Zak2018

I'm only now getting into C4 Corvettes. But to me the ZR-1 was always the top C4. I knew about the Lotus designed engine, that it was full aluminum and that it was the most powerful C4.

But now reading up a lot on C4s I keep coming across critics on the the ZR-1's weight. I was surprised to find out it's actually heavier than the standard Corvette C4. Because the LT5 is fully aluminum. So the ZR-1 should have been lighter or so I thought? What is it which makes them heavier?

The heavy critics on the ZR-1 weight really surprised me. Some of it is quite unflattering and severe. From all the problems I could ever imagine a ZR-1 would have, weight never crossed my mind.

To me it is still the ultimate C4 and among the ultimate Corvettes if not the ultimate one.

81c3

The LT-5 is a 5.7 liter engine, but is physically larger than the traditional small block 5.7 350 LT-5 has 4 cams and the chains, gears etc as well as the head size is where alot of the weight is. Do yourself 2 favors. 1. buy or borrow a book called Heart of the Beast. Read it cover to cover... twice.... 2.Then go drive a well cared for ZR-1. Even if you don't buy one, you'll at least know for yourself rather than listen to people who have no first hand experience with one

Zak2018

Thanks. That makes sense.

But I would think if they had just added turbos or a supercharger, instead of developing the LT5, it would have also ended up heavier. So the LT5 in my eyes in an achievement.

As for listening to people who doesn't know what they are talking about, even Callaway called the ZR-1 heavy it seems.

But I'm not criticizing it. I'm just trying to understand where the extra weight came from as I always thought the all aluminum engine actually saved weight.

Thanks for the book tip. I'm actually in the process of selecting a C4 book. I have seen a couple of titles mentioned but haven't decided which one to buy first yet.

PerKr

As for the engine... you would expect a bit of weightsaving but maybe it's not really all that much. But a ZR-1 would usually be loaded with stuff that would be optional on the C4, wouldn't it? Plus wider wheels. And a slightly wider body. So it being heavier than most normal C4's isn't all that strange after all. It was the luxury GT version of the corvette after all.

Greg Gore

GM spent a lot of money developing the LT5 and expensive engineering costs rolled into the price of the option package served to push ZR-1 out of reach of most of Corvette's traditional blue collar buyers. The shining star achievement of ZR-1 of course was its sophisticated world class engine but mounting development costs positioned ZR-1 in a market segment typically populated by high performance European imports whose buyers are sensitive about the brand image parked in driveways of their upscale neighborhoods. Other features of the ZR-1 package were mostly appearance items which offered little to enhance other performance characteristics beyond the car's impressive straight line top speed. ZR-1 also shared the base car's rather heavy multi-piece Uniframe which by that time had become a little long in the tooth because lighter and stiffer advanced one-piece hydro-formed frame engineering was still off in the future waiting for C5 to take over. Another factor was the "gold chain" image Corvette was beginning to wear in the marketplace which Chevrolet soon became well aware of and addressed with the de-contented and de-badged C6.

Paul Workman

Well, consider the source(s) of the criticism before drawing conclusion(s). Some people have actual experience with the ZR-1, and some just read about it (and spout off as a self-appointed 'expert' later).

It goes way beyond simply being aluminum. The two motors (small block Chevy V8 and the LT5) are entirely different animals - NOT the same - completely different internal and external structure; beginning with architecture: one is a single in-block cam OHV pushrod motor, and the other is a 4 cam DOHC 32 valve architecture with ladder frame main bearing partitions and massive (21# worth) head bolts, Practically speaking, there is very little of the SBC that can be directly compared to the LT5 - it is a vastly different animal

I find when trying to explain the experience overall, it's kinda like attempting to describe sex to a virgin. The actual experience far outweighs just reading about it!

Zak2018

Don't get me wrong. I'm not agreeing with the critics or laying criticism myself.

As I said before, I'm trying to understand the reasons the ZR-1 came out heavier. It does weight more than the standard cars.

So I hope this won't turn into a ZR-1 defense thread. I don't think it needs defense.

81c3 's and PerKr's replies are more in line with what I was looking for. Analyzing and explaining the reasons.

81c3

I was not disagreeing with the car being heavier.... I was telling you why it was in regards to the LT-5

Zak2018

Absolutely. I didn't say you were disagreeing. I just wanted to bring up that the sources don't seem to be all clueless.

81c3

No, not all, but many.... After you hang around a while, youll see the ZR-1 bashing come from people who really have no experience with them. I dont claim to be an expert by any means, and have had only 2 ZR-1's thus far... some guys have 5 and 6 of them.... But through allot of reading and working on my own cars, Ive learned quite a bit so far. Also having owned 3 generations of Corvettes, I can give what I think is a fairly educated hypothesis or analysis of those cars. And again, I would really suggest a copy of Heart of the Beast if you can grab one.... its extremely interesting reading for any Vette enthusiast.

bb62

Besides the engine, the rear fascia was larger to fit the wider 11" wheels & tires. The doors likely also weighed more as they fanned out to meet the larger rear fascia. Interior was mostly the same, but a small amount of weight was likely added for the power key. The rear mounted stop light was not integrated into the rear fascia and likely weighed a little more. One area that likely gave a bit of weight savings was the A/C system which was smaller on the ZR-1 due to packaging with the LT5 (and led to the reflective front windshield).

As others discussed, the engine was far bigger physically. The small block did have AL heads as well, but the LT5's heads, being DOHC, were much larger. 4 camshafts versus 1 (and associated chains), 32 valves versus 16, larger intake system to include the dual runners, larger sump with more oil.

ZR-1s were also fitted with every available option. Even with the extra weight, the HP per pound in the ZR-1 was still significantly higher.

Jackie Chan

most over head cam v8s are as large as push rod big blocks once you visualize things like this you can understand why the car weighs what it does.

Dredgeguy

The LT5 has 12 quarts of oil
Charlie
92 ZR-1

vetteLT193

The other thing that kinda screwed up the Z was the cost of each engine. The engines themselves were over 20k to build... so they were so expensive they really had to fully option the car to help justify the cost. The ZR1 came with every option available. The only thing you could get extra was swapping to the clear roof or choosing the dual roof option. All of those options aren't light and since they were standard the car was weighed in accordingly. The weight differential on a fully optioned regular C4 vs a ZR1 won't be as much as the listed weights because of it. The LT5 only weighed 39 pounds more than the L98. I'd take a stab and say the 39 pounds for the engine plus another 40 pounds in wider rear wheels/tires and the body work is all the weight difference is. Likely even less than that.

FAUEE

Like the others have said, the weight comes from the addition of "stuff". Dual overhead cams adds weight. The engine design added weight, so on and so forth.

OHV is a very compact and light engine design, that's one of its many benefits. So that's why it had to be heavier, OHC engines just weigh more

MatthewMiller

Do you have any solid references for that weight difference? I've tried to find something reliable for the weight of an LT5, but have never been successful. I don't believe that it's 200lbs heavier, as some sources say or imply. The 39lb seems credible to me, but I've just never found a source.

81c3

This is interesting.......... Post 10 & 11 Also post 19 says 596lbs dry for the LT-5

https://www.corvetteactioncenter.com...t4-weight.html

MatthewMiller

Yeah, those numbers are way, way off, starting with post #7. Any iron-block SBC, including LTx engines, weighs in the 500s - probably 530ish for those with aluminum heads and 570ish for those with iron heads. The LT1 and LT4 should have weights within a pound or two of each other. That's just common sense. The "dressed" LS weights are probably accurate but they include the flexplate or clutch/flywheel assembly (which is why the manual versions weigh so much more - again common sense tells us the engines alone weight the same). In post #10, the L98 are probably accurate, but again they include the flexplate or flywheel/clutch assembly. And an LT1/4 would weight very close to an aluminum-headed L98, too, because they are practically the same blocks and heads with the only structural differences being the water pumps, distributors, and intakes...so within a few pounds of each other.

Zak2018

Ok. It's getting easier to understand now why it's heavier. But to be honest, the LT5 is so sweet that it basically doesn't matter. And the power to weight ratio is still up. Maybe if one would like to lighten it up a little, he could just lose some of the luxury options. Maybe there are things which no longer work anyway at this point and can be thrown off? I hear FX3 doesn't work in most C4s anymore for example.

Zak2018

By the way, this is a nice watch about the ZR-1 breaking the world record. Most probably seen it but I thought I would leave it here: