terlox

I'm seriously considering selling my bike and picking up a 4th generation LT1 Z28. However I know they made slight changes between 93-97; some that matter more than others. I was talking with Kyung about these differences this past week and he gave me a pretty good list and explained to me why '95 is the 'best' and easiest year to modify. Here's what we came up with so far:

-Vented Opti Spark
-Hardened Pushrods
-OBD1 Programming
-Single Cat (except late production '95 autos that got dual)
-Less oxygen sensors

In 1996 the pushrods are no longer hardened, OBD2 programming is introduced, 4 oxygen sensors total, and dual cats-whcih make headers more expensive.

So far I'm pretty much set on a '95 for the above reasons. Is there anything else that can be added to either of these lists? I want to know as much about these cars as possible before I buy one. Thanks!

Zepher

96+ also has a sensor on the bottom of the timing cover. It's a crank position sensor I beleive.

I'd go with a 95. Or if you get a 96+, convert to OBD1 if you plan on tuning it.

terlox

TTT

turbo_Z

id either go with a 95 or 97.

the 95 has all the luxuries you mentioned above and one can be picked up relatively cheap since its an 8 yr old car now but then mileage could be kinda high.

97 on the other hand has the new interior styling which IMO makes all the difference in the world. i couldnt stand the looks of the 93-96. of course its also OBD2 dual cat car but they are rated 10 hp higher because of it.

ibanez6rg

I'd either go with a 94 or 95. With the 94s you could always convert to a vented opti.

ZZtop

Was 95' the only year that got hardened push rods? I say get a 95'

IrocManiac

I didn't even know about the hardened pushrods for 95...thats definately good to know.

SlowAssTA

damn hardend pushrods are only $36.95...

TheHeadFL

In my opinion, this is about as important of differences as whether your car came with Mobil 1 or Valvoline from factory. 95+, all the way, I agree. OBD1 is better for tuning maybe, and thats an advantage. OBD2 can be converted to OBD1, but as far as the hardened pushrods, single cat, all that, who cares? If you ever plan on replacing headers later on, as long as you don't get shorties they cost the same. I think the interior styling of the 97 is a big attraction.

GREGG 97Z

I was just going to say the same, it's not like were talking hardened connecting rods or something. Still, if you are choosing between a 93-96, I'd take a 95 for all the above reasons. I beleive the 10 hp difference in 96-97 may have had more to do with the slightly better flowing heads (10 cfm more on the intake) than the dual cat headers. The d/c headers were certainly no great engineering design

IrocManiac

96's have different heads???? Thats something else I didn't know...damn I feel like a newbie in this thread...To be honest I haven't ever seen a dyno difference that was significant between the 93-95s and the 96/97s.

GREGG 97Z

The castings were a little different in 96-97 from 93-95's from what I've heard, and the 96-97's flow a little better on the intake side. Nothing major but there apparently was a slight improvement.

IrocManiac

Damn...where the hell have I been...you'd figure with 4 magazine subscriptions and many of them dating back to the late 80s early 90's I'd have known something about that...o'well

Red96Lt1

Q: What's the difference between the '95s and '96s?

A: Dual catalytic converters became standard on all Z28s, Formulas, and Trans Ams. This raised the advertised HP up to 285 from 275 for all such cars. The oil cooler (KC4) was dropped altogether. Recyclable cooper/lead bearings replace cadmium/lead bearings. Low-resistance ignition wires were designed to improve idle quality and cold-start performance. A redesigned ignition coil has half of the primary inductance as the previous coil allowing the primary current to "pour in" much quicker for much improved output at higher RPMs. Revised pistons used a new positive-twist top ring that improved the piston-to-cylinder seal and reduced blow-by emissions at high speeds. The pushrods were no longer hardened as they were in previous years. The exhaust manifolds got tri-layered stainless steel gaskets for improved durability and reduced leaks. The biggest change was that of the on-board computer. 1996 was the first year of OBD-II ECM technology to better diagnoses engine problems. This was good for reliability, but bad for some modifications in that some heavy modifications to the engine could result in a Service Engine Soon light. OBD-II also required oxygen sensors just before and after the catalytic converter for before and after measurements. Although the ones after the converter really only measure the performance of those before it.

Physically there's not much different. The exhaust tips on the Pontiacs changed from the dual-circles to single oval outlets on each side. The year brought a number of new packages. The Buick 3800 3.8L V6 was the only engine in the base Camaro and Firebird. There was also the return of the Ram-Air Pontiac (originally debuted on the late '60s GTOs). This was part of the WS6 performance package. It's just like the Firehawk except the openings on the hood are a little more forward. The package had a freer-flowing exhaust, tighter suspension (32mm front sway bar, 62 Nm front springs, 23-30 Nm variable-rate rear springs, and new valved shocks), and 17" 5-spoke wheels. HP was rated 305. SLP made the WS6 modifications at their plant after the cars left GM's factory.

Other new options included a remote, factory installed, 12-disc compact disc changer (U1S), content theft alarm requiring keyless entry (UA6), 5-spoke chrome wheels (P05). The base Firebird and Camaro models could get a sport package (Y87) with a posi rear, rear discs, 3.42 gearing in the A4, exhaust pipes/tips on both sides, and sport steering ratio. It required the 235/55 16 inch tires (QBC) though. Interior colors available on all cars were graphite, taupe (tan), and red (leather only). A new exterior color of red-orange metallic replaced medium red. As for the 1LE option, it came with A/C for the first time which was standard on all Z28s and Formulas.


I got my info from:
http://ls1.divetx.org/4thgenfaq.html

bruecksteve

Q: What's the difference between the '94s and '95s?

A: No major changes were made to the '95 cars. Goodyear 245/50 16" RS-A All- Season tires became an available option on the LT1 cars. On the Formulas and Trans Ams, 5-spoke 16" polished aluminum wheels became standard (chrome option is set for next year). On Z28s. the black roof and side mirror treatments can be deleted such that they will be the same color as the body of the car. In mid-year '95, a version of the Buick 3800 3.8L V6 is being offered as an option in the base Camaro and Firebird (estimated at 200 hp). A power antenna was added to the hi-end stereo package and the Pontiac steering wheel was redesigned (which was actually taken from the Grand Prix). The Trans Am GT (name) was dropped and the wild wing and upgraded stereo/performance options which made up the 94 GTs became an option to add to the base Trans Am. The Formula badges on driver headlamp and rear bumper only said "FORMULA" (whereas they had "FORMULA V8" in the past).

The camshaft, distributor, and drive mechanisms for the distributor and water pump are different. The changes were basically made to improve the distributor by adding a ventilation system that is connected to the air intake. This draws air through the distributor to eliminate moisture buildup in the optical mechanism. With the low distributor mounting, plus the water pump being directly overhead, there was a tendency for moisture and coolant to seep into the distributor leading to the infamous "optispark" problems. The drive mechanism between the cam, distributor, and water pump was also improved.

California, New York, and Mass. emission options add an extra catalytic converter connected at the end of the driver's side header pipe. This gives an estimated 10 HP extra. But such an increase was not advertised.

Same place