496 MAG Cams

[desertbird]

Allright gang. The old hot rodder in me says I can swap out my Mag Cam for the HO cam and it'll run.
It's been verified that the only difference between the HO and the std MAG (besides 50 HP) is the cam and the computer. Some S/N's have noted a Throttle-Body difference, but I can't imagine what major differences there could be.
Another point, Raylar puts his cam, heads and intake on the 496 all day and runs stock Mercury programming. What gives? If I pick up an HO cam from a Raylar convertee, why not slap it in? Does the computer control any injector timing that could be tied to the cam grind?
Has anybody tried, considered or even talked about this yet?

[Beer-30]

Well, I'll tell ya. I personally wouldn't crack that far into the motor unless I was putting something other than stock items into it. You are talking a lot of labor to get a cam in and out.
As much as I would love to change cams myself, I wouldn't dream of doing it until the heads were going to be changed also. As all the rockers are loose for a cam change, you have the intake off, all sensors and wiring layed aside. That is time to just unbolt the heads, replace, and go back with the better intake. There is just no since in doing all of this labor twice.
As I mentioned before, you can easily get to HO level with a rocker change. Raylar has the studs and 1.8 rockers that will fit under stock covers. Well, maybe not the conversion studs, since they use new heads, but you can get these anywhere. So, for around $400 including gaskets, you can get to the same point, if not better, since you are freeing up a lot of friction, too. Later you can use the same rockers with the Raylar kit.

[desertbird]

I didn't know about the Raylar rockers! I'm looing for inexpensive upgrades and I am not afraid of the cam. I was planning on making the top end roller if I were to pull the cam.
At that point, why not a cam from Summit? See, I just don't know about the injection timing vs. cam duration. All else, no worries.
I have all but decided not to Whipple this one. It seems like a risky reward for the gains. Even if the motor stays together, most are reporting only 100's of hours. That's scary, since I've put 25 hours on this season.... :frown:
Perhaps I need to leave it alone, but that's just not my style....... :umm:

[franky]

Well, I'll tell ya. I personally wouldn't crack that far into the motor unless I was putting something other than stock items into it. You are talking a lot of labor to get a cam in and out.
As much as I would love to change cams myself, I wouldn't dream of doing it until the heads were going to be changed also. As all the rockers are loose for a cam change, you have the intake off, all sensors and wiring layed aside. That is time to just unbolt the heads, replace, and go back with the better intake. There is just no since in doing all of this labor twice.
As I mentioned before, you can easily get to HO level with a rocker change. Raylar has the studs and 1.8 rockers that will fit under stock covers. Well, maybe not the conversion studs, since they use new heads, but you can get these anywhere. So, for around $400 including gaskets, you can get to the same point, if not better, since you are freeing up a lot of friction, too. Later you can use the same rockers with the Raylar kit.
I was informed by Ray that the Raylar rockers/studs will only work (fit under the valve covers) on their heads and not on stock heads. Do you know different?

[Beer-30]

I was informed by Ray that the Raylar rockers/studs will only work (fit under the valve covers) on their heads and not on stock heads. Do you know different?
Well, I was informed by Shadow, who is pretty tight with Ray, that their rockers are designed with the adj nut down inside the body, to fit under stock covers.
I am pretty sure their heads are the same dimensionally as stock, since they are exact replacement heads.
I know for a fact that the Comp Cams stainless rockers, that look exactly like Raylars, will fit. My local engine builder just built a smog-legal 526 gen VI for his 1995 Chev dually. It has GM iron heads, 1.8 CC rockers, and stock valve covers with the drippers ground down.
Cam lift:
496 Mag int = .282 exh = .284
w/ 1.7 = .479 .482
w/ 1.8 = .507 .511
496 HO int/exh = .300
w/ 1.7 = .510
w/ 1.8 = .540
See, by just changing rockers, you put your cam lift a little better than a stock HO. I would imagine there is a little more duration on the HO cam, but it can't be much at all. Much easier to change rockers than cam.

[Nordicflame]

The rockers apparently will get you the lift of the HO cam but even though they add a slight bit of duration, it will not be close to the duration of the HO cam and will not make up the 50 hp by itself. You may see 10 hp from the 1.8 rockers at best
No easy hp here
Also the ECM controlled rev limiter is at 4750 on the Mag and you'll need to get the HO cam up to 4900-5000 to make the power.
Dave

[desertbird]

Hey B30, you post a lot and seem to be a pretty good source of info. Thanks for that. Where did you get the cam #'s from? 1.8's are the way to go! Maybe even better, but definately easier than the cam.
With the extra lift, you'll also get a smidge more duration out of the 1.8's, that's just a law of physics. I wonder.......just a little more lift......just a little more duration.....same computer means maybe just a little less fuel......and maybe......
:supp: JUST A LIITLE LESS SOOT!?!?!?!?! :supp:
Dude, I wonder if we haven't stumbled on to something here....I'm full tilt on the research now.
I also wonder about the rockers, understood that they most likely won't fit under stock covers. (Grinding the drippers makes them not stock) but that's back to where my thread started. I've been grinding windage trays and drippers forever!
What's the Crane P/N for those rockers? Can't find 'em on the website.

[Beer-30]

The rockers apparently will get you the lift of the HO cam but even though they add a slight bit of duration, it will not be close to the duration of the HO cam and will not make up the 50 hp by itself. You may see 10 hp from the 1.8 rockers at best
No easy hp here
Also the ECM controlled rev limiter is at 4750 on the Mag and you'll need to get the HO cam up to 4900-5000 to make the power.
Dave
Much more than 10. Just changing from stamped rockers to rollers gets you 10 easy. Getting rid of the friction and weight alone is easily 10 HP. I changed from Crane rollers back to stamped on a small block one time. Lost 200 rpm AT IDLE. Lots of friction there. Most dyno reports are 15-20 real world HP. And that's at the same ratio.
RPM limit should be around 4900. The book says max is 4400-4800 for the Mag. HO is 4600-5000, but we all know it is set at 5150.
Gaining .030 on lift is going to be another 15-20 HP, and that's probably being conservative. It is pretty obvious that the extra lift is the key player in Mag - HO upgrade. The duration would be minor.
Got the cam specs from the Mercruiser #30 Service Manual for 496/8.1L.
I will look up the Comp Cam part number. Don't think Crane does them. I don't believe 1.8 ALUMINUM rollers will work with stock covers regardless. The body takes up too much space. 1.7s will, with some clearancing (like on Rev.Williams motor), but barely. 1.8s w/ stock covers would be stainless-type only.
Comp cams# 1128-16
http://www.compcams.com/Technical/Cu...ML/JPG/313.jpg

[Beer-30]

CAT products make a similar rocker. I am thinking this is the one Raylar uses, but I am not sure. They are about half the price as the COMP CAMS ones. I am leery of this, as I am a firm believer in you get what you pay for. If it seems too good to be true, it usually is.

[Beer-30]

CAT stuff. Note the price they list is $233
RKSS-454B1.8 GM396/427/454/502 15-5 S.S. Rocker, R1.8, 16pcs/set, 65-00 233