Josh Carr

Rotax, Rockers aren't the issue, lifters are. If you run more than .575 lift the GM 17120061 roller lifters are not long enough and could come out of position with the guides supposedly (according to what I have read - haven't verified this yet). Some say they have ran the 731 cam with them though, so I'm not sure? I can't remember where I read it (comp or cranes sites maybe?) - but others on oso have mentioned something about it also, guess probably don't have problems with all over .570 lift cams - I suppose it depends on the base circle. The lifters only have a few hours on them so I really want to use them

I had those blue gm roller rockers, but one failed and I am running Harland Sharps now.

I'm going to call RMbuilder after the holidays and see what he can come up with for me. Every one I talk to say's he knows his stuff with marine cam's.

Outdrive1

I'm using a 741 with stock gm lifters on a gen vi motor. 100 hours without any issues. I think it was the early motors that you had to change lifters on. I tried to buy lifters from Clay Smith and he told me all that was avalible for the gen vi were going to be the same as what I already had.

69-CHVL

I'm running a 600 lift lunati and the lifters were pretty much in the same position and the stock cam. I could of went even bigger safely.

Basically, it all comes down to the base circle of the cam

Josh Carr

Hmm, good to know. Guess I won't stress about keeping it under .570 cuz the lifters... The 502 is on temporary hold, I pulled my old motor out yesterday and found the transom to be rotted out BAD. Port stringer (one that engine mount on) is loose from floor also. Looks like I have an even bigger winter project on my hands ;(

mikes280

my first pick would be the 741 i have run this cam in motors as small as 496 and as big as 540. i have two in a boat now in a pair of 496,s that idle at 775 and make 640 at 6100. the next pick woud be the smaller 731 still a good came, For those of you that think these cams are to big go look at what merc. puts in there blue motors ie the 500 efi and the 525

Josh Carr

I went with RMBuilder. Bob cam up with a custom grind that should work well for me, and with a base circle that will still work with the gm roller lifters (dog-bone style).

Hey, anyone know the pre-load on the GM roller lifters that cam in this ZZ502?

thanks, Josh

Kidnova

Now call RM back, and tell him you want that ZZ cam "lope". Oh.... and ask him if he knows a homie named "Yoda" LOL

ROTAX454

Please correct me if I am wrong, but can't this issue of lifter length be corrected by having the correct length push rods?
And yes, the base circle of the cam has alot to do with it, but it ALL gets measured in the total sum.

ROTAX454

Question: Does not length of the rocker arm relative to the ratio of the rocker? In other words, a 1.7 rocker from xyz vendor would have the same length arms as the 1.7 rocker from abc vendor?

What specific failure did you experience with the GM blue roller rockers?

Noise Pollution

I running the 741 also with the stock lifters. Gen vi block.