Cam question (Whipple 500efi)
 

There isnt near enough cam talk happening :hitfan: but I can't find an answer here...
Commonly I noticed guys opt for the 525efi cam, I believe Whipple offers this cam in an upgraded package. My question is: When does it make sense to bump up the intake duration/lift to match the exhaust?? I've read articles and talked to people on here with no straight answer. I understand favoring the exhaust vs intake helps expend the charge. But what does just increasing the intake to match exhaust promote (not lowering the exhaust profile, but increasing the intake)? More low end torque at expense of top end? Wet exhaust play a role? This is a whippled 500 a builder spec'd. Peak power 5800-5900. Stock heads.

Example -

525 Cam (Common Upgrade)
Duration (advertised) - 298/306
Duration (@ 0.050) - 236/244
Lift - .610 Intake, .632 Exhaust
Lobe Center - 114*

Single pattern (I'm questioning from builder)
Duration (advertised) - 306/306
Duration (@ 0.050) - 245/245
Lift - .651 Intake, .651 Exhaust
Lobe Center - 114*

I think generally, when it comes to cams and supercharging, there are simply a ton of fallacies out there. You'll hear things like " it needs to be a 114 LSA" , or it needs "10* min of split in duration" , and so on.

Theres lots of factors that play in. Cylinder head flow, RPM range of engine, amount of boost that will be run, and so on.

Speaking theoretically, you take a look at the crowd favorite, the "651" crane cam. It has a 244/256 duration, with a 114 LSA. That cam might might work better, with a build using stock GM iron heads, and a supercharger making 10-12lbs of boost. It might not work as well, with a build utilizing a very good exhaust port, and 5lbs of boost throughout the same rpm band.

The LSA itself, isn't what determines how much "boost" is blown out the exhaust during overlap. The overlap itself is. One might think the 114 LSA 651 cam is going to blow less boost out the exhaust, than another cam that is on a 112LSA, or 110LSA, but it isn't that simple. You may find, that going with a cam, that has say, 240/245 duration, on a 110 LSA, will have less overlap, or close to the same overlap, and generally perform better, in the application, making more average power from say, 3000-6000rpm.

Back to your original question though. The 245/245 vs 236/244 cam, both with 114 LSA. The power may actually be fairly similar up on plane, or on a dyno pull. There is something though, the 236/244 cam will probably do better. And thats idle quality. Having the intake valve close sooner, will have less intake reversion at low speeds, and more than likely, result in a better idling engine. The single pattern cam, might work better with a cylinder head that has mediocre intake port flow, but excellent exhaust flow. The 236/244 , might be better in a setup that has a good intake port, and poor exhaust port. Or, if say, a centrifugal vs a roots. The early closing intake, might work better off boost and low engine speed, where with a screw or roots, that just isn't a problem. The 236/244, will probably work better from idle to mid to upper rpm thanks to the early closing intake, and the 245/245, might start gaining ground in the mid to upper rpm, depending on the overall combo. just my thoughts on it.

Often i believe many marine engines, are cammed incorrectly due to the LSA misunderstanding. Most assume 114 LSA is the ticket for marine engines. So they go pick a cam that has a 114 LSA , and ignore the camshafts actual overlap. While the 114 might work ok, the better choice, may have actually been a smaller duration cam, with a narrower LSA. Instead of making 600hp at 6000rpm, they may have made 600hp at 5600rpm.

If you look at the HP500 carb engine, it had a 110LSA. The 500EFI , and 525efi had a 114LSA. I dont have the cam specs in front of me, but the overlap on them, is probably not what you think.

Lsa determines the shape of the power curve. The important thing when determining LSA is the length of the rod and stroke of the crank. Trying to pick a cam based on .050 and LSA #'s is a poor way to pick a cam. The most important thing is where the duration occurs in relation to the crank.

Heres an article comparing LSA's. However, that is comparing two similar cams duration wise, but changing LSA.

It gets deeper, when you now throw in, different duration cams, to different LSA's.

http://www.compcams.com/technical/FAQ/LSAproperties.asp

you have a dyno sheet of this build?

Another article explaining the importance if the proper timing events, and overlap.

http://www.compcams.com/Pages/416/va...-tutorial.aspx

Theres alot more to a cam than .050 numbers and lift. You can pick a cam thats 242/248 @ .050, with 630 lift on a 112 lsa, and another cam with the identical specs, but have completely different timing events, based on seat duration, ICL, etc.

...

must be a light dyno,,that thing would be into heavy knock retard w/ those lean afr's.

lets see the fuel lbs burned.

Thats all i got for that dyno sheet. Eliminated sent it to me a while back.

Those afrs are certainly showing lean. Ive had supercharged engines on dyno that started there for afrs, and never shown any signs of knock. Of course they got fattened up from there.

I do believe these engines went into a 388 Hustler, and have ran great all season. The power numbers look clean , dont see anything weird going on?

I could show you my dyno pull, that started at 2900rpm to 6500rpm, at a sweep rate of 150rpm per second. Wanna talk about loading an engine down.....dyno pull was like 30 seconds long. I see some of the guys here do a 4k to 6k rpm pull at 800rpm per second and call the tune perfect. Dyno pull is over in blink of an eye.

What do you guys typically do for your dyno pulls?

Correct... If this was blown carbed application IMO it would be larger cause for concern. Engines now have 90hrs and counting.

the systems I use look at the knock sensors,,hell,I trimmed the fuel so much in my boat,its on the hairy edge all the time,,~month old gas will show knock retard.
dyno pulls,,depends,,I'll hold an engine at 3-4000 rpm and load the bag out of it to get the fuel right.

heres a true story

38 fasttech,,vortech hp500efi's,,arnesons,,rebuilt the drop boxes,,they have the gear ratio,,go out to tune mefi4b's.4 guys on the boat that want to watch me work.strap boat to dock,,set up in/out of gear idle.few tweaks and off we idle out.
go to get on plane,nothing,floor it,cough sputter weaze,,pull back throttles,,make some tweaks,,again nothing,,guys aggrevating me,,saying tunes fcked,,so back to the dock.strap it down again,,more tweaks more timing ect...
still nothing,,hearing the same schit about tuning,,I jump up,go to the throttles and pin them,,I say,what do you want me to do,,this thing thinks its at full load all the time.
I say,,either your shaft bearings are seizing or the gears are in backward,,,turns out,,gears were in backwards,,we were trying to get on plane w/ I think a ~.75-1 ratio,,boy we did idle out quickly.motors ran for years before heads rotted
out.
new afr headed 540's I tuned in the boat from a base tune,,fastest so far,,115mph.

how fast is this boat?how many actual miles do you hold this thing strung out,,quick blip or 5,10,20 miles?

That dyno sheet tells me the cam is to small for a boat motor that you want to run close to 6,000 rpm. The LSA is not tight enough and the duration is to small.

your not getting that much more out of a 2.3l whipple.

I think its a 388 hustler that runs upper 90s.

If you want to run that motor close to 6,000 in a boat the power curve is all wrong. That motor is petered out at 5,000 rpm. I'll bet it pulls like a freight train up to 5,000 and hits a brick wall. If you want to spin 6,000 the curve needs to move up.

It's an inland boat. Maybe 30 second WOT blasts. Goal RPM is 5600 with 3.125 pullies should be close to 7psi. He currently runs the 3.375 uppers at only 5000-5100 rpm. 5psi. That dyno sheet is also 5psi

Baja why would you say the duration is too low? This cam is close to same duration on exhaust as 525efi but more intake. Dustin sells the 525 cam as whipple upgrade for the 500's... He doing it all wrong you feel? Please elaborate

There's nothing to elaborate on look at the dyno sheet. The motor is out of steam at 5,000 rpm. The cam is to small. I see it all the time. I don't care if Jesus himself designed the package. If you want to run that motor in close to 6,000 rpm the cam is to small.

Well, there is 50 more HP to be had above 5k.... I will agree the 2.3 is holding it back but it is gaining power at a decent rate still. 5600 is where I want to run it. Seems like a good spot for this engine. Here is picture at reference. Rear entry top mount.
[ATTACH=CONFIG]562589[/ATTACH]

Dustin says 18k max rotor speed. Changing to the 3.125 upper with 8.75 lower the speed will be 15,680 at 5600. Overall I'm
Just curious on the increased intake duration and it's affect.

That motor needs at least 8* more duration on the intake. Don't focus on peak hp. Your boat doesn't care about horsepower. Torque is what moves the boat. Look at the dyno sheet and see where the torque starts nosing over. If you want the motor to perform past 5,000 rpm you need to move the torque up in the motor. To have a noticeable difference in the power curve you need atleast a difference of 8 numbers in duration. I think it could also benefit from a tighter LSA. With the tighter LSA you will Loose peak numbers however your horsepower and torque numbers will not run away from each other as fast. And that's what you want in a boat. When they run away from each other to quickly the motor is done.

You mean 8 degrees less duration on the intake? So turning it into a 525 cam?

8 more

8 more on intake? Reverse split like a turbo grind... 253/245... this is a new thought

If torque is all that mattered we would all be limiting our boats at 4600 rpm. And my duramax would pull those LOTO hills much better at its peak torque of 1600... which is not the case. Sorry, not buying what you are selling Baja.

I never said a reverse split. I said if you want to move the torque up in the motor you need a minimum of 8* more on the intake to see a noticeable difference. I never even mentioned the exhaust.

So you're saying you need 250's+ duration cam for good power up to 6k in a 502ci engine... I see :/

Bingo

im not getting involved in another cam thread but i will tell about a similar build i did for a buddy about 10 years ago,it had edelbrock marine heads,509 cu in,8.5 compression ratio and a crane 741 cam.the exhaust is imco power flow with silent choice that only gets run in quiet mode when in a marina.to my suprise it has no reversion issue but it idle,s at 900 rpm.dustin did the tune and it peaked at 740 with dyno headers.it sees about 25 hours a year and had had no problems and other than oil changes it has had no work done to it,still has the origional ngk plugs.ADD IN,it has had several water pump impellor replacements. i don, t have the dyno sheet,s because i gave them to the owner so i don,t remember what peak rpm was but i think it was just under 6000 rpm.

There were a few of us that had some talks about dyno simulations (N/A form) on 502ci engines (Stock headed, single plane, 850carb) with various cams. Results were actually fairly close. Mike, the 741 did very well. Obviously with boost or higher flowing heads in the equation would vary greatly.

HP500 cam. 222/230, 110LSA, 536hp/606tq 68* Overlap (Peak HP at 5k)

525 EFI cam. 236/244 114 LSA . 566hp/586TQ and avg 466/470tq overlap 70* (Peak 5400)

Erson 230/236 112 LSA . 570HP/598TQ and avg 464HP/471TQ overlap 71* (Same peak but notice the power/torque increase vs the larger duration 525 cam. Says LSA alone can trump duration)

Custom Comp Single Pattern 245/245 114 LSA. 651/651 lift. 573HP/582TQ and avg is 474/475 overlap 78*.

Crane 741 236/244 112LSA 580HP/590TQ and avg 482HP/485TQ overlap 78*

Lunati 242/252 114 LSA 582HP/584TQ and avg 487hp/486tq Overlap 78*

Lunati 240/245 112 LSA 577HP/591TQ and avg 477HP/480TQ overlap 77.5*

crower 236/244 114 LSA 565hp/597TQ avg 455/465. overlap 64*.

Custom Comp 243/251 112 LSA. .627/.632 . 585HP/593TQ average was 486hp/497tq, overlap 77*.

Crane 651 244/256 114LSA .632/632 594hp/561tq. average is 493/488tq. overlap 84*. (Peak HP over 6k/ peak torque over 5k and larger overlap - Bit big for 502 with standard induction)

Still trying to understand your logic here. Out of steam at 5000 RPM? If I was to look at this sheet, I would say prop for 5600... She's still building at a decent rate from 5k-5600... What you are saying is confusing at best IMO.. Looks at 525efi curves, and where they are propped for max speed.... Anyway, here is the sheet in graph form:
[ATTACH=CONFIG]563709[/ATTACH]

Why would you prop for peak torque unless you want to go slower and break drive parts regularly? If that theory was true then according to this graph you would prop for 3600 RPM.

I agree... if the power is there, it's there. The old rule of thumb is to put them at just before power flattens out.. could mean right before peak or a few hundred earlier (as seen above).

If you are looking for max speed prop it to max HP.. If your racing throw that out the window..

I agree with that. Torque needed for acceleration would be of great benfit. But for pleasure boat, I don't see how this engine shouldn't be propped around 5600ish... plenty of "steam" above 5k

have you run this engine?if so what prop and what rpm?

So far it's been over propped. 95GPS 5000-5100rpm 31 p5x 1.36 gear 3 3/8 upper pulleys 8.75 lower pulleys making 5psi. I think it needs 29 p5x props and 3.125 uppers. Should bring boost up to 6 to 6.5psi. Rpm likely would land in the 5600 range

Maybe try some 1.50 ratio drives ?