Cam lobe lap and valve clearance

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Model T Ford Forum: Forum 2012: Cam lobe lap and valve clearance
Top of pagePrevious messageNext messageBottom of page Link to this message  By Scott Conger on Monday, May 14, 2012 - 02:40 pm:

To start:
I've read at least 12 threads on valve clearance, so believe I've done my due diligence in trying to get this answered without asking...

I have an engine with unknown cam and varying valve clearances to start with. Engine has history of running hot and had #3 and #4 valve exhaust seats considerably erroded. Compression was 50, 50, 30, 28 while cranking with 12V battery (briskly, obviously). #1 wasn't firing (ignition problem with coil box), and #3 and #4 barely changed engine performance when shorted.

My attempts to set valves so far:

I have used Glen Chaffin method of setting valves and get significant overlap, in that exhaust and intake are well open at TDC starting into intake stroke (about .025" each). This is with valve clearance set to approx. 0.015".

I have tried the KW method as well as the "Ford method for worn cams" and ended up with valve/lifter clearance at .040" and greater (even with allowing intake to open at TDC, not even trying to delay it to piston travel .0625" down on intake stroke like manual says)...to delay intake opening that long would have required clearance well beyond .040" to delay opening of intake that long...presently have 55psi across all for cylinders.

So I'm assuming this is either improperly ground or some sort of performance cam? As you can see, I'm a bit confused...haven't seen this before...


Top of pagePrevious messageNext messageBottom of page Link to this message  By Fred Miller, Sequim WA on Monday, May 14, 2012 - 03:25 pm:

These things come to me:
(1) Sloppy timing or crank gear.
(2) Cam gear advanced.
(3) Aftermarket Camshaft
(4) Worn lobes on Camshaft.
(5) Worn Cam bearings.

Maybe this will help.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Cecil Paoletti -- Rrnton WA on Monday, May 14, 2012 - 07:52 pm:

My method is simple but perhaps time consuming. Look at the valve lifter you want to adjust and turn the crankshaft until the lifter is at the peak of cam lift. Note the position of the crank handle and give it one more complete turn. This turns the camshaft one half of a revolution and puts the valve lifter on the base circle of the cam. Adjust the lifter and move to the next valve lifter. If the plugs are out it is much easier. I make no attempt to adjust the lifters when hot.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Scott Conger on Tuesday, May 15, 2012 - 06:00 am:

Well...color me stupid. Thanks, guys for the replies. As I was going home yesterday it dawned on me what I had. I'm certain now that this is a Stipe or similar modified grind. Refering to the MTFCA engine book and NOT the Ford Bible, I can clearly see the valve action is that of a modified cam for touring with late closing exhaust and early opening intake.

Even with the "detuned" wide valve lash, I still had about .260" lift and if I set valves to about .012" then I'll have about .285" lift which appears to match lift of a modified cam. There's no way a stock Ford cam would have that lift/duration, so using the Ford method would be (was) a waste of time.

This is a quick and easy goof to overcome, at least.

Thanks again for weighing in, and Cecil, your method is how I ensure setting at back of lobe...it's a good and foolproof method of ensuring you're off the lobe.

scott


Top of pagePrevious messageNext messageBottom of page Link to this message  By James Michael Rogers on Tuesday, May 15, 2012 - 07:03 am:

Scott, I have talked to Bill several times about his cams and his recommendation for lash is .010. This should give you a duration of .280 with the cam you are using. His cams also have his company name etched on them on the rear end.


Top of pagePrevious messageNext messageBottom of page Link to this message  By James Michael Rogers on Tuesday, May 15, 2012 - 07:07 am:

I also use the same method as Cecil with one difference. I remove the cam gear and use the cam nut with a gear with no teeth to turn only the cam. Doing it this way, you don't have to remove the plugs and just turn the cam till the lifter is full up to adjust and then 1/2 turn to check. Mind you, I generally have the engine on a stand and only partially assembled.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Scott Conger on Tuesday, May 15, 2012 - 12:36 pm:

update:

I've had several nice conversations with both Bill Stipe and Glen Chaffin today. This cam is neither of their products. Appears to be a custom grind of unknown origin, with really poorly concieved overlap on exhaust and intake.

With .010" lash, intake opens well before TDC during exhaust, and exhaust remains open well after TDC during intake. It would take a pretty good RPM to make mass air flow work correctly under these circumstances...not something the T experiences under much of it's operating range unless on the highway, I think.

Well, it is what it is. I'm very appreciative of having suppliers/manufacturers who are so accessable and supportive of their products and the hobby...Kudos to Bill and Glen!


Top of pagePrevious messageNext messageBottom of page Link to this message  By Doug - Braidwood (glow in the dark), IL on Tuesday, May 15, 2012 - 06:03 pm:

Is it possibly an OHV Model T cam?


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