pelle

Tomas, I would recommend crane 133801 w/ 222`/234` at .050 and .529"/ .525" lift. It made 450hp@4700rpm, and
stayed flat up 5500rpm. My engine was with 269cc Merlin ovalport heads, 9:1 CR, RPM intake and BG750dp.So I think you would get 425hp to 450hp. It took my boat from 330hp`s 47 knots to 55,5 knots. But as we all know, things are changing in the long, cold winter time of north. In goes hyd.roller cam, RPM Air-Gap, and BG850dp + drive is moving
up at least an inch or two, waiting for summer...in eastern
neighbour of you.

Pelle

KAAMA

iTrader: (1)

I believe the Vortec heads are much more efficient than the old junk GM heads my cousin has/uses, but that is what he was stuck with at the time and he wanted to make the best of what he had. I only brought his heads up in conversation to show you that with a little bowl/pocket porting, and valve size increase that even they could be a decent running head for what they were----and they did fine for what he was after.

My cousin was using a GIL DRY aftermarket exhaust system could have easily have gone with a larger camshaft close to what Griff has suggested----I was thinking more something like a 222*/230* on either 110* or 112* lobes. However, my cousin wanted to run the boat at about 5000 to 5100rpm tops because of the cast pistons and stock rod bolts and he was advised not to spin the engines over that RPM level with those parts. As it turns out the engines made peak power at 5100rpm and a TON of torque 510 lbs from 3600-5000rpm. I should also mention that he also had the cylinders bore notched which I believe has an advantage. You could run the larger 222*/230* cam if the engines were going to be used with a decent aftermarket exhaust system, but would stick with the 218*/226* cam (even as Sutphen30 has agreed to) if a stock Merc exhaust system is going to be used on the engine.

That's just my .02---it's not set in stone, but I will admit, when deciding on a camshaft selection I tend to like or "errr" on the smaller side of duration-----but not too dang small...ya hear me son???

tomas_wallin

Cam 1
Cam 2
Cam 3
Cam 4
Cam 5

Have I forgotten some of your recommendations?

Which one should I go with then? There are getting a slight too many to choose from now...
Cam 1,2 and 5 are the ones I think could work fine, but since I have really bad knowledge about this I might be completely wrong too... What does KAAMA think of pelle's suggestion (cam 5 - 133801)

Pat McPherson

No one like GM high performance stuff?
There are 3 cams in the GM HP catalog that would also work...

tomas_wallin

Is this one of them?

tomas_wallin

Honestly I don't really know. I bought the engine this summer and never got the old carb to work the way it should.

Cruise rpm: perhaps around 3500?!

I just filled in some new info in my first post:

Pat McPherson

No Tomas, That is a roller cam...

The ones I am referring to are something like this:
Gen V 454HO cam 220°/220°, .500/.500, 114°LSA
Second- 218°/228°, .500/.500, 114°LSA
Third- 228°/238°, .540/.540, 114°LSA
Each of these cams will make more power than your stock 330HP cam.
A buddy of mine put the 218/228 in his 454mag last year and she pulls nice up to about 5300rpm.

Tomas,
If you use an aftermarket cam you will need to go to an adjustable rocker setup. Not a big deal, just more parts and $$. Any of these cams are going to require new valve spring and rotator eliminators...
Good Luck with your project.

PatriYacht

If you're going to run 4000 rpm or more for periods of time like poker runs, roller rockers are a good reliability upgrade. I've seen stamped rockers fail. Merc put them on 420hp and above.

tomas_wallin

sorry...

What is the difference between a GM cam and aftermarket ones then? What parts do I need, to be able to use a aftermarket cam?

tomas_wallin

What makes the rockers fail? If the rockers are a fresh set, shouldn't they hold for some longer 4000+rpm runs?

This upcoming summer there is actually a nice Pokerrun taking place here in Stockholm. It's about 80miles long and at 35 of them there is real offshore with no sight of land... They are planning for 40-50 boats to participate.

It would be nice if the engine would last for 80 miles without failing... But as most of us know - take it cool and it will last!