P216 Valve Cleanup - Lap/Grind?

[Tuneup 1,452]

Hi guys,

 

Clear me up. Reading the manual, there is a 1° difference between the seat and the valve face. This suggests that only machining can "clean-up" the seal. I have to get in there to replace the head gaskets so was going to address the intake seals - may as well, cough, lap the valves with fine compound in the usual manner used since I was a tike of 16. A bad thing? Just to clean the surface? In this layman's mind, it seems fine to clean it up minimally if the run-out is in spec and valve life should not be shortened.

 

On a related note, this is my 1st ever blown head gasket. I'll have to go Stens or genuine Onan this time. In the old minibike days running engines found in yards, we'd make head gaskets and they ran fine. With the cheap eBay gasket, she now chugs like a steam engine when attempting to start - now difficult. Yup, proper torque sequence and stepping was no help here. Mea Culpa.

[Tuneup 1,452]

It's Sunday so I have time off and decided to pull the front head - no engine removal needed. Yeah, the bolts were loose - I have not yet reached the 50 hour point to re-torque but I can't imagine them being this loose. It took a socket wrench but very little effort. I do everything twice to make sure I don't miss anything - well, it is what it is. I thought you'd appreciate a picture of the gasket carnage...

 

[lynnmor 7,817]

I am not a believer in lapping valves, I grind them and re-cut the seats to get the proper seat width.  While you may get away with cheap gaskets in some places, I find that the head and intake gaskets is not the place to use them.  Make sure that the head and block are flat before installing.  The 50 hour re-torque may be a good idea, but do you think the hundreds of thousands of engines made by Onan were ever re-torqued when new?

[Tuneup 1,452]

That would give me an opportunity to learn something new! Thanks.

[bc.gold 3,406]

Your head gasket top image, no fire ring - cheap gasket prone to failure.

 

Bottom gasket American made for Kohler engine, has fire ring.

 

 

 

 

 

 

Edited August 3, 2020 by bcgold

[JoeM 8,337]

8 hours ago, Tuneup said:

the bolts were loose

Is the torque wrench okay? Oil the threads when torquing? 

[Tuneup 1,452]

Yeah, my Kohler gaskets are sweet. Buy from China and get from China. Onan parts on their way...

 

The torque wrench was verified by another and I clean the bolts and lightly lubricate them, yup. I pulled the 42SD and put it on the restored C-125. Now it looks like it should with a good clean and former owner spray painted deck under it. Her old RD is mechanically rebuilt but needs a restore this winter. The C worked like a champ, though ags are not good on dirt/grass mix and 35° inclines. Turfs still the best.