Hey Brad, how is the new blower?
 

Have you tried it out yet? I haven't been on OSO much lately due to a new job I just started and was curious to how deep into three digits you are now running. Later!!!

deep in the 3 digits?....
 

Refer to above statement, "My **** is always broken!"

Seriously, Parts delays have killed me. I'm always waiting on something, and usually it is a second try on getting the correct part to me :rolleyes:

My stock distributor isn't clearing my new blower shop intercooler and my shift bracket won't clear the valve covers on my new lightnings. All the water plumbing for intercooler has to get larger to meet the increased fitting size. DOH!! It's small problems, really. I've got the MSD distrib. on order. I hope to have it cranked in a couple of weeks. I can't wait to see how those Demon carbs work along with locked out timing.

Usually, setting engine alignment is something that sends me to the nut house, but this time, it was right on with my first attempt.

I sure would like a ride in that Baja! I bet that engine sounds sweet.

Your comments on a high and flat torque curve is interesting. I've been fooling around with desktop dyno a while back. It matched two of my motors torque curves incedibly closely. If it can be trusted, there is much to learn with it. The results with longer duration cams did not exactly give the results I expected (i.e., a peakier torque curve).

Alpha-bits! :D

Finally got a chance to respond to this one. My feeling is you want a broad Flat TQ curve wether you run a small block or big CID engine. I made a cam change last yr to shift up my peak TQ to a higher level (curve stayed broad) and picked up 40hp in the process. I picked up about 100rpm on top end. Despite the HP gain there was NO TQ gain, it just shifted everything up the curve (another words the average TQ was higher at a given rpm on the big end) The old addage of no substitute for cubes is very true, I run a 632" so there is a ton of TQ down low regardless. I run 280/288 duration @.050, but the motor willl still jump all over it at 2500rpm even though the cam is designed for 4800-7500 rpm. How things are packaged makes all the difference in the world, (heads,cam,intake,carbs) My tunnell ram has 2X775 race demons, if I had 1150 Dominators it would never work at low rpms and idle like ****.;)

JDNCA,

do you think the dominators would give any more tq on the top end? I wouldn't want to throw away the idle either, just curious. Is the better idle due to a better vacuum signal with the smaller carbs?

I'm a little confused at some definitions of flat tq curves. I consider a tq curve that is somewhat broad, but doesn't start until a relatively high rpm (3000?), non-flat because there is a void in the low rpm ranges. This was my reason for saying that if you had plenty of tq to get up into your tq band (or slip to instantly wind into it as Wette suggested), excess tq would be better spent moving the tq band up in rpm (more hp). I would view a boat/engine that has gobs of NA torque way down low to be a great pleasure boat, but not the best for top end. I would tend toward the type of curves that both Wette and you have, but didn't think of them as flat. I guess there can be peaky curves as well as ones that are shifted left-right in the rpm band. Unless I'm missing something, it would seem that a truly peaky curve would almost be indicative of a mismatched combination, unless said motor is driving a generator.

5 years ago, I heard about how one never wanted to have a motor that had anything less than near full tq at low rpms, lest the boat could never see the top end tq potiential due to the inability to get up the load curve. Now my opinion is that this problem of not having enough specific tq to get up the load curve, is not near as likely, with examples such as Wette's (omitting yours, JDNCA, due to the likely non linear load curve of your tunnel, for simplicity).

Could you give head/cam specifics so that I can fiddle around with desktop and get an idea of what your torque curve looks like?

Thanks.

Brad;

I do think the Dominators would help HP up top and maybe TQ to a lesser extent. HP gains would probably be 25-35. But I feel the boat would not idle well below 1300 and bog down low. Yes the idle is due to the vacuum signal and relatively high velocitys. To me a "broad" curve is one that only gradually rises and gradually falls off...regardless of where the peak is. Many drag racing motors have very "peaky" TQ curves. (A rapid run up to peak and a rapid fall off from it. A lot of that comes from relatively narrow LSA's (104-108), so a wider LSA will naturally have a broader "less peaky" TQ curve and help idle. (The LS-1 in a Corvette has a 122 LSA)
My motor is a Merlin 632, Dart 360 fully ported and polished heads (flow 420 @.700 lift on intake and 305 @.700 exh) 10.5:1 compression, 2X775 Race demons, cam is 280/[email protected] .760 /.735 NET lift on 115 centerline)

I actually just had a lifter fail so I toned down the lift to .700 net to help them live and am going to a Dual valve spring from a triple.

Here are my actual DYNO numbers from before.

rpm TQ HP
4900 805 758
5000 803 764
5100 800 777
5200 795 788
5300 792 799
5400 791 813
5500 783 820
5600 780 835
5700 771 842
5800 771 848
5900 765 852
6000 753 860
6100 743 862
6200 730 868
6300 727 875
6400 718 886
6500 711 893
6600 706 897
6700 704 901
6800 694 900
6900 685 900
7000 668 888

Although we didn't do any pulls below 4600 the other side came up as gradual as the big end fell off. I might be wrong, but this is what I call a broad flat TQ curve on a NA motor.

I see your point.
 

I was not aware of the impact that lobe center had on the shape of the curve. I did know the direction that it pushed it. I also was not aware the peaky tq curves were ever desired. This might answer why some I bumped into years ago (in the biz) said what they did. They were talking about strip car motors. Perhaps they did have high but peaky tq curves and I'm sure they had narrow lobe centers. I would guess this might be desireable in a drag car due to the ability of high stall converters to let you efficiently use the high peak numbers that the narrow lobe center would generate. I can see how this would not be desireable in a boat, no matter what the speed.

At 10.5 compression, are you able to do without race gas? I wonder what Wette's lobe center is?

This is good stuff. I appreciate the info. I need to spend some time on desktop to get a feel for some of these interdependencies.

I think everyone's definition of a broad (flat) tq curve is right on this thread. I mis-represented a broad curve that is shifted higher in rpm as peaky. Wrong verbage. At 280+ degrees of duration at .050", most would not call your cam a low end tq monster, but it's obviously flat and broad where it works. It's funny to see that your dyno run starts at close to where others finish!!

Brad;

I run 93 Octane with never a sign of Detonation, but my cam was designed to help bleed down excess cylinder pressure. I occcasionally spay a 175HP NOS shot on the same 93 octane...Of course I run very cold plugs (all the time) and pull out 6 degrees of timing on the juice.

Remember many drag cars have gears, this allows them to operate in a very narrow RPM band, like 8800-9800rpm. In drags they care more about HP and less about TQ....the HP gives them more momentum. The opposite is true in a boat, they need the TQ to get to a given momentum. Too bad the Bravo can't be coupled to a powerglide.;) :rolleyes:

A good buddy of mine has a Natural 360 Ford with a single Dominator that makes more power than my motor. 942HP at 9800 rpm @17.5:1 compression with a much larger cam than mine (over 1" of lift) . Of course he only gets 3 passes on a set of vavlve springs and runs a wicked 120+Octane brew.

Wette Vettes centerline is 112 and about 10 degrees less duration than mine, his CR is 13.2:1

JDNCA1, What boat, prop, pitch, ratio, and WOT mph and rpm do you run? With a TQ curve like that it probably doesn't matter what prop you run. Your hull will have a specific TQ requirement for every mph and as long as you are above the hull requirement you will have acceleration. Tomcat was working on this very idea with his plotter.

Man, this is an interesting thread!
 

Now all we need is Tomcat to chime in and we'll have a party!!

When the time comes to build a wicked NA motor, I'll know who to talk too!

I would guess that your friend's 360 ford is a real example of peaky torque.

That's incredible that you can make that kind of power on 93 octane. Of course it's also easy to forget that you have over 11 liters of displacement!

Nice talking to you.

Cobra;

A 26 Carrera cat, 1.50 ratio with a 30 (non lab bravo) turns 6100 natural at 101mph, 6700 "on the juice" at 109mph.

I turned a 28 labbed bravo 6500 at 98mph on a hot humid day. Acceleration was WICKED with this prop.

Next, will be trying a 30 lab and 32 lab, which I think might be the fastest.