Need Cam Recommendation

[Ric 232]

I currently have a 1998 Baja 232 Islander w/ a 454 Mag MPI (serial #0L035450). The boat runs 66 - 68 at 5000-5050 rpms with a stock 23P Mirage Plus. The motor has 150 trouble-free hours. Compression is stock (8.6:1). I have recently made the following mods:
1. Gil Magnum Choice exhaust
2. Vortech flame arrestor
3. ECU reprogrammed by Arizona Speed & Marine
4. Adj. fuel pressure regulator - set at 48psi per Arizona's instructions.
Unfortunately, I have gained NO noticeable increase in top speed. So, being persistant in throwing good money after bad, I'm considering a cam upgrade. I would like to stay with the stock valvetrain. I also have to be careful with my cam profile so as not to have water reversion with the exhaust.
I was considering GM cam #24502611 (211/230 dur & 511/540 lift), but a VERY well-respected (nationally) marine engine expert (whom I should probably never second-guess) has told me that I might not gain much performance and should go with GM #12366543 instead(the 502/502 cam) w/ 224/234 dur & 527/544 lift. I'm concerned about having water reversion with this cam and the possibility that I will lose a great deal of low-end power.
All suggestions and comments are invited and welcomed.
Thanks,
Ric Adkins
Orlando, FL

[Dennis Moore]

Dear Rick,
Thanks for the kind words. :)
When I was writing my book I had a hard time coming up with the exact camshaft timing specs for the stock Chevy marine camshafts. I actually pulled some cams out of some marine engines and sent them to Comp Cams. They measured them and sent them back with a camshaft spec sheet. I would suggest that you do the same and then ask them for some recomendations on a more powerful camshaft for your engine. They are really nice people, they perform services like this everyday and the turnaround was very short. The price was quite reasonable too.
As far as roller camshafts are concerned they will also regrind your stock camshaft (this is a real deal because it will save you the cost of a new core). The only problem I had was that they couldn't make the lobe sep angles as tight as I would have liked (the camshaft had 115.5 and the tightest they could make it was 113 after regrinding the cam). The cams worked great and I think the total cost was around $100.00 - $125.00!
I just slid the cam back into the engine and sent the engine/boat on its way!
I hope this helps someone! wink
Sincerely
Dennis Moore

[Dave F]

Going with a larger cam without increasing your compression ratio can end up decreasing performance.
Where that point may be, is where you'll need to do your homework. You'll need to inspect cam cards and see where valves will open and close and inspect the recommendations of the cam company for compression ratio.
Nothing is more important than matching your parts.
The 502/502 cam has around 9* of overlap. If I remember correctly it's set on a 107 intake centerline.
In contrast the HP 500 cam has a little less duration (222/230) but is set on a 105 intake centerline. It has 6* of overlap. The lift is a tad higher at .576/.598 So springs may be an issue as stock springs tend to bind after about .550
Now, not to disagree with Dennis, because I don't. I am, however, offering you an additional choice.
I am also raising the question, would you actually get more performance with the larger cam without increasing static compression ratio?
In my opinion, I'm not sure you would. The 502/502 and the HP500 engines are both around 9.5:1.
Maybe I'm right, maybe not.
Maybe Dennis could comment?
DAVE

[Ric 232]

Dennis,
I'm glad you realize that I certainly don't mean any disrespect. I'm simply being ultra-conservative. If 9 out of the 10 most respected marine engine experts in the country told me that a certain cam was okay, and you were the sole dissenting person, I'd go with your recommendation.
I'll tell you specifically where my concerns come from on the 502/502 cam.
1. I've seen in Powerboat Mag at least twice that Bob Teague has said that the 502/502 engine is not good for marine use. He specifically says that with the 502/502 cam, "water reversion is likely." And my guess is that he's talking about reversion with an exhaust system with longer risers than mine (i.e. WITHOUT diverters).
2. Similarly, I learned from reading Bob Teague's response to a reader letter that the early HP500 (carb) motors were ingesting water with the Gil manifolds (again, even w/o diverters). He mentioned that Mercury later changed the risers to a higher/longer riser to prevent this and then, of course, switched to CMI's on the HP500 EFI. From a water reversion standpoint, it doesn't appear that the HP500 cam (222/230 dur & .576"/.598" lift, 110deg LSA)is as radical as the 502/502 cam.
Anyway, thanks for the advice on Comp Cams. I will contact them. Do you think they know much about the water reversion aspect of the cams?
Thanks,
Ric

[Dave F]

Oh! Another issue you might need to consider heavily is the MPI might have a problem at idle with a lopey cam.
DAVE

[Dave F]

It is true that there were reversion issues with that cam and gil exhaust.
I'm thinking with the MPI to stay some where in the neighborhood of a 218/226 114 depending on which springs you want to use depends on the lift you can use.
Just some more ideas
DAVE

[Ric 232]

Dave,
The 502/502 compression is 9.6:1, BUT the HP500 is only 8.75:1, comparable to my engine.

[Ric 232]

Just to clarify, I'm trying to stay with the stock valvetrain, so I don't want to go any higher than .544" lift.
Ric

[565edge]

Ric 232:
Just to clarify, I'm trying to stay with the stock valvetrain, so I don't want to go any higher than .544" lift.
RicGet a hold of bullet cams,john partridge knows his shit,I can get ther number for you,also remember bigger cam means more idle rpm,which in turn bangs the outdrive when shifting,i am a jet guy but i talked to partride about my buddies 502 and his cam was similiar to the one teage sales for the upgrade to the 502/502 cam,my buddy has a 25 daytona with a bravo.

[BBC502]

Last year I went the 502/502 route. I had the heads slightly massaged, roller rockers, and reground the cam from 527I to 563I and 544E to 585E (cost $125 at Crower). The 502 dyno'd at 600ft/lbs of tq at 4,200 rpm and 540 hp at 5,400 rpm. I am running lightning water injected headers and I added a valve to shut the water down prior to idle due to reversion. Reversion was not much but I didn't want any. The valve springs are capable of .625 of lift according to GM performance. I don't think I'd go more than .600 at the most. It's a strong motor but I think a different induction system would help. dual plane vs. single plane and a professionally done carb. My quarters worth

[Ric 232]

This is an excerpt from Bob Teague's column in Powerboat Mag (I'm not sure which issue). This is what I'm concerned about, although it seems he is being awfully conservative saying a 114deg LSA is the minimum.
***********************
WATER REVERSION?
Question: I have a 454 that has been bored to a 468 with 11:1 compression. The cam is a .540 lift with a lobe center of 110 degrees. I have EMI Thunder exhaust. Do I need to worry about water reverting up the exhaust and coming in the motor? If so, what do you suggest?
Dave (last name not available)
St Louis, Mo.
Answer: Unless the risers/tailpipes on your setup are “dry” all the way through the transom, it is likely that you will have some water reversion with your combination.
The compression ratio is really not an issue. It is the cam profile. With a 110-degree lobe center in combination with the manifold-style exhaust, that could result in unwanted water entering your cylinders through the exhaust. You could probably get away with the cam profile if your exhaust were headers or completely dry. Otherwise, a more desirable cam lobe separation would be about 114 degrees.

[Dennis Moore]

The issue of lobe separation angles is only applicable with an apples to apples comparison. You must compare camshafts of the same durations.
A smaller camshaft works fine with a tight lobe separation angle, for example the stock Chevy marine camshaft for the small blocks have 110 LSA for the flat lifter cam and 109 LSA for the roller lifter cam. They never have a problem with water reversion at idle speeds. To make a blanket statement that all camshafts need a 114 degree LSA is flat wrong! The more duration the camshaft has, the wider the lobe separation angle needs to be. I believe that 110 is fine up to a certain point and then it should be 112 after that. For a really large camshaft you may need 114.
The most important engine factor about LSA is that closer centerlines increase mid range power with a rougher idle and wider centerlines will increase power through out the rpm range (sacrificing some mid range power) with a smoother idle (less reversion). Unfortunately we boaters like mid range power so we need the closest LSA we can use without reversion. High performance car engines have LSA's of 116 or more for a smooth idle and high manifold vacuum for power brakes. I believe that the 455 Stage One Buick Gran Sports had a LSA of 118!
The worst point for reversion is when the engine is idling at a lope. To keep reversion to a minimum the idle speed should be increased until the lope just goes away. Then just before you shut off the engine rev it up a few times to clear the water out of the bottom of the exhaust manifold (besides it sounds cool too).
Sincerely
Dennis Moore

[Ric 232]

Dennis,
As usual, your words make perfect sense. I was just comparing the cam specs of the HP500 vs HP500EFI and it seems to be consistent with your comments:
HP500: Crane #169611 222/230 576/598 110LSA
500EFI: Crane #169612 230/236 598/610 114LSA
By the way, on a slightly different, albeit very relevant topic, why is the HP500EFI so much more powerful than the 502 Mag MPI? Not only is it rated 55hp higher, all the tests I've seen indicate suggest that the difference is actually bigger than that. In addition, acceleration is always significantly better with the 500. I know the cam and valvetrain components are different, as well as the intake system. Are the heads different? It seems like it would be easy to make a 502Mag run like a 500. What am I missing?
Ric

[Dennis Moore]

The heads are the same except for valve springs and rocker arms. You haven't experienced (because you have an EFI motor that really has not been recalibrated) the big difference that an exhaust system makes on a big block marine engine. If the air/fuel mixture is on the money the exhaust is the biggest performance improvement you can make. The Merc HP motors really make a lot more horsepower because of the better exhaust systems, well chosen aftermarket camshafts and good ECM calibrations. Unfortunately this comes only with lots of dyno testing and adjustments, something that Merc can afford to do and that the local engine builders can't.
Sincerely
Dennis Moore

[Ric 232]

(Geez, this is frustrating.) So, even though I spent $2000+ on a presumably good exhaust system (Gil) and my ECU was reprogrammed for my mods by Arizona Speed & Marine, I'm still not getting ANY performance improvement because the ECU really isn't done right ???
I believe it, Dennis, but it really sucks. Especially $3,000 and 0 mph later.
Ric

[KC]

I love this thread... I have learned a ton through this thread and others relating to cams.
Just picked up a copy of Dyno2000, so it is fun to take these cam specs and be able to visually see the different torque curves. The software is not perfect, but it works for my purposes. Currently I'm researching and collecting information, dropping it into the software to help me learn and eventually make some "informed" decisions for my winter project motor. The winter project is starting with a 2001 Gen VI 454 Mag, it will probably get aluminum heads from AFR and a CompCam - and some type of fuel system.
Does anyone have the flow numbers for the heads on a Gen VI 454 Mag.
More later... KC

[Dennis Moore]

KC,
I love the Dyno 2000 also. Like you said, it may not be perfect but it sure helps to see which way the power will go with selected camshaft mods.
Sincerely
Dennis Moore

[Ric 232]

Okay, I just ordered Dyno2000. Maybe that will keep me busy for a while.
Ric

[KC]

Everyone - thanks for your posts in these cam threads. The Dyno2000 is a touch clunky until you get used to it. Once you enter in the specs for your motor and head flows, you have a mathmatical based tool to compare components and get a feel for the deltas - lots quieter than a dyno!
The ability to compare AFR, DART and Brodix heads side by side is pretty interesting, then comparing to stock heads and things get real exciting.
Dennis, ordered your book...
Does anyone have a set of aluminum heads off of the ZZ502 crate motor for sale - saw a set go for $700 on ebay. Now that I have learned a bit, it looks like they would be perfect for building a high torque motor with an aftermarket cam, not to mention the weight savings.
KC

[KC]

Today I called CompCams, told them the story of my motor and they passed onto me the following:
01-000-8 Grind G63343B\3344BHR112+4
219/224 .510/.510 LSA 112 4 degree advance
With the rocker arms that I have, at 1.73 it works out to an approximate lift of .519/.520
Dropped all of this into the Dyno2000 software, it spanks any cam that I have seen on this board, especially if you drop out the 4 degree advance. More torque sooner, and way taller then the cam from an HP500EFI.
This might be a done deal! KC
RPM Torque HP
2000 506 193
3000 567 324
3500 571* 380
4000 548 428
4500 514 440
5000 470 448*

[kevnmcd]

KC-While you are doing this winter project, I expect step by step pictures showing your progress. :D

[KC]

kevnmcd...
yeah, yeah.... your all talk, I got your photo CD and your address....
Actually, it should be very interesting, I'm learning things fast and with less effort than the last time I attempted to build a motor some twenty years ago. The internet is a wonderful thing, makes it really easy to order books, find phone numbers and ask questions.
My simple call to CompCams resulted in a three minute conversation, where I was able to give them the information that they needed so that they could give me the cam reccommendation that I need - love that!
At the moment the motor in my boat is just fine, it starts every time and gets me where I need to go faster than most other boats, fair hull design. Building the new motor will keep me out of trouble, gives me something to tinker with on cold winter nights, and will be a significant increase in power over my current 310hp. Should be able to step up to a 28P Bravo One, maybe 70+mph without blowing apart my outdrive.
All in the name of wave jumping! KC

[Ric 232]

KC,
I just called Comp Cams and the recommended the same cam for my 1998 454 Mag MPI (Gen VI). I ordered Dyno 2000 yesterday, but I probably won't see it for a week. Would it be too difficult for you to plug my application in to see what the difference is over stock?
My motor is virtually stock, cam is 224/224 483/483 115.5 LSA.
Thanks,
Ric

[KC]

Ric....
I'll do that late tonight, have a date with a pretty lady and then I can get close to my pc.
I dropped the stock cam into the software the other night as a baseline for comparison. I'll post the numbers from both cams using the flow characteristics of the AFR heads - as well as a set of heads from the software, probably "wedge, pocket port, large valves". Unfortunatly, I do not have any flow numbers for the stock 454 Mag heads, I did find out that the Gen V heads are rectangle ports with I think 315cc intakes. You will notice a significant difference in the numbers between the two cams, especially when you drop aftermarket heads into the equation - lets hope that those numbers show up in the actual performance of the motor.
My part number is CompCams 11-445-8, an off the shelf cam for Gen V with the following specs:
218/224 .510/.510 112 LSA 2 degree adv
I was able to confirm with another one of their techs that this should work nicely for my boat, especially since my exhaust is below the water line at idle. Cam should be delivered within the next few weeks, complimented with roller rockers and the stud kit for 3/8 to 7/16.
Now, I need an MPI system to complete my motor followed by a decision on heads... need to check my budget before I get my hopes up too high.
KC

[Ric 232]

KC,
If it helps, the Gen VI rectangular port heads have 325cc runners.
Ric

[KC]

I must have confused myself with the software, numbers not all that much better.
Stock CompCam
454 @ 8.6 HP Tq Hp Tq
2000 176 461 184 483
2500 228 479 242 505
3000 289 505 303 530
3500 342 514 348 522
4000 373 490 371 487
4500 386 450 374 436
5000 377 395 354 371

[Ric 232]

Okay, I'm thinking this for my stock 454 Mag MPI (Gen VI):
Custom cam: 245/255 deg duration @ .050" lift; .699"/.715" lift !!
Stock 8.6:1 compression
Stock valve springs
Stock rocker arms
42deg total ignition timing
85 octane fuel
Big cams are ALWAYS good, right?
(The only good news is that the thing probably wouldn't even start, so damage would be minimal.)
Just having fun,
Ric

[carreraboat]

hey dennis my cam specs are intake 591 exhaust 601 hyd roller lightnings dart intake 454 stroked a quarter i need to raise my idol why do i have reversion in only my 2 front holes also 112* lobe seperation

[waterbum]

Ric 232:
Dennis,
As usual, your words make perfect sense. I was just comparing the cam specs of the HP500 vs HP500EFI and it seems to be consistent with your comments:
HP500: Crane #169611 222/230 576/598 110LSA
500EFI: Crane #169612 230/236 598/610 114LSA
I find this very interesting.I called Crane for a cam recomendation for my 99 hp500 with Nickerson stage V carb,ported Dart intake and AFR CNC 315 heads.I find it suprising that they gave me the part # for a stock hp500 efi cam.All they told me was that it is a custom marine grind.Summit price,$319.39 .Do you guy's think this will work well for me or could I do better.Excuse me for hornin in on this thread. :confused: Bum
Ric

[waterbum]

Oops,looks like I did something wrong up there. :rolleyes: Bum