Engine Need Some Serious Help Guys!! Dyno Results Are Pathetic!

Discussion in '1994 - 1995 Specific Tech' started by N8sGT, May 6, 2012.

  1. N8sGT

    N8sGT New Member

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    The dyno showed a total drop in power at 4000rpms on up. I've heard of valves floating but at higher rpms.
     
    #21
  2. Venom351R

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    You would think that with a set of heads that were set up with that kind of port work done to them they would have the proper valve springs in them. I would not think that valve float would happen at 4,000 unless the springs are just crap
     
    #22
  3. Noobz347

    Noobz347 Stangnet Facilities Maint Tech... Er... Janitor
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    Spring rate and adjustment are two things that come to mind. More common on blown apps at lower rpm but not unheard of on N/A apps.

    Have you verified that the pushrods are the correct length?
     
    #23
  4. N8sGT

    N8sGT New Member

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    Yes, I'm using 6.4" pushrods. I called the company that made the heads and told them my rocker size and they gave me the length. After install I did a valve check and the roller is riding perfectly on the middle of the valve tip.
     
    #24
  5. Noobz347

    Noobz347 Stangnet Facilities Maint Tech... Er... Janitor
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    Please excuse my multi-posting... Work network is seriously FUBAR for some reason.
     
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  6. chaos254

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    If you plan on going with a supercharger or Turbo, why swap the heads? It runs like crap now because you need bigger injectors, maf, custom cam and a tune.

    Sent from my ADR6425LVW using Tapatalk 2
     
    #26
  7. N8sGT

    N8sGT New Member

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    Not really sure when I'll be putting on the charger. I really don't wanna drive around for the next 6 months or so with an awesome sounding 176hp stang... LOL. Just can't do it. I'm putting on the gt40 heads on sat and I think I have the heads sold already so thats a plus.
     
    #27
  8. N8sGT

    N8sGT New Member

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    I have been looking for a cowl induction hood for about a month on CL thats going to clear the intake. I found one the other day and drove the 8 hrs round trip to pick it up, I also picked up a saleen front bumper and 24# injectors. It was worth the drive as I got all 3 for a GREAT price. My friend is doing the body work on the hood and bumper right now and should have it painted for me in the next few days. Here is a pic of the last mustang we painted. It wa a '90 fox. Bought it for $500 (yes it ran pretty good but the body was beat up). I didn't do anything to the engine minus a bbk cai. We painted it Candy Apple Red with an Orange Diamond Pearl. Came out pretty good.
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  9. revhead347

    revhead347 I have face herpes.

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    The valves aren't floating. You can scratch that idea. Stock valve springs don't float at 4000 rpms on a b cam.

    Kurt
     
    #29
  10. N8sGT

    N8sGT New Member

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    I just sent to heads out to have decked and checked. Should have them back tomorrow. I think I'm gonna put on a set of 1.7 rockers and sell the 1.72. What's your guys opinion on that. Is there much difference between them both. I'm preety sure i can use the stock pushrods on the 1.7s but won't know until its on. Thanks for all the insight and help in everything guys...its much appreciated.
     
    #30
  11. revhead347

    revhead347 I have face herpes.

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    Most rockers advertised as 1.7s are actually 1.72s. You will see no difference between the two. Pushrod length has to do with the height of the top of the valve. It has nothing to do with rocker ratio. The distance between the top of the valve and the top of the lifter varies with a whole bunch of things; block deckheight, head milling, valve installation. etc. Most likely the heads were not originally machined to have 2.08" valves. The heads were remachined for that valve, which caused the valve to be raised up inside the cylinder head. With a set of heads like that, or really any aftermarket head, the valve geometry has to be figured out with a pushrod measuring tool, and then you buy pushrods with the correct length.

    Kurt
     
    #31
  12. Venom351R

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    You will also need a solid lifter or a hydraulic lifter that has been welded. You cant allow the plunging effect of the lifter to come into play when checking for pushrod length.
     
    #32
  13. N8sGT

    N8sGT New Member

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    Isn't that why you always check them with the lifters pumped up? I always thought you primed the engine and made sure all lifters full and then checked push rod length. I like the idea of a solid or welded lifter.. lots easier.
     
    #33
  14. revhead347

    revhead347 I have face herpes.

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    I've always done it with a hydraulic lifter. That's the way my engine builder does it. Just soak the lifter in oil for at least 24 hours so that it's full of oil, and all the air leaks out.

    Kurt
     
    #34
  15. N8sGT

    N8sGT New Member

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    Sorry its been awhile guys but i finally got the stang running sweet! Swapped out the heads with a fresh set of GT40 cobra heads, and also installed a new Walbro 255 fuel pump, with a bbk fuel pressure regulator and 24# injectors. I bumped the pressure up to 45psi and took her out for a cruise. Lets just say I'm finally running on full hp now. Car burns all of 1st all of 2nd and finally hooks up somewhat in 3rd gear. I'm finally hapy with the setup and wish i could put it on the dyno now and see what it pushing. Looking to get just a few most bolt on mods for her and then i'm done for a lil bit.... well until the wife gives me the ok to boost it. :) Thanks for all ur guys help!!!!!!!!!
     
    #35
  16. Venom351R

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    Thats awesome glad you got it all sorted out and and are now happy with it. Also another thing that may help you out power wise is getting rid of all those bends going to the intake. Do a fox TB swap, you will thank me later.
     
    #36
  17. N8sGT

    N8sGT New Member

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    Ur right about those bents, deff. a crappy design. lol
     
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  18. Noobz347

    Noobz347 Stangnet Facilities Maint Tech... Er... Janitor
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    Nice! :nice: So you figure it was the other set of heads that was the issue?
     
    #38
  19. N8sGT

    N8sGT New Member

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    Honestly I think it was a combo of things. I was only pushing out 25psi of fuel pressure before the fuel pump went out. After I replaced the heads it ran alot better but i knew it still wasn't running right. I installed a fluid filled fuel pressure gauge on the rail and come to find out about 20 mins of driving the fuel pressure would drop from 32psi to about 25, an hour later it would drop to about 10psi and not run. I replaced the pump with the walbro 255. that brought the pressure back up to 35psi and about 43 with out the vacuum off. I then bought the BBK adjustable regulator for it and bumped it up to 45psi with the vacuum on. Car is running really really good now, so I'm happy.
     
    #39
  20. rj95svt

    rj95svt Member

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    i wish i would have seen this thread before you sold those heads. Those heads although big would have been fine with a stock cam or a custom cam. a b303 cam is a big time mismatch with those heads on a stock bottom end. you may still need a tune with your current setup. ever see a boss 302 engine? They had huge heads (351 cleveland 4v heads) on a 302 ci engine. they also had more compression which helps with large headed small ci engines.
     
    #40

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