I have only looked at these two so far, and I was WTF with how low the power was..then noticed 'Wheel HP' and 'Wheel Torque.' Can that be taken out ? Of all if they all have it ?

Another question, are the averages taken from every 500rpm figure shown, or is it done every 100 rpm like a normal dyno test?

you said this was most power at 6k,,right.:party-smiley-004::lolhit:

the ole 741 cam,,that junky 20yr old tech wins,,now who would have thought.

Correction factor was way off. And the carb was way off too. :D

So in my thread every single person said my cams were WAY too small, now the 741 cam is best that was smaller then what I got? I don't get it...

uf course I'd never build an n/a engine w/ 8,4-1,,hell,not even in a blower package,unless I;m adding 15lbs of boost.

I didn't.:party-smiley-004:

If you want to spin the motor to 6,000 IN the BOAT. You need to look at the numbers from 5,000 to 6,000 the 741 isn't going to make it to 6,000 it will stop dead in it track right where torque and horsepower cross. Actually if you want to spin 6,000 in the boat the Howard cam you choose looks to be the best.

.

Now, here's the catch. As we know, its a combination of parts, that makes power. Its not just a cam, not just a head, not just an intake, and so on. Modeling this build, the options for single planes, are STD flow, high flow, and max flow. I chose the high flow intake for the test. Now, going to a "max" flow intake, which would resemble say, something maybe like a ported super victor, or something along those lines, the power went up.

He has a 1050 CFM 4150 style carb. I used 1050CFM for the test. Coupling the "max" flow intake, to an 1150 cfm carb, again, the power went up. The HP peak rpm did a little bit as well. The big cams werent showing big gains up top, probably because, the engine was simply running out of components to compliment the larger cams. But, when you changed those components, the gains from a larger cam, become more noticeable, and begin to offset, what they give up in the lower rpm torque department.

Basically, a 741 cammed 540 thats making 647HP with a mediocre intake, mediocre carb, and 9.5:1 static, can be transformed into an engine that now makes, close to 750hp, at 6500RPM, with the big cam, that only made 678hp with the mediocre characters in the cast. Now we're making some steam in the upper powerband.

Of course, there's always going to be a trade off with big cams. What you gain up top, you lose down low. That 6500RPM 750HP engine, isn't going to make the torque at low rpm/midrange, that the 5500rpm small cam is going to .

My general opinion on this stuff, is a cam is only a small part of the combination. The heads, the intake, the carb, the compression, the EXHAUST, and the tune, all play an equally important role.

Generally speaking from what I've seen between actual dyno's, and computer simulators, is exhaust a major player on these marine BBC's. Out of all those cam swaps, nothing HUGE was gained. But, simply switching from a large tube header, to a small header, The change is significant . The bigger headers on this build , make significantly more torque, and peak power, than a smaller header.

What exhaust is Tim running? I see the test sym was with big tube headers, maybe new exhaust is in order, or try a Sym test with a different Exhaust? I don't know much about this stuff so maybe it won't change the numbers anyway.. Just a thought

The exhaust is a huge player. More so than the cam it seems in this particular combination. I think generally, more people are concerned with cam numbers, and forget how important the intake, the exhaust, and the head flow is for an engine. A cam is just one ingredient in the recipe.

Heres a comparison, of the 236/244 741 cam and combo that won best average power, and the 248/256 cam, that has a better flowing intake and carb. After 4500rpm, the bigger cammed combo starts walking away , power wise.

For those who say "torque is what swings the prop", which combo is making more torque above 5k rpm here? Which one you think will spin the prop better at wot? The one making 673ft lbs of torque at 5500, or the one making 617ft lbs?

Hate to b a pain in the azz. But what happens when we close the Lsa on the 248/256 2*?

So the cam that made the most power at 3500 won.

That is true, the goal from the beginning was to spin 6000 with my 25 plus's as I want to stay with a 3 blade for that little extra slip pushing Trs limits.

Yes I learned that and I can assure as soon as funds are there I will be upgrading that too, not sure what headers or exhaust is best to not have the leaking issues, I will address that personally after things are done, may be slightly corked this coming summer unless funds roll on lol

Question; Have you run the numbers on the existing cam with the changed/upgraded parts to see how hit matches up with the lest of the choices listed here?

Not really possible. MK, does not provide enough data on the cam profile, to do a fair comparison. .050 numbers, lift, and lsa won't cut it. Need some accurate seat timing to see how it would perform.

Its kinda funny, that when you get an off the shelf crane cam, you get just about all the info on the camshaft, and when you get a "custom" cam, you get very little. You'd think it be the other way around.

Now if Tim had brought his old cam to a cam doctor or audiopro and got some measurements, then sure, it would be a good comparison.

FWIW, I had asked about the higher lobe lift, and short duration thing a while back. Generally speaking, yes, it certainly can be done. For the lobe to not be so aggressive with the higher lobe lift and short duration, the seat timing could be spread out, to calm things down. However, by doing so, this particular cam grinder, felt that doing that, would negate any gains, from adding the extra lobe lift.

With comparing the camshafts from crane, there's one thing I noticed, which related to what i was told about high lift vs duration. The lifter acceleration, on all the cams, generally stay within a certain range. Even when going to the 680 lift cams.

On cranes "632" lift cams, the difference between seat timing, and .050 timing, is 62* . Doesnt matter if its a 248, 242, or 256 lobe. . Now, when you look at their .680 lift lobe, the spread is now 70*. Again, doesnt matter if its a 254, or 270 lobe. If they had kept a 62* spread, with a .680 lift lobe, the lifter acceleration would be quite a bit higher. While that could certainly help build some low end power , with shorter seat timing, kinda making the cam "smaller" in a way, they are probably thinking about reliability, valve float, spring pressures required, and so on..

A 298/236 hyd roller lobe, with .610 valve lift , in flat tappet hydraulic comparison, is 296/236 with .553 valve lift. Its a fact, a flat tappet can actually open the valve off the seat quicker than a hyd roller, but it slows down right after that.

Dumb question, why would one choose the 731 cam over the 525EFI cam or vice Versa with only 2* lsa separating the two?

you mean 741,,731 is 226,234

Yes.

edit: oops, read your thing wrong.

:whistle: Crickets

For those who like this kind of stuff, I really recommend purchasing these programs, or putting them on the xmas list.


http://www.proracingsim.com/dynosimmainpage.htm

http://www.maxracesoftware.com/

http://www.controlledinduction.com/

Some engines might like the tighter LSA . Is it gonna make a difference how the boat performs, between those two very similar cams, nah. Not in my opinion at least. The 114 LSA version of it, will idle a bit smoother.

Thats another topic as well . With modern EFI, or programmable ignitions with carbs, alot of the idle quality issues, can be tuned out with bigger cams. If a smooth idle is what you like, a cam with less overlap and duration will do better, as long as its tuned properly. I know that by getting away from locked timing on my blower engines, its night and day how they idle around the docks now, with the same camshaft.

I know there's a lot of what ifs. Change this and change that but I'm glad you stuck with the actual cam specs. There's a couple I'd love to see lsa changes but it is what it is and you stuck with off the shelf cams as it. That's good.

I hate to ask as questions will never end but since the 741 got it I still think numbers would increase with smaller runner as mentioned in other post like the 305 cnc but I realize you have enough time into it as is.

These software programs are interesting I only wish iPad Apple Store offered something but they don't.

Funny we were using that cam back in mid 80's prior to even having a part number. i know shops that continue to use in builds to date in anything 496-540 with success. Not wild builds but extremely reliable. Something to be said about that I guess.

I'm am pretty surprised by that, and it's great info. Thanks for doing all the leg work. I knew the 741 was a good cam, but never expected it to outdo all those. Especially with a modern cylinder head package.

the 741 and the 525 efi cam is a good choice for 3500 to 6000 rpm but imo not the cam to use if you want more hp at a higher rpm..for ff tim-either one of these would be good for reliability but not max hp.i am curious as what camshaft you will use next tim.

Great post!

The thing I find most interesting is that none made 700 hp, which was tims original goal and seemingly easily attainable. Is it because this was wheel hp, or carb ad exhaust limitations? :nicethread:

I will say, this is just a computer program, I wouldn't take anything here as "gospel" so to speak, when it comes to camshaft choice.

I have a separate cam design software program, the "controlled induction" , that some engine builders utilize, and I know for sure, one of the "custom" cam sales guy is now using since it came out this year.

That program, for tims combo, suggests a 255/260 cam, for tim's engine, seeking 6000RPM max power. For 5500RPM max power, it suggests a 242/246. Pretty much EXACTLY what we saw on the dyno, with his 241/246 cam. It was about dunzo at 5500rpm.

For 25 bucks we can have the MK cam run in the cam doctor.

Not saying how it would perform, just that it could then be introduced into the equation.

The first and second column has the flywheel hp and torque, the thrid and fourth have wheel hp and torque. Just ignore the third and forth column!

could you for the fun of it,,run a set of afr ovals,,see where that ends up.

There you go, start a go fund me for ff and we'll get him bustin drives faster than he can replace em.lol:evilb:

Like the 290s?

Actually, the builder that dyno'd tim's engines, built a set of 540's using those 290's, with a crane "651" cam, not long before tims went on the dyno. He pulled the dyno sheet from that build, and overlayed it against Tim's. From about 3500rpm, to 6000rpm, it kicked tims combo's azz. Made 670ish hp if I recall, and better mid-upper rpm torque. Below 3500, tims actually made a little more torque, which you wouldnt think with the 290's vs the 325's.

Sheet, now I have to start all over ! Pain with this tablet and chitty dsl.:poopoo:

I tried the tablet thing, I just cant get to liking them. I'm old school. I gotta have my PC. Even laptops, I hate them.

Especially when you're a dork, and sit on your computer playing with cam and engine software for hours and hours. It would take me a month to try and do what I did here, on my laptop.

I bet the 300 Ovals would kick the crap out of all the other Afr's on a 540...