valve timing with high compression pistons

[pgbaresel]

I have a question on adjusting valves and valve timing with high compression valves.
I use a dial indicator on the high domed pistons to find top dead center. I have adjustable valve lifters and have attempted to get the correct valve lash.
The valves are the hardened steel type with new seats. I am getting confused with all of the feed back on the forum what the correct valve lash ought to be for the engine.
I understand the valve timing process with standard, flat top pistons, but can a high domed piston time its engine valves?
The engine was rebuilt and I believe the cam shaft is suppose to be new, but who knows?
Any suggestions to guide me in valve adjustment and timing?
Thanks Paul

[Mark Gregush]

If you have new or reground cam .010 on the intakes and .012 on the exhaust. Adjusting for piston travel is useful with a worn cam, but is not needed with what you say has been done with your engine.

[Scott_Conger]

New engine?

Don't do it!!

Contact the engine builder and get the cam spec's...typically the lifter gap is .010" all around, but many like .010 on intake and .012 on exhaust. With a new cam you will not believe how incredibly screwed up you will get your car, since you do not know the lift nor anything about overlap or any performance enhancements put into the cam as ground.

Do not join the "I have a new T and just have to screw around with things and really mess it up" club.

Just enjoy the car.

[pgbaresel]

I would love to contact the engine rebuilder, but he died quite some time ago. His reputation for rebuilding engines was good. The engine was bought to use and never made it to a chasis. The engine was not just a rebuilt block, but a complete engine. Paul

[Erik Barrett]

Valve timing only works with a stock cam and pistons.

[speedytinc]

What you need to do is document valve opening/closing evens for EACH cylinder in relation to TDC & BDC. Compare the data timing events. Can be shifted by changing valve lash one way or the other. .010" would be the minimum. These data points can be compared to known cam specs from cam providers like Stipe. Tdc is not nearly as important with relation to Exh close & Int opening as the data of when Exh opens & Int closes.(not much is happening @ this point) These "bottom" numbers make the magic of a good running motor & should be near the same for ALL 4 cylinders. What those numbers should be? Depends on your optimal RPM range, low end torque, HP, weight, gearing, etc. (demands & expectations)

[bgarrett]

Valve timing only works with a stock cam and pistons.

Is a Model T different from every other engine ever made???
Valve timing is important no matter what the cam and pistons are

[speedytinc]

Valve timing only works with a stock cam and pistons.

Is a Model T different from every other engine ever made???
Valve timing is important no matter what the cam and pistons are

What he's saying is the ford method of setting valve clearance by piston position is not applicable with a modern CNC, accurately (presumably) ground cam. The ford method on an original ford T cam can is noted to be more effective than using a set dimension, like .010" through out. Because of the inaccuracy's of the ford cam.

[Kerry]

Valve timing by piston travel was not the "Ford way", just like the in car magneto charge of which took a long time for Ford to approve of, Ford adopted the practice for worn valve train late in the T's life, November 1926 for service bulletin using a K R Wilson tool. But as far as the service book go's it was still just done by thickness gauge. So as others had posted a fresh valve train only requires the lash set by a thickness gauge.

[speedytinc]

Valve timing by piston travel was not the "Ford way", just like the in car magneto charge of which took a long time for Ford to approve of, Ford adopted the practice for worn valve train late in the T's life, November 1926 for service bulletin using a K R Wilson tool. But as far as the service book go's it was still just done by thickness gauge. So as others had posted a fresh valve train only requires the lash set by a thickness gauge.

Excuse me, the KRW method. The point is, you dont use piston travel to set valve clearance with a new cam.

[Kerry]

John you are excused , and like I posted and Ford said, the piston travel way was for worn valve trains. That was the point.

[bpresslylsmo]

"The method of accurate valve timing on a Model T Ford engine is to time the valves by piston travel" per Ford Service Bulletin released December 1924. It accommodates a worn cam, but also works with a new standard cam. I figured out an alternate way to use the KRWilson method of adjusting 'valve timing based on piston travel'. I am using domed high compression aluminum pistons, so I couldn't use the tool designed for standard flat top pistons. I designed and fabricated an adjustable tool which registers off the top of the domed pistons. It's based on the inlet valves closing at (9/16" piston travel) past lower center on compression stroke and the exhaust valves opening at (5/16" piston travel) before lower center on powerstroke (dimension appropriate for motors later than 1913 Model)
.

Here is the original method described in a 1914 Ford Manual
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These next 3 images are from the Ford Service Bulletin

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Here's the tool I created to use with my domed high compression pistons
The tool has two grooves machined in the top. One 9/16" deep (inlet valve adjustment groove) and the other 5/16" deep (exhaust valve adjustment groove)
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More in an additional reply

[bpresslylsmo]

Tool inserted in the bore with piston at 'bottom dead center'. Threaded rod adjusted and locked with the top of the tool even with the top of the block.
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The crank is positioned with the tool up 5/16" before lower dead center on the powerstroke, which is when the exhaust valve opens.
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Using a parallel bar to check for groove position relative to the top of the block
Then adjust your exhaust valve to be touching the valve seat by feeling friction as you push on and rotate the valve
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Crank positioned so tool is up 9/16" past lower dead center on compression stroke, which is when the inlet valve closes.
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Again, Using a parallel bar to check for groove position relative to the top of the block
Then adjust your inlet valve to be touching the valve seat by feeling friction as you push on and rotate the valve
.
.

[bpresslylsmo]

Here's a sketch of my tool in the cylinder
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After all valve adjustments were completed, I double checked the valve lash gaps and compared them to the gaps listed within the original manual - all within the range listed!!!

[Scott_Conger]

You get an A+ for cleverness, but if you don't have a stock "T" cam, that was quite an exercise in futility. A new cam has been designed for a VERY small pushrod gap and now that you have a new cam and wide open clearances (as listed in the manual), you've gained a noisy engine and have probably de-tuned the cam.

At least your valves will run cooler. Even so, I wouldn't put this one in the "Win" column.

[bpresslylsmo]

You get an A+ for cleverness, but if you don't have a stock "T" cam, that was quite an exercise in futility. A new cam has been designed for a VERY small pushrod gap and now that you have a new cam and wide open clearances (as listed in the manual), you've gained a noisy engine and have probably de-tuned the cam.

At least your valves will run cooler. Even so, I wouldn't put this one in the "Win" column.

Scott,
My lead-in statement was... It accommodates a worn cam, but also works with a new standard cam (meaning, Standard lift (Stock Grind 250)
Are you referring to the Super Lift and Duration Cam's (280 and 290)? If so, that's not what I have. I have a slightly worn stock cam.
Not sure what the original author of this post has, not sure he does either.