. an hour later..
put hands on balancer and try to rock it back and forth..
4) put two bolts in balancer if you want.. thread size and pitch 3/8 20

me I don't like getting brocken bolts out so I'd

a)get under truck
b) remove inspection cover for transmission near starter gear in flex plate (automatic) flywheel (manual) and use a long screw driver or prybar on the starter gear teeth on that flex/fly wheel..

[71cheyennesuperlongb]

The best way is to remove sparkplugs then turn flywheel with prybar

[Mike C]

Make sure it's out of gear...

If the motor is loose you may be able to just grab the fan and rotate it. I have a 153 on the run stand in my shop right now (basically a 4 cylinder 230) and it easily rotates that way.

[Love 70 Chevys]

How I ended up doing it. Chased the threads on the balancer as they were filled with paint. (3/8-24 UNF) Cut a 1/4 thick piece of steel and drilled two clearance holes in it. Made it just wide enough to fit into one of my breaker bars. Secured it with two 1" long bolts. Removed the plugs. They did not fight me and looked to have been burning fine. Squirted in some PB blaster. Took the truck out of gear. Was going to wait, but I just had to know! Pulled on the bar like a kid on Christmas morning. The crank turned like butter. She was not locked-up. Previous owner told me it was running fine when he parked it years ago. No reason to doubt that yet, but this old girl is bound to have a few surprises for me before we are done!
http://67-72chevytrucks.com/vboard/a...1&d=1491776078

http://67-72chevytrucks.com/vboard/a...1&d=1491776078

[Love 70 Chevys]

http://67-72chevytrucks.com/vboard/a...1&d=1491776487

[100%Chevy]

Originally Posted by Mike C

Make sure it's out of gear...

If the motor is loose you may be able to just grab the fan and rotate it. I have a 153 on the run stand in my shop right now (basically a 4 cylinder 230) and it easily rotates that way.

I thought I was the only one around with a 153!In fact,I have 2-A 120 hp and a 140 hp.Good little engines!
Mike.