getrdunn

iTrader: (7)

Wazzup with the voices in your head??? Lol. Just noticed that but gotta admit I've had a lot of that going on lately but not snowmobiling. No snow up here...

SB

iTrader: (1)

Maybe the Crane 651 is also doing those specs for heat management ?

getrdunn

iTrader: (7)

In regards to splits I did look up lunatis and did notice their blower cams do have less split than others. 4+- on blower cams and 8+- for non blower cams. Just a quick search I didn't go through all of them but..

HaxbySpeed

With a hydraulic lifter, the exhaust opening can be fairly critical in a boosted application. In theory, and as seen in software modeling, opening the exhausts sooner to initiate blowdown pays off in hp. What I've seen in the real world is, opening too early against all that cylinder pressure can cause the lifter to bleed down, or beat your valve train up if you've got really stout lifters. Sometimes a slightly later exhaust opening will actually make more power due to better valvetrain control. It can also be boost dependent. A cam with an early exhaust opening might work great with 6 or 7 lbs boost, but start to have issues at 10-12.

HaxbySpeed

And to clarify. That's not a knock against simulation software, which is an incredibly valuable tool. But some one who has never built a supercharged marine engine before could sell a hobbyist cams designed by that software and run in to trouble. Just because it says you make more power with a bunch of lift and an early exhaust opening doesn't mean it will live in the real world.. But I digress.. Does the 651 cam have a boost psi recommendation?

getrdunn

iTrader: (7)

Good post... never really thought about the lifter bleed in that regard but then again my personnel experience with hyd lifters suck. But certainly can see the extra pressure if events aren't right on Q especially in SC builds.

MILD THUNDER

iTrader: (3)

Crane says max boost is 20psi with 8.0:1 max static.

MILD THUNDER

iTrader: (3)

That part I get. My question was more or less related to actual valve timing events. People tend to get so wrapped up in LSA's, ICL's, .050 numbers, and rarely look at what the valves are doing relative to all that, and that imo, is what matters. The engine doesnt know or see, LSA's, ICL's, etc. It just sees what the valves are doing.

I think Haxby nailed a topic, mentioning opening the exhaust valve too soon, can be hard on parts. The cylinder pressure can be very high at exhaust valve opening.

Performance wise, I am guessing , that opening the valve earlier, with a poor flowing exhaust port, might get the cylinder evacuated better, but with a good flowing port, might be a waste? I don't really know. Or, maybe its relative to the level of boost..

Maybe I'll have to run 2 dyno sims, one with stock GM heads, and one with a dart or afr head, using both cam designs, and see what happens.

Good stuff.

TylerBurich

Joe, you have the wheels turning on this topic for sure. Reminds me of what Bob Teague told me when degreeing my cams, he said to forget about all those @ whatever #'s and use the valve events from the grinders cam card. It makes sense, most people get hung up on the advertising of a cam and forget about the true #'s. Smokey Yunick says anything over 5 degrees advance or retard and you have the wrong cam, but we all know the 651 makes good power. You for sure have made me pay a lot more attention to the actual lobe on some of these cams vs what is advertised.

sutphen 30

isn't it just easier to google a supercharger build to fit your needs and copy it.will save you a trash barrel full of cams that were suppose to work on paper and in an computer syms.