Measuring A Cam

[GazRallye 0]

I bought a complete engine for cheap as the guy I bought it off claimed it had a 285 cam in it of an unknown type. I was skeptical but bought it anyway as it was cheap, is there anyway of telling what cam it might be, theres no stamps on the dizzy end .

How can I tell for sure what duration it is?

 

If I measure it at its widest point with a micrometer or vernier gauge, what will this tell me?

[RossD 44]

It won't tell you much in all honesty. You can roughly measure the lift by measuring the height of the lobe and subtracting the heel of the lobe. This will show cam lift. Multiply by 1.4 to get an approximate valve lift (The rocker ratio). Companies like Kent will do a cam analysis for you if you send it to them for not much money.

[base-1 17]

Use a dial gauge on the spring cap or whatever you can get at and turn it over by hand. Use an angle gauge on the end of the cam to check duration, don't forget one cam revolution is 2 crank revolutions

 

That should give you a reasonable idea of what is in there. Take all the spark plugs out first so you can turn it easily/smoothly

Edited April 8, 2008 by base-1

[christopher 5 1 Cars]

The duration is angle that the valve is off the seat. As mentioned you should be able to do this by rotating the cam in the engine with a dial gauge to measure lift. This is assuming that the clearance has already been correctly set.

[christopher 5 1 Cars]

The duration is angle that the valve is off the seat. As mentioned you should be able to do this by rotating the cam in the engine with a dial gauge to measure lift. This is assuming that the clearance has already been correctly set. It is of course impossible to know what the clearance should be on a unknown cam. It will however be often less then standard on an uprated/reground cam.

[Sandy 191]

Different manufacturers guide the duration of the cam in different ways, open to close is the most optimistic duration, but not massively relevant in reality. 0.1mm or even better 1mm lift means much more. The gap from opening to 0.1mm can vary from around 2-12 degrees, which means that two cams could both be described as "295 degrees" open to close, but really one could be about 290 degrees at 0.1mm, the other 275 degrees and this could change again at 1mm!

[GazRallye 0]

OK guys thanks for the help, i'm gonna try and find some local engine specialists and see if they can tell what it is and what sort of condition it is in, if not i'll have to contact Kent and see what they can tell me about it.