Anyone ever use a degree wheel for cam timing?

[WERK I]

If you have, can you provide some details(pics welcome) on its use and where one can be purchased?
Thanks in advance,

Dave

[TimT]

I havent used a degree wheel on a 911. Every 911 Ive built I've followed Porsches somewhat obtuse valve timing procedure.

Ive wondered about using a degree wheel, and even have one from (big block days)

you can get a degree wheel at most american hot rod shops. if there isnt one near you try summit racing, or jegs

[snowman]

I do not use the Porsche lift figures to set cam timing. I use a degree wheel. I use the lobe center as a reference and set the cam timing accordinly.

I also use the degree wheel to determine actual TDC. I use piston stops as the method to determine TDC. I also use the 0.050" before and after top lobe center to find lobe center. I know for a fact that this is good to within one degree on any engine.

[ChrisBennet]

snoman,
Have you done any experiments to compared the degree wheel method to the factory method? What did you find?
thanks,
Chris

[snowman]

Yes I did, but I didn't write down the result and I have forgotten the number of degrees that represent min to max porsche setting. The next time I will write down the result and post it. I do know the Porsche method sets the cam at the center of the intake/exhaust overlap point.

[john walker's workshop]

a degree wheel is nice for finding TDC, but you could do it with a bolt down the plug hole. turn one way until it touches the piston, mark the pulley, turn the other way until it touches the piston, mark the pulley, then split the difference. what's wrong with the porsche method of cam timing? intake valve open X amount at overlap. simple. most DIYers here relate to simple better.

[snowman]

The only thing wrong with the Porsche method is that the TDC mark can be wrong. In my case it was off by over 3 degrees. The other thing wrong is that is is imprecise. The lobe center can be derermined much more accurately, as in the case of TDC. The real difference is imaterial for the most part, but sometimes it can make a real difference in aftermarket cams. In the case of a 912 engine with an Elgin 7805 cam there is a suckout that is present if the cam timing is off by only one or two degrees! It means that the engine either falls on its face at 4000 RMP or dosen't. The same can be true of 911 cams.

[911pcars]

Someone correct me if I'm wrong, but I haven't seen any cam specs from Porsche that describes an opening "ramp" measurement (valve preload) that specifies when the valve "officially" opens and closes relative to a degree wheel. This has a bearing on determining opening/closing location and thus duration. All I've seen is Porsche's method of measuring valve lift at TDC, overlap. What kind of information do aftermarket cam manufacturers include?

I also suggest using a mechanical stop to determine actual TDC.

Sherwood Lee
http://members.rennlist.org/911pcars

[snowman]

Cams are specified in several ways. Advertized duration, which means whatever the manufacturer wants it to, 0.050" duration, and 1.omm duration. All in valve lift as far as I know.

The cam mfg will tell you how he measures the cam and will supply the info on a cam card.

The advertized duration is somewhat meaningless as the mfg will start the lift at some insignificant ammount of lift, like 0.010", or -.005" to come up with BIGGER duration numbers. Unfortunately nothing is happening until somewhere in the 0.050" or 1mm lift point. There is a small difference here and can be generally ignored.

A street cam will have something less than 200 degrees duration at 0.050" lift, a real hot street cam will have something like 220 degrees duration at 0.050" lift and an all out racing cam will be in the area of 285 degrees duration. All this info is usually supplied by the cam grinder.

A good referance point is the cam lobe center which will be in the area of 105 degrees, plus or minus 5 degrees. This is the point where the cam is at max lift. this point is usually specified by the cam maker and Porsche as well. I personally like to use this point for setting the cam as it relates to intake flows, and max piston velocity in a way that it can be set for optimum performance. Porsche choose the crossover point for whatever reason. Its probably better than most other ways mfgs use to spec cam timing setting. As to setting the cam the way I do you will have to get pretty involved in the actual head flows and other things before you can use this method. In other words its one of the so called speed secrets that only the blessed few can know.