C1000

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

MILD THUNDER

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.

MILD THUNDER

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?

Black Baja

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

kvogt

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

Full Force

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.

Full Force

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

Panther

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?

MILD THUNDER

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.

Baja Rooster

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