I was just reading godsends dyno #'s out of his 468 that is similar (different intake and EFI, different brand heads with similar port CCs) and I had to scratch my head. I know dyno numbers can vary, but I was still a little shocked.

I made like 555 ft-lbs and 563hp (4400 and 6000-6200), granted it was through my full exhaust and with my alternator and water pump, but.. I'm not going to change anything I just want you guys to look at my parts and see what the story is?

dart 320cc runner rectangles (116.5cc (milled))
crower roller rockers
stud girdle
GM 4.00 stroke forged crank
lunati titanium retainers, nice locks, decent pushrods
isky red zone (or is it red line?) roller lifters
comp 933 springs (I think a little light, but builder said they are ok for my rpm range)
comp SR (CR lift rule lobes) 287/291 256/260 .643 112
performer rpm
holley 4779 (750) DP with 4776 (850) baseplate 72/78 jets, milled choke horn
462 (+.032 454)
eagle 6.385 rods
SRP 10.14:1
93 octane pump gas
exits through (too large) 2" primary hooker super comps, to an x-pipe (jury is still out on the sound) 3" pipes with 20" case dynomax hemi super turbos (no HP loss compared to a tiny set of spin techs on the dyno) and full tailpipes.

His cam and mine are pretty similar, his intake is different, and he has efi but I watched my carb be tuned on the dyno for a few hours and I am pretty confident is is running about as well as a carb can, keeping a pretty steady a/f ratio at most times. I don't plan on changing anything, but I am sort of confused why he has 100+ hp more out of what I would call a "similar" combo that is operating at similar rpm ranges?


matt

Matt ... I noticed that too ...not to get into a discussion on dyno's and there operators but you may find this article interesting ..bottom of first paragraph
http://www.stahlheaders.com/Lit_measurement_1.htm
FWIW Bill

I thought you made 563 with the HR.
UDH claims over 600 with his similar SR.
You might ask UDHarold about the CR rule cam. Not sure what they do for that.

Just a few guesses at your combo..
CR a little low for AL. heads and that cam.
Carb a little small for combo.. It's not a 950HP which flows similar to yours. So not sure on the fuel curve.
Since he has EFI, he probably has a single plane intake.
Don't recall the flow comparison on Canfields vs 320's out of the box.

These are enough differences to account for a portion of the 100. Probably some dyno & or conversion math too...
None SAE correction factors used etc...

Just read the Stahl link... who knows now. :(

If it's a Mustang Dyno then it will be a conservative number.I heard the reason why is due to the fact that Mustang dynos factor in wind drag and other "real world" variables that others don't.The local shop near me has one and I know guys that have dyno'd anywhere from 30-80hp less than what they Dyno'd on a Dynojet brand dyno they've used down in Dallas.

I've never heard anything good about box stock BBC Dart heads. I also think (as I've stated before in email) that your cam is TOO big given your compression ratio. What little cylinder pressure you have is being bled off in a hurry by that cam. Don't feel too bad, for the intended use of your car it will be more than adequate as 550HP is nothing to sneeze at. Afterall, mine only makes ~460 at the wheels, so your's should be about the same ;)

Thanks for the replies guys. I'll check out the stahl article when I have some time later tonight. The hydraulic roller made more hp-- 570-- with a 1" spacer. but this was on a dyno with a velocity stack, dyno headers, no accessories, so on and so forth.
The current dyno session (not a chassis dyno) was done with my carb in a room with 88* temp, with the air filter on, with my headers, my exhaust, my mufflers and 10" tailpipes (not mine) 180* water temp. I think that must account for something.
Ken I had thought about you cam vs mine. I actually asked my engine builder to use that same cam numerous times but he kept giving me reasons not to. I know UD harold said his 287/295 has never made less than 625 on a dyno in a 468, but dyn's do vary. My 1st choice was the UD grind, 2nd was the XR286R, but I ended up with the seleciton of the cam shop.
The thing that gets me Ken is that the advertised (.015 for you, .020 for me, I have .018/.016 lash) numbers really aren't that different. 286/292 (I think) for the XR286R and 287/291 for me. The only real difference is the .050 numbers, which mine are quite a bit bigger, but the .200 numbers yours are a tad bigger.
My dart 320's are used, I bought the used set from the engine builder when the engine was first built.
I am thinking of doing a chassis dyno run with the stock everyday converter in because the cam swap shop said that that converter would give the most accurate readings, versus my pretty slushy converter.
I don't plan on changing anything, the car only goes to the track like 4x a year, and gets a few thousand miles on it a year. The only thing I don't like is how the engine feels like it "kicks in" at 2k when the old cam didn't do that. hopefully whenI get my converter back that effect will not be so prevalent.
I wish I had some way of knowing how accurate the dyno reading (like how it was set up) for my 1st build, with the UD HR4, which made a bucket more torque than the "eqivalent" comp HR. UD was going through its transition to lunati when I was trying to get a cam, and it didn't work out.

ok-- back to work!
matt

Great article from Jerre Stahl - his knowledge comes from his hard won experience that started before there were any musclecars.

Beyond the obvious is that results from different dynos in different locations will differ, not to mention the varience of different pulls made on the same dyno.

This is why we race cars, not dynos (except for the Engine Masters Challenge!). The bottom line will still always come down to your 1/4 time/mph slip.

More is at play than just the list of horsepower creating ingredients that you mix into a particular engine build up. It matters how it is mixed, and how well all the parts complement each other (or not).

I look at engine building this way: 1) Cylinder heads are the gateway to horsepower and one of the better ways to spend your time and money. 2) The camshaft is the brains of the engine - what exactly would you like it to tell the horsepower and torque departments? 3) Compression ties it all together - it enables the brains and the gateway to be used most efficiently if everything is well chosen.

I'm never really to sure how to respond after hearing how someone built an engine "almost exactly" like another engine, yet the results are not even in the same neighborhood. Usually always that means that at least one of the components was not complimentary to the others. Take a look at where you are "different" and you will surely find the missing power. You will need actual cylinder head flow data to fairly compare two similar engines that make dramatically different power.

Good luck, there are some excellent ideas in the other replies.

Thomas