and why did you promise Adam a 731, and not give him a 731, but a cam that was "close".? Once again you say you are gonna do one thing, which is pretty simple, and can't even do that right.

Even though it was not what you promised, you gave it free. Why would you give away something free, if that was not your claimed cause of the problem?

Just so you know the next time, those are not stock Merc exhaust

At what degree was it 76?

Ding, ding, ding, ding. We have a winner.

You'd think he'd learn this by now.

I don't know if you saw this some years back, but he cammed a set of engine's with dry (to the very end of the tailpipe tips - as they normally are) Stellings, and they reverted. Yup, who would think that was possible ? But, he did it. And yes, I got pulled into that fiasco to to help.

That is the most blatantly inaccurate remark on this entire thread. On every engine we consider multiple compound variables, including bi-directional wave motion and pressure excursions, from the intake tract to the atmospheric end of the exhaust tract, that factor into the propensity toward water ingestion. Then you recognize and mitigate the factors you can alter, adjust the valve events accordingly, while building a margin of safety. Only then can you proceed with generating a valve path.

At that juncture you consult with the client, advising them that the components they will be utilizing (if they are prone to supporting reversion) will detract from the targeted specific output by a factor of X. That provides the end user with two valuable tools, accurate information and the opportunity to make an informed decision. There is every opportunity to exert “control over what happens with used wet exhaust. “

Bob

I believe cstraub is at the Library thumbing through a Dictionary and a Thesaurus franticly trying to figure out what Bob just said!!

I just put a Rosetta Stone tape in my cassette player to try and translate his post into words I can understand! Lmao. Just kidding Bob, good post, glad you chimed in.

and not surprisingly he is absent from this thread.

Soo I just want to chime in . Mike told me about the 731 cam and he got kinda crucified but I'm seeing I guess that it is a good off the shelf cam?? While everyone's fired up here I'm just curious what is the best centerline to go with on a cam to not have reversion? And since you guys have built engines should I do my 502 block to 540 or just get a dart. I will be running about 5-7 pounds of boost and now that my butt stopped hurting from buying the crank ,rods and pistons I want it to be ok.......

Soo, you bought a 502 rotator and just got over the cost but you're wondering about going to 540?

Not sure he realizes what a 540 is. Or the fact everything he already bought would be useless

Not a big deal to make a 540 out of your 502 block but the block leaves alot to be desired. The oil system in a Dart block is much better. As far as a cam centerline it depends when you want the torque to come in and how much your gonna spin the motor. If your question was worded wrong I would go with a 114.

No red I have a 502 block. Sitting at the machine shop. I bought a magnum Xl 4.25 stroke ,Oliver rods 6.385, and je pistons .30 over .. 4.50 bore. I have a 8-71 littlefield blower and was just trying to see what opinions on the block I have vs dart block that's all. I also just wanted to know about reversion and when it starts on a cam and that's all. Like I said before my first high performance boat.

And haxby it was a error what I wrote. That's all. I bought everything for a 540 but have a 502 gen 6 block that I'm putting in a Daytona.

You spent the money on some good parts. Minus well get a nice block to put them in. Sorry I can't help you on reversion cams after my first milkshake I've always ran dry exhaust.

How much money you want to spend? What heads are you going to use? what RPM you going to spin to? what boat is it going in? 731 is a really mild cam for a NA 540. Even a 741 in a 540 is a less than you need. I don't do blowers, so the others will need to tell you that. The 502 block is fine for a 540. Unless you have $$$$ to burn you don't need a Dart block.

Gotcha, that makes more sense. If you've already got the gen6 block and it sonic checks ok, (they're usually pretty thick) then id run it.

Black my question is worded wrong. I was just curious when reversion would kick in or is it manifold or header specific. Also haxby and red you got to understand this is my first big engine boat. In cars I never worried about sucking water. I'm not a ****in idiot go to June 2001 super chevy mag and the Malibu they did a piece on is mine runs 7.73 181 mph and I drive it to sonic every other Friday. Except for engine I did everything else including stitching my own interior inc. the leather wrapped 14 point funny car caged bars. Go to Barrett Jackson last year loom up 69 chevy camaro yenko. Yep I did it but didn't own it. It sold for 175,000 moral of the story is I'm not ****in stupid.

Money isn't the issue. It's a how much am I gonna have in a boat that will be sold in a year issue. But I don't want someone else taking on a problem that could have been rectified. If it's a good block for say. 750 - 800 hp than cool. I got ****ed from the beginning on the boat and I want it to be right. I want it built like I'm gonna keep it then we sell. As you can see from all other posts I sold the gauges. Old rotating assembly. Etc,etc. this year before summer will be all mechanical and this winter we will repaint with kickass graphics and sell in 2015 with new interior also. Some say its fine some say dart. Just was wondering.

Wow that's impressive. I fixed a Camaro that sold at Barrett Jackson for 140000 and almost burnt to the ground cause someone Mickey moused the wiring.

I would not run the 731 cam in a blown 502 or 540. I would do the 741 in a 502 or 651 in 540. If cranes were the only option

Thx mild but they aren't. I did send my stuff to bob madera and just waiting on response. He's a nice guy but I want to weigh all my options cause I don't want to throw cams at it. When I raced sometimes I go through 10 cams just to pick up a tenth. Not gonna do that on this she's already pissed I bought another toy that's gas powered. But her and those god dam horses are no fun for me lol! ****ing things bite and are lucky I didn't split it's head open with 9 rounds of .45 . I also just like to learn from a lot of the guys on here.

You won't be disappointed with Bob's cams. He's done this a time or two. If you don't wanna mess around and do it right the first time, just have him grind ya a cam and be done.

Sounds like your in the same boat I'm in. The boat is a very sensitive subject around the house :-) Bob will set you straight on a cam and he does stay up on new profiles and at the forefront of valve train technology.

That's what I have heard. When I talk to drag guys about some stuff I might as well speak Spanish and I know why cause I'm in same boat as they are. I never would have guessed a cam can cause you to suck water. I'm just cross eyed about that. I have cmi headers and they spit water out the back and yet I've been told it will suck it back uphill mind you and ruin engine. Just floors me.

Yeah black baja I've thought about putting arsenic and razor blades next Halloween in apples , put in my kids bags and tell them to give to horses and blame it on the neighbors down the street. Lol! For two of those dumbass creatures that produce 2 h.p. I could have 700. But it's what she likes and looks hot doing it. So if I pretend I care and go to a barrel race with her once in awhile I usually can get away with it. I bought her a rxtx255 seadoo that's goes 0-55 in 2.8 seconds and she putts around on it because it scares her but being six feet in the air spinning around barrels is fine and I don't get it!

Does your boat have tips or do the tails go through the transom?

Straub won't believe it either, and thus why he has caused so many problems in the I/O world.

Overlap is when both valves are open. It starts when piston is near the top, problem is when you still have overlap when the piston is going down past a certain point and gaining speed going down, You are creating a void that mother nature will fill..it's physics. Since the exhaust valve is still open, everything in your exhaust is fair game to fill that void in.

So, engine rpm, overlap events, exhaust drop, where the water enters, cid, intake design, exhaust wave tuning and etc,etc is important with boat builds. Not just performance, but also to keep it alive.

This is information you'll only get from people who've been there and done that - be it builders or individuals.

You seem to have a good enough head on your shoulders - use it.

Tails go thru transoms. That's another thing is headers for this dam thing where outrageous I'm glad they came with it. I remember buying a set of lemons headers for car where 2400 and I got mad that don't even buy one side on the boat. I couldn't imagine have a twin . After this if I get a twin it will be stock power 7-800s and leave it alone.

You shouldn't have reversion issue. I've ran some pretty wild cams with the same setup and not had any issues. The tails are jacketed to the end aren't they?

Yes sb. I know enough that marine is completely different . If my drag engine guy built my marine engine I know it wouldn't last. That's why I want marine people. We talked about clearances and he knew they where wider but didn't think that was to big of a deal. Well it takes 20 minutes to pull my Malibu engine and a lot longer for boat. I bought this boat the same weekend my friend brad died on lake Cumberland. I called him 30-45 minutes before the skater flipped about how good some of the stuff I got with the boat was and told him we are pulling to bring to freshen up. He was 20 minutes from me and very helpful. Now I'm just trying to do it myself but right. It took the guy that reworked my heads a month to convince me not to run a solid roller because of all the idle time I guess. He did all brad smiths heads. That's part of why I have so many questions on cams. If it was racing it would have a solid roller 800 lift on 107-108 lots of duration. But this is not a drag car it's a boat and that's where guys like you and others come in. I learn everyday man and never will I say I know it all. We do some cool stuff but a friend of mine dean louckes makes me look like a finger painter compared to his work. I'm just saying marine experience from you guys is very important to me then what a drag builder can do for me right now. 2 completely different animals I have come to find out.

Yes black they are and that's why it amazes the **** out of me. I did watch a video of reversion with kinda the same setup and low and behold a little bitty stream was started and it had me wide eyed enough that I had to get drunk to believe what I was seeing instead of the other way around and I don't drink.....

Eliminator As you stated drag racing and Boats are totally different. let's start with running time and RPMs drag cars very high rpm short bursts 8-10 seconds, boats 5500-6000 rpm average for extended lengths of time 15 min or more. Cooling Systems are #1 priority. As you know Cams are an exact science that are taylor made to each engine combs, Hull designs, weights, gearing and props, NA cams are completely different from blown cams due to intake air inertia and exhaust gas scavenging as related to exhaust valve closing timing for optimum cyl filling. On a blower motor It is very important to keep the incoming charge in the cyl. and not blowing the fresh charge out the exhaust. you don't need a Stupid amount of duration and/or lift depending on your desired RPM range. In my opinion lobe separation on your blower motor will most likely fall in the 114 Range. Now with all my rambling just scratching the surface Please wait for Bob to get back to you or contact one of the other engine builders on this site!! Sorry for rambling on!

Yep I agree . I have had some people say you shift at 8000 rpm .... Wow!, then I explain rpm is runs per minute and I'm done in 8 seconds so do the math. And that is why I need good advice for marine stuff without people being ****ty. 6000 every Saturday and Sunday for hours on end is a whole hell of a lot different then spinning 8-9000 for 7- 8 seconds. I'm looking forward to bob recommendation. He kinda gave an idea a week or so ago but now I have flow numbers etc etc so he will nail it down I'm sure from what some have said. Thx

Good choices, sorry for the confusion. You're wording about 502 vs 540 sucked lol, as did my interpretation of what you meant.

Doug,
The cam came straight from Crane. Period. Exact numbers.

Bob,
The compound variable with what either of us has to deal with is what the customer does have we have advised him on what he needs to do. Just had a customer come to me with a 434CID SBC that does not run, runs slower than this 406CID. He wants a cam change. I remembered talking to him several months ago and at that point we discussed his oil pan and headers. Pan is not a rail kick out, headers are 1 5/8". I asked him if he had changed the headers and pan. He said no. I told him no cam change was going to improve the car until he got the supporting components to achomplish his goals.

If we advise the customer on what to do and he chooses not to all of it then we have NO CONTROL.

will you just go away con man,we have no use for a liar and an incompetent sales something or other.

Chris - you do realize that, you, entering into an exchange with rmbuilder, is like you, pissing into the wind?

well the con man thinks he's smarter than Rmbuilder.