second chance

I told my engine builder that I wanted a reliable engine and that's what I got, not one issue so far. Just wondering how much HP was left on the table with the cam that he used. It's a comp cam .547/.547. The motor has dart pro 1 heads, roller valve train, 850 quick fuel carb, msd ignition, stainless marine exhaust,and 9.3-1 compression. Wondering how much HP I could gain with a larger cam?

brian41

iTrader: (1)

Was it dynoed? How much did it make with the current set up? Not very much lift but what are the other #'s? how was the cam timed? What length riser, silent choose or not?

second chance

Did not dyno the motor. Cam card says 284/290 .547/.547 112.
Timing is set at 35, not sure how he degreed it.
No silent choice. Not sure about exact length of risers, but the are not very tall.

Griff

Probably would gain 40hp with a well matched roller cam.

MILD THUNDER

iTrader: (3)

My guess is your builder picked that cam out of a catalog, because its labeled 'marine'. Comp cams xtreme marine.
HYDRAULIC ROLLER: Good for jet boat with A impeller. Great for pleasure or mild performance use.


230/236, .547/.547 112LSA.

I think that cam is a bit light for a 509 with Dart Pro 1 heads. Its similar to a 500EFI cam, which was a 502CI making around 500hp and ran 4800-5200RPM. Its much smaller than a 525EFI cam.

I think your leaving some power on the table. A longer duration cam, with more lift, would probably net really nice gains with those heads on a 4.500 bore, with a little extra headroom as far as peak RPM goes. Call Bob Madera.

mike tkach

iTrader: (3)

i agree that some power could be found with a different cam,but not enough to change it now.imo.

Budman II

iTrader: (1)

Swapping to 1.8 ratio rockers gets you up to around .580 lift, but keep in mind that it also increases your effective duration and overlap, so if you are on the edge of reversion, this could conceivably put it over the limit. This would be the quickest way to get a little extra power, but probably still not worth the money and trouble.

Keep in mind that valvetrain durability is highly dependent on the quality of all of the valvetrain components - cam, lifters, pushrods, rockers, springs, retainers and valves. Cost cutting in a single link in that chain can toss the whole thing in the trash. The builder may have gone conservative on the lift to try to help with valvetrain longevity (similar to Merc's philosophy with their motors), but if he skimped on lifters or springs, for instance, it could be all for naught.

liquidlounge

iTrader: (1)

I actually like your setup. Yes, you would probably gain 30-40 hp with a longer duration/ higher intensity cam, but that comes with a pretty hefty investment in better lifters, springs, etc. Also, for your style and length of exhaust, going to a 525 spec cam would probably spell trouble. With those heads and cam, I'll bet you are in the 530 hp range. Like Mike said, probably not worth it.

second chance

I'm not gonna touch it. This motor has been flawless and the boat will run 69-70 all day loaded, touched 73 once. I'll save my $ for beer