Farmall Cub

So, I started my Super A, everything seemed fine, it was idling smoothly and everything seemed to be in order. I left the garage for 15-20 minutes while it was running to do few things in the house, I wanted to warm it up so I could finally retorque the head bolts. I came back out and the tractor had stopped running. I assumed it was because it ran out of fuel, as I was having carb issues (could have still ran out of fuel). After I retorqued the headbolts I went to put the rocker assembly back on. I went to turn the engine using the hand crank so I could pop the pushrods back into place without fuss and here is where my heart stopped.

It was really hard to turn the engine. It wasn't a smooth turn, and I heard a strange grinding/scuffing noise. My first thought was the cylinders/pistons are messed up. I had straight 20w oil. This is the longest run of the engine since I put the head back on. Could the oil have thinned out too much or something?? I put the proper amount in and it was flowing out of the rocker assembly all the way up top like it should. Coolant level good.

Everything I have done to the engine is the following:
- New head with seated valves.
- Adjusted governor bumper screw to stop hunting
- adjusted governor rocker/clevis to carb according to I&T manual
- 20 weight non-detergent oil, filled until it came out of top petcock on pan. (I previously used 30 weight non-detergent)
- gapped/lashed rockers at .016 (cold)
- New spark plugs (Champion D21)

The engine still turned when I pulled the starter, so its not seized. Its just... honestly scaring me.

Okay, so it might not be as bad as I thought... I still dont understand what is going on. After the engine cooled again (3 hours later), I went to turn the handcrank just to see what it what was going on again. I noticed something that red flagged instantly in my mind: As I tried to turn the crank it got real easy to turn and then hard again the easy then hard and so on, It wanted to rotate back a couple degrees towards my hand, not just stop in place. I instantly knew there was a vacuum in the cylinders. I took every spark plug out and tried rotating it again by hand.

Guess what happened? It rotated freely without any resistance and was perfectly smooth. Like perfect. I really can't explain it.

So, is this vacuum effect normal? My old head had bad valves as Artc pointed out, is it possible that I'm not used to this kind of resistance from a good, solid seal on the valves/head when trying to turn the engine manually? Or maybe an intake valve isn't opening correctly?

If I read your post correctly, you were turning a recently rebuilt engine that had just been run without the valve rockers operating. with a newly rebuilt engine, warm and well lubricated, yes, you would have been drawing a vacuum on cylinders, as well as compression on others. Let it set a minute or tw and it will bleed off and let you turn it some again.

havoc1482 wrote:It was really hard to turn the engine. It wasn't a smooth turn, and I heard a strange grinding/scuffing noise.

What's going on with this??

ricky racer wrote:

havoc1482 wrote:It was really hard to turn the engine. It wasn't a smooth turn, and I heard a strange grinding/scuffing noise.

What's going on with this??

That's what made me quickly panic. For all we know it could have been just the hand crank scraping against the guide under the radiator. I didn't hear it when I took the plugs out to eliminate vacuum. In hindsight I overreacted, but turning the crank was never that hard before haha. I guess it's good in my nature to question everything.

If you have the push rods out of place, you have 2 cylinders coming up on compression at each half turn of the crank. The other 2 drawing a vacuum will add a bit more, but not much.