Whats the diference between these 7m cams?

[kemicalx]

Ey guys,

I'm currently reassembling the replacement 7MGTE head i bought, I'm about to install the cams back in but have noticed some diferences between the rusty cams this head came with, and the ones off my busted head. Pictured is the 2 exhaust cams

picture 1

picture 2

The middle cam is the exhaust cam off my new head. The bottom one, the exhaust off my old head (out of an '86 mz21) . Notice how the holes in the new cams are larger than the ones in the old one. Also the newer one is labeled 5 the older one 3.

Anyone know what(if any) the diferences will be? Besides the bigger holes the 2 intake cams seem identical so i don't think the cams are from a 7MGE.

Finally, regardless of which cams are better. I won't be able to use the cams from my bent head anyway will I?

Cheers everyone,
Ashlin.

[gianttomato]

Firstly, make sure there are no obvious differences in journal diameter or oiling between the two cams and their respective heads.

Then you should check for runout, particularly if the cams are unknown to you or you suspect you bent them by cooking the head. Put the cams in some V blocks - just use some chunks of aluminium - and set up a dial indicator on the centre journal. According to the TSRM, you can have up to 0.03mm runout. Any more and it becomes a nightstick, tent peg or anal dildo.

As for whether there are any subtle differences in lift or duration, I suspect you'll need to work this out for yourself. Here is a basic way I use.

Put the cams in your stuffed head.
Put a degree wheel on the front of your cam lining the zero opposite the peak of the first cam lobe.
Then set up a dial indicator on the first cam lobe so that it reads zero.
Grab some graph paper. The x axis should read degrees 0 to 360, and the y axis should read lift (in whatever units you desire).
Mark current measurement on graph paper.
Turn cam by 10 degrees, make another measurement and plot it out.
Repeat process till you get to 360.

Repeat above process for other 3 cams.

Alternatively, you could give your local cam shop a call and see if they will do it for you on their cam doctor.

Now you can compare and contrast the cam profiles.

HTH

[kemicalx]

thanks for the info mate, I'm pretty sure they are all standard 7mgte cams. I have a feeling the only diferences are from the generation of 7m they were pulled from.