New Cam

[Anonymous]

I have never changed a cam before, and I have a few questions about doing soo in my 66' 200CID (all stock). On the cam guide for the site, it gives a few popular cams. On most, the lobe lift is more than .420. It also says most stock engines that it can tolerate usually about a .500 inch lift before the valves hit the pistions. So with the rocker ratios(1.5:1?), would the total lift of the valves would be more than .630 inches. Would that not cause problems? Or is solely for modified engines? I am having trouble finding a cam that has a lift small enough to be below .500. And also, once the cam is replaced, is there any more work that must be done on the engine(timing, etc.), or does it depends on the cam, or what? Thanks for any input.

 

[CZLN6]

Howdy Agreenagent:

The lift you are referring to is a gross rating. It includes the lift at the cam plus the rocker multiple, For example, a cam with a lift of .266" at the lobe, X the rocker ratio of 1.5 equals .399" gross lift. Most aftermarket, performance cams are listed with a stock ratio rocker.

Valve to Piston clearance on a stock engine is almost never a problem.

I'm not sure of your goal or your need, but you'd be far better off, bang-for-the-bucks, to put you hard earned dollars into improving your cylinder head first. In truth, a stock cam is about as good as you get with an otherwise stock engine. It might be best to come up with a total plan before you select a cam.

Replacing a cam on our engines requires that the head or the pan be removed. Ideally, both. Lifters are best installed after the cam is in place. As ling as you're this far into it you might as well rebuild the block too.

If you replace your cam, plan on doing new timing gear, cam bearings and lifters. You will also need to address the difference in the thickness of the stock OEM steel shim head gasket at .025" to an aftermarket composite at about .050", otherwise you will lose compression.

Timing gear for your 200 is straight up, neither advanced or retarded. Later 200s used advance or retard buitl into the gear to meet EPA requirements, or to gain a little more power on the bottom or top end.

I hope this helps.

Adios, David

 

[Anonymous]

Thanks, yeah I was going to work on the block too, but I was totally confused as to the cam specs. That helps a lot, thanks.