info on n/a engines what cam
 

wondering if anyone is using a 731 crane cam in a 540,572..... with good aluminum heads and and and...

what kind of hp and torque you got.??

getting ready to order parts here..

Thanks in advance,
Don

731 is WAY too small for 540 and esp 572. 741 at a minimum for 540 and next one up for 572

where is the power range for the 741 at ?

3000-6500 per Crane

peak TQ is ~4600 and it starts running out of power above 5800. 741 is ground on 107* and it works well there but even better installed on 112* from what I've heard.

741 is an excellent Cam for a 540. A 572 would be a little choked in my opinion.

Don,
There are many data points to consider when making the correct choice of camshaft;
Compression ratio
displacement
head flow
exhaust configuration
desired power band
You would not want the 651 cam in a pump gas 8.8:1, wet exhaust motor that wasn't going to see 5500 rpm
Bob

what is the 651 cam...

for the record... my plan is this..

572. 4.5 bore and stroke. tall deck big M
either 8.75 or 9:1 compression
aluminum canfield heads.. 119 cc, fully ported 350's. with 1.900 and 2.325 valves
dart intake and demon carb... 1090 cfm or whatever it takes...
dry exhaust to the transom.

Don

Use the 651 cam.

what are the specs on the 651

244/[email protected] .632/.632" lift

3800-7000 range per Crane...A 572 needs at least this much cam if you want to make power.:cool:

Hey jdcna1:

I was told years ago that when you read the RPM range that Crane or anybody else lists for their cams you should adjust by the ratio of CID.

For example, if the cam book says 3800 - 7000 for 454 CID then that cam would run between 3000 - 5500 in a 572 CID. I think this assumes that the same heads are being used, so air velocity in the ports, at any given RPM, is higher due to the greater displacement being filled.

Same heads and same cam means the same HP, just at a lower RPM. If you use bigger ports on the bigger engine then RPM goes back up, and with it the HP.

That's what I was told. Does this sound right in your experience?

Tomcat;

That is correct from my experience, but my experience comes from large CID and SOLID ROLLERS....Hydralic has to behave similar but I don't have any hands on experience from that side...just witnessed what friends have done and seen from the result side. As you know, if you want to make power there is no substitute for a solid roller. My 632 makes peak power @6300 running a 280/288 @.050 115 CL .730/.730. The cam before that was a 272/278 @.050 114 CL...that was out of power @6000 these cams would obviosly never work in a 454 or 502 but really aren't that big for a 632" motor. Going up 10 degrees picked up power by 40HP. This is on a 10.5:1 93 Octane motor; TR with Fully ported Dart 360 heads.

IMO you need as big of a hydralic roller as there is made in engines 572" and larger. A better route would be a "mild" solid (250-260ish duration .700 lift) which would still make more than a "radical" hydralic. Put a set of Jesel rockers on and lash rarely needs to be set. I think the lifters would live nearly as long with this set-up as with the radical HR set-up. Again, these are just my assumptions.

i want to make power and torque wanting a good all around engine...i'm planning on setting the msd chip at 5500 for most times... but maybe 6000 now and then for a hot run...

Don

I'd run the 651 then in your 572.

Just something to keep in mind when selecting a cam for your motor.

This is a common problem with high HP motors;
If a motor produces it's max HP at 6000 rpm and say the peak torque is at 4800 rpm you can't decide to run the motor with a WOT rpm of 5400 to save the motor. It has to be propped out with the WOT rpm at least 1000 above the peak torque rpm, preferably 1200 - 1400 above peak torque. If you look at most dyno numbers that's about where peak HP is anyway.

The problem comes in when the boat is propped out 500 - 600 above peak torque. The drive train becomes torque loaded and requires a large pitch prop, this in turn lifts the stern of the boat which results in a large prop slip. Which requires an even higher pitch prop which lifts the stern even more, it's a no win situation.

It's OK to set the rev limiter at a lower rpm like chromecat was talking about but ti still needs to be propped out so it could run at the higher rpm if the rev limiter was not there.

Just trying to save someone a lot of headache in the future.

So, if you overprop a boat it tends to lift the transom? Even with a bow lifting prop like a Bravo 1?

The 651 is the correct cam for this engine, however 8.8:1 is not the correct compression ratio. The 572 certainly has the displacement to support the 306*/318* duration of the 139651 cam, but the 8.8 static compression ratio/late IVC and the resulting low cylinder pressure will significantly degrade performance. The 86* ABDC intake valve closing angle will bleed off a great deal of cylinder pressure on the compression cycle, killing torque in the process. In the current configuration will have a DCR of 5.8:1 with cylinder pressures in the area of 115 lbs. The Canfield Aluminum heads are good for a point more CR than iron heads and can easily support 10.25:1 on 89 octane pump gas. Keep the ICL @ 109*, as retarding it to 112* will delay the intake closing further bleeding of additional cylinder pressure and elevating the tq/hp curve. The minimum recommended CR by Crane for this cam is 10.5:1 - 12.5:1.

Bob

I will add that the Canfield has a super effiecent exhaust port and no more then a 4 degree split in duration is needed to obtain optimum power. Any more duration split and you are blowing the torque out the pipes.

Chris
Stef's Performance

Chris,
Welcome to the board!
Bob

Patriyacht,

Whenever you increase pitch transom lift increases as well. Whether it becomes detrimental is a case by case scenario.

Matt

I always considered bravo1 props stern lifting and mirages bow lifting.

BT

I think his point is that within the world of 4-blade props, the Bravo 1 is on the "bow-lifting" side of the spectrum, as opposed to Hydromotive's Quad IV.

ok... so does anyone have a desktop dyno.. or familiar enough to give some type of hp and torque for this engine ?

Don

am i missing something or does that 651 cam and some of the specs i'm looking at without some of the compression ration look like this motor from GM... i thought this combo would make more hp

http://www.paceparts.com/product.asp?3=180219

Don

I could run numbers for you. Provide airflow numbers for every .100" lift in/exh and cam specs along with all other engine vitals.

BT :cool:

Blue Thunder,

What other specs do you need other than what I have already posted..

Thanks
Don

With a set of cnc AFR's or Canfields and a larger carb would work wonders. The heads on the crate motor sound like the same ones on the 502/502.

Heads on the ZZ502/502 are same size valves but oval ports with 110cc combustion chambers.

I assumed the difference was in the head... but it doesn't make sense to me why GM would choke that engine that way, when they seem to do so well with the ZZ 502/502...

Don

This build is more similar to what you are doing, 38 less cid, 700+ hp, closer to your Canfield heads, similar cam, and notice the compression ratio.
700+ HP 534 cid Pump Gas
http://www.sdpc2000.com/cart.asp?act...=1579&pid=2597
Bob

Chrome;

I'd go 10:1 CR and run 92 Octane. Dart single plane with King Demon, IMO you'll need more carb than 1090. Talk with Demon and they will set you up..nailed my TR set-up. Big Inch motors need a lot of carb especially running singles.

The set-up you propose will put you ~750HP give or take and ~750 TQ. I did not run desktop dyno numbers, but that will be very close.;) :cool:

not sure i want to do that much CR... may do blowers down the road. if i get beefier drives...

You don't need King Demons or Dominators. They will make about 10 more hp but you will loose about 30#/ft of torque.
I pulled the dyno numbers on our 540 CID for air usage

3600 506 SCFM
4400 673 SCFM
5000 778 SCFM


572 CID

3800 528 SCFM
4600 720 SCFM
5200 815 SCFM

The 540 was 645HP at 5200 and 680#/ft at 4500
The 572 was 702HP at 5200 and 731#/ft at 4400.

You need a good prepped 850 or a out of the box 950HP carb.

Chris

I don't know Chris, I alway thought you sized the carb at ~130% of cfm for best performance depending on intake selection. 130% would give 1011cfm for the 540cid you listed and 1060cfm for the 572 at the listed rpms. 950cfm would be restrictive on the top of the rpm band.

Dave

My 632" liked 2X775 Race demons that flowed 980 each.

900HP@6300; 820 Ft/# @5000

Agree with Blue Thunder, a 950 and esp. 850 is choking a 572, even more so if you turn it 5500 or above. A Lot has to do with how your heads flow and how well matched the cam is as to how efficient the motor is. More efficiency = more carb, especially as rpms rise.

Talk with Demons tech department, give them your exact set-up and see what they recommend, they are pretty good. Only thing I had to do to my TR set-up was add 2 jet sizes all the way around, perfect otherwise. :cool:

I agree there are a lot of factors in carb size
 

I know the basic rule of thumb is

carb cfm = VE*(cu. in. * max rpm)/ 3456

Now that said, dynos most of the time show an engine likes more carb or less carb, etc than this basic rule. So, VE is how efficiently your heads flow... how does this relate carb cfm and to posted flow numbers of the head manufacturers? If we assume 100% VE (Factor of 1), on a 540 turning 5500 rpm, then carb cfm = 860cfm.

Now we add a more efficient set of heads that raise the VE to 105%, that still does not account for the huge carb size some of these engines seem to like?????

So again, how does the posted flow numbers of manufacturers relate to carb cfm?

Thanks
Zack

case in point, jdnca 1's 632"
 

This is what I'm getting at... obviously jdnca 1's 632" is a great running engine...100% VE at 6300 rpm shows a cfm of 1152 cfm. However he was best running carbs of 1550cfm. That's 134% VE!?!?!?!?!?!?

I don't know of any head that will flow that efficiently without a blower/ turbo....so what is the explaination???

Zack

When testing these combos, we through alot of products at them. Budget on this was unlimited so we ordered it to try it. Engines were targeted to sport boats with single and twin bravo drives.
Yes the big carbs made more HP on both engines, but we lost torque. The torque plateau is what turns that drive, not HP. Both of these motors had real good VE numbers, the 540's were 101.5% at 5000 rpm and the 572 was 98.5% at 5K. We were shoot for reliable power at the 48 to 5400 rpm range. We got it. I have the dyno sheets in front of me, I don't mind faxing them to anyone so they can see it's not BS.

SCFM is what the engine is actually using at that rpm, not a theoretical calculation, so to use some of the info here if the 540 is using 778 cfm at 5K and I have a 950HP Holley on it that really flows about 990, then I have 127%.

The canfield is an excellent flowing head, small runner, very very good velocity, and an excellent exhaust port. Should have it was designed by HVH. It makes effiecent use of the air it takes in.

Pro Stock stuff will get into the 118% to 120% VE range and the cup cars are a tad higher. That is reliable info because those are our customers.

Last but not least, the cams in these motors were both small.


Chris
Stef's Performance

Chris

Not trying to be argumentative here, but I do have a question for you that I'd like your theorys on. Why is it that A Tunnel Ram always makes more TQ and HP than a single plane single quad? Obviously the long runners and straight shot keeps lots of air and fuel suspended, but carburation is always on the big side of where it should be from a theoretical standpoint. (Mine is 1960CFM) Even 2 X 600's on a 502 this would be true and no one would put a 1250 dominator on a 502 if they expected it to run. So again, interested in your thoughts on why this is true.

Signal strength and . . .what am I looking for word wise. . .ahhh. . .more consistant air path. On a single your carb signal has to changes more frequent, 4 venturies feeding 8 cylinders. Air has to slow as valves close and open. . .has to change direction. What a dual carb intake, TR or Fabricted does is locate the venturies over the runners, more consistant signal, does not need time to change paths.

Does this make sense to you? I sometimes can't type what is in the head. People say I type in code.!!!!

No offense at all, I've been wrong, I've been right, and I am still learning. But one thing to remember. Torque is measured, HP is calculated. Torque is what moves that drive to spin that prop. People talk about "asking the right questions", next time ask the engine builder not what HP the engine makes, but what is the torque peak and how broad is it.


Chris
Stef's Performance