Upon checking the lift of my reground camshaft I'm coming up with .225" at .012 clearance. Does this sound right for a stock regrind? This is measured with a dial indicator set on the valve face.
The stock Model T cam has a nominal lift of .250", but in my experience using the same measuring techniques that you describe, they usually comes in closer to .218". If you are getting .225" you are doing well.
The Sipe "280" is my favorite cam for rebuilt Model T engines. I set the valve lash by piston travel using a degree wheel. The cam is designed for a valve lash of .010", and I generally get pretty close to .270" lift when I am done.
Good seats are essential in a Model T, and I spend lots of time carefully machining the seats so that the total run out is no more than .0005. I grind the valves to get the same run out. The idea, as I understand it, is to stuff as much air/fuel mixture into each cylinder as you can, bottle it up tight with really good valves and seats, then light it off, preferably under a higher compression cylinder head. So far this has worked for me.
Your results may vary.
If you measured the "lift" by the regularly accepted method, you would say that your cam has .237 lift. Which for a stock T cam is about normal, as Trent explains above.
The difference is, you measured actual valve lift. The usual method is to measure the cam lobe at it's widest, then measure at its narrowest, then subtract the two numbers to arrive at the "lift". In other words, you would eliminate the tappet clearance from the measurement. This is done to establish the true condition of the cam and to compare relative lifts, from one lobe to the next, without introducing the variable of tappet clearance.
Philip, Assuming your cam is a stock cam with 250 lift your cam is not ground properly. If it were you would get 238 lift with 0.012 clearance.
I told the cam grinder to give me a stock 16 cam grind. Not going to mention who did it as I'm not trying to bash anyone at this point. Just wanted to check to see if the readings I got were good or not.
I did not measure and I am not that technically familiar with the lift measurements. I can tell you that the regrind I just got from Chaffin's made my engine come alive, better than the Z-head did previously. They will be getting any further regrind business for future engines at a substantial savings from me. I would highly recommend their cams.
Thank you Tom. Your comments are appreciated and true. We put a lot of time into designing our cams and the results speak for themselves. I do not claim to be a cam design expert as some others do but I believe that we have the best cams available. The first thing we learned was that by reducing the valve clearance from Fords 0.026 to 0.015 improved the high end by 20 percent. We then adjusted the lobe separation, duration and advance to give the best performance at the high end without harming the low end. The result was a cam that can pull a hill in high gear and still go 50 MPH.
Glen, do you run an advanced cam gear with yours? Is your regrind similar to that of Ford n More?
Doug, No you don't need an advanced cam gear. Our cams are already advanced to the optimum point 2 Deg ATDC. I do not have Ford and Mores cam specs. If you do please send them to me. Thanks Glen
Glen, I used one of your performance 280 cams AND advanced the timing gear 1/2 tooth... in your view would this combination be detrimental compared with the standard timing gear position?
I am running one of Glen's 270 regrinds with a nylon 71/2 degree cam gear and the car runs great!
Chris: No, do not advance our 280 cam 1/2 tooth. That is a 7.5 deg advance. The cam is already advanced to the optimum point which is 2 deg ATDC. Advancing the cam another 7.5 deg will cause a 7.6% decrease in high end performance. Tom: A little advance for our 270 regrind is ok but not more than 6 deg. Advancing that cam 7.5 deg will increase the high end about 2.5% but will decrease the low end about 2.4%.
The car runs better than ever. Are you suggesting that if I replace the advanced cam gear with the original cam gear it would run better yet? I am not sure my neck could take much more acceleration! (grins)
Tom, I am pleased that you are happy with the cam. But advancing it 7.5 deg is too much. You will definatelly get better performance with a stock cam gear or one advanced no more than 6 deg.
You cannot tell whether your cam is stock by measuring the lift alone. A worn down T cam cannot be reground back to stock cam timing. We had this discussion about 15 years ago, which led to the Stipe cams. See "Cam Design Factors" under the "Cam Designs" button.