Lt4 vs lt1 vs ls1

[thomas]

Can someone tell me the difference between the ls1, lt1,lt4. Just doing nothing and figured Id start some conv.

[ryan34]

I believe most of the differences come in the heads and intake manifolds. I think the block is the same and i would guess the computers were different. I would assume that those are the main differences.

[N20LT4Bird]

I believe most of the differences come in the heads and intake manifolds. I think the block is the same and i would guess the computers were different. I would assume that those are the main differences.

Actually, wrong on most counts The LT1 and LT4 are similiar, but a true LT4 has a 4 bolt main block, the heads and intake are superior to the LT1. THey share the ame optispark distributor.

The LS1 is whole different animal and doesnt share much in common with the LT1 or LT4. The block is aluminum and has different heads and intake. It has coil on plug ignition - no distributor. There are many more differences, but others will chime in.....

[DJ Taso]

I got a feeling Fred's gonna be all over this thread

[ryan34]

So the LT1 has an iron block?

[tclelland]

LT1 & LT4 = Iron Block.
LS1 = Aluminum Block.

[Dave M]

Lt1 and Lt4 were iron block/aluminum heads and were 350 ci. Heads and intake were different between the two, and the LS1 is different yet. The LS1 is 346 ci, and aluminum block and heads, plus the coil on plug mentioned earlier.

[thomas]

Well what about performance differences? I know the lt1 is the slowest and least powerful but how big a difference are we talkin here?

[Dave M]

well, if you go by factory numbers, the Lt1 was at 285 or 305 with ram air. The Lt4 was rated at 330 if I remember correctly, and the LS1 is rated at about 225 hp, but it's power is distributed differently than the LT1/4. The LT1/4 makes a lot of power down low, where as the LS1 as a much broader torque curve, which makes the car faster than you would think for only having a few horsepower more.

[Injuneer]

There is NO version of the LS1 rated at a lowly 225HP... not even the 4.8L iron-block version in my Silverado has that little HP... its (the 4.8) rated at 265. The C5 LS1 was 350HP.

Think of it this way.... in 1955 Chevrolet sold their first "small block Chevy" (SBC) V8 engine. 265cubic inches. They kept upgrading the basic design for nearly 40 years. That is what is now known as the "Gen 1" SBC. In 1992, they sold the first "LT1" SBC. This is the "Gen 2" design. It was virtually identical to the Gen 1 SBC, except that it had a "reverse flow" cooling system (coolant flowed to the heads first, instead of the block), and the traditional intake manifold mounted distributor was replaced by a combined distributor/optical cam position sensor (OptiSpark), mounted on the front of the block and drive off the nose of the cam. The reverse flow cooling, plus some very good aluminum heads allowed the engine to make (for that period in time) excellent HP. Basically the same as the engine was 40 years earlier.... just a couple of upgrades.

The LT1 block came in both 2-bolt main versions (F-Body, Caprice/SS/Roadmaster/Fleetwood) and 4-bolt main version (all Corvettes). The LT4 was simply a higher HP version of the LT1, achieved with a higher compression ratio, higher rpm capabilities, better flowing heads and intake. It was only used in the 1996 Corvette as a factory production car. In 1997, it was installed in 100+ Camaro SS and 27+ Firehawks, by SLP. It was not a "factory" install. Very simple... in a nutshell, better heads and intake made better HP. All LT1/LT4's were 4.000" bore x 3.48" stroke, for 350 cubic inches (5.7L) There is no such thing as an LT4 block.... they used the exact same block as the LT1. The LT1/LT4 is pretty much limited to 396 cubic inch displacement, although their have been a few high cost 409 and 421ci strokers built. I have seen one person claiming to have built a 427ci version using sleeved cylinders for a 4.012" bore.

The LS1 came along in 1997 - the Gen 3 SBC. It was a TOTALLY DIFFERENT ENGINE than the Gen 1 or Gen 2 engines. It shares only two items with the LT1/LT4 - the same cylinder bore spacing, and the fact it is made by GM. Everything else is differernt..... all aluminum block with integral oil pan, 6-bolt cross-bolted mains, 15-degree heads with replicated intake/exhaust ports (no siamesed exhaust ports for cylinders 3/5 and 4/6), no distributor at all. It is a much more powerful engine because it is a much newer design... primarily the heads. They also make iron block versions for the GMC/Silverado trucks. The factory makes at least 6 different versions of the LS1 family of blocks, including the 7-liter (427 cubic inch) C5-R racing engine. The displacement of the block seems almost unlimited. Once they developed a reliable steel sleeve for the aluminum block, they have taken the engine to over 460 cubic inches.

Based on my experience, the LT4 was a 30-50HP improvement over the LT1. The LS1 in base form was probably close to the LT4 in power. The LS6 (think of it as LT4 is to LT1 as LS6 is to LS1) was a 50HP improvement over the LT4 or the LS1. The new LS2 (6 liter version of the LT1) is equal in HP to the old LS6... and rumors are the replacement for the LS6 in the C6 Corvettes is going to be mind-numbing... possibly dual camshafts, still located in the block, with variable valve timing..... a true "exotic".

There are some very good online sources for LT1 vs LT4 comparisons:

http://www.malcams.com/legacy/misc/LT4.htm

http://www.malcams.com/legacy/misc/headflow.htm

http://www.lt4.com/

For the LS1:

http://www.idavette.net/hib/ls1c.html

The new issue of HOT ROD magazine has a great article on the Gen 3 SBC. There is an intriguing picture of an LT1 block with LS1 (style) heads on it... apparently one of the early test setups built by GM. I'd like to find a pair of those!!!!

[Dave M]

I meant 325 hp, 225, as installed in the f-body.

[xxRillixx]

Since the LT4 has an even higher compression than the LT1, is it more difficult to add a supercharger? The high compression in the LT1 can only run 6-7 (at the most 8) lbs of boost (stock), will the higher compression of the LT4 not handle as much boost?

-- I want to eventually make my LT1 -> LT4.

[Injuneer]

I wouldn't recommend over 6# boost on either engine in stock form. The LT4 is 10.8:1 vs. 10.4:1 for the LT1 (sometimes shown as 10.5:1).

There really is no benefit in a full LT1->LT4 conversion. Some of the LT4 features were problematic.... "cambered" piston rings to reduce flutter and excessive blowby, some interesting sodium filled exhaust valves, an overweight cam sprocket to counteract high levels of cam torque displacement, etc.

If you wanted an "LT4" and a "blower".... you rebuild your engine with forged pistons providing 9.0-9.5:1 compression ratio, and get a set of well ported LT4 heads and intake. Then you can run upwards of 15# of boost and make huge HP. A friend of mine was close to 1,000HP on a 383 4-bolt LT1 block, Lingenfelter LT4 heads and a Vortech S/C with almost 20# of boost. He eventually upgraded the heads to some custom Canfields, a bigger cam and a little more boost and made 1,125HP. But that is about the limit of the LT1 block. Now he's running an aftermarket Gen 1 SBC block, still a 383, 22# of boost and making 1,325HP.

[thomas]

Guess I need to get some forged pistons!!!! What kind you recomend? And how much$

[alenstein]

Ifyou pick up this months copy of Hot Rod magazine, they have a great article on the historya nd development of the III gen. small block.