LS1 or LT1

[lgoodson@pacbell.net]

Just a quick question for all you experts which I certainly am not. I almost ready to by a Z with a LT1 but I wonder if I should be looking for a LS1 or better. This LT1 has about 118,000 miles on it. Is there any problems with these LT1's or for that matter LS1's that I should know about before it's to late? 118,000 miles, does that sound like a lot for a LT1 that reportedly has had good maintenace prior the 93 firebird's demise. I have heard that there were problems with the LS1 engines, spun bearings and the like. Does anyone have an opinion? Thanks

[wheelman]

The only issue you might run into with a 93 LT1 is the opti-spark. The early ones have a reputation for collecting moisture which then corrodes the contacts and causes problems with the opitcal sensor.

Of course this assumes the engine has been maintained.

 

How much can you tell us about the Z you are looking at?

Is it running? If not, how much is left to do to get it running?

How is the engine mounted?

What transmission is in it?

Etc...

 

Wheelman

[janaka]

I think people are going to be biased towards what they have. I have an LS1 and personally didn't even think about the LT1 motor when I was looking at a transplant. The other option was carb'd sbc.

I'm fairly familiar with the GM motors since I worked on my last GM myself. I know how they work and what works well. The LS1 has got to be one of the best current motors that is out there for performance for the $ spent. The aftermarket is HUGE on these motors from cams, heads, EWP's etc etc. The motors themselves are fairly inexpensive even at this point. There are a few different ways that you can do the tuning for the PCM at home with a laptop and a cable so its 'easier' to tune even though they are computer controlled.

The only 'reliability' issues that I've personally heard of is the pre-'00 rod bolts stretching if the motor is rev'd absurdly high (still not a 'common' failure based on my reading) as well as a weaker oil pump on those same motors. I'm running a '00 LS1 with a stock oil pump (42k on it) and I have tons of oil pressure, I've also spun my motor to 6800 at the track with no issues either. That said I have proper valvetrain modifications, upgraded to the LS2 timing chain (much stronger/better) as well as good oil in the car at all times for extra protection.

To get an LSX to 400rwhp+ isn't that hard, many do it cam only even. To get north of 400rwhp on an LT1 is a lot more work and the drivability suffers greatly. I'm only making 363rwhp with a small cam (224/224 .567" lift) and an LS6 intake. There are a few members on here with north of 400rwhp with slightly larger cams and one I think has stock Z06 heads (243 castings). Those guys are running 7.1 in the 1/8th which is low 11's! Not bad for a cam/head change. My car idles like stock and pulls great milage (for a V8) on the highway with the 6spd.

 

I guess I like what I have and I would recommend the LS1 for reliability, performance and their aftermarket.

$.02 deposited

[rags]

Isn't the LT1 OBD1? Is so, it will be a little harder to find someone to tune the ECM if you modify the internals. The LS1 has a huge following in the ECM tuning arena.

I'm not saying one engine is better than the other, just something else to think about.

 

Joe

[deja]

Isn't the LT1 OBD1? Is so, it will be a little harder to find someone to tune the ECM if you modify the internals. The LS1 has a huge following in the ECM tuning arena.

I'm not saying one engine is better than the other, just something else to think about.

 

Joe

 

94 LT1s are OBD1, after that they are OBD2. I don't know about the 93 but the 94 can be programed in the car with the right cable, software is the same.

[lgoodson@pacbell.net]

Thanks for the info

The car is a very clean 71 backed up with a t56

Not running, just sitting in the frame. As I am told it needs the drive line shortened 3/4", a high pressure fuel pump, Exaust and of course the wiring. This came out the same car complete with all of the electical still plugged in. Owner say all that is need is to connect to 12 volts and it

should fire. JTR complete kit was used including the headers(sanderson) and alluminum radiator. Body and paint is near mint, the paint MIGHT have a small ding or two, Interior is new, Dash pad is cracked, no air.

 

The rated hp for the year model engine is 300 ponys. Not a lot but respectable pushing 2800 lbs.

The rear end is unknown at this point. It has been changed out once or twice. Doesn't have real low gears. Should get pretty good mileage.

 

The owner seems to think that the opti-spark is a plus.

 

For this price I don't think I could touch a complete & clean LS1. That was my first choice. I can alawys swap it out later

 

Anyway I'll be into this thing for $4500 with the 2.8 pull ou that has been dressed up with poilsh and header.

[RTz]

94 LT1s are OBD1, after that they are OBD2.

 

OBD2 was Federally mandated in 1996. 'Some' 95's LT1's had it, but not all.

[Bartman]

I'm running an LT1 and the main reason for selecting the LT1 over an LSx engine is the ease and cost of the swap into a 240Z. LT1 engines can use the same JTR kit as any other SBC. LSx swaps require a different solution that will likely be more costly, require you to have fabricaton skills, or both.

[getZ]

Personaly I would think about what you want to do long term, how you plan to drive it and your future horsepower goals.

 

If I were to do it again, I would go with an LS series engine, the aftermarket has really come around to bring the pricing down on everything: heads, bottom end assy, rockers, etc.

 

Also realize the LS engine was built with a clean sheet of paper based off of what was learned with previous generations of engines, valve angle, intake runners and head chamber design. I look at the power numbers the guys are making with the new LS series engines and how smooth they run and you can't compete with the old sbc and LT-1. 500 horsepower is easy with an LS engine and the thing idles almost like stock.

[rejracer]

http://forums.hybridz.org/showthread.php?t=140809

 

I have a 94 impala SS which came from the factory with an LT1. They are potent motors and mods are available. However GM only produced these motors for 7 years. They have some weak spots, such as water pumps are prone to failure, the Optispark does not like to rev much past 6k or the rotor tends to fail. The factory PCM cannot rev past 7200. The factory iron manifolds crack (I assume you would be going with headers).

 

If you get a LT1 make sure the optispark is vented, and that the car comes out of a Vette Y-body or camaro or F-Body to get the aluminium heads. Try to avoid the 97 aluminum castings. Although they do flow better than the original castings they are thin and lack enough material in them to be ported.

 

My suggestion based on the aftermarket support of the LT1 versus LS1, LS1 is the clear winner. Aluminum blocks, heads, your choice of stroke from factory cranks, better rods, better heads, coil on plug ignition, composite intakes. It's just a better upgrade path in my opinion.

 

The initial investment may be slightly higher, but the long term cost I believe would be lower as there is much larger supply of used parts on the market.

 

Hope that helps

 

 

Since I posted the above in the aforementioned thread the 94 impala has cracked another manifold. It's a great car when it runs.... I live 2 miles from work, and I believe the short trips are part of the problem.

 

Concerning 118k miles on the engine.. It's just getting broken in! I pulled the heads on the impala at 205k and there was still cross hatch and no ring ridge on any of the bores. Just in case you are wondering, I ran it without coolant due to a failed water pump and cracked the heads. It failed due to neglect on my behalf.

 

I have not heard of LT1's having lower end problems when properly built. I have 225k on it now and it still maintains 40-55 psi at idle depending on temp using 0w30 castrol syntec. Anyone who know's me, can attest to the fact that I am not the easiest on wheeled mechanical equipment.

 

The above almost sounds like a plug for the LT1, but it's not, just trying to share my experience here. Now if I had a choice, I would hold out for an LSx car.

 

The best advice I can give you is to spend a few days in the impala ss forum. It's a more mature crowd over there compared to the fbody crew. I think they will be a bit more objective if your looking for advice. I suggest taking a look in the performance and engine problems sections. In the performance section you will find that fellas are blowing holes in pistons on 11 and 12 second runs in a 4k pound car. hrmmmm dunno why that would happen!! in the maint section you will find problems with oil leaks, "how do I replace spark plug wires" and very basic stuff. You usually don't find off the wall engine failures except on high mileage engines, and that being 250k plus. There are of course exceptions.

[deja]

Thanks for the info

The rated hp for the year model engine is 300 ponys. Not a lot but respectable pushing 2800 lbs.

Doesn't have real low gears. Should get pretty good mileage.

 

The owner seems to think that the opti-spark is a plus.

 

 

Not sure what he means by th opti being a plus...over what?

 

Here's a link to LT1 history. http://en.wikipedia.org/wiki/GM_LT_engine The 93-95 F-bodies were rated at 275 horsepower, not 300. The 92-93 LT1s used speed density fuel management, batch-fire fuel injection and a dedicated engine control module (ECM), not the ideal setup. Among other things I think that means you can't flash the computer but need a chip programmed and swapped.

 

I am running a bone stock 94 LT1 with close to 130,000 miles (only modes are Sanderson headers and cold air inlet and some small tweaking of the PCM) and a 4L60E auto and when I ran it at DNI it had an open 3.54 stock rear. The car weigh 2905 with a full tank and no driver. Not sure what you consider respectable but I turned consistent 12.9s at around 103 by simply stomping on it when the light went green. I've switched to a LSD and 3.7 gears but haven't had the chance to run it yet.

 

I get 18.5 mpg in town and 25 mpg on the highway running at 80 mph.

[getZ]

I'm biased towards the LS, but don't forget the 6.0 caddy,the 6.0, 5.3, 4.8 truck engines are alternatives as well. I just don't know if the manifolds off the corvette and f-bodys are a bolt in deal to clear the hood. Sombody around here may have done this.

 

Lingenfelter performance was geting about 380 horse out of the 5.3 truck engine with a simple cam swap and I assume some reprogramming.

[lgoodson@pacbell.net]

Well I bought the LT1 pictured. Now all I have to do is get running. JTR installation but the tunnel looks way to small for the T56 in there, A electical sender of some type is hard up against the tunnel wall, Does any one know what this connection might be, The JTR install really doesn't talk about the LT1/T56 install much but I haven't finished the book yet and the I will start the fuel injection book next.

 

What is a good source for air intake part for this 240z with the LT1. What is every one using, Thanks for the help. Maybe I can return the favor

[deja]

If you're talking about the sending unit on the driver's side rear of the block its the oil pressure sender. I had to cut out the entire stock tranny mounts and beat on the passenger side a bit to get my 4L60E auto in the tunnel, others can comment on the T56. I picked up some mandrel bent 3.5" aluminum tubing and several silicone rubber connectos to make my own air intake.

I don't think anyone makes one that will just fit without modification.

[m1noel]

The sender that is tight against the tunnel wall with the T56 is the back up light switch. You can easily massage (read pound) the wall to make it fit. Or using a pry bar with a rag aroung the sharp edge just move the wall a little- it will fit. You will have to remove the ears from the old z tranny mount but shouldn't have to remove the solid parts. There are pictures on here if you search.

Mike

[lgoodson@pacbell.net]

Deja, would you mind telling me where you got the mandrel bent polished tubing and is that an air Condensor in front of your radiator? Any heating problems? I am using a JTR kit and their alluminum Radiator. Not running yet.

 

M1noel. Thanks for info on the switch but what did you do for a Seedometer connection on the t56, Did you use a modified tail housing from stealth products like JTR reccomends or something else?

[lgoodson@pacbell.net]

I have read both the JTR books for the first time this weekend and I will read them a few more times before I am through with this conversion but as I read the books, it was clear that they weren't too interested in LT1's or T56's. All they talk about is TBI this and TPI that. For my installation, is these books the right ones for the job? Any comments would be appreciated.

[janaka]

sticky goodness from the SBC Gen III and IV section

http://forums.hybridz.org/showthread.php?t=123533

[gvincent]

Deja, would you mind telling me where you got the mandrel bent polished tubing and is that an air Condensor in front of your radiator? Any heating problems? I am using a JTR kit and their alluminum Radiator. Not running yet.

 

M1noel. Thanks for info on the switch but what did you do for a Seedometer connection on the t56, Did you use a modified tail housing from stealth products like JTR reccomends or something else?

 

I have pics of my trans tunnel and what I removed in my gallery pics.

As for the switch on the T56 yeah it was really tight so I drilled a 1-1/4" hole in the side of the tunnel where the connector was and used a soft rubber plug I found at the junkyard from some trunk. Now I have access to the connector and you don't even know it is there unless you pull back the pad and carpet.

I suppose you can find an appropiate firewall rubber plug somewhere as well.

 

As for the LT1, I am about to install my second one, I had some unusual bad luck with the first one. Cold air, make your own out of rubber elbows and aluminum pipe or buy one of those cheap Ebay ones for the Camaro and Firebird as a starter kit, you need 1 more elbow though.

If your looking for HP yeah go LS1, harder to install but if you just want a great EFI cruiser the LT1 is a good choice.

I personally wanted a old school 400/406 SBC but I am an old school guy.

This computer tuning has me baffled.

I would trade both of my LT1's and all my performance stuff, computer, software everything for a good old school 400/406 to mate up to my T56.

Greg

[deja]

Deja, would you mind telling me where you got the mandrel bent polished tubing and is that an air Condensor in front of your radiator? Any heating problems? I am using a JTR kit and their alluminum Radiator. Not running yet.

 

I picked up the aluminum and all the fittings on EBAY. I polished them myself with Mothers, but they were pretty good when I got them. Yes AC condensor and tranny cooler all in front of the radiator and I have had no overheating issues. I'm running the JTR rad and a Taraus fan controled by the LT1 computer (you need to do some rewiring for the 2 fan controls to run the 2 speed taraus fan).