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  #1  
Old 09-06-2003, 03:41 PM
NavyNorm NavyNorm is offline
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Default bad? dyno results

Hey guys,
got a 70 challenger with a 440 4-speed manual tranny and 8 3/4 rear end....3.23 gears. The only work done to it is headers and exhaust and supposedly some mystery cam (all I know is that it's a mopar performance camshaft) I couldn't find any info on this cam with the paperwork from the guy I purchased the car from so I can't even be certain there is an aftermarket cam. anyways I took this car to the dyno and was fairly dissapointed with the results. My peak HP of 266HP@4500RPM and Torque peaked at 355@3300RPM now this seemed rather low to me and I was wondering if anyone agrees...I've been in quite a few cars with around this much horsepower and I know my car feels quite a bit stronger than these.
Can anyone give me any suggestions on why the numbers would seem so far off? I was thinking it might be what gear he dyno'd the car in?
sorry this post is so long but this has been bugging me all weekend.
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  #2  
Old 09-06-2003, 04:00 PM
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23T 23T is offline
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Chassis dyno? If so not too bad a numbers lots of things affect #'s on a chassis dyno. It shows what you are putting to the ground

Like has been said before a dyno is a tool, If you are happy with the performance of the car be glad, If you want a dyno sheet to whip out to compare and brag about go back and have your man puff one up
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  #3  
Old 09-06-2003, 04:42 PM
Maxwedge Maxwedge is offline
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There are alot more things to consider outside of the cam. I have heard as much as 50-75 hp to be gained on a chassis dyno for a fairly mild street rod.
Everything adds up, a few questionable pushrods, a carb that isnt giving you everything or a rear pinion that isnt set perfectly.
Is your igntion perfect? Is the intake manifold port matched? Do the heads themselves have good casting quality and well shaped ports? Those things alone can cost you 30-50 alone and be undetactable if you dont open up the engine.
just something to consider
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  #4  
Old 09-06-2003, 07:02 PM
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ehostler ehostler is offline
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Proper phasing and advance of the distributor is good for 20 hp.
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  #5  
Old 09-07-2003, 12:06 PM
MitchB MitchB is offline
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Default Re: bad? dyno results

You can figure you have roughly 330 crankshaft horsepower and 440 lb-ft of torque. Aside from your tune, your results depend, in part, on what kind of dynomometer used, what correction factors used, ambient conditions...

Mitch

Hey guys,
got a 70 challenger with a 440 4-speed manual tranny and 8 3/4 rear end....3.23 gears. The only work done to it is headers and exhaust and supposedly some mystery cam (all I know is that it's a mopar performance camshaft) I couldn't find any info on this cam with the paperwork from the guy I purchased the car from so I can't even be certain there is an aftermarket cam. anyways I took this car to the dyno and was fairly dissapointed with the results. My peak HP of 266HP@4500RPM and Torque peaked at 355@3300RPM now this seemed rather low to me and I was wondering if anyone agrees...I've been in quite a few cars with around this much horsepower and I know my car feels quite a bit stronger than these.
Can anyone give me any suggestions on why the numbers would seem so far off? I was thinking it might be what gear he dyno'd the car in?
sorry this post is so long but this has been bugging me all weekend.
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  #6  
Old 09-08-2003, 10:42 AM
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biggerhammer biggerhammer is offline
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Default dyno

don't forget, dodges like it when it is cool. next time you dyno, let it sit a couple hours prior to dyno-ing it will improve the readings. it made a difference of almost 10 horses when I did my ram, just letting it sit for 30 min. after the first pull, but bear in mind most dyno operators go by time on the unit, so go when he is real slow in business and most likely will let it sit a while.
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  #7  
Old 09-08-2003, 11:48 PM
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Rear gear is a direct effect on engine torque. Those look like fairly good numbers for a 33 year old engine thats bascilly stock. What kind of numbers were you looking for? As mentioed before some tuning will get you to near 300 horses at the rear tires. And maybe bump your torque up near 400 ft/lbs. Do some tuning with basic add on's like cam intake and carb, add a 3.91 gear and watch how the tires will go up in such smoke with such little effort. Seems you have a good running engine there.
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  #8  
Old 09-09-2003, 05:58 PM
NavyNorm NavyNorm is offline
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Thanks for the help guys,
maybe I was looking for an unreasonable amount at the rear wheels...I was thinking I could get like 350RWHP and near 450 torquue...after listening to you guys I might have been expecting to much from the stock engine. I guess it's because I had just watched my buddies 02 lightning pull 400HP and 500 ft-lbs then again he's got 14psi and a brand new engine. I did find out that I have a pretty bad slipping clutch so I'm sure that cost me...well I'll keep you guys up to date on the mods I make...wheels and tires next. Oh I can almost keep up with my buddies lightning so I don't feel too bad.
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  #9  
Old 09-09-2003, 06:55 PM
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ehostler ehostler is offline
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The thing is, you were expecting to see the big number that most of us talk about. Those big numbers are taken at the flywheel.

An engine dyno will show a lot more power than a wheel/chasis dyno.
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  #10  
Old 09-10-2003, 05:09 AM
DartGT66 DartGT66 is offline
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With a manual it's very easy to find the drivelines power consumption, at least the wheel dynos I know have the propierty that they can turn the wheels and measure how much power it takes. I think that the numbers are decent for a slightly hopped up rebuilt 440; that's about what they should put out. It's a pretty mild combo looking at the peak hp and peak torque rpm. Typically a stock 426 Hemi makes a little over 300 rwhp; many think the hemi was underrated hp wise and the 440 magnum was overrated. Different dynos also may produce very much different results, and usually the easiest method of picking up horsepower is taking the car to a "good" dyno. I have not done a lot of dynotweaking, but at best we have picked up 60 hp tuning the engine in the dyno and for the two last times we couldn't pick anything. Still it was worthwhile to see that everything was up to par. 500 hp from the rear wheels is a very very good number and rarely seen.
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  #11  
Old 09-10-2003, 10:19 AM
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cuda66273 cuda66273 is offline
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Here's a few Saturday afternoon things you can do to pick it up some:

1. 70? does it still have a points distributor? Loose it and get a distributor that's phased and curved to your engine with all mechanical advance.

2. You can swap out the stock rocker arms for a set of 1.6 ratio on the intakes.

3. Look at the manifold you can probably run bigger plenum volume.

4. A Demon 750 and good fuel delivery would probably whip you up a bunch of pony's.

5. If you want to get deeper into it, yank the heads and install a set of Cometic MLS gaskets at .025, that'll put about .5 more compression in it.

6. While you've got the heads off touch up the ports, polish the combustion chambers, gasket match the manifold and have a valve job done.

Each of these (except the Heads)can be done in a day easily with a low degree of difficulty.
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  #12  
Old 09-11-2003, 03:23 AM
DartGT66 DartGT66 is offline
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Aren't the stock steel shims only .019" thick?
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  #13  
Old 09-11-2003, 09:10 AM
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cuda66273 cuda66273 is offline
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Interesting point....016

And pretty much every Mopar you ever see that has had a head off it now has the .040 Felpro.
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  #14  
Old 09-11-2003, 11:14 PM
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Quote:
Originally posted by NavyNorm
Thanks for the help guys,
maybe I was looking for an unreasonable amount at the rear wheels...I was thinking I could get like 350RWHP and near 450 torquue...after listening to you guys I might have been expecting to much from the stock engine. I guess it's because I had just watched my buddies 02 lightning pull 400HP and 500 ft-lbs then again he's got 14psi and a brand new engine. I did find out that I have a pretty bad slipping clutch so I'm sure that cost me...well I'll keep you guys up to date on the mods I make...wheels and tires next. Oh I can almost keep up with my buddies lightning so I don't feel too bad.
If you clutch is bad that will cost some HP rating, so will the condition of your rear tires and how well they match the dyno drums as far as diameter ( may get flamed for the last part but I've seen the closer the tires are to drum dia the better the reading and no if you dyno with the fake spare it wont give you 1,000,000 hp)
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  #15  
Old 09-12-2003, 03:17 AM
DartGT66 DartGT66 is offline
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I have used almost nothing but the steelshims with iron headed BB's, they come in the MP gasket set.
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