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Valve lapping update.

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Rob

07-09-2003 09:53:21




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Can't get one valve guide loose so I'll lap and adjust it without taking it out.
Valve lash is zero on some and one valve has .004 inch; spec is 12-14. Not good. Why? I did some reading.
The spec is cold engine and the lash is there mostly for thermal expansion to normal operating temps. The valve stem gets longer. More pronounced in engines subjected to heavy loads <<< read tractors. It's not the opening too soon, closing late thing.
With too little or no lash the valve doesn't ever properly seat at normal operating temp and it's alway 'open' some. Compression falls off at operating temp, so you won't see it with our famous wet/dry comp test, and I would think you could see a lot of other things going on at extremes. Backfiring, carbon smoke because of poor ignition and the list goes on.
This can quickly develope into a more serious <<< read expensive situation because the smaller exhaust valve especially relies on heat transfered to the valve seat for cooling. If it never fully seats then the valve can overheat and burn. You can end up having to replace the valve and seat.
My engine has one exhaust valve with zero lash that has not seated properly for some time. the valve and the seat are coated with hard carbon, it's hard and it's a poor seat; it's not flat and the faces generally don't mate. The comp on that cylinder is 87 dry and higher wet. I think the oil improves the seat and raises the comp. I had another like that and when I lapped off the carbon the seat was pitted and by rights was a candidate for replacement. That cylinder had 75 comp on it and after I lapped and adjusted that valve the comp went to 110-112psi dry. These engines require regular valve adjustment.
A note on Zane's technique of drilling a hole through the boss around the push rod and into the push rod so you don't need the LH/RH wrenches. You might want to drill a 5/32" hole and pin that rod with a 5/32" allen wrench. The wrench is tough and won't be sheared (don't use a nail) if you have to torque the adjuster and you have a handle to pull the wrench out. Not having those this-hand that-hand wrenches in there will give you more room to work the adjuster too.
This engine doesn't have adjusters so I do like Henry did, I grind and I will leave it that way. Less weight then the adjusters and less wear on the cam and rods and stuff.
Did I mention cheaper too? And 8N's is out.
Maybe I have a broken oil ring. I'm gonna get these valves lapped and adjusted, put the head back on and see what she got.

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arthur

07-09-2003 15:49:36




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 Re: Valve lapping update. in reply to Rob, 07-09-2003 09:53:21  
old saying noisy valves never burn. i always gave my valve jobs .002 more clearence than specks . it would let the valve on the seat a slight bit longer to cool more.and as the valve face wears the clearance last longer



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Rob

07-09-2003 15:55:54




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 Re: Re: Valve lapping update. in reply to arthur, 07-09-2003 15:49:36  
Yeah that sounds like the stuff I've been reading. How often should a guy check to adjust the lash?



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Steve(OR)

07-09-2003 15:25:02




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 Re: Valve lapping update. in reply to Rob, 07-09-2003 09:53:21  
Now a more serious question. You said these engines need regular valve adjustment. Valve lapping seems like a rather intrusive procedure to be needed very frequently. How often do you consider regular?



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Rob

07-09-2003 15:53:42




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 Re: Re: Valve lapping update. in reply to Steve(OR), 07-09-2003 15:25:02  
If you adjust em you shouldn't have to lap em.
I tried to find someone talking about just what 'regular adjustment' means but I can't find anyone to spell it out. I have no idea when these valves were last adjusted.
I'm going to check the adjustment after a year. I'll see how fast they are wearing. That's about 100 hours for me and I expect I won't see much wear. I imagine I will need to adjust em at 500 or 600 hours and if I do adjust em I won't live long enough to have to lap em again. Ford didn't say to check em every year so it may be 10 yrs before they need adjusting again.
Guy says you can adjust them without removing the manifold. Guess you could, I like lots of room to move myself and I removed the manifold. No big deal at all.

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Steve(OR)

07-09-2003 14:01:49




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 Re: Valve lapping update. in reply to Rob, 07-09-2003 09:53:21  
I don't beleive a 5/32" allen wrench would fit into a 5/32" hole. The measurement of 5/32" is between the flats on the wrench.



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Steve(OR

07-09-2003 14:15:38




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 Re: Re: Valve lapping update. in reply to Steve(OR), 07-09-2003 14:01:49  
Try a 4/32" allen wrench. (I just figured out the math)



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Steve(OR)

07-09-2003 14:29:05




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 Re: Re: Re: Valve lapping update. in reply to Steve(OR, 07-09-2003 14:15:38  
Duh - I should have said 1/8"



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or....bg

07-09-2003 16:02:26




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 Re: Re: Re: Re: Valve lapping update. in reply to Steve(OR), 07-09-2003 14:29:05  
8/64ths!



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MickPB

07-09-2003 12:25:34




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 Re: Valve lapping update. in reply to Rob, 07-09-2003 09:53:21  
Keep the updates coming. I think I may be getting a head gasket and manifold set soon!



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Rob

07-09-2003 15:20:12




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 Re: Re: Valve lapping update. in reply to MickPB, 07-09-2003 12:25:34  
I recommend you check the valves before you pull the head. See if they have any lash and adjust em if you can.
All you have to do is remove the manifold and those two valve chamber plates. Feeler gage and you can check em. I don't know what clearance you get into trouble but I can see here that if the exhaust valve is .004 or less you better figure on removing the head and lapping some valves and probably even replacing the exhaust seats. This one was 4 and it was burnt.
This 1944 2N doesn't have seat inserts on the intakes but those seats aren't pitted and burnt and they clean up and adjust out fine. The exhaust valves are a different matter but even just lapping and setting the lash I got that great increase in compression. Seat is still full of tiny pits but I lapped out the burn cut. Takes a lotta elbow grease to lap out a cut. LOTTA elbow grease.
6 bucks for a seat insert, 3 little beads on the inside of the insert and it comes out...so they say. Dry ice or some other way of getting the new insert real cold and it drives right in...so they say. That might be the way to go. No lash on the exhaust then figure on a head gasket and exhaust seat inserts and get in there.
I'd have to destroy this one exhaust valve to remove it. That would be another $10 and something for a new guide. They don't cost much. Maybe it will free up by tomorrow. Doesn't matter because I got it lapped and I'll be done with it tonight so I don't care if it comes out.
Near as I can see from reading up on flatheads is that you don't have to worry too much about the valve stem-to-guide clearance unless you got noisy valves.
One poster said 'centering' is a problem with worn guides. Well see.

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