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Victoria, British Columbia


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1981 Pontiac Trans Am Twin Turbo 454 Convertible (MUSCLE)

Last updated Jan 17, 2007  

Photo of a 1981 Pontiac Trans Am Twin Turbo 454 Convertible (MUSCLE)


1981 Twin Turbo 454 Trans Am Convertible. This car originally equipped with the 4.9 Liter (301) engine and then replaced with the potent (7.4) 454 CID Chevrolet engine. Corporate swapping of engines made this decision very easy since there are more Pontiacs on the road with Chev engines and parts being cheaper/more selection.


Engine: 1976 454 (Hi Perf)
Fuel System: upgrade to fuel injection
Turbo System: 2X Air Research (Garret) Turbochargers
Transmission: upgrade to 4L80E (4 Speed Overdrive)
Computer System: GM ECM (Transmission and Engine Control)
4 Wheel Disc

Factory Options

Factory Ordered Convertible
4.9 Turbo Engine
3 Speed Auto
4 Wheel Disc
Cruise Control


Chevrolet 7.4 liter (454 cid) +.030, TRW Supercharger Pistons (7.5:1), Manley Aluminum Rods, Camshaft (forgot profile, but 20 to 21 vacuum @ idle), Heads 120cc Chambers Matched, Polished Chambers, Bronze Guides, Stainless Valves (2.220 and 1.880) Weiand Intake Manifold, (currently upgrading to fuel injection) HP: 640 / 720@4300RPM / 8 PSI

I built this car for high speed driving but do enjoy what it can do in the 1/4: 11.3sec street tires + poor traction = great smoke :) This car is the fastest one I have been in yet, capable of maintaining a high speed with out feeling/sounding like the engine is about to grenade. Here is some math to back my claims.

The formula is MPH = (RPM x TD)/(GR x 336)
3.08*.7 = 2.156 (.7 overdrive and 3.08 final)
MPH = (4300 x 26.5) / (2.156 x 336)
MPH = 113950 / 724.41 = 157.3mph or 253kph

3.08 axle/26.5 tires/.7 4th gear/rpm
Any doubts, run the numbers on a calculator

This car has an excess load of torque in the upper half of the power band and climbs easily past 4000rpm in overdrive. Drive is the equiv of a passing gear. I get that notion "if something lets I am done for" in the pit of my gut. It’s a rush!

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Car Blog for “MUSCLE” 1 – 2 of 2

I got a Computer/Harness

I found a wreakin yard which had a computer for a cube van installed with a 454 and 4L80E transmission. Excited here :D. The parts will be here tomorrow.

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Transmission/Fuel Injection

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I mentioned the trans problem I had put up with. How about this. I got my hands on a 4L80E and will be installing it shortly. The fuel injection will be a challenge because I...

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