I'm under the impression you can legally swap a LS1 and the accompanying T56 into an older ('93-'97) 4th Gen Fbody for ESP. So, assuming that is correct what do you think would be the better combo?

* LT4 built to the limits of ESP rules + the '93 Trans gearing

or

* LS1 built to the limits of ESP rules + '98+ Trans gearing?

Let's assume this is in a '97 Hardtop Z28 built to the full limit of ESP rules also. The car generally would run on a large, fast, smooth, ultra-grippy concrete lot. BUT it would hopefully see Nationals in the next 2-3 years so it'd need to work on smaller, slippery surfaces too.

Running the numbers on 2nd gear only (since that’s where the car will spend at least 90% of it’s AutoX time) the ’93 Trans gearing would give about a 14% increase in RPM vs. the ‘94+. For example, if the ‘94+ gearing would have you at 3,000 RPM the ’93 would have you at 3,420 RPM.

I think it’s safe to say that the LT4 can match the LS1 on torque/hp until maybe 4500 or 5000 RPM. Only losing out a bit right up to ~6200-6300. But can a LS1 make as much torque/hp at 3,000 RPM as a LT4 could at 3,420 RPM?

Thoughts?

-TJ

PS- Yes, my head hurts too.

This post has been edited by tjZ28: Jul 11 2007, 12:53 AM

The LS1 will be lighter. Less weight on the front is a good thing.

Very true. Does anybody have the weights for a dressed LT1/4 vs. LS1?

Also, if you go w/ an LS1 can you mix 'n match over the years? For example a '00 cam w/ '01 heads? If I'm reading the rules right the answer is "NO" since you have to update/backdate as a "unit." However, if you are using all factory LS1 parts does that still count as a "unit" even though the parts are sourced from a few different years?

Garrrrr, I hate rule books.

-TJ

Nope. As you have pointed out, any swap must be complete and as a unit.

I would go with the LS1 combo personally. With the allowed computer programing, the low end torque can be obtained from the LS1. Plus they seem to be more reliable. A late '00 LS1 will have the same heads as a 2001. I have one of each and they have the same heads (at least if you go by the casting numbers). The '00 with and LS6 intake makes more power than a stock '01 which already has the LS6 intake.

I'd go LT4 combo only based upon my experiences with the LS1s and my LT1 with 93 trans. Great throttle response out of the slow stuff and gearing to help you a little, plus all of the breathing and HP you need up top. It's the best of both worlds.

Hmm, if late '00s had the '01+ heads but the early cam that should mean you could put an early can in any '01-02 since that combo was originally available from the factory. The catch of course would be documenting it.

I know I can make as much low end torque with a LS1 build as a LT1 build, probably more in fact. I'm a huge fan of the Gen III/IV motor and like them a lot better than the LT-funs for many reason. They seem to be much more reliable. Hell, just the OptiSpark is enough of a reason to stay away from LTs. But LT's are also known for oil leaks, are weak 2 bolt mains in the LT1s, don't like to rev as high etc. The LS1 really is an amazing motor, and I'd much rather build one. However, it's still hard to argue the 14% gearing advantage you can gain w/ a '93 Trans behind a LT motor.



Thanks for the input... so you're still with an LT1 not a LT4. Do you have it modded to the full extent of the ESP rules? What are you dynoing?

-TJ

LT4 is 4 bolt, and GM had the oil leak issue pretty well resolved by the time the LT4s came out. Also, the optispark is not an issue after 95.

With proper tuning, my LT4 Hawk makes 311RWHP, which peaks at 5800rpm, and only drops to about 295 at 6200. By comparison, my stock 2000 TA made 304RWHP peaking at 5400, and dropping to 290 at 6200. TQ on the LT4 is ~326 and flat as a table until 4700. The LS1 made peak TQ of 317, peaking at 4000, but was started at only about 290. You can check out dnyo graphs of all my previous cars (LT1s, LS1, LS6, LT4 at My Website

Having owned both an LS1 f-body, and an LT4 f-body, I would definitely go with the LT4, especially if you're going with the 93 tranny.

I know the LT4s are 4 bolt... was just baggin' on the LT1s. (IMG:http://www.frrax.com/rrforum/style_emoticons/default/wink.gif)



Anyway... I notice you said "with proper tuning" on your LT4 Hawk... but did you have LS1 tuned? Tough to compare a tuned dyno curve to a non-tuned. There is a LOT of low end to be picked up on LS1 cars due to the conservative fuel/spark curves factory.

I know I can make more HP w/ a LS1, bottom line. I know I can make as good low end TQ. I just don't think the extra top-end HP is going to make up for the lost RPM not getting to use the '93 Tranny.

But I also would much rather own/work on a LS1 so that factors in too.

So much to think about.

-TJ

No, the LS1 wasn't tuned, and while I'm sure you can get some improvement on an LS1, I honestly don't think it's going to be 36lb/ft gain on the low end. I was just trying to give a decent comparison of numbers, the LT4 cars came with LT1 ECM tuning, which significantly limited the HP, allowing for a way larger jump with proper tuning than you'll get tuning an LS1. I honestly don't think there's going to be enough difference between properly setup LT4/LS1, and the driver would make a much bigger difference. I personally just like the LT4 better than the LS1 after having owned both. (IMG:http://www.frrax.com/rrforum/style_emoticons/default/smile.gif) The bigger difference would be that you can run the 93 tranny with the LT4.

I currently own both an LT4 and an LS1, and I wish it was two LS1's. (IMG:http://www.frrax.com/rrforum/style_emoticons/default/biggrin.gif) In the context of ESP it may not be that big of a difference, but LS1 + long tubes + cam = very happy me. On top of that, no opti-spark! That is reason enough to get an LSx!

There more room for improvement from tuning on the LS1 than you might think, at least with the later LS6 manifold. I found more torque all through the curve, but the biggest improvement was at the bottom end. You can't "tune" the 2.66 trans into a 2.97, though.

I have a fresh M29 I would sell.

So all other things being equal, its probaly safe to say an ESP built LT4 with the M29 vs an ESP built LS1 with its 6 speed is a fairly even match, or just too close to call? I like the idea of 100 less pounds of weight upfront.

Gearing is always going to work both ways, depending on the course.

In general, I think the 2.97 is ALWAYS better for launching, even in slick conditions. I've always preferred controlling wheelspin with my foot instead of by bogging the engine. With 2.97, I can launch with however much wheelspin I choose (down to none) and still drive out of it without bogging.

After the launch, it all depends on the course layout. Sometimes 2.97 is better and sometimes 2.66 is better. Besides the top speed, it also depends on where the good shifting points are. If the course starts getting busy right off the launch, there's sometimes no good place to shift without upsetting the tail. If there's no place to short-shift and not enough headroom to make it to a short straight, then shifting in the middle of a slalom or whatever is going to hurt your time.

The 2.97 trans is certainly more fun coming out of a turn, though (IMG:http://www.frrax.com/rrforum/style_emoticons/default/smile.gif)

I don't have a dyno graph as the car is now. It is not even nearly modded to ESP ruleset. It's a 145,000 mile unopened '95 LT1 that has had regular maintenance and has an underdrive pulley, CAI, and C.A.M. tuning. I have the cast iron manifolds and a Stainless works y-pipe/cat with fabulous pieced together cat back.

Ask Phil how it compares with his LS1, he drove his and mine this weekend.

Yep Brian was nice enough to let me take a run in his car, since I haven't driven his car with the 93 trans. That trans really woke up his LT1. The course had a few slower pin turns and his car did pull out of the slow stuff better then mine, it's not huge but the LT1/93 trans was a better out of slow corners. The LT1/93 torque was right there when I rolled into the throttle, my LS1 still pulled hard, but needed to pick up a few RPM to pull really hard. I honestly think down low and low to mid range (~3k) the motors make similar torque (or a least similar enough that it's not a big deal), but the gearing advantage really made Brian's LT1 shine. If we had a really tight/slow course it might be different, but the course wasn't that slow. However, my LS1 pulls like a bat out of hell til redline and Brian's LT1 ran out of steam in one section of the course.

Sean is right that the gearing goes both ways. The 93 trans helps you out of corners, but you hit the rev limiter faster. Considering that at the ProFinale last year Brain's LT1/93 trans was edging out Eguina's car (LT4/93 trans) off the line, I'm not so sure an LT4 has the same low end torque as an LT1. But we are all bench racing at this point. (IMG:http://www.frrax.com/rrforum/style_emoticons/default/wink.gif)

I would say build what you want the combo's are really close. There maybe a slight advantage to an LT4/ 93 trans, but it's not that much. Plus documentation for the LT4 is hard to come by unless it comes with the car. If you plan on running any big events you better be sure to have the proper documentation for the LT4.

I should probably replace the original valve springs, eh? (IMG:http://www.frrax.com/rrforum/style_emoticons/default/blink.gif) (IMG:http://www.frrax.com/rrforum/style_emoticons/default/unsure.gif)

Considering that the only LT1's that I have ever driven are your's and Karen's Green machine, I'm not sure what to think. Your car still drove nice. I was rolling into the throttle expecting your car to pull hard like mine did going through the tight offset after the first 180, but it just didn't. (IMG:http://www.frrax.com/rrforum/style_emoticons/default/dunno.gif)

I haven't really driven enough LT1's to know what a fresh motor feels like, but valve springs are probably reasonably cheap. A lot cheaper then headers. (IMG:http://www.frrax.com/rrforum/style_emoticons/default/ph34r.gif)

PS I need to e-mail you about something else, but work has been crazy today.

Me too. I'm thinking of doing mine this winter (or maybe sooner if I can come up with the money for headers).

Last I checked, a new set of springs was only something like $40 from GM.