What to look for when picking a CAM
 

In the marine world is there rule(s) of things not do when picking a cam, like dont go over x LSA or x amount of lift.

Reason I'm asking is I'm building a LS motor for a pontoon :party-smiley-004: and a simple cam swap will gain one almost a 100hp up top.

For instance stock cam
Lift 0.466/0.457
Duration 190/191 degrees
LSA 116 degrees
Idle vacuum 22.5 in-Hg
Cranking compression 175 psi
Peak power 353 at 5,200 rpm
Peak torque 384 at 4,300 rpm
Average HP 286 Average TQ 353

A readly availble aftermarket cam
Lift 0.590
Duration 224/232 degrees
LSA 115 degrees
Idle vacuum 17.8 in-Hg
Cranking compression 176 psi
Peak power 442 at 6,200 rpm
Peak torque 412 at 5,000 rpm
Average HP 315
Average TQ 380
TQ gains (over LM7 cam) at 2,500 -25 lb-ft
3,500 -8 lb-ft
4,500 +16 lb-ft
5,500 +69 lb-ft (72 hp)
6,500 +105 lb-ft (130 hp)

Is this aftermarket cam to big? Will I have revision issues.

Thanks
Mike

I'm no expert, but I'd like to know how a cam that closes the intake valve later in the cycle and has more overlap with exhaust events can make more compression than one that closes it sooner.

Faster cranking rpm.Believe it. Difference between fresh battery, low battery, faster spinnig starter, lower spinning starter, etc, can effect that greatly.

Psst: Circle track restricted rules: I used to reduce voltage to the starter , to crank it slower, when being teched for cranking compression. LOL.

Cranking compression was a dumb rule because way to many things effect it.

Okay, back to boats ! LOL.

I don't see that cam making the boat any faster. It just moves the rpm range up, you'll have to switch a smaller prop, rev the hell out of it all the time and hope it still gets on plane well

Hmmm I'm not following. Care to explain that. More rpm will allow me to spin the prop faster at high rpm(kinda of what everyone wants todo)

FYI boat planes with a 140hp at 21mph. Won't have a problem with planing.

Give us some other choices.

Here is where I have been getting some of my info. There is 1000 cam for the LS but they were testing the popular ones.

http://www.hotrod.com/how-to/engine/...st-comparison/

If you dyno an engine with that cam it's not going to make anymore over than what you have, until it gets above the rpm the stock one peaked at.

Correct but when the stock cam falls off at 5500 Rpms and this one pulls to 6500rpms and 80hp more that will push the boat faster thru the water. What we all want todo.

Im more worried about idle, revision, things like that. After all this boat will spend 80% of its life below 1800 Rpms cruising around with a adult beverage in my hand.

An engine is good for X amount of power, and the cam more or less decides where that is delivered. You can optimize torque on the lower range or trade that for horsepower via revs up top. The problem develops when you don't have enough torque to get the boat moving enough to utilize the HP on the top end.

Just by cams you given, that Crane 210 cam seems better for your wants + needs.

Thanks everyone

SB why com 210. Just wondering. Trying to learn!!

I got lost in there charts. I was looking at the 3500/5500/6500 part. I read back and saw where they posted peak torque and hp and such.

A peak hp of 6200rpm is not so bad on the bigger Crane 224 cam.

Anyway, I'm no LS guy, but I'd be willing to bet something just under or near 220 will work puurrfect. lsa 112-114 (LS cam guy will make the choice here) and you'll get your cake and eat it too - no reversion, high 5k power peak, very wide power band, and yada, yada, yada.

I went thru all this with my 1960 Cadillac that I am putting a 5.3 LS1 into. peak horsepower really means nothing in a boat. we dont have gears to shift. all the cams that I looked at made more power well above 4k rpm but lost a lot down low. since the caddy is heavy and a cruiser I didnt see the point in making power above 6k when it would make it struggle up to that point and labor where it spends the most time running. in order to compare you really need to see the dyno sheets and what average power it was seeing at what points other wise you may spend half the lake trying to get it to the point is wants to go.