Cam and exhaust set up question (reversion)
 

I'm having a motor put together and was going to run a schneider .646 lift cam with in. Duration (.050) 258 ex duration (.050) 270 and a 110 lobe seperation, it will be wet exhaust but imcos with the "s" riser so the water will dump in pretty far back and below the exhaust ports height wise, do you think I will have any reversion issues? Any other input on this cam set up? Thanks

I'd say pretty good possibility with that cam. How big is this engine??

468ci. And pretty good possibility I will have issues?

That is a huge cam for a 468ci. You will be very lucky if it does not revert water.

Aim for something closer to 114 LSA if you plan on keeping wet exhaust.

Thanks for the input fellas, do you think this cam would work well? I'd like to make as much power as possible without having issues and break downs


COMP Cams Xtreme Marine Camshaft Hydraulic Roller BBC Gen VI 454 .566"/.566" 2,800-6,200 RPM Operating Range

Sorry the link didn't work right, it's a 112 lsa

Look at this on eBay:

http://pages.ebay.com/link/?nav=item...d=390823011169

COMP Cams Xtreme Marine Camshaft Hydraulic Roller BBC Gen VI 454 .566"/.566"

Don't think you'll like that RPM range. Remember, you don't have a stall speed converter to help. You're going to want to be into the power before 2800 rpms

What heads are you using?

Gm performance heads, that are ported and polished and I believe a little but bigger valves as well, 850 holley and 10.1 comp wiened intake

http://www.cranecams.com/140-143.pdf

Something closer to the 168791 might be better for you. Big lift, with 114 LSA and a lower rpm power band.

That sounds like a pretty nice cam shaft

The original cam you listed was way to big. This comp cam in the link, imo isnt very good either.

The GM heads you have, have a poor flowing exhaust port. You can help the port out a little with specific cam timing events. You need to remember, a 468 is a small engine by todays standards, and its a marine engine. If you want a good idling, strong performing, reliable package, I think you need to size those cam choices down a bit. A cam that makes peak power at 6500, does you know good if you're gonna spin the engine to 5500. You'll give up idle quality, power and efficiency in the lower rpm range.

For what you will pay for a shelf cam, I think you'd be better off having Bob Madera spec a camshaft for your application. Also, keep in mind the lifter/spring/pushrod/rocker is the key to reliability.

I'm glad you have the patience to type all that lol

That seems like alot of compression for a pleasure boat. Are you in an area that you can always depend on good gas?

Thanks for the info, I'm by no means an engine expert that's why I asked, I'd really like to get a cam bought this week and get my motor back in soon, do you have any recommendation on a shelf cam that would work well on my set up? Thanks again for the info guys

Call Bob or call cam motion. Why rush in the wrong cam?
Custom cams run about 100 bucks more.

Custom cam from bob is about the same price as one from crane.

Actually if you purchase a cam from Bob I think it comes out cheaper if you add in the cost of the distributor gear he supplies. I don't know anyone else you can order a custom cam from and have it the next day. Bob makes stuff happen and his prices are better than retail and sometimes jobber. He knows what he's doing and not gonna sell you the wrong parts just so he can make a dollar.

The S Pipes can use more cam because of the major free fall of the exhaust. Never would have really thoought that but many west coast boats like Eliminator use that set up to get exhaust under swim platform and their owners have shown to be able to use more cam than others without sucking water.

That said, still doesn't mean you want to overcam an engine. LOL.

http://imcomarine.com/cal_store/medi...-02-8338_1.jpg

That's an awefully short runner exhaust manifold. Any useful scavenging it could provide would have to be at pretty high RPM I'd think. Anyone ever dyno'd back to back with them?

http://www.cranecams.com/product/car...detail&p=24283

or

http://www.cranecams.com/product/car...detail&p=24282

Personally, I prob pick the smaller 731 for a 468ci. It will make more torque in the lower and midrange rpms.

I just got my shipment of parts in from Bob @ Marine Kinetics last Friday and can't wait to start assembling. He is an absolute stand-up guy to work with. I was also amazed at how competitive his prices were. I couldn't beat him plus his service and knowledge is second to none. He is not just cams, but total engine development expertise.

How much HP are you hoping for and what RPM are you willing to spin the engine to at WOT?

If you truly are 10:1 with those GM iron heads, I'd be careful here. I may want to error slightly to the larger side with cam choice, watch the tuneup, and keep the engine running on the cool side. 10:1 is a little too high for my liking with iron heads for a pump gas pleasure boat.

I would like to get around 525-550 hp but that's just kinda a guess I'm not sure what it will make, how big of a cam would you recommend?

And SB those are the manifolds I will be going with

Somehow, whenever I see anything you post whatever you're commenting reads like blah-blah-blah when I see that avatar! Can't seem to focus on anything else...That is Grade A material my friend!

You know he's just doing that to distract you so you won't realize that his posts are total BS. :bsflag: I think ICDEDPPL does the same thing for the same reasons.


:whistle:


Just bustin' your ballz guys - I owe a few of those after all the grief I've taken on my epic 489 build. ;)

:evilb::party-smiley-004::eekdrop::lolhit:

Thing about that bunch is they can take it just as well as they can dish it out. Never hear them crying because somebody hurt their feelings.

+1 on what everybody has said about Bob. He's the man as far as I'm concerned.

I'm actually local to you. Live off Rt 4, south of Lebanon. I've been dealing with Bob for a few years now, and have 2 of his cams. I CANNOT speak more highly of someone. For the little amount of money I've spent with him he has SPENT a great deal of time with me on the phone, countless hours, and always been good to give advice. I would HIGHLY recommend you call him. That being said I have a cam I had spec'd out for a 502 that I'd be willing to get rid of, and would probably meet your needs quite well.

It was a cam ground by bob, on a 496 core, so it has the 18726543 firing order.

It's on a 112 LSA. 234.5/240.8 duration. .6462/.6298 lift. I can send you the entire cam card if you're at all interested just PM me. I actually have a plethera of random big block parts I need to get rid of.

Either which way you're going to want something with some decent lift and lower duration for your application. Good luck.