Valve Adjustment..

[Michael72]

Hi Folks

Just to ask your thoughts on briggs valve adjustment....I see so many vids today where OHV'S and flat heads are adjusted at TDC and not turned over so the piston is down 1/4" as specified by Briggs....

To add... on a 3.5 classic im working on at the moment the piston will travel slightly above cylinder block so to measure from top of block will give you more than 1/4"... either way the feeler gauge is giving the same reading from valve stem to rod weather I turn down 1/4 or not!... i dunno

 

[Carscw]

Best way to adjust valves.

Turn the flywheel counterclockwise 2 times.
Stop when one valve is open adjust the closed valve. Repeat for the other valve.

Sent from my iPhone using LMF

 

[Michael72]

Hi

Thanks.... makes sense to do it that way...proper reading etc :thumbsup:

 

[pugaltitude]

Hi Folks

Just to ask your thoughts on briggs valve adjustment....I see so many vids today where OHV'S and flat heads are adjusted at TDC and not turned over so the piston is down 1/4" as specified by Briggs....

To add... on a 3.5 classic im working on at the moment the piston will travel slightly above cylinder block so to measure from top of block will give you more than 1/4"... either way the feeler gauge is giving the same reading from valve stem to rod weather I turn down 1/4 or not!... i dunno

I think you are being a bit to precise when checking valves on this engine.

Usually a screw driver down the plug hole and turn past TDC on the power stroke and measure approx. 1/4" or 10mmish.

The reason for doing this is because if it is before TDC then the decomp on the cam shaft is in the wrong position and may open the valve slightly which would give you a wrong reading.

Also I cant remember the last time I set valves on a classic due to them being so reliable.

 

[Michael72]

Hi

Thanks for the reply...I had the head off anyway as compression was down so I suspected valve seating issues...yes being to fussy good advise ...thank you

 

[motoman]

CAUTION , DO NOT READ IF ALLERGIC TO TRIVIA :laughing:

Mike, Some blather which might explain what you observe measuring the same in different (small) rotations of the engine aroung TDC. A "mild" cam lobe grind has a very "pointed" lift shape so the bottom portion of the cam lobe is a symmetrical circle. When you note an unchanged clearance with a feeler gauge you are reading this unchanged contour. If you ever see a "radical" cam grind pictured it has "ramps" that start much sooner to slam open the valve instead of gently lift it. On such a cam you would see the clearance area around that same area greatly reduced.. If you are interested in "messing" around while you still have the head off you can determine a precise TDC mark by using something bolted to head wich stops the piston from reaching TDC. Rotate the piston one way until the piston is stopped and mark; remove the stop and go past, rebolt and rotate the other way and mark. Remove. Half way between the two marks is TDC. I put a small center punch mark with red ink on my Intek. This is overkill for such slow running engines. I do not know why the factory did not put on such a mark, but perhaps it is with the same marketing philosopy which publishes the Intek owners manual without a required valve adjustment , but then includes unadjusted valves as a problem in the troubleshooting secion.

 

[SeniorCitizen]

Hi

Thanks for the reply...I had the head off anyway as compression was down so I suspected valve seating issues...yes being to fussy good advise ...thank you

Have the valves ever been lapped?

 

[Michael72]

Thanks all for the info...much appreciated... not my first rodeo with this but always good to have other opinions and advise....learn something new everyday until I forget it all the day after :smile:...the valves needed attention (some lapping) so compression issues solved....slight pitting but mainly some carbon build up...thanks again..:thumbsup:

 

[Michael72]

CAUTION , DO NOT READ IF ALLERGIC TO TRIVIA :laughing:

Mike, Some blather which might explain what you observe measuring the same in different (small) rotations of the engine aroung TDC. A "mild" cam lobe grind has a very "pointed" lift shape so the bottom portion of the cam lobe is a symmetrical circle. When you note an unchanged clearance with a feeler gauge you are reading this unchanged contour. If you ever see a "radical" cam grind pictured it has "ramps" that start much sooner to slam open the valve instead of gently lift it. On such a cam you would see the clearance area around that same area greatly reduced.. If you are interested in "messing" around while you still have the head off you can determine a precise TDC mark by using something bolted to head wich stops the piston from reaching TDC. Rotate the piston one way until the piston is stopped and mark; remove the stop and go past, rebolt and rotate the other way and mark. Remove. Half way between the two marks is TDC. I put a small center punch mark with red ink on my Intek. This is overkill for such slow running engines. I do not know why the factory did not put on such a mark, but perhaps it is with the same marketing philosopy which publishes the Intek owners manual without a required valve adjustment , but then includes unadjusted valves as a problem in the troubleshooting secion.

I can do trivia lol....good read and thanks

 

[Rivets]

Why don't owners manual include valve clearance? CYA by the manufacturers, because 95% of owners would cause more damage or injuries if they attempted to adjusted the valves. I would say that 90% of the techs out there, under the age of 30, don't know how the adjust or lap valves on an L-head engine.