Now, what's that difference in time due to? Is it because the C6 platform is superior to the C4 platform, or the LS2 is superior to the LT5? The C6 is lighter and does have a better chassis setup than the C4 ZR1.

The LT5 certainly is a phenomenal engine for late-80's, mass-production technology and has an intimidating look, but it's just too far out of reach $$$-wise for the average Joe.

 

As someone that's owned a ZR-1 and was actually old enough to be part of the hype when it was introduced and splashed on just about every magazine cover in America, I can tell you this much - the LT5 was a hell of an engine for its time. It was in 1989 something like what the LS7 is today, but much more.

When it was on the drawing board in 1985 at Group Lotus, GM, after giving up on a turbo V-6 design, had never really developed a production DOHC V8 engine before so they went outside the company for help in creating their goal of a 400hp engine that would fit in a C4 and retain good fuel economy and driveability. Were it not for GM's stipulation on certain aspects of the Lotus design (namely the retention of the 4.4" bore spacing) the original version would have achieved the 400hp target too. This was HUGE at the time. You have to remember that the base Corvette L98 was putting out 250hp at the time, so the increase to 375hp is 50%. In comparison the 2007 LS7 at 505hp is only about 26% increase over the base Corvette LS2 and, of course, even less compared to the LS3 now. When the new "ZR1" debuts in 2009 with 650hp its going to be more comparable to what the C4Z was in its day. FWIW, Lotus already had an updated version of the LT5 ready to intercept the Viper GTS for 1996 that would have been in the 450-475hp range. Eight engines similar to this (aka DRZ-500) made it into the famed "Black Widow" ZR-1's in 1993.

Now for the bad news. The LT5, as a couple of you have noted, was HUGE. If you've ever sat in the driver's seat of a ZR-1 with the hood up you can see that intake plenum from the cockpit (not necessarily a bad thing ). The LT1 with its short runner intake in comparison sat at least a couple of inches lower. Also, the LT5 was so damn wide that you could barely get your arms down next to it to work on anything (anyone that's had to change the #8 sparkplug on one will know what I'm talking about). The biggest problem with the LT5, though, wasn't anything to do with the engine - it was the damn C4 chassis that it was cursed with. In this respect, the C5/C6 Vettes are head and shoulders above the old ZR-1 IMO.

While I think its pretty clear that the current crop of Vettes and the LSx have made the old LT5 obsolete there is no denying what it did for us all as enthusiasts. Those of you that can remember the media blitz and the excitement in the air that the ZR-1 and the LT5 generated almost 20 years ago will probably agree that it really signaled the revival of the modern "muscle car era". Finally, after decades of crap, GM was really gunning for the likes of Porsche and Ferrari. They really wanted to build the fastest and best Corvette ever and one that could compete with the big boys at the track and then drive home in traffic. They did that too. Then came the LT1 and the Viper and pretty much the rest is history.

What was learned on the LT5 program lived on many years in the form of the Aurora V8, the Northstar, and probably many other engines that GM has built since that time period including the LSx.

Now for a conversion project there would be a ton of novelty to using an LT5 (see Tim Allen's old Impala SS project), but LSx would be a much better choice for many reasons.

 

The LT5 really isn't a GM motor.

It was designed by Lotus (see above) and built by Mercury Marine, in Stillwater, OK.

I think from a technical standpoint, the LT5 was pretty neat. However, the fundamental feature in a truely outstanding design is SIMPLICITY. The LSx platform motors have simplicity, reliability, compactness, light weight, high power density (with a reasonable powerband), and durability (which is different than reliability).

I vote LSx all the way. There's a reason that the LT5 production run ended. It was replaced by a better engine.

I'm still amazed that we've got 500+hp production engines that knock down 28+ mpg. That's pretty damn cool.

'JustDreamin'

 

I bet each of those LT5 engines cost several times what the current LSx engines do. Nice technology demonstrator -- but for those of us swapping engines: good luck finding an LT5; if you do, good luck getting it re-built; good luck finding any performance goodies for it; good luck integrating its PCM or finding anyone who can re-flash it (or chip it -- it is from the days before flash memory was available). If you've got 6k for a swap, do an LS1&T56. If you've got 60k, go for the LT5 because you gotta find one, and find someone who has the technical ability to deal with it.

 

I would love to see a LS5 pop up sometime in the new camaro or corvette...

hell yeah a DOHC alum. 6.2L would be badass

 

If you have ever gone for a ride in a 402"+ Zr1 you will know why people love the Zr1. The car just keeps pulling.

If you have the cash the Zr1 is amazing but bang for the buck goes with the LSx motors. However, parts and prices for LT5s have been blown out of proportion.

Most were in the 12s and you can get very close to 400rwp with full bolt ons and a ported plenum.

I am around Zr1s quite a bit and never had an overheating problem.



SGC built a TT ZR1 and turned over 565rwhp in a C4 using a stock LT5.
http://forums.corvetteforum.com/show...ighlight=boost
Another TT LT5
http://forums.corvetteforum.com/show....php?t=1700188

They are also being stretched out to 427s now.
http://forums.corvetteforum.com/show...&highlight=427

 

LT5 is cool, but the LSx beats it, and so you guys know, I wind mine up to 9k all the time

 

The plugs are in the top of the head, not the side.

Changing plugs on an LT5 should take no more than 10 minute.

 

You must have VTEC, i'm scared to rev to 6200, lol.

 

I have both cars and have to agree with most of the comments made here. While I love the LT5 and I have both a relatively stock one with light porting, and an all out 415 conversion, its hard to argue with the advancements that have been made. When I have the 415 at car shows along side the LS6, the 415 of course gets more attention since its unique and a lot of people have never even seen a stock one. Let alone one that has been tricked out and powder coated.

Now a couple comments. I would really like to know who has a set of LT5 heads that flow 400cfm and are running on the street with these. The heads on my car are in the 360cfm and they are ported out to the point where we hit water a couple times in the process. It has lightened larger valves, and the entire upper injector housings have been cut and rewelded. Coupled with this the plenum was sliced into more pieces to be ported and the floor dropped several inches. All of this was done to keep the flow up. The cams we are running are in the .450 lift range and I could get about 10-20cfm more if we went to another custom cam with .460-.480 lift but then we get into more work on coil bind and lots of cost for 4 more cams. All of this nets you 585hp at the wheels without NOS or anything else. Will it run? you bet, but I tell a lot of folks its now like owning a 70s chevelle with a BB 454 LS6. Fun to drive around and take it our for a bit, but after about 3-4 hours it begins to wear on you a bit. It still knocks down 22-25mpg on the highway and is fun to drive. On the other hand the 01 coupe with about 535hp and an ls6 engine in it does really nicely too and the c5 chassis is stiffer than the c4 even with the 4 point roll bar in the back of the c4. So technology marches on. Cost wise you are going to be about the same if you really put the dollars into either one, but the LS series stuff is so much easier to get a hold of in general. more choices I would say. If you want to build a good running lt5 with more stroke or bore than an LS engine then there are a handful of really great shops left in the country that are more than happy to do it for you, which if you look at the LS community the list is rather short too. Lots of people can do it, but there are a handful of truly outstanding ones out there too. Its a great engine that was far ahead of its time and I still love winding it out on occasion but I also really love the 480ftlbs of torque that my supercharged LS engine has at 2000rpm too. Peace.

 

I'm about to be on my second 93 ZR1 and my father has had his 90 for quite a few years. I have taken my first 93 and my fathers stock 90 with 4:10's to the 1/4 mile track and ran a 12.27 with cheaters on mine which is stock with headers and 4:10's but did dads with street and Cheater tires and did 12.71 and 12.48 with the ET streets. I believe the 90 has 351 rwhp and mine was at 371rwhp funny enough. They were under rated and under driven in all those old tests.
You better drive that z06 real hard to stay ahead. BY THE WAY, I let my friend drive my car and is also the reason I had to find my second ZR1. He slid into a pole. Looking for a buyer for the LT5 and zf tranny/clutch actually

 

ive seen a lt5 swapped 3rd gen camaro. it its a nice showpiece. im sure its strong. but not practical imo for a serious build.
it does have that wow factor however

 

You are right about the LS being more practical. But people should remember that the ZR1 still holds endurance speed records today. That engine is very reliable and more durable than most

 

im sure its prolly more reliable than a lt1.

but idk bout compared to an lsx. the 4.8 lsx in dd has 320k miles
the 700rwhp 6.0 longblock in my uncles dd 97 c5 has around 180k miles and turbo has been on there for over 3 yrs now.
the main thing about ls engines is that they are plentiful, powerful, reliable and easy to source and reconfigure with parts from other versions of ls motors.
i have 5 ls engines in my garage on stands and all my vehicles are ls powered. what im saying is the ls easy to get ahold of.
ive never seen or heard of an lt5 in the places i get my engines and cores
ive never had the chance to work on, machine or assmble a lt5.
but have built many ls motors when i was a automotive machinist engine builder.
lt5 is a nice motor to have and has that wow factor. but thery are not easy to source of find parts like an ls. which is quickly catching the sbc in aftermarket sources.

 

There are good reasons why the LSX is here and the LT5 is no longer. They are too damn expensive to build. It'd be fun to rev to 8000 rpms but thats it.

 

I'm definitely not arguing that point otherwise I'd put it in my blazer. I wouldn't want to have to worry about pulling a trailer to the sand dunes and not having a part if something goes wrong.a person just has to want that engine specifically

 

lt5 is a thing of the past. it was great in its time but not much of anything to todays standard especially when there are V6's making similar power

 

Interesting debate. If you just say which the best is, then you do have to consider cost, because you have to consider everything. But, some might interpret best as not taking into account cost. Depending on which point of view you have, could determine the answer.

To me there is no comparison between the LSX and LT5. It's not a fair fight. Had gm developed the LT5 for mass production, and abandoned the pushrod engine, while not sacrificing displacement, the two overhead cam 4 valve per cylinder engine would eventually hold the advantage, but with more cost.

It is interesting how things turned out as we have a cost effective and still efficient alternative to everything else. Had gm not pioneered the DOHC 4 valve V8, we might have never had the LS. We might have had an anemic OHC 4.6 liter.

 

Definitely been a great read this thread. Being a Lotus enthusiast and a Corvette admirer, I have always had a specific interest in the LT5 and its development.

I entertained the idea for sometime to try to fit one into the Lotus Esprit, as it is rumoured Lotus actually did for tests or other reason. However, much of the rationale in this thread stood in the way. I eventually settled on the LS series for my project, and it is slowly taking shape.

There is still a part of me that would like to have tried the LT5 route, but it's more for reasons of nostalgic idealism of a missed opportunity than any practical basis of performance or efficiency.