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? :confused:

[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. :confused: 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 :rolleyes:
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 :rolleyes:
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/CurrentCatalog/HTML/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

[desertbird]

Wow! What's up with CAT? :squiggle:
For those of us that say the thread about the CMI headers....Check this out. I raised the Bull$hit flag, and they sent me the dyno sheets. I'll post this in that thread too.
WOW. 56 Horsepower. It's not 60, but it's big, and I didn't believe it until I read it myself.
http://www2.***boat.com/image_center/data/520/250107-01-_1dyno.JPG

[Infomaniac]

Call me before buying anything Comp. I get exceptional deals.

[Beer-30]

Ok Infomaniac, thanks for the offer! Even with shipping to you and to ?, you think it will come out ok pricewise?
Summit=
Rockers, CCA-1128-16: $409.99
Conversion Studs, CCA-4514-16: $72.39
Guide Plates, CCA-4806-8: $46.69
$529.07. I think there is an $8 handling charge, free shipping so:
$537.07 shipped.

[Beer-30]

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? :confused:
The timing is fine for either motor. Raylar has found that the fuel/timing mapping in the ECM is a good match for their entry-level kit. They just up the fuel pressure to around fitty pounds and the a/f ratio come out right.

[Infomaniac]

I can beat that. I will PM you tomorrow. Saying Summit is enough.
Ok Infomaniac, thanks for the offer! Even with shipping to you and to ?, you think it will come out ok pricewise?
Summit=
Rockers, CCA-1128-16: $409.99
Conversion Studs, CCA-4514-16: $72.39
Guide Plates, CCA-4806-8: $46.69
$529.07. I think there is an $8 handling charge, free shipping so:
$537.07 shipped.

[Nordicflame]

Yes I was wrong on the rev limit. I had a relapse back to my 7.4L days.
The 4950 rpm rev limiter should allow you to reap the benefits of the very small increase in duration you’ll get with the 1.8 rockers.
Just thinking out loud here but what makes the power in a cam is “not” primarily the lift. The more important factors are the intake and exhaust duration, the aggressiveness of the flanks and lobe separation. The lift pretty much just follows these characteristics and should also follow the head flow numbers. Lift “will” help if the heads flow much better at those lifts which would not be the case in the stock GM 8.1 head. A more aggressive duration cam (such as the HO or Raylar cam) with quicker ramps and longer durations will open the valve quicker and leave it open longer at the increased lift. This is important due to the long dwell created by the long 496 rods and will allow for much more air to be ingested and gasses exhausted.
Raylar has verified several times a 26 hp max increase in his real world, back to back, dyno testing with the addition of 1.8 rockers. However, this is with “his” heads, an increase in fuel pressure and another point of compression to work with. Still pretty impressive but then again his heads flow much better than the stockers at the increased lifts. With all that being said and further thought, my guess is your probably looking at a ~15-20hp max increase with the stock heads and much less aggressive cam to start with.
With the slight increase in hp and no fuel pressure increase you might indeed help the soot problem. That may be worth the $$$ itself but for the hp alone it may not be cost effective. If your not afraid of the work, pick up a cheap HO takeout cam and stuff that in there with the new rockers (watch valve to piston clearance), up the FP a bit and you should be ready to rock’n’roll. Again, just thinking out loud :idea:
If you do add rockers regardless if you change the cam, I would also make sure you closely check you geometry and make sure nothing (such as push rods) hits or rubs on the stock heads.
I’m sure Ray could shed some of his experience on this and these are just my thoughts that may or may not realign your thinking.
Let us know how it turns out and good luck.
If you do come out with a 40 hp gain with the rockers I’ll be the first to run out and get a couple sets of rockers and a couple sets of the new 60hp CMIs and have me a set of HP525EFIs. Life is good… :wink:
Dave

[desertbird]

If you do come out with a 40 hp gain with the rockers I’ll be the first to run out and get a couple sets of rockers and a couple sets of the new 60hp CMIs and have me a set of HP525EFIs. Life is good… :wink:
Dave
Exactly. While your at it, we can go in on a joint venture capital property with some coastal condos in AZ......
I bought this boat as an "unfinished project" The guy who started it, put the std MAG in. If it were the HO, I'd be a happier fella. With a baseline 375, if I could squeeze 50-75 HP TOTAL out of her with just some simple mods like these, then I'd be a happy camper. Unfortunately, 3600 pipes are not in my budget at the time, but I wonder what a set of CMIs behind a Raylar would do for you?
The 1.8's are definatley in my future (next season) and I'll probably try the CAT ones......I have planted some other seeds to try and find more info on CAT. We'll see.

[CrazyHippy]

What's the attraction to the stock valve covers? You are digging a ways into the motor, changing out a bunch of stuff, why let the stock valve covers alter your choices? :confused:
BJH

[Raylar]

:shift: Just to help keep you guys from grenading your 496's do not put any cam or rocker combination in a stock 496 block that takes the intake valve lift over .520!! If you do you will find your intake valve dancing on top of the hypereuctectic pistons and the rest will be history. Also, all other BBC valve covers do not fit 496's, they are drilled in a different pattern. The stock valve covers have no oil drippers underneath and if you put in any roller rocker on stock heads you will have to change the rocker studs to SAE threads and use valve cover spacers to clear the adjustment nuts. Why do ours fit? because we engineered and built our new aluminum heads to accept our special rocker studs, adjustment studs and the like. Just remember guys, be careful who tells you what, unless you know the exact inner parts and workings of a 496 you may get yourself or others in deep do do! "A little bit of knowledge can be a dangerous thing!" :hammer2:
Just some assistance here.
Ray @ Raylar

[franky]

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.
Well.....see Ray's post.

[Beer-30]

Understandable, Ray. I know you know more than probably anyone else here about this motor........but.
You have got to be kidding me that there is only .010 right now between my valves and the pistons. HO lift at the valve is .510, and you are telling me that with a little extra heat (expansion) and a quick out of water over-rev, the pistons are gonna hit? C'mon. GM has never put out a motor with that tight of clearances, even back when they had .600 lift cams in the '70s.
I am sold on your kit, ok? There are just some of us that don't mind tinkering a little until we get there. We have been through this before. If you want us to use your rockers instead of Comp Cams or another, fine.
For the other comment about stock covers, besides the slightly different bolt pattern, there is the stock coils to be mounted. I know that Eddie and I think Rex (at least) are working on new covers with a coil bracket for under the exhaust.
Ray, I know there are spacers made, and maybe they are mandatory, but I have a hard time believing that GM has changed the spacing between the valves/rockers and covers from previous big blocks. I know of at least two 454s that are running either Stainless, like yours (or whoever's you use) and Aluminum under stock covers. The alum are not 1.8s, but I know the Stainless ones are. I have see the 1.8 motor with the stock covers on, and running. Is it really that different from a standard Gen V-VI head?
Additionally, you are saying you have moved the valve up and away from the pistons for you to be able to run 1.8 rockers or your larger cams, but the valves are still not hitting the valve covers? I don't get it! Did you space the valves away from the pistons? or the covers? I don't see how it could be both, unless you layed them sideways????

[Raylar]

The problem with going above .520 lift on stock 496's is not just the clearances, its the fact that the stock springs are weakies. They have just 90lbs on the seat and about 260lbs open pressure. The stock big heavy valves have a tendency to start the lifters into pump up around 4900 to 5000 rpms and if you have any more than .520 lift on stock springs no matter how you get it, cam or rocker ratio you can start to see valve float and lifter pump up (solid lifter) and you will probably have an intake valve kiss a hypereutectic piston, bend over its gone! The stock 496 valve covers are 3/4" approx. shorter (lower) than the gen 6 covers and hence there's less clearance for roller rockers and the poly lock adjustment nuts needed to adjust the rockers. The rocker studs in 496's have a metric adjustment nut and thread and after market kits come with SAE threads, won't work. Wan't to know how we did it, buy our cylinder heads and rockers and you will know.
Everybody loves to tinker and try and make improvements, just be careful you check your tinkering carefully before you put the hammer down! If you have a problem, call us we have complete motors ready to go.
We also have our stainless coil remount brackets in stock that mount the coils under the exhaust manifolds. And our new valve covers with polished stainless tops should be ready shortly. More "Bling" for the 496!
Good Luck with the tinkering!
Ray @ Raylar

[Beer-30]

Thanks again, Ray.

[Raylar]

You guys are all very welcome! :wink: Hope I can always help fellow boaters. These forums can be great for everyone!
Regards
Ray @ Raylar

[franky]

Ray, do you have flow bench data for your heads vs. stock mercs?

[franky]

Or you can mount the coils behind the heads, out of the way like these:
http://www2.***boat.com/image_center/data/505/2622PDRM0728.JPG
http://www2.***boat.com/image_center/data/505/2622PDRM0729.JPG

[Beer-30]

Nice. Good job, Franky.

[Raylar]

Franky;
The flow bench data on our heads is on our website, go to the cylinder head page and click on flow data. Not to say it hasn't improved since this pro-type data was done 1-1/2 ago. We like to keep the real numbers close to the vest.
Ray @ Raylar

[franky]

I have real numbers if you want to see them.

[Beer-30]

I have real numbers if you want to see them.
Hey Franky. Do you have numbers from an ASM intake? Curious how it compared. I saw you were putting a motor together with said intake. Was it on Raylar heads? Stock? Can you spill info?

[franky]

Hey Franky. Do you have numbers from an ASM intake? Curious how it compared. I saw you were putting a motor together with said intake. Was it on Raylar heads? Stock? Can you spill info?
Soon my friend, soon depending on how a few things pan out. :)

[Infomaniac]

Man I can't believe I lost this thread. Could not remember which one it was in. Sorry
OK total for all these parts with shipping will be $450.00 even.
Rockers, CCA-1128-16: $409.99
Conversion Studs, CCA-4514-16: $72.39
Guide Plates, CCA-4806-8: $46.69
$529.07. I think there is an $8 handling charge, free shipping so:
$537.07 shipped.

[franky]

Man I can't believe I lost this thread. Could not remember which one it was in. Sorry
OK total for all these parts with shipping will be $450.00 even.
Rockers, CCA-1128-16: $409.99
Conversion Studs, CCA-4514-16: $72.39
Guide Plates, CCA-4806-8: $46.69
$529.07. I think there is an $8 handling charge, free shipping so:
$537.07 shipped.
Info,
and this will get you roller rockers on a stock 496 head? but you will still have to deal with the valve cover clearance issue?
Regards - Franky

[Infomaniac]

Just quoting prices for parts man.
Whether it fits/works is up to Mr. Beer-30

[Beer-30]

Thanks, Info. Nicely put. That's quite a savings.
It appears that cover spacers would be in order for trying to squeeze them onto a stock 496. ASM has them for $280/pr. There's that much more money that one could just stick in a Raylar fund, and wait it out.
However, anyone with a gen V or VI 454 or 502 in a pickup or Mercruiser could get away with this setup, no spacers.

[Infomaniac]

How thick is the spacer? We have a full industrial and automotive machine shop. That sounds pretty expensive.

[Beer-30]

How thick is the spacer? We have a full industrial and automotive machine shop. That sounds pretty expensive.
I thought so too. They offer 3. 1/4, 3/8, and 1/2:
Arizona Speed & Marine has introduced Valve Cover Spacers for all the new 496 Mercruisers. These Valve Cover Spacers allow crucial room to run an after market adjustable rocker arm. Three sizes are available: ¼”, ½” & 3/8". 60/61 Billet aluminum C&C machined, complete with O-ring seal.
L18 VCS$279.95Height: 1/4"3/8"
http://store1.yimg.com/I/azspeed_1853_8108996

[Sweet Addiction]

So from what I am collecting here it seems that if I was going to put roller rockers on that I need to also install new valve covers? So with this combination it will work? Just trying to clarify.
Thanks, Jared.

[Beer-30]

So from what I am collecting here it seems that if I was going to put roller rockers on that I need to also install new valve covers? So with this combination it will work? Just trying to clarify.
Thanks, Jared.
You will need the spacers from ASM. I have the 1/2" ones (tallest) on my Xmas list. Looking around the engine, I don't see any clearance problems off the bat. Nobody has valve covers out yet.
Nobody really knows if the valve float will actually occur. One could add 1.7 rollers for a modest HP increase - by way of friction reduction. The 1.8s would be a little more HP with the increased lift. I am now looking at beehive style valvesprings which have been dyno proven to release HP by reducing valvetrain weight. With better springs, I would not hesitate on the 1.8s. I am considering 1.75s right now as a happy medium.
None will fit under the stock 8.1L covers without using spacers.

[92562]

FYI
Teague sells Crane Gold rockers that have been machined for clearance under the stock valve cover.

[Beer-30]

FYI
Teague sells Crane Gold rockers that have been machined for clearance under the stock valve cover.
That's nice of them. Cool.

[Sweet Addiction]

So these would be the rocker arms we need
Arizona Speed and Marine rocker arms (http://www.azspeed-marine.com/496rockerarms.html)
and these would be the spacers we need
Arizona Speed and Marine valve cover spacers (http://www.azspeed-marine.com/496vacosp.html)
So with this setup you can get the rockers on there?

[Beer-30]

I wouldn't use those rocker arms, personally. They are fine, I am sure, but if I were to run Crane rockers, I would spend the extra money for the Golds.
The rockers I would run would be the Comp Cams stainless. They are lighter at the tip than aluminum rockers and stronger. Plus, INFOMANIAC here can get them dirt cheap. They have better clearance also. They are about the same price as those entry-level Cranes that ASM shows.
Yes, those are the spacers. Still don't know of anyone making new valve covers for 8.1s.

[Nordicflame]

Larry Peto, of Larry's Engine and Marine, has a set of Lunati rockers that will fit under the stock covers for a reasonable price as well.
Dave