What are the valve clearence in a 20hp onan

[Dball 12]

What are should both the exhaust and intake valves be set to 

[GMan 82]

DBall,

 

Intake @ .005 and exhaust @ .013......................Hope this helps...................Gary

[Dball 12]

Yes thank you gary

Im getting. 010 exhaust and .004 intake at tdc i dont have the heads off to be 100% but im pretty sure i am at or close to so think all is good 

[lynnmor 6,761]

Turn the engine over by hand,  Watch the valve being pushed open, and when it is at its max, mark the pulley and give it one more turn.  That doesn't have to be exact, just turn it near your mark.  Now adjust that valve.  Repeat three more times and done. 

 

This works with nearly all four stroke engines ever produced, all you are doing is getting the cam turned so that the follower is opposite the "lump" and on the base circle.  Many instructions tell you to be at top dead center, but often the follower is dangerously close to the lump.

[WH nut 553]

10 hours ago, Dball said:

Yes thank you gary

Im getting. 010 exhaust and .004 intake at tdc i dont have the heads off to be 100% but im pretty sure i am at or close to so think all is good 

Id try to get at least the exhaust  to 13. Remember when the motor heats up your clearance drop. The exhaust could hang open a little.

[entropy 104]

Here is the shop manual with clearances, torque specs, oil recommendations for varying temps and electrical as well. 

P216_P218_P220_P224_Service_965-0762S.pdf

And lots of other good info.

 

[boomers_influence 106]

lynnmor

you are WRONG on your procedure of setting valves.

onan twins such as the P series ARE NOT

set from the base circle of the cam.

they are set when that cylinder is at TDC of the compression stroke.

 

dball

the onan service manual listed will give you the correct procedure

for adjusting the valves. ( page 16-2 )

 

thank you. boomer ( the used onan engine parts guy, also NOS and new )

[lynnmor 6,761]

34 minutes ago, boomers_influence said:

lynnmor

you are WRONG on your procedure of setting valves.

onan twins such as the P series ARE NOT

set from the base circle of the cam.

they are set when that cylinder is at TDC of the compression stroke.

 

thank you. boomer ( the used onan engine parts guy, also NOS and new )

Of course that will get you on the base circle, so what is the problem?

[boomers_influence 106]

lynnmor

the base circle of the cam is never the

same for the intake and exhaust.

if it were you would never get valve overlap.

i believe that onan came up with this procedure

to make it SIMPLE to adjust the valves.

have you ever looked at an onan camshaft?

 

someday when i get BORED i will use your procedure,

and then the factory way.

i will use a  piston stop, a dial indicator and a degree wheel.

thank you. boomer

[lynnmor 6,761]

First, a circle is a circle, the lobes are a portion that extends above that circle.  Yes, I have rebuilt many engines of all types including Onan.

 

The Onan manual describes a procedure that does allow adjusting both valves without turning the crank.  That takes a few minutes off the time and also gives direction to those of limited mechanical abilities.

 

The OP apparently was not aware of, or couldn't find, the timing marks.  He mentioned head removal so he could see the piston. The procedure I described will work just fine and is somewhat better than the shortcut procedure provided by Onan.

[Duramax7man7 505]

Isn't valve clearance all the same (obviously it's different per intake/ exhaust) whether one valve is closed by itself or they are closed together?

 Being only a 2 cylinder engine, there is not really any need to do each valve by itself. Is there? And technically speaking, couldn't all engines be adjusted the Onan way, per cylinder in lieu of the per valve way? Just catch the valves both closed at TDC? Now if we are talking about Race Engine, that might be a different story.

 

 Or is the Adjustment per valve (1 open/ 1 closed) yielding a more accurate adjustment? I would think that it the cams lobe has passed, then the valve will be all of the way closed, regardless.
 

 But if the per valve way is better, I may actually readjust mine that way if it's going to yield better performance and a cleaner combustion chamber/ in/ ex ports. But once again, I didn't think that it would...

 

Thanks.

Edited November 21, 2016 by Mastiffman

[lynnmor 6,761]

I suggested the method for two reasons; there is no need to find and rely on timing marks, and this way you can be absolutely sure the lobe is well away from the follower.  That said, you are correct in your statement, I provided the information so that there would be no doubt in accomplishing a successful adjustment.

 

Since you mentioned high performance engines, they do have lobes that are a longer duration and give less room for error in positioning the cam for adjustment.  Again, the procedure I suggested gets the lobe opposite the follower.

[Duramax7man7 505]

Gotcha. Thanks. All that I've done before unless I've had the head off was to bring the Piston to TDC to the point that I could rock the flywheel back and forth a tiny bit and feel no movement in the feeling tool used (wood dowel). As long as both vales were loose at this TDC. I would notice when I started to see/ feel movement of the piston in both directions and then bring the flywheel to half way between opposing movement positions. Then once those valves were adjusted, I then rotate the flywheel one full revolution and check for the movement again and stop it half way, check for loose valves and then adjust them accordingly if they were.

 

 I can understand the more precise method on high performance engine and the lobes are larger.

 

 Me personally, I'll stick with Onan and Boomers method as it's faster and works like they suggested.

 

 I do know that Boomer has been around and working specifically on Onans for many years. Probably longer than Most. So I definitely trust his judgement when it comes to these Onans... Not other that other don't know though either, on the same token.

 

 Seems like Onan was trying to follow the K.I.S.S. rule with a few things. (keep it simple stupid) ha ha.   

Edited November 21, 2016 by Mastiffman

[lynnmor 6,761]

It would require two additional rotations of the crankshaft which could likely result in two minutes of your time wasted.

[Duramax7man7 505]

Yes. That's it.   

 

Edited November 21, 2016 by Mastiffman

[Dball 12]

Thank you all for the good tips and advice