Both factory fresh 1991 Z28 1LEs.

305 T5 3.42 posi
350 TH700R4 3.23 posi

The 350 one was only a half second faster...Conclusion was?

For the dragstrip, get the 350, for the twisties or autocross, get the 305.

But also..The 350 was hampered by the taller rear gears & the slow shifting stock auto tranny. A shift kit and shorter gearswould help it even better.

 

A shift kit and converter and the 350 car would just kill the 5sp car.

 

Very true. The article makes a similar point that setting up the 350 a little differently would open up the differences . . .
But the article is about comparing what Chevy had to offer, not what I can do in my garage. Despite it all, I'd probably still go for the stick because I enjoy playing more of a role when driving any car with better than average performance.

 

I've always said the 350's were faster but you'll never end the arguing by people who think a 305/5-speed was just as fast, even with a measurable comparisons like this.
Like worse heads, smaller cam, smaller manifolds and 45 less cubes just magically all got forgotten when you put them behind a stick.

Mod for mod that 350 walks away even harder from it too.

 

A good article. I used to have that magazine, but gave it to a friend of mine who has a red 91 1LE Z28 5 speed.

I've always wondered if the 1LE was really worth it if you bought the 350. I mean let's face it, the 1LE is meant for racetracks, autocross etc. On the other hand, if you live in a northern climate where A/C isn't of much use, why not buy the 1LE brand new had you had the chance.

I used to rub it in though when we'd both leave a car show in the summer. I'd have the air conditioning on MAX, feeling the wonderful relief after a day of being out in the sun all day, while he'd be sweating and heading for the nearest 7-11 to grab a slurpee.

Let's be honest, four tenths isn't too much to overcome between 305 vs 350. On the other hand, a 350 is always going to have the advantage when it comes to adding HP. I would argue that my Pro Built Automatic street/strip shift kit makes the car as much fun as a 5 speed car. On the other hand, the guys with 5 speeds don't have to buy shift kits, coolers, and torque converters.

 

I used to have an 88 IROC 350 that somebody had put 3.42 gears in prior. (I'm guessing it was originally a 2.73 car?).

The difference between the GTA's 3.27 and the IROC's 3.42 was definitely noticiable. The 3.42 seemed to want to change gears at 30 mph while the 3.27 didn't want to change gears until 40 mph. On the highway it was about a 200 RPM difference between the cars.

But when you really wanted to get on it and go for a WOT 1 and 2 gear run, those 3.42's were just perfect.

 

I can't believe no one has commented how inaccurate that article is.

 

If YOU have knowledge & proof of how inaccurate it is....Share.

 

OK...
1 The 1LE was not offered as a 1LE until 1988,
2 The 11.65" Rear Brakes, Special fuel tank baffles, engine oil cooler was not specific to the 1LE... Only in 1988 were the rear brakes special, The Gas tank is the same on 1989 or 1990 & up I forget... I will give it to him as it was on the car, but it was not 1LE specific as the reader is lead to believe. The Engine oil cooler was standard on ALL 350 cars to my knowledge, and I suspect the LB9/M5 cars as well with the 3.42.

And that was the first page

to help some of you that did not know that starting in 1990 ALL cams were the same for the TPI cars, it did not matter if you got the A4 or M5 or the 350, GM made one cam for all three applications... A 3.27 gear was the tallest gear EVER available on a 350, and a 3.45 was the tallest gear ever offered with an LB9/M5 application... Starting in 1990 when the B&W axels ran out the 350 got a 3.23 and LB9/M5 got the 3.42 as the tallest gears...

Actually most of the information is correct, just some little things here & there...

John

 

I can confirm that at least for my 1988 GTA, it has the engine oil cooler for the LB9/MM5, 3.45 posi rear combination.

 

Both cars were 91s, so how does the 88 part even figure into this?

The 89/90 up baffled tank is a myth & have been PROVEN, by MANY MANY later models not having baffled tanks. NONE of the post-89s had a baffled tank. Other than B4C & 1LE cars, I doubt any others ever got them.

Quite possibly, GM provided some altered "off the assembly line" car to the magazine, to tilt the tests in their sales favor.

 

What we have to go on is the 1Le Tank was originally unique... starting in 1990 or 1991 the tank ended up being the same part number... Baffles or not apparently... But the tanks all ended up using the 1LE part number...

John

 

My IROC has a tank from a 92 Formula 350. It's got an extra wall at the bottom that the stock 88 didn't as well as the other 86 tank I had at the same time. It's the same as the tank in my friends 1LE.

The article states that the 1LE option first started with 100 cars in 1986, and the way it reads, makes it seem like the 350 was an option back then as well. As okfoz points out, it was 88 with only 4 cars. WAY off.

What's worse, that's not the first article Car Craft did on the 1LEs. I had an issue that tested some from 89 which correctly stated there were only 4 in 88. The owners volunteered their cars for testing by the magazine and were somewhat dissappointed with the results of their special edition cars not being really any faster than a stock IROC at the drag strip or oval track lap times.

The article also states the cars come with dual exhaust, though the sidebar correctly points out it's not.

It's also amusing how the articles refers to them as strippers, but never says they are supposed to be like that... plus it points out how they started adding options that were not available on previous 1LEs such as radios.

 

Are you talking about the "swinging fuel pick-up" rumor on the 1LE cars? Because every newer thirdgen I have seen has a plastic "bowl" in the tank commonly referred to as baffles. I have pictures.

 

No. The baffle itself, not a swinging part. I've don't post 90's myself...No baffle in them. And you are the first person to say that YOU'VE done them. Lots of "They have them." claims, yet when I ask the same person if they've SEEN it with their own eyes, they shut up. Which tells me they haven't.

Since I seen a BUNCH of posts of post 90 owners that DIDN'T have them, and you are the ONLY person to say you have....Sorry, but I'm gonna be skeptical still.

 

EVERY fuel injected thirdgen I have seen and removed the tank from has the plastic bowl baffle My 86 v6 tank had it, they need it to keep the fuel at the pump.
The only difference in my 92 tank is an extra wall at the back of the tank. Sorry but I am not about to drop my tank and take pictures of it to prove my point. I've SEEN it, it is fact. Believe or don't.



Best I have. That's when I was swapping my old stock 88 leaking tank out. I had the tank from the 92 Formula 350, and one from the 86 V6 car. I had all threee out at the same time, along with the sending units/pickups. The 92 pickup WAS different in that the arm for the fuel gauge ha an extra bend in it to clear the added wall at the back of the tank.

 

From what I've seen from pictures others have taken, all the tanks had the "soft corner" baffle. Like a trim ring that sat at the bottom of the tank. The 1LE tanks had 90° edged corners on the additional baffle that the regular tanks didn't have.

Regular = 1 short walled soft corner baffle.
1LE = 1 short walled soft corner baffle with square baffle inside that.

Kevin91z, post some pics. I'm always interested to see how these things looked up close.

All I know is I'd be kind of disappointed to shell out the money for a 90+ tank only to find out it's exactly the same as my 89 tank.

 

So what did the 1LE 305 have over the '92 305 TPI?(power Wise) It says the 1LE is making 300ftlbs, but my book says the 92 305 TPI makes 285ftlbs.

 

Nothing that I know of. The 1LE would have had dual cats, but I'm pretty sure dual cats were standard by 92 anyways.

 

My book says '92 305 TPI 230hp/285tq.
Where is 15tq coming from?

 

That's an easy one to answer....GM supplied a ringer for the test!

 

I think the only difference between the LB9s is the dual cats on the MM5 cars and probably a little bit less parasitic loss with the manual trans.

 

Wouldn't dual cats hurt the car? I don't know much about cars so thats why I'm asking.

 

Actually the Dual cats help with extra flow by not restricting the exhaust gasses. A car with Dual cats get better fuel economy and better power, its a win-win.

John

 

Your book is wrong. 90-92 305 single cat cars are 205 HP and 285 TQ. 90-92 305 dual cat cars are 230 HP and 300 TQ.

Pics of the baffle in my gas tank: