John Deere B Leaky intake valve

[Michael-1976]

I just rebuilt my 1945 John Deere B I had the block bored out the same as a late B and I put some 50 pro pain pistons in it and the late b camshaft. had all new valves and guids and seats put in the head. when I got it running I figured it would have a lot more power than it did with the all fuel pistons but it didn't! So I did a compression check on it and the left had a 155 psi and the right had 125 psi. So i got it on top dead center pump air in the left cylinder and no leaks. got the right side on top dead center and it is leaking out the intake. So my intake valve is not seating. I was just wondering when I get it fixed do you think I will see a big difference in the power it makes?

 

[JDJACK]

depends on what you call big. You will notice a difference.

 

[[email protected]]

Id say Not at all. 125 & 155 are both pretty far below the 'big power " compression point. And thats not that big a difference in my opinion. Not normal, but not extreme. Ignition timing makes a big difference on power, make sure thats right. Seems very strange the valve leaks that bad after a head job though :-(

 

[Anonymous-0]

Re-check your tappet clearances. .020

 

[Michael-1976]

Thanks! I hope I do! I know it is hard to tune with it pushing air back in the carburetor and I think that will also affect the other cylinder to by contaminating the fuel mixture.

 

[Michael-1976]

I did that and it was ok.

 

[JDJACK]

I had the same problem on an A. Just had a valve job done. Just because it's new or rebuilt doesn't mean it's good. My valve was ground off center. You are right about pushing air back in intake. Think about it at 1000 rpms what is going on.

 

[cleddy]

I have an H John Deere so follow this forum. I redoing a 602 Minnie Engine and having trouble getting the Intake valves to seal even after grinding and lapping. An old Mechanic suggested maybe the springs are weak and the retainers are beat up pretty good. He suggested making- adding spacer to see if that tightened them up enough to hold. I think it worth a try since the exhaust hold prettty well and this engine is almost 50 years old. Any ideas about this suggestion????Cleddy

 

[Michael-1976]

Im taking it back apart and taking the head back to the place that rebuilt it! Im gonna fill up the intake and exaust ports up with gas when I get it off and see how bad there leaking! lesson learned I"ll check it next time first before I put it on.

 

[cleddy]

The more I thought about this it is one of the more stupid ideas yet. If the valves are right they would hold almost with out a spring. I lapped them and I think that will be the best solution after all.cleddy