Dyno'd my stang

Discussion in '1974 - 1978 Mustang II Talk & Tech' started by Eos, Jan 25, 2004.


  1. Eos

    Eos Oh Heather Oh yeah... I want your pink taco

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    I dyno'd my stang today. The hp was like OUCH....142hp at about 3400 rpm's the torque was good at 240 at 2800 rpm's For some reason though it just dropped quick after 3500 rpm's. I'm guessing the engine I got was rebuilt to 79 5.0 specs :nonono: It had close numbers with that original engine. We are sure the problem is the stock exaust manifolds, the car cant breath and the cam is crappy. I was pretty disapointed. I was hoping for 200 hp. But atleast now I have a base and I have an idea of what I need to do first. I need headers!!! What can I get with a 5 speed tranny? :shrug:
    #1
  2. Power Surge

    Power Surge Founding Member

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    Megan, get me some info on your dyno session. What gear was the pull made in? Did you get air/fuel readings? What brand dyno was it? Can you send me a scan of the graph? I do dyno tuning for a living and can help shed some light on your dyno session. :nice:
    #2
  3. 77sleeper

    77sleeper GO BUCS! Founding Member

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    I would wage it is a stock heads and cam that did you in
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  4. 77CobraII

    77CobraII I gave 77sleeper my rear end for free!

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  5. Addicted_2_II

    Addicted_2_II New Member

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    Don't most specs come off the crankshaft? So 140 HP at the rear wheels may be 200HP at the crank? I know there is an equation somewhere to determine the drivetrain loss but I can not find it right now!
    Chad
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  6. danimaltheanima

    danimaltheanima New Member

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    Hp

    Geez Meg sorry to hear about your lack of power on your mustang. I would have loved to of seen your face when you found out that you were only pushing 142hp at the wheel. Its not the end of the world though. At least you have a MII and apreciate it, and give it the respect it diserves. Sounds like you have plenty to do in the future though. That will keep yuh busy.

    Dan
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  7. Eos

    Eos Oh Heather Oh yeah... I want your pink taco

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    the guy said there wasnt anything wrong with my air/fuel. I'm starting to figure out all about the heads cam, ect....We did the dyno in 3rd gear because it was pulling higher numbers and was just dropping off in 4th. Someone in my mustang club was going to sale me some 87-95 GT heads for 20 dollars hes a friend of mine and he said theres nothing wrong with them, i think i'll take them.
    #7
  8. 77sleeper

    77sleeper GO BUCS! Founding Member

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    e7s do flow better than c8s but not dramatically i would guess no more than 20hp
    #8
  9. 78CobraII

    78CobraII Moderator

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    Usually a '73-'76 302 will make about 200 HP with flattop pistons, mild cam, small 4bbl carb and intake, headers, and grinding off the EGR bumps in the exhaust ports. I've seen one make 195 HP. Chassis dyno's measure HP at the rear wheels, but I've heard that you could get a decent approximation of flywheel HP (with a C4 trans) by adding 20%.

    The larger combustion chamber '77 - '79 heads probably give up a half-point of compression so will make less HP, but I wouldn't think it would be 40 HP. Its probably your heads, exhaust manifolds and maybe pipes/mufflers choking off flow past 3400.

    78CobraII
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  10. Eos

    Eos Oh Heather Oh yeah... I want your pink taco

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    yeah thats pretty much it 78cobraII
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  11. Northern J II

    Northern J II New Member

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    I saw a dyno sheet on a 66 Mustang Shelby GT350 "300 hp 289" that only laid down 125 rwhp, so a mild 302 at 140rwhp sounds normal. :shrug: Nothing a 100 hp shot of nitrous won't fix, ask me how I know :D :rlaugh:
    #11
  12. Thinkkker

    Thinkkker Founding Member

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    do heads, headers and full exhaust.....

    That should net you some, for the $20 on the E7s if they are ready to bolt on, do it.

    All in all for that year build on the motor, Im not to surprised. If you get the heads and such done, what is the cam spec? You can prolly get a cheap crane or something and drop it in and add a few more ponies on top.

    Been awhile since Ive been around guys, hows it going? So I dont remember your specs real well.
    #12
  13. zwhitr

    zwhitr Founding Member

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    200 Thats it ---Is that at the wheels

    Desktop dyno may be alittle inflated but it shows closer to the 300-350 range

    I would expect alot more especially with the headers,cam and alittle porting the 4 BB is alwaysa must but shy of a breath of fresh N20 whats left?
    #13
  14. jeffnoel

    jeffnoel Founding Member

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    My little Mustang book shows a stock 77-78 II with the 302-2v is factory rated at 139HP @ 3900rpm. I don't know how many miles you have fastmustangII but sounds like you have a good base to build from.
    #14
  15. Eos

    Eos Oh Heather Oh yeah... I want your pink taco

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    I would never put nos on my car its the easy way out
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  16. Eos

    Eos Oh Heather Oh yeah... I want your pink taco

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    Motor was just rebuilt in october
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  17. Northern J II

    Northern J II New Member

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    I am building my way up to having the Edelbrock Performer engine:

    Gottem:Cam, chain, intake, carb, fuel pump, nitrous kit

    Needem: cyl heads.

    Edelbrock gets a dyno proven 300hp at the crank (without the nitrous kit)
    Think of nitrous as a poor-man cyl heads or blower :D

    Nice thing about nitrous you can have a 300hp totaly drivable car and flick the switch for an extra 100hp and run with the too deeply geared, over cammed race cars at the track. When your finished putting the purest on the trailor (litterally) un-arm the nitrous kit a cruise the burger stand!
    Cars are ment to be driven! I could put in a radical cam a loose convertor 4.56 gears and run similar times as the big dawgs. Or run nitrous, a mild stall, small cam and 3.55 gears and drive it all summer long ADVANTAGE Nitrous.

    P.S Nitrous does not blow up cars, it's a chemical way of forcing more air into the pump. (like any other performance modification done to an engine) :D
    #17
  18. 78CobraII

    78CobraII Moderator

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    Correct, its not the nitrous that blows up the engine...its the lean condition that occurs when additional oxidizer (nitrous) is introduced to a fixed amount of fuel. Lean combustion = detonation = damaged pistons, burned valves, and blown head gaskets.

    Any nitrous kit that you install has to compensate for the changed oxidizer/fuel ratio with more fuel or damage will occur. The nice thing about a good EFI system is that it will read the oxygen in the exhaust and attempt to adjust the fuel to correct the ratio (within its capabilities). Carbs are too dumb to do that without help (i.e. additional fuel delivered with the nitrous). I would think that a 100hp hit of nitrous would require more fuel.

    78CobraII
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  19. Joeverb

    Joeverb Founding Member

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    Oh no question about it. The carb systems have a dual spraybar and 2 solenoids one for N2O and one for fuel. You actually have to split your fuel line and connect one end to the solenoid to get your extra fuel. I think the cheat for not shooting extra fuel is well below 50 hp and is still not a good idea. At best a lean out on an N2O pass will pop your head gaskets.

    I believe NOS used to make a kit called a sneaky pete that didnt require extra fuel. If i recall right it claimed a 25 hp increase???
    #19
  20. Power Surge

    Power Surge Founding Member

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    EFI cars need fuel enrichment just like carb setups. The O2s are not read at WOT, so the PCM cannot adjust for it itself. Dry EFI kits raise fuel pressure and force extra fuel past the injectors. Wet EFI kits take fuel from the rails and put it in with the nozzle along with the nitrous.

    The biggest mistake people make is running their nitrous systems too lean. Many people are under the common misconception that nitrous adds power. Nitrous does not add power. The FUEL is what adds the power. The nitrous is just extra oxygen. You need the fuel there too. Many people "lean" their nitrous systems under the impression that it will make more power. THAT'S where the mistakes and damage come from. Of course nitrous IS harder on parts than boost, so it should be used on a healthy motor. It's also important to have larger ring gaps with nitrous.

    I'm an NX master distributor, and we do a lot of EFI nitrous stuff. Our 10 second Lightning runs quite a bit of the spray :D .
    #20

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