3.0 140HP cam install issue...

[saint056]

I have a 1984 Mercruiser that I have rebuilt, an am just getting ready to install the cam and whamo... no dot on the cam gear! How is it to be reinstalled If I can't get the dots aligned? I've never seen this in auto engines. I know I can go by the lobes to get close, but one tooth off of the exact place can advance/retard timing at the cam! Anyone run into this? If so, how the hell did you get installed properly? (This is the last time I don't mark these gears on the breakdown):facepalm:

 

[fishrdan]

Re: 3.0 140HP cam install issue...

Have you looked at the underside of the cam gear, maybe the gear was installed on the cam upside-down. If there is no mark/dot, I'd say it's a defective cam gear.

 

[Don S]

Re: 3.0 140HP cam install issue...

It may just be very hard to see. Look at the location of the 2 holes, the gear key position and the location of the dot. Maybe you can see it looking only in the one location.

 

[dollarten]

Re: 3.0 140HP cam install issue...

If you can not find any marks , there is a way to install it . Put # one cylinder on top dead center , and start out with the cam lobes for that cylinder at 10:00 and 2:00 position . Then put the lifters in for number one cylinder . Now roll the crank back and forth a very small amount . meaning less than one degree . If the cam is in the correct position you will see the exhaust valve lifter and the intake valve lifter rocking back and forth l Looking at the lifters they should both be in the down position and both moving when you rock the crank in either direction . If either lifter is higher than the other one take the cam back out and rotate it in order to position it so both lifters will be moving slightly . This is what is called cam "overlap" . It is the point where the intake is just about done closing and the exhaust valve is stating to open . This theory apply s to any 4 cycle engine Good Luck

 

[Fishermark]

Re: 3.0 140HP cam install issue...

Here's a pic when I did mine:

 

[gpolkin]

Re: 3.0 140HP cam install issue...

I installed a new cam on a 140 hp earlier this summer and also could not find the dot. There was a mark on the cam I pulled out the cams seemed to match so I used the old cam to determine the mark. Now I am worried as my mark was not in line with the access screw holes like the manual picture shows. Is the mark on 140 cams always in-line with the access holes of does it vary?