View Full Version : Adjusting Valves on TRactor Motor

02-23-2008, 03:14 PM
I adjusted the valves on my TRactor motor (engine rebuild) using the "Rule of Nine". However, I noticed that I had excessive valve lash on the exhaust valve on #1 cylinder when the engine was at TDC. I checked some others, and it was the same thing. I have a reground cam in there (282 deg. duration), which I think is causing this problem. If so, what is the best way to adjust the valves, because the "Rule of Nine" does not seem to be working.

BTW, I broke one of the adjusters tightening the lock nut, so I'm going to replace them all and start over again. :eeek:

And what's with the new way the smilies are arranged? :crazyeyes:

Geo Hahn
02-23-2008, 03:24 PM
Are you saying that the gap on #1 exhaust was greater at TDC than what you set it to when #4 exhaust is fully open?

02-23-2008, 03:37 PM
Are you saying that the gap on #1 exhaust was greater at TDC than what you set it to when #4 exhaust is fully open?

My mistake, not the exhaust valves, the intake valves. :blush: #1 intake valve lash (2nd valve) was greater at TDC (for #1 piston) then when #4 intake valve (7th valve) was fully open. Does that make sense??

Edit: Or am I misinterpreting the "Rule of Nine"??

Geo Hahn
02-23-2008, 06:03 PM
You have interpreted the the 'rule of nine' correctly. I'll let someone with experience with modified cams chime in on whether this is a symptom of longer duration.

I would probably just set the lash with the cylinder at TDC on the power stroke but maybe it isn't that simple.

02-23-2008, 06:48 PM
I'd double-check your data ... but if it's correct, I think your cam is incorrectly ground. The symptom is known as "base circle runout", and Crane says it should be less than .002".

02-23-2008, 09:05 PM
I dun know about y`all, but I adjust each and every cylinder to specs cold at T.D.C. one by one. Then fire it up, warm it up and adjust em all again while the engine is at idle speed and at operating temp. I know, old school, but it is the way I was taught. {that`s a solid lifter engine}. For hydrarolic lifters each and every cylinder individualy at T.D.C. to zero lash and whatever the specs are
additional 1/2 turn or 1 1/2 turns ect.
with hydrolics I don`t bother with the warm up adjustments.

02-23-2008, 09:28 PM
Well, since I'm going to change all of the adjusters due to the fact that I broke one, I start afresh. I'll adjust the valves first by bringing each cylinder up to TDC on the compression stroke, and then see how they pan out using the "Rule of Nine".

02-23-2008, 09:36 PM
I always just do TDC myself; easier because you only have to turn the engine 4 times instead of 8. Easy to see, too, just look at the valves for the opposite cylinder in the firing order. If it has both valves moving, and they are nearly the same opening, then the cylinder is very close to TDC. And if one cylinder is at TDC between intake & exhaust, then the opposite cylinder is at TDC between compression and power (for any even fire 4 stroke engine).

But since I've only got a spec for clearance cold, that's the way I set them.