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Discussion Starter · #1 ·
I recently went to the dyno in my 1990 fox, and was a little unimpressed with the results. I thought the horsepower seemed about right, but I'm trying to figure out why it made max power at 5200 rpm. I have an Anderson n41 cam that should put the peak power higher than that. Any advice would be appreciated.

  • Stock bottom end 302
  • Gt40p gasket matched, valve job, (bought used with unknown springs, but claimed they held up to a b cam just fine)
  • 24lb injectors
  • Megasquirt 2 ecu
  • Anderson n41 cam
  • Explorer intake
  • 70mm throttle body
  • 1.6 scorpion rockers
  • Hardened pushrods
  • Cold air intake
  • All other basic bolt on's
 

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I don’t know why you would do a n-41 cam and not invest in a set of springs. A b303 and n41 are a good bit different.

It would’ve been nice if it got pulled a little further into the rpm range. Kind of tough to tell. It looks to drop off, but that might just be from the operator letting out. Maybe they heard valve float on another run.
 

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Discussion Starter · #3 ·
I don’t know why you would do a n-41 cam and not invest in a set of springs. A b303 and n41 are a good bit different.

It would’ve been nice if it got pulled a little further into the rpm range. Kind of tough to tell. It looks to drop off, but that might just be from the operator letting out. Maybe they heard valve float on another run.
Yea I'm kicking myself for that one. This was my first ever engine build, so lesson learned. The current valve springs do have dampeners in them, so I assumed (which I shouldn't have) they were fine. I'm currently looking at the trickflow tfs-2500100 set for the gt40's. Do you think this would fix my problem? Thanks
 

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We put a set of crane 99893-1 on a head suffering valve float under a boosted application. It was on a e303 cam with a turbo and it revs cleanly to 6300 on 17lbs. I like how it turned out. I don’t know if you need that much spring, but I’d rather err on the heavy side.
 

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Yea I'm kicking myself for that one. This was my first ever engine build, so lesson learned. The current valve springs do have dampeners in them, so I assumed (which I shouldn't have) they were fine. I'm currently looking at the trickflow tfs-2500100 set for the gt40's. Do you think this would fix my problem? Thanks
Will it fix the problem? Who knows until you try. It will not hurt anything by putting a better spring package on it. Outside of using one of those valve spring pressure testing tools to see what you actually have, all anyone can do is make a "best guess". And it looks like trying a better spring package is a good guess.
 
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AFM N41: 278/290 - 222/232 - 136/145 - 110* +4* - .512”/.512” w/1.6 rocker

This will work.

 
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Regardless of whether the springs are not keeping the valves from bouncing, isn't that RPM about where an unported GT-40/Cobra/Explorer intake will fall off?
 

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Regardless of whether the springs are not keeping the valves from bouncing, isn't that RPM about where an unported GT-40/Cobra/Explorer intake will fall off?
You're right, power should peak there and drop gradually, but he shouldn't have that sharp dropoff.
 
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