Om617 cams and lifters, how many versions? - PeachParts Mercedes-Benz Forum

leathermang · #1 09-29-2011, 06:57 PM

Do those numbers on the end of the cam have anything to do with the ' constant ' used to figure the chain elongation ?

Dieselkraut23 · #2 09-30-2011, 12:40 AM

As far as i have been able to find out i actually have a turbo style cam and lifters now.

From talking to some older wiser experts they all say changing the cam will not effect fuel that much.

Q: On a non turbo what difference will it make if i set the valve lash to .35mm instead of.30mm?

They basically say im chasing a ghost.

So for the record i am now running a turbo model cam and lifters in a 79 om617 912 series motor.

I am playing with my ip timing for the billionth time now.

Stretch · #3 09-30-2011, 03:48 PM

Quote:

Originally Posted by Dieselkraut23

As far as i have been able to find out i actually have a turbo style cam and lifters now.

From talking to some older wiser experts they all say changing the cam will not effect fuel that much.

Q: On a non turbo what difference will it make if i set the valve lash to .35mm instead of.30mm?

They basically say im chasing a ghost.

So for the record i am now running a turbo model cam and lifters in a 79 om617 912 series motor.

I am playing with my ip timing for the billionth time now.

Did you get access to EPC to check the part numbers for the turbo rockers?

How about pre-chambers and pistons - have you got the older type installed?

Stretch · #4 09-30-2011, 03:38 PM

Quote:

Originally Posted by leathermang

Do those numbers on the end of the cam have anything to do with the ' constant ' used to figure the chain elongation ?

It would be pretty scary if it did. The turbo cam has a higher lift but I guess (and I can only guess as I don't have a turbo cam to measure) that the rise of both cams are similar around this initial lift area <= Is that well explained?

Here's what I measured for a non-turbo cam

Also please note you are not measuring a 2mm rise on the cam - but a 2mm deflection of the valve - after the cam has pushed down onto the rocker on to the valve stem...

...I'm planning to get round to making a measurement of this valve stem movement and comparing with the cam measurements I've already made.

leathermang · #5 09-30-2011, 04:03 PM

Quote:

Originally Posted by Army

It would be pretty scary if it did..

Why ?
Do you think I just imagined that question ?
*****
When you are measuring these cam lobes..
Can't you just cut a hole in sheet metal , split it at the hole , which was the size of the main cam shaft....and then put the two sides up against the side of a lobe and trace around it ?
Then measure on a table ?
If you make witness lines in two directions when drilling out the hole... you can use that to measure the height ... and you have the profile traced...

Stretch · #6 09-30-2011, 04:13 PM

Quote:

Originally Posted by leathermang

Why ?
Do you think I just imagined that question ?
*****
When you are measuring these cam lobes..
Can't you just cut a hole in sheet metal , split it at the hole , which was the size of the main cam shaft....and then put the two sides up against the side of a lobe and trace around it ?
Then measure on a table ?
If you make witness lines in two directions when drilling out the hole... you can use that to measure the height ... and you have the profile traced...

No not easily partly 'cos you've got the camshaft bearing bits in the way - it would be a real pain trying to get metal to reach up against the side of a cam lobe - and partly because the tips of the lobe are narrower than they are on the shaft. They taper...

I'll stick with the tried and tested line up the teeth on a cog and measure with a DTI method I used last year.

As for the first comment - did you imagine the question or have you read something I haven't somewhere? I did the 2mm lift method as per the FSM to check if my new timing chain was good - paranoid eh? - and it was at (drum roll please) zero degrees.