True duals on an old Pontiac 400

[TripleTransAm]

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[Rider90]

Sounds very nice.

[marauder307]

I have no idea when the cat disappeared on my car,...


Probably when the dog ate it...:D

Seriously though...that is a VERY nice lookin' set 'o wheelz there...makes me a little nostalgic. When I was but a wee lad, my father used to take me on trips to the local high school's outdoor basketball court. There was another gent who had (at the time) a brand new '77 T/A, white with a blue "chicken" on the hood and matching blue graphics all around. I vaguely remember looking at it and seeing lights in the hood scoop, something about boost...my memory isn't perfect. It's been too many years to recollect clearly.

Big :up: to you man...

[Ozz]

I can't hear the .wav files at work... but - I don't see a cross over tube on that exhaust. Do you get some 'pops' out of it when you decelerate? My '69 Mustang had a dual exhaust setup w/o cross over tube and it seemed to pop a bit. I was told that a cross over tube would eliminate that and increase the hp slightly... I had a cross over tube installed and I prefer the new sound... I did change the whole system at the same time so maybe it's more to do with the headers and mufflers I used...

[TripleTransAm]

Do you get some 'pops' out of it when you decelerate?


Yep, and you're right, a crossover of some sort should help in equalizing the pulses. As far as sound quality goes, the only description I seem to get out of people is that the sound will be "mellower". Okay, so my exhaust note will be on drugs? Nonetheless, I will try the H-pipe this coming spring if I have time.

Once I retuned my carb a bit in September, the popping got a bit better. The car was already running a tad lean and I think the lower backpressure must have made it get leaner yet. So going a little richer on the idle circuit seemed to have helped the popping and spitting (more like a hollow huffing sound than an outright pop), which helped the deceleration situation as well because the throttle is pretty much closed there as well.

[TripleTransAm]

I vaguely remember looking at it and seeing lights in the hood scoop, something about boost...

The 301 Turbos of 1980-1981 used boost lights on the rear flat portion of the offset hood scoop. This offset scoop was there to provide clearance for the carb, now that there was extra plumbing under the hood. There were apparently differences between 1980 and 1981 when it came to those lights, but all I remember is 3 square lights with the words "low" "medium" and "high" over or under them, to represent boost levels. Without intercoolers, boost was limited to something low like 5-6 psi, and the knock sensor would usually pull back so much timing that the cars used to fall fairly flat on their faces after 3000 RPM or so.

The turbos were the only ones to use this molded offset scoop (similar in style to the offset scoops used on the 1982-1984 T/As and 1987+ Formulas, after the turbo 301 was cancelled). The non-turbos until 1981 used the usual shaker scoop.

Speaking of scoop: As I've mentioned to some of you privately, the lettering "T/A 6.6" on the scoops should be reserved for the optional Pontiac 220hp 400 from 1977-1979 (200hp in 1977). My car has the base Pontiac 400 (180hp, available until 1978) which should read "6.6 litre" on the scoop (same as with the optional Oldsmobile 403 with 180-185 hp also available 1977-1979). Most likely during the repaint of 1987, this car must have inherited cheap replacement vinyl decals indicating T/A 6.6, but I make no effort to mislead people into thinking the car has the more desirable hi-po motor.

[Shaft333]

What heads you have on the 400?

[TripleTransAm]

6X-8 stockers, giving me a whopping compression ratio of 7.6:1 ;)

One day I might spring together the cash for a set of 6X-4s or something equivalent but I don't know if I should bother on what is essentially a cruiser. If I lose some bottom end (which would happen with the W72-spec cam used in the 220 hp version), I certainly wouldn't be able to keep the 2.56:1 gears, and then that would mean changing the carrier to a 3 series, then I'd need a new valvetrain to handle the constant higher RPM, etc. etc....

In the meantime, my cruiser is able to smoke the tires at will from a dead stop for as long as I stay on it... good enough for me, for now.