Jrod_sf

Im new to the boards but this has been my go to site for boat info since I got my boat last summer. Lots of good information, but I can't quite find what I need.
We took it out for the first time this year for the 4th of July and had some oiling issues and spun a few rod bearings. We're doin a quickie refresh so we can get some use out of it yet this year and while its apart, might as well upgrade the cam.
It is a 1990 Rinker 236 Sport with a 454 and bravo one. It has a weiand stealth intake with a holley 750 and long tube style headers. I checked upon teardown, and the headers dump the water at the end of the collector. I also have a set of harland sharp rollor rockers to put on. Its running a 23 prop. Its mostly used just for cruisin and but a couple times a year we pull some tubes around. I'd like to get a nice sounding idle and it would be nice if I could pick some power up and take advantage of the other parts. Just would like to get some opinions on what cam I should go with.

I was originally gonna go with comp xe268 or 268ah(marine version) retarded 4 degrees, based on the recommendation by Bob Madara to another member here with a similar combo. The 110 lobe separation should make good power, and putting the intake centerline at 110 raise the upper rpm power. But I can't really find anybody runnin this cam or find any opinions.

Then I seen the comp xm270. Its on 112 lsa, and its a little bigger. I seen some one said to run this advanced 2 degrees to help the low end and idle since its a jet boat cam. Is this necessary?

Then theres a lot of recommendations for the merc 420 crane, which is similar to the comp xm270, but with 114 LSA. Also, cost an extra $100.

Or the Isky mega 270/280.

I was leaning towards the xm270. I'd like to pick up a few mphs. Last year it ran about 60 at 5000. Also, whats the most you should rev a stock mag motor? Any experience or opinions will be takin into consideration and greatly appreciated. I've been reading and looking at cam spec for so long my head is just spinnin. Thanks.

CC230

Welcome to the forum. Give Bob Madera @ Marine Kinetics call, aka RMBuilder on here, he'll answer your questions, and stop the head spins. But you may ending up wanting more after your conversation!

Jrod_sf

I forgot to mention I did call and talk to him already. He said hes no longer doing flat tappets for the public. He gave me some recommendations but nothing real specific. He said around 224 230 and 111 lsa, or if I think I may have reversion to go to 112 or 114. He didn't really say anything about intake centerline. I know marine engines usually run around 109. He also gave me a few more examples what worked for him, 220 226, 222 228. I don't think I should have problems with reversion unless I go crazy, so should I just get 110 or 111 lsa, shouldnt that make more power? The xe268 was the closest to his original recommendation, but its on 110lsa. I'm new to marine engines so I dont know if reversion is likely or not? People say not to run them, but with the relatively low duration and tight lsa the exhaust valve closes pretty early, and I have headers. I may have to call him again now that Ive looked at some options. But I hate to keep calling with a bunch of question when I'm not even buying any of his products.

Griff

Crane #134241
Kit w/ lifters is #134242

MILD THUNDER

iTrader: (3)

you have your numbers backwards. A 110* LSA will have more overlap than a 114LSA. A 114LSA is a favorite in most marine applications, as it will have a wider flatter powerband, where a 108-110 might make a little more Peak torque/hp, it tends to fall off faster. AS far as reversion, a 110lsa is more likely to revert than a 114. Duration also plays a huge part.

I wouldn't reinvent the wheel here. You have a basic 454 MAG. A ton of people have done cam swaps in this engine. The cam Griff posted up will work just fine.

For lifters, I'd use the crower cam saver lifters. They get a bit more oil to the lobes, to help with the whole flat tappet flat lobe thing.

http://www.summitracing.com/parts/cr...make/chevrolet

FIXX

iTrader: (2)

what mild said but you want this part number,,,it has a snapring at the top instead if the wire ring that has 4 holding points to keep the plunger in.. http://www.summitracing.com/parts/cro-66000rx3-16

MILD THUNDER

iTrader: (3)

Good catch mike. Nice lifters

Jrod_sf

Ok. Thanks guys.

I know most marine cams are 114 lsa and have a broader power range, I just wasn't sure if it was for the broad power curve or to prevent reversion. And I know 110 will make more peak power, but if its over a too narrow range its not gonna be much help. I just didn't know if the the range was too narrow or not. And obviously I want the most power out of it that I can get. Don't we all.

I am just over thinking things. Most of the similar cam recommendation threads where based off stock exhaust limitations. I just needed some reassurance I was going the right way. I hate buying something and having regrets or what ifs. Looks like the way to go. Looks similar to the xm270 with a little advance built in. Yeah, I'm definitely using the camsaver lifters for a little extra insurance. I was looking for the snap ring ones and couldn't find them. I see they just say Heavy Duty, so that must be why I had a hard time finding them, so thanks for the link.

Jrod_sf

Also, I know the mag has some pretty good parts but how high is it safe to rev a stock mag motor?

Griff

I used to rev my old 454mag with the cam I posted to 5400-5500rpms at WOT.