Setting valves by piston position

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Model T Ford Forum: Forum 2016: Setting valves by piston position
Top of pagePrevious messageNext messageBottom of page Link to this message  By Dave Eddie on Thursday, November 03, 2016 - 11:17 pm:

Does anyone have the instructions on how to set the valves opening position using a dial indicator, rather than just adjusting the valve clearance using a feeler gauge ?
I have the engine out of car going through the transmission, seems like a good time to set the valves correctly.

Dave Eddie


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Noonan - Norton, MA. on Thursday, November 03, 2016 - 11:28 pm:

Dave, here is a great thread that i used when i did mine. Hope this helps.

http://www.mtfca.com/discus/messages/179374/232260.html?1314751773


Top of pagePrevious messageNext messageBottom of page Link to this message  By JohnH on Friday, November 04, 2016 - 12:00 am:

The instructions I have say to have the inlet valve just start to open when the piston is .0625" down from TDC on the intake stroke.
The exhaust valve is set to just close at TDC after the exhaust stroke.
I've always set my valves this way and like the results. The instructions came from an article called "Timing by the Third Method" which another T owner gave me years ago.
timing


Top of pagePrevious messageNext messageBottom of page Link to this message  By Larry Smith, Lomita, California on Friday, November 04, 2016 - 09:22 am:

It's in the Ford Service Bulletins, more than one time too!


Top of pagePrevious messageNext messageBottom of page Link to this message  By Gary Blake, Kansas City on Friday, November 04, 2016 - 09:49 am:

I've worked on a wide variety of engines for decades and have never heard of setting clearance based on piston position. This does remind me of the procedure for degreeing a cam with a degree wheel when blueprinting an engine but that requires an adjustable cam gear.

If at the end of this procedure (setting clearance based on piston position) your valve clearance is greater than the .010 to .015 called for in the thread posted above then you will be running with reduced lift and duration. And a tapping sound while running. All of which are undesirable

If the cam is well worn, you would likely be running something less than .010 after completing this procedure so the valve might never fully close and you would run the risk of burning the valve.

Remember, for all practical purposes there will be no wear on the heel of the cam since the follower (thanks to the clearance) is not subjected to valve spring pressure at that point. Wear will occur on the cam lobe from the opening point of the valve to the closing point with the greatest wear at the peak since that would be the point of highest spring pressure combined with the least amount of contact between the follower and the lobe. A worn camshaft looses lift more than anything else.

I will grant that valve clearance has a slight effect on valve timing, lift, and duration, but valve clearance for any engine is optimized for valvetrain longevity and low noise, not for optimal timing of the opening and closing of the valves.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Royce in Dallas TX on Friday, November 04, 2016 - 10:00 am:

Gary is 100% correct.

This set of instructions was used by folks back in the day to get a Model T engine to limp along another couple thousand miles despite having a junk camshaft. You need to remember that. It's not going to yield a better running Model T than what you would have if you installed a good reground or new camshaft.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Charlie B actually in Toms River N.J. on Friday, November 04, 2016 - 10:14 am:

AH.... That clears this up for me. All the "bad" stuff listed here and in the address posted above made me wonder why the heck someone would go thru this difficult and time consuming procedure. Compensating for a worn cam. OK.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ted Dumas on Friday, November 04, 2016 - 11:37 am:

If you have a worn camshaft and tappets, it's the only way you can set the valve clearance and have a good running engine. You will likely have noisy valves.

If the engine is out of the car then have the cam reground and install new adjustable tappets as others have stated. You can then set the valves by clearance and get an excellent running engine.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Glen Chaffin on Friday, November 04, 2016 - 01:02 pm:

You guys are correct. setting valves by piston travel was designed to compensate for badly worn camshafts. The results were slightly improved performance and a very noisy engine. The improved performance wasn't worth the noise or trouble. Bruce McCalley wrote several articles about this and it was all wasted paper. No one in their right mind today would bother with this procedure. First of all, Fords original timing specs used about 0.026 valve lash. Reducing valve lash to 0.012-0.015 increases valve duration and significantly improves engine performance. This improvement is much greater than setting valves by piston travel. So just set the valve clearance to 0.012-0.015 and you will have a good running engine. Better yet replace the worn out cam with a good regrind or new cam and get even better performance.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Dave Eddie on Friday, November 04, 2016 - 03:44 pm:

I have neither a worn camshaft nor a worn cam gear


Top of pagePrevious messageNext messageBottom of page Link to this message  By Royce in Dallas TX on Friday, November 04, 2016 - 04:24 pm:

Dave if that is the case then your car will run best setting the clearances of the cam lifters the typical way.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Nicholas Lingg - Tarboro, NC on Friday, November 04, 2016 - 05:04 pm:

OK! I'll concede that setting the valves with all new parts can be done with a feeler gauge. BUT how many of the running T's have new parts? Is't the idea to keep as many of these cars running as possible.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ted Dumas on Friday, November 04, 2016 - 06:11 pm:

Dave,

What does the tappet face that lifts the valves looks like? Usually on a worn engine the valve end wears a recess in the tappet such that you can not use a feeler gage to set the clearance.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Tim on Friday, November 04, 2016 - 06:27 pm:

Dave - If you have a new cam and adjustable lifters - move the dial to the valve you want to adjust and dial in 0.010" lash. I did an article on this a few years ago. I'll try to find it and put it up on my website.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ted Dumas on Friday, November 04, 2016 - 10:53 pm:

If you have a new or reground cam and tappets and set the valves all to the same clearance then they will all open and close at the same piston position. At least on my 24 that was the case.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Larry Smith, Lomita, California on Saturday, November 05, 2016 - 10:46 pm:

I have new Stipe cams in all of my cars. He recommends .010". The only thing that pisses me off is he doesn't make both styles any more, only the late style!


Top of pagePrevious messageNext messageBottom of page Link to this message  By Tim on Sunday, November 06, 2016 - 10:39 am:

How is that bad - you're going to replace the bearing anyway right?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Frank Harris from Long Beach, CA on Sunday, November 06, 2016 - 12:30 pm:

Hey . . listen up. I have said this before . . . The piston position valve timing is old school and was used because no one had feeler gauges in olden days. Our 1913 Cadillac had a marked flywheel with opening and closing positions stamped in the outer surface of the flywheel and it also had a marker arrow for alignment. Henry couldn't do this because he hid the flywheel.

Our Cadillac also had roller tappets but then it was an expensive car made well. But then because it was a very fine automobile it also had a disk brake mounted on the drive shaft with a foot operated pad connected to the clutch pedal which acted as a form of a synchromesh system for easier shifting. Henry used the piston position valve adjustment method because most farmers had a wooden ruler but no feeler gauges. Remember the worn dime used as a spark plug gap adjuster ?

So if you have a worn camshaft that was whittled by hand out of soft iron by boy scouts then by all means use the piston position method to adjust your valves if your block deck has not been resurfaced and you have cast iron pistons. If not then use a feeler gauge.

But just for fun if you have adjustable valve tappets you don't even need a feeler gauge. Every ten degrees of rotation of your wrench is one thousandths of an inch. So turn the engine so the heel is on the tappet surface and turn it down until the tappet locks. Then back-off the wrench 100 degrees to get .010" for the intakes and turn it 90 degrees plus 30 degrees for .015". Then lock the second nut unless you have a self locking nut.

I simply remove the valve cover or covers and push the car backwards and forwards in the garage to get the tappet aligned with the heel. No degree wheel is required. Your cam is in an adjustable position for a full 360 degrees of crank shaft rotation unless it came from Mars. People just love pain and suffering and making things difficult.

Here is the math. Adjustable tappets use a 1/4 28 bolt. These bolts move or advance and retard as they are rotated. 28 rotations of the nut moves the valve stem one inch. One inch divided by 28 equals .035714285714" and so on. I round that out to .036" So every ten degrees of rotation is .001" valve lift. 90 degrees plus ten equals .010". If you don't believe me try it and you will be within .0005" either way if you can rotate 90 degrees plus 10 degrees.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Frank Harris from Long Beach, CA on Sunday, November 06, 2016 - 12:42 pm:

CORRECTING A MATH ERROR: I meant to say .012" rather than the .015" I accidentally posted. Also since you can adjust a valve anywhere on the heel you only have to push the car backwards and forwards two revolutions of the engine in high gear since all valves are closed for one full revolution or more of the crank shaft, again unless your car was built on Mars. We have an old saying around here, KISS . . . Keep it simple stupid !

CORRECTION: But just for fun if you have adjustable valve tappets you don't even need a feeler gauge. Every ten degrees of rotation of your wrench is one thousandths of an inch. So turn the engine so the heel is on the tappet surface and turn it down until the tappet locks. Then back-off the wrench 100 degrees to get .010" for the intakes and turn it 90 degrees plus 30 degrees for .012". Then lock the second nut unless you have a self locking nut.


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