weak motor?

[buffblazer]

well i finally finished the 86 k5. my build thread has some pics of the motor and later i will add the rest and update it with pics of the axles and tires and such, but im stumped about my motor.


now im running a 350 bored out to .40 .60 cant remember what it was. i bought the motor and it came with rebuilt stock heads, then it has a comp cams extreme 4x4 cam, edlebrock performer intake, holley truck advenger carb, MSD off road box, and stock ignition parts other than accel super wires.


then its bolted to an SM465/208 and then it runs through D60's front and rear with 456 gears and 35/12.5 bfgoodrich mud terrian Km2's.


no more emissions at all, so i expected the motor and truck to run pretty dang good with the setup. ya know throw your head into the back of the seat kinda thing.


well i went and had the truck dynoed and at an almost 14.7-1 ratio it only makes 198 ft lbs of torque and 155 HP at the rear wheels.


now i know i have bigger tires but i figured i made up for it with the gearing and also the motor has a few goodies on it.


so what happened? are the heads limiting me that much? what can i do to bring the motor to life? i was hoping for around 250-300 at the rear wheels.

 

[us74k5]

456's and a manual trans, and those are the numbers you got? Man, i feel sorry for you. I am no expert when it comes to those things, but my mildly built 396 with 4:10's and 38" tires and a Turbo 400 was pushing over 400 rwhp.

 

[buffblazer]

i know thats whats got me so stumped, i cant figure out what the hell happened.

 

[80' 427]

First it depends on what kinda dyno it was on. My 660hp camaro made 400 on a mustang and 475 on a dyno jet. My 355 in my k10 made 200 on a mustang. Did you adjust the timing? What about the air fuel at WOT? Dynos are tuning tools, worry about what you got at the start and what you finished with. Plus Whats your elevation? Plus you can adjust the weather correction and make a 100hp motor read 400hp.

 

[WannabeRacing]

Dynos are tuning tools, worry about what you got at the start and what you finished with.

Definite quote of the day. People get lost with numbers. Performance is what matters. And finding power is the only reason we own dynos. Cuz racing pieces of paper really SUCKS!

 

[buffblazer]

First it depends on what kinda dyno it was on. My 660hp camaro made 400 on a mustang and 475 on a dyno jet. My 355 in my k10 made 200 on a mustang. Did you adjust the timing? What about the air fuel at WOT? Dynos are tuning tools, worry about what you got at the start and what you finished with. Plus Whats your elevation? Plus you can adjust the weather correction and make a 100hp motor read 400hp.

they dyno tuned the truck before the test. then they told me they got it to within as a close as they could to 14.7 to 1 air/fuel ratio and then ran the max power numbers.

i belive they adjusted the timing cause they were adjusting the carb also. the elevation at which the truck was tuned was about 5300.

whats the weather correction?

 

[Hogback Fabrication]

456's and a manual trans, and those are the numbers you got?

Gears make no effect on the dyno, they don't affect power at all and torque is compensated based on the gear ratio you have.

 

[80' 427]

they dyno tuned the truck before the test. then they told me they got it to within as a close as they could to 14.7 to 1 air/fuel ratio and then ran the max power numbers.

i belive they adjusted the timing cause they were adjusting the carb also. the elevation at which the truck was tuned was about 5300.

whats the weather correction?

Elevation certainly isn't helping you, horsepower changes with weather (air densisty, humidity etc) you use a correction factor to correct for this. If your happy with how it runs don't worry about the numbers.

 

[WannabeRacing]

14.7 to 1??!!

 

[KansasTwister]

14.7 to 1??!!

ideal air/fuel ratio, 17.7 pounds of air to 1 pound of fuel IIRC.

 

[buffblazer]

ideal air/fuel ratio, 17.7 pounds of air to 1 pound of fuel IIRC.

14.7/1 is the most effecient setup for equal power to fuel usage.

17.7/1 would make me run a little leaner than i would want, actually i should have had them set it up around 12.5-13.5/1 for power cause thats all im really wanting.


i like the way it runs as in smooth throttle but it dont get out of its own way for nothing.