To explain what makes the turbocharged 4.9 Pontiac V8 so special, we should first look at it’s history as a non-turbo V8 also known in the Pontiac community as the 301.
The Pontiac 265/301 V8, introduced in 1977, was designed to be a lightweight economy V8 during the dark times of gas shortages and strict EPA (Environmental Protection Agency) emissions regulations. With increases in CAFE (Corporate Average Fuel Economy) standards and the assumption that American car buyers would not want to give up their beloved V8’s, the auto manufacturers set out to produces small, lightweight, cubic inch V8 engines with MPG and emissions being the goals, not horsepower. Most of them were based off of their existing larger displacement engines to minimize tooling costs. Some examples are the Oldsmobile 260 and 307 V8, the Chevy 267 and 305 and Ford’s 255 cubic inch engine.
There are many differences between the 265/301 vs. the conventional Pontiac 326-400. Many of these changes were done to save weight which helped in fuel economy.
The 265/301 has the following:
With the strict emission regulations coming down from the EPA every year, Pontiac was having a hard time keeping performance in the lineup for the Trans Am and Firebird Formula. The Pontiac 400 V8 would not return after 1979.
The only engine Pontiac had that could pass EPA was the 301. And a decision was made to increase it’s performance with the addition of a Garret turbocharger for 1980 and 1981. In order to do this, changes needed to be made to accommodate.
Now when it comes to comparing a 1980 4.9 Turbo to a 1981, there are some big differences. Mainly with fuel management.
Differences between 1980 and 1981 Turbocharged 4.9s.
Q: Can conventional Pontiac heads be used on the 301 block?
A: Yes…kind of. The 301 uses the same head bolt pattern as a regular Pontiac head. The issues you run into are:
1.) the shorter deck height requires a custom made, narrow intake manifold. You cannot use the 301 intake due to the siamese ports.
2.) A regular Pontiac head gasket is needed and the top corner oil drain holes become very close to a water jacket port in the 301 block. Conventional heads have been successfully used on a 301 block in a non-turbo application using Butler Performance head gaskets and a custom made intake manifold. The gasket sealing surface at the water jacket hole is very small, but it did work.
Q: Can I use a 326-400, 3.75” stroke crank in a 301 block?
A: Again yes…kind of. The 301 does use the same diameter main bearings as the 326-400 but the issue is with the narrow thrust bearing of the 301. It has been done successfully on a non-turbo application using a custom made spacer on the block to use the 326-400 thrust bearing and main bearing cap. Also, the bearing locking tab is in a different position on the 301 vs. 400 so another bearing “notch” needs to be added to the block.
Q: Was the Turbo 4.9 offered as a 4 speed?
A: No. In fact all 1980 Trans Ams were factory built with automatics. No manual transmission was available. In 1981 the 4-speed returned, but with the 305 Chevy V8. A non-turbo, 4-speed, 301 was available in 1979 in the Firebird, Trans Am, Grand Prix, LeMans and Grand Am. This is a special flywheel due to the external balance of the 301. Using this flywheel, or one of our billet steel flywheels, along with all the other 4-speed parts, one can convert a Turbo 4.9 to a manual transmission.
Q: Do Turbo 4.9’s have special heads or camshaft?
A: No. The turbo engine uses the same heads and valves as the non-turbo 301. It also uses the same camshaft as the low-performance, non-turbo 301.
Q: With such a short stroke and a short deck height, the 301 should really be able to turn some high RPMs?
A: Not really. The heads are the main problem. They are restrictive and the engine just doesn’t make power past 4800 RPM.
Q: What octane fuel should I use in my Turbo 4.9?
A: With any "forced induction" car (turbocharged or supercharged), you should use the highest octane fuel available. Lower octane fuel will lead to detonation which can cause engine damage.
The early 80’s were a dark time for performance. GM had a corporate policy that all their engines were to be able to run on 87 octane, no lead fuel. Low octane fuel is not good for a turbocharged engine. It is more prone to detonation and the knock sensor would see this, retard the timing and kill performance.
Everyone was used to the tire shredding torque of the big cubic inch V8’s of years prior. In fact 4 short years earlier, you could still get the Trans Am with a 455 cubic inch V8 and a 4 speed transmission. Now, with the standard 3.08 rear axle ratio, hefty curb weight and the delay until boost came on (aka turbo lag) the Trans Am was not the stop light terror everyone was used to.
But, it was refined into a great touring car. With the WS6 suspension package you got larger sway bars, 4 wheel disc brakes, quick ratio steering and 8” wide wheels (7.5” wide in 1981) and the Trans Am became a great cornering machine. The Trans Am still had a presence about it too. The Camaro looked like it could kick your butt, but the Trans Am looked like it was coming over to do it.
My experience with my 1980 Indy 500 Pace Car, is that it is a fun car to drive. Yes, punching the gas pedal from a dead stop is not going to instantly set you back in the seat and send the tires up in smoke, but when rolling at 30+ MPH and hitting the gas, it will get up and go.