Changing cams

Crimmo · newbie Joined: 23 Oct 2001 Posts: 2

since the workshop is down, and im changing my cam tonight, it need to ask a few questions about changing my cam.
Firstly how is it done? is it just remove the rocker cover, undo the crank nut on the end of the cam, and all the huts ontop of the springs, remove cam, put new one in, then put everything back?
and secondly, crank chain timong, can i leave it the same as it was by just not moving it?
thanks
its a racing cam by the way and i dont know what grind it is

Fastgem · tinkerer Joined: 04 Oct 2001 Posts: 166

Thats pretty much it, Turn the engine over until its at Top Dead Center and the cam shaft marks should line up with each other to make things a bit easier. you also need to release the tension on the timing chain which is easily done on the 1600 by pressing down that white bit of plastic with a flat head screw driver on the chain tensioner and turning it 90 deg. to hold it in the released position. As long as the camshaft sprocket doesnt fall off the chain then you wont have to change anything and make sure you lubricate the new cam with oil before you put it in otherwise you will probably do some damage when you go to start it up. Also you will need some feeler gauges to adjust the tappets. Just make sure you can turn the engine around by hand before you go to start it. If you get to a point where you cant turn it, dont try and force it because its probably the valves hitting the pistons.

MatMan · tinkerer Joined: 04 Oct 2001 Posts: 280

Is it a brand new cam?
If it is, then you will have to run it in. Coat it generously with molybendulum grease, and when you start the engine, hold the revs at about 3000 or so for about 15 - 20 minutes. If this is wrong, please, someone correct me.

murray · rice boy Joined: 08 Oct 2001 Posts: 15

why do you have to hold it a 3000 rpm?
Murray

MatMan · tinkerer Joined: 04 Oct 2001 Posts: 280

So it beds in properly or somethin, I dunno I just remember reading it Street Machine. I'll try to find the issue and tell you why then. Smile

Ben Wight · backyard mechanic Joined: 04 Oct 2001 Posts: 946

This is only necesarry for new hydraulic lifters, most of the cars in street machine are pushrod engines with lifters.
The gemmy obviously doesn't have these and a running in period is not necesarry.

Ben Wight

Gats · newbie Joined: 08 Oct 2001 Posts: 7

Sorry Ben, I disagree with you. When I bought my new cam from Gemispares in SA, they told me to run the engine @ 2000 rpm for about 20 minutes. They told me this was to bed the cam in. Make sure you grease the cam up as well.

Hope this helps

Cheers

Ben Wight · backyard mechanic Joined: 04 Oct 2001 Posts: 946

Did they say why? I mean they obviously said it had to bed in, but the thing spins in bearings, and steel feet slide on its lobes. What part of it has to bed in?

When running an engine for the first time, you have to bed the rings in, this is where there is actually wearing of both the ring and cylinder surface slightly, so a better seal is formed, I think thats how it works anyway.

I cant see what there is to bed in with a bearing and follower application. The cam just spins in the bearing, how will holding it @ 2000rpm do anything at all? Maybe the feet of the rocker arms have to bed in on the lobes, but both the lobes and rocker feet are hardenned steel, which are supposed to not wear easily, unlike rings and cast iron cylinders which are generally ductile and can wear easilly in the wrong situation.

Ben Wight