rb marine engine

[TimD]

Please don't make a decision based on how many ports are in the sleeve. It's how the ports work and the area of the ports in relation to each other that is critical for performance.

The argument about the more ports giving a better top end isn't always entirely correct. Look at the pylon racing, tethered cars and control line plane engines that require all top end - not all 9 ports etc.

In a lot of ways, More ports = charge more money for it! Especially in the car scene or when you are trying to sell into a super-competitive market.

I know nothing about this engine so I'm not saying don't buy it - jsut voicing my concerns.

James - how did you go?

 

[TimD]

James,

What is the taper angle on the sleeve? Difference top to bottom in thou" ?

Tim.

 

[TOM MOORE]

I don`t think its the same motor.The nova rossi has 9 ports and the C5 has 11.It may be a nova rossi based motor but the insides are different.

Dont go by the number of ports in a engine. Seems to me that novarossi changes the sleeve every year ive even seen different sleeves in the same year model powerheads. Ive got a rex21 also made by nova only differance is the outside diameter of the sleeve and the crank pin dia. But its a screamer. Ive run nova rossi on my out boards for a long time. save your money bye the nova you want be disapointed.

Just my 2 cents Tom.

 

[TomMoorehouse]

my C4 was a rodey modified engine.....paid big bucks for it! i'm telling ya don't do it! they just aint right for boats. timing is wrong, designed for cars..... don't waste your money..... if ya want the best with no $$$ restrictions get either a Nova Rossi or a MAC and before you ever run it send it to one of the well known engine tuners to have it gone over. Then you will be sure to have a real HOT engine.

think of it this way..... you can spend your big $$$ on the NR or MAC and be sure you will have a HOT engine or you can get the RB and you might have an ok engine you might have a paper weight...... mine was a paper weight.

i've used MAC's RB's OS's Nova Rossi's..... only the MAC and OS worked right straight out of the box. The RB never worked even close to right. The Nova Rossi is a great engine if you have someone knowledgeable go over it a little. I'm pretty sure my next .21 will be another MAC

 

[eagle21895]

This has turned out to be a very good discussion.If I did get a mac engine who would I send it to to be gone through?I never thought about the timing I assumed rb would change it for boat use but I doubt he did.Good call

 

[Bob Kensill]

I run my Mac engine stock with only a head clearance check done on it. I tried different carbs,but the original is the best. I made my own pipe. I think the Mac will be the engine to beat this year. BTW we sell the Mac for $319.99 at the shop I work at,if anyone is interested.

Bob

 

[Slideblues]

Tell ya what guy's,

Before ya go converting a car engine over to outboard, take a close look at what Tommy said in the SAW post, he ran a STOCK Nova and set a record that STILL stands!!! The problem seems to be the hyper timing on the car engines, hard to get one right on a outboard application, I had one found and was going to do it and backed out cause I DID NOT want a expensive paperweight. Go with NR or Mac and spend your time on the setup of hull and prop,

Just echoing the O' Master here

Gene

 

[eagle21895]

I will be interested in 2 weeks krpnova.PM me with contact info please.It looks like its the Mac for me.Does anybody know some setup info on the Mac such as head clearance and pipe length and somebody that does a little engine tuning?

 

[GTR]

Hi Guys

There are alot of good engines out there and there are a lot of good tuners if $$$ is no object - Frank Orlic is good example for NR engines, Mr Brown (spped god) for Macs, Rod Geraghty for just about any engine, John Ackerman etc. etc

Some real expert tuners out there. If you want to use a car engine in a boat get a buggy version. They have slightly more conservative porting with a bias towards torque. Road race car versions are biased towards RPM because they have the benefit of 2 or 3 stage gearing. A lot of European design marine engines are designed for geared use and really aren't suitable for direct drive.

Just my $0.02

:blink:

 

[eagle21895]

So if I understand this right you can buy a Mac engine and have Mr. Brown do some tuning to the engine?

 

[Guest_JAMES IRWIN]

THERE IS ONE THING I STILL CANT GET INTO MY HEAD,?? WHY IS EVERY ONE HUNG UP ON MUTI PORT MOTORS, YOU DO NOT HAVE TO BE A ROCKET SIENTIST TO FIGURE OUT WHICH WILL FLOW THE MOST FUEL , GIVE ME A LARGE 5 PORT LINER ANY DAY . ASK ANY ONE THAT WAS AT THE CELINA OH. RACE LAST YR , AND THEY WILL ALL TELL YOU MY ROSSI HAD RPM LEVELS DOWN THE STRAITAWAY LIKE YOU HAVE NEVER HEARD BEFORE , AND ALL WE DONE WAS WENT BACK TO THE BASICK 5 PORT SLEEVE . AND IT WON 1ST PLACE .

 

[AndyBrown]

The MAC is a 3+2 port design. The Off-Road(Buggy) MAC and the Outboard MAC use the same port layout and timing #'s on the P/L and crank. The Buggy engine is doing extreemly well in the Major Buggy races (Top Quailfying and Winning) against RB-Ws7's, RB C-5's, Novarossi P5's.

The Outboard is getting off to a slow start because the set up is a little different than all other O.B. engines. I recommend to listen to the guys that are having success with the MAC such as Bob Kensill or Alfred Lanza in the West. They Know the best set up.

The MAC likes heat, so water restriction will be required. High nitro is best, 60-65%. Head clearence .005"-.006".

We now have the New 2004 version availible.

The main difference is a tighter, better sealing P/L. The first P/L were a little loose and were deficient in idle and milling capabilities. The new Piston taper and fit keeps the fire hot at low speeds and gives the torque to get on pipe at will.

The stock carb is very good and there is no reason to change it.

And yes I do Mod. them for those interested in a modified MAC.

Bob is right! 2004 will be a big year fo the MAC O.B.

 

[topfuel443]

Sorry Tim, I just got back to read this post about your questions on the Piston and liner demensions. Ive honestly never meaured this particular engine, but I will and get back to you. I finished 64th out of 140 pro drivers.......It was a huge track with jumps big enough that I could have had a good time with my motocross bike.....that meant lots of broken parts and unfinished qualifiers (including a few of my own) I managed to snap (3) 3.5mm titanium shockshafts in half during the course of the weekend. It takes some pretty serious speed and big air to do that.

Maybe I misread the post, But I was just giving my experience with RB motors as they were intended to be used for (1/8 offroad & 1/8 onroad) which is not with boats.

Andy, I had a chance to see the MAC offroad .21 in action as several Pro Drivers had them at the Pro Series Race in Orlando. It looks like another Quality MAC product. They didnt seem to outperform any other highend eninges but it could definately hold its own. Why did you guys decide to make the cooling head size smaller than every other MFR? there were a few of the guys running pretty high temps (I saw one running 360 degrees) on some of the MACs. Granted they probably werent tuned correctly, but just wondering if this had anything to do with it.

Tom, You still got the C4? wanna get rid of it?

 

[AndyBrown]

Hi James,

Glad to hear we were not only ones to break parts at Boggy Creek. BRUTLE track!

I heard the on site shop sold 26 sevros. We're talking the high dollor servos @ $125 a pop. Lots of borken parts for sure. We had three MAC drivers break due to track conditions in the third qualifier while leading their heat.

Of coarse the MAC Buggy engine is my first attemp at any car engine and I did the design work without ever seeing an off road race or knowing the exact power requierments. Considering this, the MAC is holding it's own against the other high end buggy engines very well. However, now that I am quickly gaining experience in this Dirt racing thing, MAC power will be there.

The normal operating temp. for the MAC is 220 - 260. The highest I ever saw one go is 310. It was way to lean. 360! that is so hot/lean it could not have made a lap.

The MAC head is smaller than other heads, but size isn't everything. I designed the head to work in all conditions. In the Summer the engine runs best @260, in cold weather 180.

Design is the key. The MAC head is 2 5/8 ozs. I tested an aftermarket head that weighs 3 5/8 ozs. The bigger head ran 40 degrees hotter. We may have a bigger head in the future to run in really hot weather, but it will not be nearly as massive as most of the current aftermarket heads, some of which weigh as much as 4 1/2 ozs. All of that mass so high in the car can't be good, so my goal is to get sufficient cooling with a minimum of weight.

The best tuned MACs were coming off the track at 240. The hottest one I checked was 272 and it was lean.

 

[TomMoorehouse]

i sold my C4 for an song... i was glad to get rid of it!

 

[topfuel443]

Well when they temped the one engine at 360 it had come off the track because it had a lean bog.... The guy that had it didnt appear to have alot of experience with engine tuning. He ran it lean until it basically would barely pull itself around the track and probably fried the motor. It was during practice on friday, so there was no way to tell if he was a pro driver or a novice with a hot engine. Probably the latter.

Yep the hobby shop made a pretty penny from the affor mentioned servos to crushed 120$ pipes and every suspension component you can think of. When 10 of the best 1/8 drivers on the east coast are in the same 45 min main event and only 3 of them finish (one was running with a broken shock) you know its a tough track.

I agree that alot of the Aftermarket cooling heads are way heavier and bigger than they should be! I figured you had some sort of logic behind making yours the way you did. The next Pro Series Race is gonna be in Charlotte NC, at Lance Norricks track. It is also gonna be a very brutal track, Ill keep an eye on the Macs and see how they fare.

~ James

 

[Guest]

Yes it was very brutal.

And it was just a 30 min. main that cut a feild of ten Pro's down to three cars. Many cars came in for repairs then went out and broke again.

Not the kinda racing I like to see but some people think it's cool to sling the cars 60 feet through the air and slam dunk on hard packed clay.

Kinda like a rough water survival at a boat race.

 

[F.Orlic]

This is an interesting discusion, how many ports is too many? Different aplications require different number of ports, in many cases pylon planes, tethered cars etc. don't have more than 4-5 ports but they are not dealing with the same conditions we do. Number of ports doesn't determine RPM's but it does determine power curve. Any number of ports will give you a lot of RPM's but you might loose mid and low end. It is not hard to make engine scream, a lot of timing, short pipe and prop one or two sizes smaller but will you go faster, probably not or only marginaly. It is easy to make engine with a lot of torque, it is easy to make an engine with a lot of RPM's but but to have both in an engine is very hard (took me countless hours to figure it out) If number of ports doesn't matter than we should be buying cheapest engines (they have the least ports), as sombody said it doesn't take rocket science to figure out what ports will flow more or does it? I wish porting was as simple as drilling few holes here and there and charging a lot of cash, it is much, much more complex.

BTW I will still stick with 7 port Novarossi.

Advanced Racing Tech

Frank Orlic