Dyno results 1971 Fury III 360

[Bart]

So, I have not posted in awhile, but thought this might be of interest to you small block guys, and C body enthusiasts in general. I was able to get on a chassis dyno on Saturday. This is my junkyard 360 build from about 1.5 years ago. I had most of the parts laying around the shop, and just slapped them together. I initially went with a Performer intake, but found my Weiand Stealth far superior. This engine is running 8.8:1 compression, has heads from a 1986 truck that have been mildly worked in the bowls and had the runners cleaned up, but only has a single angle valve job. I am running a Comp Cams 268AH-10 cam 268/276 with .462 lift. I used the original pistons with moly rings, double roller chain, and a Mopar windage tray. It has a stock jetted Holley 600, Dakota truck headers (almost a drop-in), 2.25" dual exhaust with H-pipe, 2200-2400 stall converter and 3.55 open gears. I also recently converted to a Mopar Performance electronic ignition system. WHAT YOU NEED TO KNOW ABOUT THE DYNO RESULTS: I live at 4000-5000ft elevation, which robs me of about 25% of my torque and horsepower output; with my 727, I am probably losing 100hp/tq from the crankshaft to the wheels; I drop off severely around 4500rpm, which I think is because of the valve job (?); and, judging by the smoke as my engine winds down, I need to jet down a little. To give some perspective, the guy ahead of me had a 500 inch big block, and made 280hp. I hope this helps some people who are considering small block builds.

 

[Turboomni]

What kind of torque did the 500 inch big block make?
Nice job and your car looks good!

 

[1978 NYB]

Respectable results at that altitude.

Take her down to near sea level and have some fun with her.

 

[Bart]

What kind of torque did the 500 inch big block make?
Nice job and your car looks good!

I didn't see the torque figures. Sorry.

 

[CBODY67]

If the Holley has "stock jetting", it's definitely rich at your altitude.

Along about 1969, CAR LIFE magazine came out with some correction factors for power and 1/4 mile ET and speed. Hot Rod Magazine did a dyno test series on a Chrysler 383 about that same time. Using the dyno results for the (initially) stock and "build tight for longevity" motor, I determined that a 727 and the related drivetrain would absorb right at 15% of crankshaft power before it got to where the rubber contacted the roadway. The 904 family is supposed to absorb less power.

Not sure about related percentage of power loss due to altitude. Seems like the factory recommendation for extended "altitude" use is .001" jet reduction per 1000 feet of altitude? You might also get a little more throttle response with another 2.5 degrees of initial timing

Sounds like a decent engine combination. How did the Stealth intake work better than the Edelbrock? Just curious.

CBODY67

 

[fury fan]

I doubt you are losing 100hp thru the trans and drivetrain, esp if only getting to 4500 rpm. I say that as a former test engineer for an OEM transmission manufacturer. We periodically did spin-loss testing, and although the transmissions were much newer and more efficient, they also had 2x the capacity of a 'typical' TF, so much beefier parts. I don't remember the numbers exactly, but they were less than 50hp, so I would assume a TF to be similar. U-joint losses are pretty small, and I doubt the rearend is 50. Just my opinion.

 

[Bart]

I doubt you are losing 100hp thru the trans and drivetrain, esp if only getting to 4500 rpm. I say that as a former test engineer for an OEM transmission manufacturer. We periodically did spin-loss testing, and although the transmissions were much newer and more efficient, they also had 2x the capacity of a 'typical' TF, so much beefier parts. I don't remember the numbers exactly, but they were less than 50hp, so I would assume a TF to be similar. U-joint losses are pretty small, and I doubt the rearend is 50. Just my opinion.

I was just going off what the Dyno operator, and a guy with a local performance shop was telling me. Thanks for the info. I have read several times, the loss was 40-50 just through the TF, so that falls in line with what you are saying on that. I don't want to over-state what I have, so anyone with good experience/data is welcome!

 

[Bart]

If the Holley has "stock jetting", it's definitely rich at your altitude.

Along about 1969, CAR LIFE magazine came out with some correction factors for power and 1/4 mile ET and speed. Hot Rod Magazine did a dyno test series on a Chrysler 383 about that same time. Using the dyno results for the (initially) stock and "build tight for longevity" motor, I determined that a 727 and the related drivetrain would absorb right at 15% of crankshaft power before it got to where the rubber contacted the roadway. The 904 family is supposed to absorb less power.

Not sure about related percentage of power loss due to altitude. Seems like the factory recommendation for extended "altitude" use is .001" jet reduction per 1000 feet of altitude? You might also get a little more throttle response with another 2.5 degrees of initial timing

Sounds like a decent engine combination. How did the Stealth intake work better than the Edelbrock? Just curious.

CBODY67

Thanks for the input! Again, I was just repeating what the dyno operator and some other local, knowledgeable guys on site were saying. I know I need to step down the jets a couple sizes. I am running about 34 degrees advance right now, but have not taken the time to tune the vacuum advance, yet, either. I have a set of J heads I might get going to try out. It is my daily, so I have to have the time off to do without it before I can start!

I also have a 9.25:1 .030 360 in my truck with an XE 262 cam and 1974 truck heads with 2.02/1.60 Manley valves and a multi- angle valve job. I might just swap that in and see what happens...

 

[Bart]

Oh, as far as the Performer vs. Stealth intake; I did not dyno it, but just that swap increased the seat-of-the-pants performance immensely. I recommend it to anyone looking to get more out of their vehicles. The headers and torque converter were the two things that made the most difference, in my opinion.

 

[Bart]

Ok guys, did some research on HP loss at altitude, and loss at rear wheels. Comparing several articles, and finding a formula for elevation, you lose about 12.9hp for each 100 horses at this altitude. That is around 40-50 hp. Pretty close to 25% of the 207 I showed on the chassis dyno. The articles I found about rear wheel loss ( using comparably aged vehicles with older style transmission) showed an average loss of 36% at the wheels through an automatic and a Ford 9" rear with 3.50 gears.

That puts me in the 350hp range, not the 380hp range.

 

[Mopar Madness]

No Comment .

 

[fury fan]

No Comment .

Meaning???