Measuring camshaft lift

Post by **TyreFryer** » Fri Jul 08, 05 10:02 pm

I've had the heads off my 440 and while I was at it I thought I'd measure the lift on the camshaft. I believe it's a Mopar Purple cam, well it has purple paint daubed all over the end. Anyway, measuring an exhaust lobe on the camshaft with a dial gauge I got about 0.325". Measuring the lift on the top of the valve spring it came out at about 0.350". Mopar don't list a cam with either of these amounts of lift, am I missing something? Do I have to do a conversion to find the right amount of lift?

Mick70RR · Post by **Mick70RR** » Fri Jul 08, 05 10:11 pm

You need to multiply the cam lift by the rocker ratio, which is 1.5 standard.

Ivor · Post by **Ivor** » Fri Jul 08, 05 10:22 pm

Told you so, Martin!

Post by **TyreFryer** » Fri Jul 08, 05 10:34 pm

Yes I know that but that's the whole point of my question. The lift measured directly on the valve ISN'T 1.5 times the measurement on the cam lobe. (See measurements above).

Can anybody explain this?

Anonymous · Post by **Anonymous** » Fri Jul 08, 05 11:20 pm

Maybe you have 1.6 rocker arms, are you using a solid lifter to measure the lift? 1.5 would make it a 484 cam

Post by **TyreFryer** » Fri Jul 08, 05 11:38 pm

When I measured the lift on the lobe I calculated a .484" but was thriown by the measurement on the valve.

I'm measuring the lift on the valves with hydraulic lifters and turning them over by hand, they aren't pumping up of course. Could this be it?

Anonymous · Post by **Anonymous** » Sat Jul 09, 05 7:17 am

You can't measure cam lift with hydraulic lifters that havent been pumped up. Put the lobe in its lowest position ie valve closed, and see if there is any slack on the pushrod. Theres your problem

Get hold of a solid lifter, someone here should be able to post you one, you will also need an adjustable rocker to take up any play on the pushrod. then you can measure the lift at the valve.....

Post by **TyreFryer** » Sat Jul 09, 05 9:58 am

Cheers for clearing that up Dave. I've got a good enough idea from the cam lobe measurement. I'd already worked it out at 0.484" of lift from the x1.5 method when Ivor told me about this the other day. That's all I need for now. I was just confused when I didn't get the same results directly from the valve lift.

Thanks Mick70RR too!

Dave-R · Post by **Dave-R** » Sat Jul 09, 05 10:19 am

If you look at the lifter as you turn the engine by hand you can see the pushrod sinking into the lifter. You should listen to your Uncle Ivor. He ain't no fool.