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  1. #1
    FEP Senior Member E2ZZGLX's Avatar
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    Default GT40P with stock shorties or manifolds

    Anybody body running GTp's with stock shorties or better yet stock cast iron manifolds? Just in case you are wandering WHY? Simple rules...
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  2. #2
    FEP Senior Member
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    I had the same question and tried it on some loose heads. It looks like it can be done, but beating the tube was needed. I can't remember exactly what tube needed the most work though.
    85 Saleen Mustang(s)

  3. #3
    FEP Power Member STL79Coupe's Avatar
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    A friend and I have done several cars with P heads. I used BBK long tubes on my car and his last build he used a set of cheap ebay shorty headers and they worked awesome. All the plugs fit with no issues and the headers themselves fit well. If I remember correctly they were under $100 I would bypass the stock headers and buy these from ebay or find a set of used BBK shorty headers. They work as long as you use 90* plug wires.
    Keith formerly STLPONDS
    '79 V8 coupe in the works!
    Build thread http://vb.foureyedpride.com/showthread.php?t=89153

  4. #4
    FEP Super Member erratic50's Avatar
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    Do rules permit you to clean up the headers at the pinch welds? They are terrible. Most 86's only flow 90, 87 up were even worse in many instances. My 1989LX 5.0 was lucky if those stock headers would flow 85 CFM.

    In the early 90's I cut the set from my 86 apart and beat them until they were open then port matched the flanges. Made a HUGE difference. The TB and cam were also upgraded at the same time so hard to say how much, but big. Even with stock E6 heads.

    if you don't open up the headers the P heads aren't going to yield much if any benefit. Possibly some mid torque - maybe. Stock headers are a Big bottleneck - even worst than the stock EFI intake!

  5. #5
    FEP Senior Member E2ZZGLX's Avatar
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    Rules state "factory stock exhaust manifolds and intake" that being said the way I read it is "stock shortys" can be run if not maybe some "K-code" manifolds. The thinking behind the GTP's is that Exploder motors are a dime a dozen so to speak. This is for a Pure Stock/Super Stock-Chumpcar build. Stock junkyard long block, maybe throw some bearings in the lower end, stock fox oil pan with windage tray, fresh oil pump and timing set, and MAYBE a "B" cam as we are limited to lift and even that's in they WAY GRAY area being a roller , and on the intake side factory aluminum 2V intake with some secrets and a 500 cfm Holley, mechanical fuel pump etc...3:45 gears is whats requires...Rules here at CNS are GM based like most so doing anything different scares them...
    Current keepers...
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    82 GT-first new car is back home!
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  6. #6

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    You might get away with a set of motorsport stainless shorties, they age and discolor to look just like factory headers just without the pinches. Over the years they have tested shorty headers and it seemed to be about a 7-10hp gain, not really that much. One other header to try out would be the 94-95 factory headers, they have less pinches and I think the outlet is larger. If youre trying to get every last bit, you gotta visit every piece and optimize it. Good Luck with it.

    Mike
    1982 GT 351W, retro hyd roller, ported Pro Comp heads, Tremec, M2300K brake kit, Recaros...needs paint!
    1984 LX 5.0 Vert *SOLD*
    1993 Cobra #3971 mostly stock *SOLD*
    1966 FFR Cobra replica 383W, Vic Jr heads, Vortech YS, TFS Box intake, 652rwhp, crazy fast!
    1987 GT in MM&FF May of 97 "Not Fade Away" white and purple. Sold 1999

  7. #7
    FEP Super Member erratic50's Avatar
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    Even just stock style late Explorer production exhaust is going to do better than many stock fox shorties more than likely -- if its allowed that is.

    rather than a B cam an HO with 1.7:1 should do fine. A great set of heads on a 302 will make 400 HP with a stock cam and 1.7:1 rockers.

    DO degree in the cam for your rev range and power needs.

    Street performance is best around 4 degrees advance. peak power is found at higher R's with around 3-4 degrees retard.

    Mod your roller lifters for nearly solid if they let you. Build bottom end at max factory tolerances in the rod and main bearing then jack your oil pressure to the moon if they don't let you do that.

    Target 7000 RPM with your intake selection and ignition advance curves and base timing, etc, if you can. That's the mechanical design limits on a 3" stroke due to the feet per second the rings are moving.

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