So i have a 91 z28 with a 350 tpi. now i understand that the rs would be a 6cyl, or the 305. but why did GM make a z28 with the 305? i just never understood that cuz when you think of the z28 you think of the biggest best one of the year, aka 350, not 305.

 

It is odd to think now why a Z28 would have a 305 as standard equipment.But look at '82 when the LG4 4bbl and the LU5 CFI 305's were the only motors available in the Z28(or T/A for that matter).What's even more odd is the 305 came in some CA bound Corvettes(same for Z28's and T/A's) in '80-'82.
Look at a "base" '88 IROC(when it became just a 2 model lineup) - 15" 5 spoke wheels and a TBI 305.I wonder how many came off the line like this.

 

Depends on the engine options for the IROC-Z and later Z-28:
Standard motors were first a carb & later TBI 305s.
Option motors were a 305TPI @ $650 and a 350TPI @ $1050.
So if the original buyer didn't want to spend the money he bought the car with the standard & no option.

So there are a lot of IROC's & Z-28 out there with the carb & TBI.

 

I'm pretty sure that all the 305 Engines for the 91 Z28 were TPI... They were very close to the L98 with only about 10 less horsepower and about 40 ft/lbs of torque less than the 350 TPI.

Consider that many people wanted a standard transmission and you couldn't get one with the 350 so you'd have to go with the 305..

The 305 TPIs with the standard tranny were pretty quick. (I knew a guy who had a 91 GTA with this combo).

 

IIRC Like the Trans Am starting in 1990 all Z28's got TPI. THe RS got the V6 & the LO3 as mentioned above, but the Z28 was to only get the LB9 or L98 TPI engines. All Z28's were V8's (except for special cars)
85-92 LB9 - 305 TPI, legendary.
87-92 L98 - same as TPI, but with 350ci.
82-83 CFI - 305 Cross fire FI V8
83-86 L69 - 305 HO 4bbl
82-87 LG4 - same as HO, but less cam & compression (some years)
88-89 LO3 - replaced LG4.

John

 

gas mileage/fuel cost increases and federal emissions requirements is why, and insurance too, in which is why the real muscle cars went away


for years you couldnt evne get a 35o in these and billions of other cars, including civilian full size cars such as the caprice and impala nor in the half ton trucks from 1981 to '87

blame the governments and oil price increases and insurance industries,

they did it

 

Well, I don't think the 305 TPI was the base engine for 1991 in the z28. I seen two cars that were Z28's and they both has a 305 TBI motor in them. One of them is my wife's uncle's car. This is the same 305 that was the V8 option in the RS. I believe this is the L03 engine.

 

If he has TBI then its an RS, unless it was an export car, or possibly someone installed the Z28 badges.... THere was a 91 or 92 RS with a Z28 High rise wing on it locally, It was sitting at a Used car lot... Keep in mind in 91 & 92 unless its a convertible if it has a regular spoiler then its an RS, if it has the High rise (F-40) type Spoiler then its a Z28.

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Why 305 as base engine?
Back in the early to mid 70's Muscle cars were on the way out, it was not that people did not want the extra horse power, but because the Oil Embargo pushed oil prices from 50 cents to $1.50 a gallon that they did not want the premium at the pump... I remember that time and I remember my dad complaining about the high prices etc... During that time you could get those now Famous Hemi Cuda's, Z28's, Trans Am's Chevelles, GTO's for almost nothing, people could hardly give them away (sound like our 3rd gens?).

GM began design on the 3rd generation F-body in the mid 70's as sales were poor. In the mid 70's as there was no other "Muscle" Car and gas prices started to recede slighlty and as people got used to the higher price of gas. As all of the Muscle cars were gone, Pontiac still had a little fire, not much but they still offered a 400 in the Firebird until 1979. Add to that the movie Smokey & the bandit was released to add fuel to pontiacs fire. Sales once again were increasing Pontacs F-body for the only time in history sold more than 200,000 Firebirds in 1979. GM had put the F-body back on the burner because they were selling cars, thats what GM does.

By the time GM introduced the 3rd gens in 1982 several things had been put into place. People were still concerned about economy more than performance, so they designed the car to handle well. The other thing was the 301 Turbo that Pontiac was going to include with its Trans Am was cancelled because it had lack luster performance from an undersized Turbo, and a miriod of other things, really it was pontiacs attempt to keep some performance alive, but ultimaly it died a fast shot to the head.

During this time GM also was under fire for its several car companies and there was talk of breaking the giant up like they did to AT&T. GM decided that if the cross installed engines into different lines, FOr example a Chevy engien in a Oldsmobile, then they could claim that there was too much cross linking to be broken up because of the common parts.

It was finally decided that because the 3rd gen was lighter, had better aero etc. that the 305 would be more than adequate for the new design. At the time most people had gotten used to the lack luster performance of the mid to late 70's and they were reasonably quick cars for the era.

While there were some people that wanted performance most people did not want the extra insurance and the extra money at the pump, it even was actually determined that in the new C4 Corvette which was introduced in 1984 that it too would get a 305 engine in 1985 with the introduction of TPI. Much grumbling, and complaing went around the corvette circles and GM decided to stick with the 350 for that application, but they installed the engine as it was to be in the Vette in the F-body. Then the performance race begain again...

The Z28 & TA were respectably fast cars in 1985 for the days standards. So fast that people who owned them thought they were mistakenly given 350's The performance era had long but gone, but then there was these 2 cars. Ford responded the next year in 986 with their Mustang 5.0 program which really reminded people of a race car technology under the hood, combine that with Buicks Gran National which was stomping everything on the street. GM had to detune the 305 TPI because of new CAFE requirements in 1986. But Chevroelt and Pontac fought back in 1987 with the introduction of the 350, Buick introduced the GNX, which again was and still is considered the fastest sedan to ever be produced.

Then came 1988, more power in the 350 as it was more refined with bigger cam, better air intake, The Gran National Turbo was dropped because the Front wheel drive configuration of the time could not take the power from a Turbo. What defined a division as a brand in the spotlight died, Buick was on its way out.

1989 saw the introduction of the N10 Dual exhaust, performance was Back to stay and the TTA took center stage at INDY. From 1990 thru 1992 the TPI engine did not really recieve any major upgrades other than possibly some tuning.

Since GM started the 3rd gen with a 305, they were determined to make it die with one too. The primary powerplant for the 3rd gen was the 305, and it was offered in just about every 3rd gen model that Chevrolet and Pontac produced from 82 - 92. Matter of fact, I cannot think of a simgle model other than some specialty RS camaros in 87 & 88 which were V6 only.

In 1993 with the LT1's introduction into the new 4th generation F-body, did the trend end. It all began in 1980, with Pontiac not offering anything larger than the 305 Chevy, The 305 was first installed in the Camaro in 1976 as the base V8, fortunately for the Camaro it was still available with the 350 thru 1981...

If you look at HP ratings there was a peak in 1970 and then a slow decline until 1982 & 83, then a slow increase back up to where they are now.

John