Goto 540 or Tweek out the 489
 

Ok, I am just speculating here but what would you do? I have no budget for this, its the speed bug talking.
I have a 489 stoker with about 500HP.
Large oval ported heads with bigger valves.
Forged internals
RMbuilder Cam, Isky springs, Moral lifters, you get the idea.
Holley MPI, 1000cfm TB, 42lb injectors, wideband 02, ram air
EMI exhaust with long risers
Flat top pistons, -3cc, 110 chambers, with 8.9 compresion

Proposal #1
Bore out to 496 with dome pistons, aluminum large oval heads (edelbrock E bare heads with a little work), raise compresion to 9.5 or better.

Proposal #2
Swap out most of the parts to a 502 and make a 540. Use GM Rec heads with a little port work. Raise compresion a little and have RMbuilder grind a new cam.

Damn speed bug, my wifes not going to like this either way !!!!

Nice build. Sounds like you could get a cheap 100 hp with forced induction.
Don't forget the whipple option. Pistons gaskets and 5k?
B&M 250, faster than a compete rebuild. You should be able to pop near 700 hp if you invest in what you have. I guess you have to decide if you want to run the canned gas at $7 a gallon with the high compression though. I have heard that some drives can be tweeked depending on what you have for 5 - 10 mph. Look at the whole boat when you are at the point of speed withdrawls.
First I would look into square port heads 990's or 780's are redily available andd cheap.
Lay out the details of you current set up and we will gladly spend your $.

Yea, thought about supercharger, the snout would hit my hatch. I have wrap around seating, that brings up other issues. I have thought about a twin turbo, big turbo/low boost setup. If I did a 540 I would find a used 502 block, but getting harder to find. If I had 600HP that would make me happy for a while. I need to freshen up the drive, the stock bravo has been holding up well. I want to stay with pump gas, prefferably 89, the fuel sucks, that may be why I am down 2MPH from last year.

Maybe sell it and buy a boat with a faster hull? Many times folks regret to spending all of the time and money to not gain much. It may be pretty hard on drives also. The wife REALLY won't like that! Do some shopping before you sink a bunch into this one. You may still make the decision to build a motor, but then again you may not. Just the right newer boat could make both of you happy.

Well, maybe good advice. But we like the boat, way more room than others. I have raised the x up 3" and the boat looks like new. Just ask the guys here that boat with me. It is really fast for what it is, it runs 74 in ideal conditions. I am not planning on selling it, I will keep this boat and collect others before I do that. It responds well to HP I have always gained speed. I will not be sinking a bunch of money on this. I may not do anything,

I talked to RMbuilder a few days ago. He seemed to think I could get 620HP out of my engine. I would need AFR heads, new cam and bump up comp. I could do this project in two steps, the heads one year, then the new pistons and cam the next. That may be the best option unless I find a smokin hot deal on a 502 block and rec port heads.

find a high hour 502 mag complete that you can steal. turn it into a nice clean 9 to 1 injected 540 and quit while youre ahead. you'll see 550 - 560 without breaking a sweat, reasonable revs, no fuel complications , no magic, and very very good reliability.

Yea, I am already at 520HP, I would like to gain 100HP. A 540 setup would be a great, I could reuse most of the parts out of the 489. Should be able to get 600+ HP pretty easy.

For reference I got 695hp out of my pump gas 489" pretty easily.

Brodix supercat heads tweaked by my head guy is where most the power came from. No need to go to 540" for 600hp.

Procharger would get you there and then some pretty easily too.

yes it would as would any number of other combinations but the 540 is understressed at that, lower revving and without any of the complications of these procharger deals. 540 stuff is cheap off the shelf and well proven. i would suggest that the dollars per HP ratio for a 540 would be half of what a procharged deal would be and last twice as long... money and time that can be spent on far more important things like alchohol and women.

I would also suggest the new hull option. Find something about the new one that your wife wants... like a potty or larger cabin, etc... Then you can break the news that it just happens to be faster. I'd start with the 25-28 foot Nordic's. You can find one reasonably priced and they are quick with stock power, blazing fast for singles with big power.

You can put an additional 100HP in a hull and see squat on the top end. I put big power in a Formula 242 LS with unfulfilling, modest gains. In that case I went from 365HP to 620HP and only picked up about 15MPH.

The drive comment is pertinent too. When you stick big power in front of a drive on a hull that doesn't want to go fast anyway, bad things happen. I mean like bad $3000 (or more)a pop things happen. In the 242LS example above, I popped a drive within 3 hours. I then went to a Bravo X/Imco XR combination which required more investment.

The boat started with a 330 at 55MPH, I have brought it up to 520HP and raised the x dim up 3". Now it hits 74 on a good day, the boat responds well to HP, almost a 20MPH gain. Again we are just speculating here, I may do nothing else to it.
Too sum it up, many ways to get 600HP. A 496 with AFR heads and custom roller, 540 with custom roller, or anything with a supercharger. I am sure we will get some more ideas also

Go with the 540. I just got my new 540 running friday. Took it to the river Sat and Sun. Eddie Young put the final tune on it yesterday and I believe it was worth every penny spent.

Yea, Eddie knows what he is doing, he is a great help to everyone here on the forum.

I am pulling this one back up from the dead lol. 10 years after I made this post I freshened up the engine last year. Went from 489 to 496, added Flotek 290 heads with AFR valves and isky springs, bumped up the compression to 10.3 from 8.9 to 1 and had a solid 6 mph speed gain.
I reused the RM builder cam with 225/230 duration, 595/595 lift, 112 LSA.
Question is how much HP am I leaving on the table with the smaller cam?

For some of us it takes time to follow through with our “Great” ideas - Goals!

you had to pick up about 90 hp with your gain it seems. With that said and staying NA your cam and heads are about the last of your potential ponies. Could probably gain another 40/50 hp but gotta ask yourself is it worth it for another 2-3 mph. Cam is a little small for what your doing I think anyway. What rpm are you peaking at 5k + -? Just a cam change to keep it simple would definitely help. 235/242-630 ish. JMO.

edit: What size int valves?

Yep, thats what I was thinking. I went way over budget last year and the cam looked like new. I pulled a 25 pitch prop to 5500 RPM last year. Going to try a 28p lab bravo prop the first time out. It runs amazing and doing nothing to it this year. Anyone put a 100 shot of nitrous to it?

2.3 intake valves. Flow numbers are almost identical to the AFR. I actually used the AFR severe duty valves, exact same specs.

The simple way is to get a pair of FloTek's good oval port heads. Victor Jr. intake with a Dominator carb and a proper roller cam set up. You can easily run 10:1 on 89oct. in a BBC with aluminum heads. Just don't over time it.
Of course the 540 would make that power easier. But you'll be a lot deeper in the hole.

Sorry for the confusion. I pulled up a really old post and actually gave a follow up. Went with a 496, 10.3 comp, Flotek 290 heads, kept the same cam. Only question is how much power and I leaving on the plate with my old cam.

I’d guess about 40 hp or so going up 10* and similar lift.

There were a some custom Bullet roller grinds in the swap not long ago that would be something to consider. If I recall their pretty close to what I’d be looking for with that CI combo.

I just read about a thousand post on failed Marine Kinetics cams. Now I am nervous. I did not have a catastrophic failure before my rebuild and it did hold up for several years. But I did have a ton of valve leakage on the leak down test before rebuild. I had 8 rocker arms that needed rebuilt. Not sure if they were exhaust or intake. I was burning at least a quart of oil per day trip at the end. I am now getting regular oil analysis and this should give me a heads up. I had at 4 of them done last year and it was better after I added the oil thermostat. Any advise?

More round table talk….

Another note: if you are truly at 10.3:1, the cam you have is too short in duration. The cam you have was trying to achieve more cylinder pressure , which you don’t need nor want now.

Note#2: You where reving 5500rpm. My guess is that was just passed max power. 224 is a tow truck cam for near 500cid.

Somewhere 236-240 at .050” intake duration is where your motor will want to eat. Prob 240 :)
You have an exhaust to handle it?

The last 496 builds I had custom comp grinds.

244/248 with dart 310 cc heads. Peaked at 6k. Just a reference….

What compression ?

Ran a 24 pitch prop 5500 RPM with old setup, now using a 25 pitch to the same RPM, going to try a 28p Bravo prop this weekend. I have 113CC heads with a small dome piston, including the gasket thickness I have 10.3 to 1. Eddie Marine exhaust with long wet risers.

Anyone have experience with this cam?
https://www.cpperformance.com/p-1675...-camshaft.aspx

Aluminum heads 10.5

No but I like it. Very similar to mine with a little less lift but not much… like .013 less + -
This would be a little easier on VT

623 hp at 6k on my 496’s - same duration!

Specifically says "Will not work with silent choice or switchable systems".....

Why is that? Curious....

Thanks. Brad.
(937)545-8991

244/248... you better have great flowing exhaust runners. That split is to close in my opinion.

worked well in mine with 2” cmi. Non ported. JME

Not saying it wouldn't work, I just don't believe it would be the best choice if buying a new cam. If it was sitting on the shelf I would definitely throw it in.
Switched out a straight split cam with one that has a 6° split and it was much healthier and better performing. These heads were optimized and have great exhaust ports. JMO

Reversion. You have to have long risers or dry exhaust.

Here are the heads I have, great flow numbers with the big valves. 10.3 compression, EMI exhaust with long wet risers.
https://www.flotekheads.com/store/Bi...2cc-p130160438

Any downside to using this cam again for the season? I ran it last year with no problems. Probably going to switch out as a winter project.

Jeff,

I always thought the key to mitigating reversion was lob-sep of 112 or more. No?

Thanks. Brad.
(937)545-8991

-As you add duration you also add overlap.
-Tightening lobe centers (lsa) does also.
-Amt of Exhaust open degrees past TDC on intake stroke is what really means the most when it comes to reversion possibilities since the exhaust valve still open (but closing) when piston going down drawing in air from both valves (intake valve starts opening before tdc intake stroke) at lower rpms.

Look for some of my cam charts comparing the mag 454/502MPI/ HP500/Crane 731/500EFI/525EFI/Crane 741 and you’ll see seat overlap, .050” overlap (including btdc and atdc), etc, etc. Really good info that if studied, paints great pictures. :thumbs

It`s killing me.
https://cimg3.ibsrv.net/gimg/www.off...de964a2970.jpg

EDIT: didn`t realize this is an old thread .