Is that the stage 3 truck cam or regular stage 3? I'm in the middle of an 84 c10 build with a btr stage 3 truck cam.

 

If he had an exhaust or intake restriction it would usually show up as downward sloping torque nearing redline, and the power would "cap" off. The torque is just as high at 2500 as it is nearing redline so we can clearly see that the cylinder is just as full at 2500 as it is nearing redline.

 

no the regular stage 3. I do have dyno info for a 6.0/243 head with BTR stage 4 truck if you want to see them

 

Power actually does cap off. The torque never climbs from about 2500 rpm onward. Horsepower and torque are a relation of one another and the only reason his horsepower increased from 2500 rpm onward is the fact he spun it up farther and the hp climbed because of the rpm climb.

Again I think he's lacking some airflow. Lets do some math. A single 3" ID pipe has 7.065 sq inches of area in any one part of the system. A dual 2.5" ID system would have 9.8125 sq inches of area in any cross section of the exhaust. Dual 3s would give you 14.13 sq inches of area. A single 4 would give you 12.56 sq inches of area, and a single 3.5" would give you 9.61625 sq inches of area.

He should be running dual 2.5"s at the minimum or a single 3.5" (assuming 500 flywheel HP is the goal) given the size of the cam and how far up the RPM band he has moved the torque curve.

Other than the package being alittle oversized the motor seems healthy.
Personally if it were my truck and being it has a set of long tubes on it already I'd be asking the dyno guy if I could drop the exhaust at the header collectors and do a pull with open headers to confirm what I am thinking before I would purchase another part.

 

that would be awesome. Pm it to me if you like. Thanks man.

 

 

What makes you think the compression is low if the leak down came back AOK? What you see on a compression gauge is going to be affected by the overlap on the camshaft. IE a high mileage stock motor could very possibly show more compression on a compression tester, so I wouldn't put alot of stock in that. I'd rely on the leakdown results.

 

Lots of people make that kind of power with single 3" pipe, even my car made 430ft-lbs with a 3" Y-pipe. The exhaust diameter is not the problem IMO.

Checking the cam might be a good idea. I don't think it's "wrong" for the combo and I don't think it's that far off or else you probably would have bent some valves by now, but if you didn't degree it then it could be off. That's all there is to degreeing a cam, you're just checking to make sure it's installed correctly in relation to TDC.

 

That was what I meant in an earlier post. I made that mistake myself. But if you have a good merge, it is not the problem at your power level - like KCS said.

 

In for info. I doubt it's the cam. That cam looks really good for the setup. My build is 1996 c1500 SBE ls1, Frankenstein 243's, BTR Stage 2 LS3 225/238 ( really good deal on it local, planned on the stage 2-3 for ls1/2) and possibly hi ram as well. Good luck finding issue

 

you are looking for something that would affect cylinder fill across the board, but especially at 2500rpm. Thats the best way to look at this.

Could be:
-poor timing, low compression, injector tuning (injector phase)
-too high of octane fuel (you didnt use 116 did you...)
-Very hot, dyno IAT & low O2 conc. (was the engine sitting, running for a long time, esp. in an enclosed area, before the dyno pass, or at high altitude)
-dragging brakes (try pushing the vehicle by hand)
-poor converter performance / improper converter application
-unusually heavy drivetrain parts (are any of the drivetrain parts far more heavy than original, i.e. wheels, tires, driveshaft, transmission swaps (4l80e), etc..)
-Power robbing accessories like A/C compressor or smog pump dragging
-poor ignition performance (unlikely but, worth mentioning) it would have to be poor in every cylinder though, which is global and points to improper plug/pluggap/coil/wires or a mismatched head/cylinder shape causing poor distribution of fuel.


Stuff it probably isnt:
-air filter/air filter tube
-cam
-exhaust related
-head flow (unless some machining were done to the head that screwed them all up somehow)

cam theory:
If the cam were installed too far retarded the torque should be low to begin with. And the reverse if it were too advanced. The torque however fills the center like it should makes me think good cam degree in play. Low torque at 2500rpm could be **** cylinder fill from too much overlap and too large of header primary; which would correct itself and rise after around 5000rpm, which this dyno chart does not do, it has a good cylinder fill at 2500 which points to a well mated overlap/exhaust tube.


The way I would do this is compare torque from the same size engine with the same transmission. Find out where you WANT to be, what is the difference? Do most engines make 50 ft*lbs more? Then strike all the things off that list that wouldn't fill the difference, whatever is left is the next thing you check.

Judging by how good the curve is I want to say it was just a poor set of running conditions. I dont know how much torque is missing though so its just a guess. If you can, get the engine oil nice and hot, 200*F+ then let the whole engine/truck cool off completely so that the intake manifold is ambient temp again, the cylinder heads are almost cool to the touch. The oil will still be hot though. Restart the engine, give it a moment to thin the oil out again then make the dyno pass that way with the cooler parts and cooler underhood temps. I bet it would read 20+ higher. But that might not be enough for you.

 

 

116 has lead and despite needing that octane for nitrous; it’s hurting power N/A
Leaded octane slows down flame propagation

 

Ah there is the global

Truly 87 octane gasoline has the most energy per unit weight of what we find common at stations. There is such thing as 0-octane "n-heptane" and I feel that examining the structures them selves (100-octane is 2,2,4 trimethylpentane) will yield some insight how they got those octane ratings. If you have some chemistry background