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Big Ten valve issues


Chris727

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I have had this Big Ten for 5+ years. It always ran but not great. Hard to get it to run without surging. I figured it needed a rebuild if it was to be 100% but thought it should at least run smooth even if using some oil. 
 

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I considered that it may be out of time and removed the engine to check the flywheel key. 
 

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Upon removing the flywheel the key was found to be OK. I replaced it anyway. I also checked with a multimeter to verify that the coil bracket was properly positioned for proper timing and reassembled flywheel. 
       The engine appeared to have air leaks at the intake gaskets. Surfaces were cleaned and new gaskets installed with high-tack sealant. 
 

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 After some discussion with other collectors I decided to pull the head and inspect the valves and clearances. 
 

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It actually wasn’t as bad as I expected but could use to be bored oversized , though I have run worse with decent results. The valve clearance is an issue. .022 on exhaust and .014 on intake. That’s 3 and 5 thousandths too wide. I may put new valves in and renew the seats. 
 

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I got this kit second hand a little over a year ago. Have been watching videos about it’s use. Problem will be if the valve guides are too worn this can’t center itself properly. Will keep you guys updated. 
 

 

 

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Chris,

Understand when you cut and lap the valve seats you are moving the relative valve position closer to the camshaft. To set the valve clearances, the valve stems need to be ground. How do you plan on grinding the valve stems? Engine machine shops have a machine to grind them.

Edited by Bill725
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4 hours ago, Bill725 said:

Chris,

Understand when you cut and lap the valve seats you are moving the relative valve position closer to the camshaft. To set the valve clearances, the valve stems need to be ground. How do you plan on grinding the valve stems? Engine machine shops have a machine to grind them.

I was initially expecting to find the clearance to be too tight rather than too wide. I suspect someone took too much off previously. Someone appeared to have been in the engine not too long ago (price tag was still on the head gasket). In the past I have ground the stem by filing or on a belt sander taking a tiny bit off at a time and didn’t have any problem. I have a machinist available who could do the whole job for $50 but he is months out and I don’t want to push ahead of his other customers. This tractor needs to get out the door soon. 

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  • 2 weeks later...

I removed the valves tonight. I used the “new to me” automotive style valve spring compressor. It worked much better than the B&S scissor style. 
 

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The exhaust valve seat looks poor. 
 

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Exhaust valve above. 
 

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If the stems were previously ground then it had to have been done with a machine as they are very true looking with a dimple in the end. 

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