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Thread: Thoughts on Mike's GN post/"power potential" - and Pontiacs!

  1. #1
    Vulture of The Western World Eric's Avatar
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    Thoughts on Mike's GN post/"power potential" - and Pontiacs!

    Mike made some interesting points about the built-in potential of the Buick Regal GN's 3.8 liter V-6. I've never owned one, but I have owned and worked on several mid-late '70s Pontiac Trans-Ams ... and while the power gains aren't as massive, one could wick up these cars considerably via a few minor mods. These included:

    * Exhaust - The stock system on '75-'81 Firebirds sucked. Very restrictive cast iron manifolds fed into awkwardly bent, also restrictive downpipes that were quickly tied together into a single pipe that fed a hugely restrictive pellet-style single catalytic converter. From the converter (on TAs) a Y-pipe led into twin resonators and separate over-the-axle pipes that ended in 2.25 "splitters." Rplacing this system with reproduction RA III-style manifolds (which are basically cast iron headers) and a true dual system with 2.5-inch pipes and free-flowing mufflers really woke up an otherwise stock 400 (or 455). Give that the '74 Trans-Am's base 400 V-8 was rated at 225 horsepower (and the 455 at 250 hp) and both these engines were very similar to the '75-77 400s and 455s - with the chief difference being the '74s had true dual exhaust and no catalytic converter - the probable hp gain from doing the exhaust upgrade to the later "smog" engines (which were rated at 185-200 hp) was on the order of 20-40 horsepower, all else being equal. W72, "TA 6.6" cars (which had hotter cams and higher CRs and were rated at 220 hp stock) probably got boosted to 250-270 hp.

    * Intake tuning - by making the shaker scoop functional and jetting the carb from an emissions calibration to a performance setting - along with dialing up the ignition timing and the exahust mods mentioned above - one could get an otherwise stock '75-'79 400 (or 455) Trans-Am solidly into the 14 second range in the quarter mile. High 13s were doable if the car was lightened up a little and the driver was really good. This is impressive performance for a 4,000 pound car powered by a low CR "smog" V-8 with (even in W72 form) a very mild cam - remember, only a handful of the hairiest '60s and early '70s muscle cars could deliver 13 second timeslips.

    It gives you an idea what the Pontiac V-8 could do with a little work!


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    Re: Thoughts on Mike's GN post/"power potential" - and Pontiacs!

    Eric,

    Very excellent points, I agree with you 100%. I remember a few years back running into a Pontiac guy up at one of the Carlisle PA shows, he mentioned how he had a brother owned several W72 T/As along with early 2nd generation T/As over the years. He mentioned how his brother used to say just taking off the polution control devices and with a few external tweeks (he did not open up the motor), headers, and free flow exhaust would make a W72 run as fast as Ram Air III 400 and in some cases faster. He said he personally witnessed how fast the W72 was with these changes.

    The '75 - '79 400 and 455 powered T/As are like a pretty woman who does not wear make up and wears non-appealing clothes, but she add the makeup and very nice clothes - viola she is Miss America. With the '75 - '79 400/455 TAs doing what you described brings out some real serious performance. Unlike the 301 - the 400 and 455 is a solid peformance block and even in a low peformance tune it does not take much to wake it up and really make it move.


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    Re: Thoughts on Mike's GN post/"power potential" - and Pontiacs!

    Yeah, you're pretty much dead on with the assessment of the state of tune of the engines in that period. In defense of GM, I'll say that I think they were afraid of the catalytic converter. It was the first foray into unleaded fuel, and the long-term mass use of catalytics was an unproved concept. The carbs were jetted ridiculously lean, spark advances were heavily dependent upon the vacuum part of the setup (very little mechanical advance), and GM considered the HEI ignition to be an unproven quantity. For most of the 1975 model year ANY failures of the HEI module in the distributor necessitated a unit replacement of the ENTIRE distributor and the removed part was sent back to GM as a complete assembly for analysis. It wasn't until something like late summer 1975 (IIRC) that GM finally dropped this requirement of their service network.

    As time went on and GM gathered experience with the new converters, they grew bolder and started tweaking the engines in better. That showed up in the higher HP/torque ratings of the 77/78 cars.

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    Re: Thoughts on Mike's GN post/"power potential" - and Pontiacs!

    Rick,

    Very well said. Could you imagine if there was no CAFE ratings in the late 1970s and through the 1980s, and Pontiac could have kept the 400, by the early 1980s I believe that Pontiac would have had some serious ponies coming from a W72 400. But then again we can't rewrite history.

  5. #5
    Vulture of The Western World Eric's Avatar
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    Re: Thoughts on Mike's GN post/"power potential" - and Pontiacs!

    Quote Originally Posted by Pete
    Eric,

    Very excellent points, I agree with you 100%. I remember a few years back running into a Pontiac guy up at one of the Carlisle PA shows, he mentioned how he had a brother owned several W72 T/As along with early 2nd generation T/As over the years. He mentioned how his brother used to say just taking off the polution control devices and with a few external tweeks (he did not open up the motor), headers, and free flow exhaust would make a W72 run as fast as Ram Air III 400 and in some cases faster. He said he personally witnessed how fast the W72 was with these changes.

    The '75 - '79 400 and 455 powered T/As are like a pretty woman who does not wear make up and wears non-appealing clothes, but she add the makeup and very nice clothes - viola she is Miss America. With the '75 - '79 400/455 TAs doing what you described brings out some real serious performance. Unlike the 301 - the 400 and 455 is a solid peformance block and even in a low peformance tune it does not take much to wake it up and really make it move.

    Amen!

    Our "Disco Machine" mid-late '70s TAs used to get slammed a lot for being slow, but as we've been talking about, with some relatively minor backyard tweaking, they could - and did - run as hard as some of the quickest of '60s and early '70s muscle. And they did so while also offering much better handling and braking (esp. versions like your TA TA, which came with 4 wheel disc brakes)!

  6. #6
    Vulture of The Western World Eric's Avatar
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    Re: Thoughts on Mike's GN post/"power potential" - and Pontiacs!

    Quote Originally Posted by Pete
    Rick,

    Very well said. Could you imagine if there was no CAFE ratings in the late 1970s and through the 1980s, and Pontiac could have kept the 400, by the early 1980s I believe that Pontiac would have had some serious ponies coming from a W72 400. But then again we can't rewrite history.
    Ditto!

    Though as I recall "corporatization" of GM's engines was only partially about CAFE; it was also a cost-cutting measure. By getting rid of each division's once-independent engineering/engine shops and folding all that into one shop (GM Powertrain) manufacturing expenses, etc. were supposedly cut dramatically. Of course, it also helped them comply more easily with emissions regs by not having to certify as many engines as they previously did.

    Much as I miss the 400, I also grieve for the untapped potential of the little 301. As I posted before, I have always believed that with some development (and in the lighter Third Gen. cars) it would have been a potent performer by mid-80s standards - and made the Third Gen. Trans-Am a lot more interesting than it was. With EFI and a proper turbo/intercooler set-up, the 301 should have been able to make as much or more power than the L69 305 HO or 350 TPI small block in Camaro - and having a Pontiac engine and turbo power would have given the TA a unique personality and driving feel - instead of being just a nicer-looking, better-handling Camaro!

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