Pros and Cons of '94-97 LT1 + T56

[sstallings]

Guys,

I'm a new member, but I'll try not to waste your time with questions I can find answers to elsewhere. A bit of background: I've done swaps before in a '34 Chevy streetrod and a '67 Camaro. I've wired cars, and I've set up my own aftermarket EFI using Accel/DFI 7 on a 540 cid stroked '70 Cadillac with my own fabricated intake manifold with Accel and Painless Performance wiring. I buy and READ a lot of books on every aspect of a project before I start, so that I can make informed decisions. I own a '72 240 Z that will go under the knife at a later date - it followed me home last year.

 

My current project is with my son on his '77 280Z. We've had it for 7 years, with the stock 2.8L Bosch EFI, but living in Los Angeles, we are at the point where it will no longer pass the bi-annual smog inspection, so it's time for a V8 (we're not even considering rebuilding the L28). I have everything that JTR has written on the topic, as well as anything else I can find from Motorbooks and others on EFI. I'll be buying the Helms manual as soon as I know which model/engine to buy it for.

 

I know the simplest swap would be a 77 L82, L48, or the anemic (170 BHP) LM1, carburated, with a T5, with the minimal smog equipment and wiring that it would require. In fact, I have a complete rebuildable LM1 engine that I picked up with the 240Z from a guy that never finished his swap. I'm just afraid that as soon as I finished it, I'd wish I'd gone the rest of the way and put in an EFI LT1, LT4, or LS1 and T56.

 

What really has my attention is the '94-97 LT1 with a .50 over T56. I've found a couple of '94 candidates in the $3000-3200 range (complete) with under 70K miles, but I'm holding off until I know more. After searching your site for anything related, I have a few questions:

 

1. Will the AC compressor fit around the right front frame area usng the JTR engine/trans mounts?

2. If not, are there brackets to switch the AC with either the alternator or the smog pump to make it all fit?

3. In a couple of threads I've read about problems with the opti-spark (opt-crap) on the '94, with references to the vented '95 being the "preferered" LT1 year. Why?

4. I've read that the '77 280Z fuel pump will work with a TBI/TPI motor, but will it work with an LT1?

5. I've seen the T56 mods (and costs) to adapt a mechanical speedo cable. Has anyone just bought an aftermarket electronic speedo and re-used the 280Z gauge face (seems a lot easier and about the same cost)?

6. I'll need to pass Calif. smog inspections, so I'm interested in talking to anyone who's already been there and done that. I have met with a very competent CARB Referee, Gus Romo, who is also an Auto Technology instructor at Rio Hondo College in Whittier, CA. He seems like a very helpful resource for setting up the LT1 to pass, but he doesn't know 280Z swaps specifically. Does anybody have information to share?

7. I'd like to avoid as many pitfalls as possible, so if I've forgotten something really important regarding an LT1 swap, please educate me.

 

Thanks. And, I've already seen a few threads I could contribute to, but I'll start off slow here until I know the site better.

Steve Stallings

[Bartman]

1. Will the AC compressor fit around the right front frame area usng the JTR engine/trans mounts? Not without notching the frame. I used bowers kit to move it to the upper left side of the engine http://www.bowersrodshop.com/info_pulley.htm

2. If not, are there brackets to switch the AC with either the alternator or the smog pump to make it all fit? I haven't seen one that works in the Z engine compartment.

3. In a couple of threads I've read about problems with the opti-spark (opt-crap) on the '94, with references to the vented '95 being the "preferered" LT1 year. Why? Venting with fresh air from the intake system (no water) instead of from outside air which could include water (especially since it's right under the water pump). I switched my 94 non vented to a 95 vented unit.

4. I've read that the '77 280Z fuel pump will work with a TBI/TPI motor, but will it work with an LT1? Yes, I used one for a while.

5. I've seen the T56 mods (and costs) to adapt a mechanical speedo cable. Has anyone just bought an aftermarket electronic speedo and re-used the 280Z gauge face (seems a lot easier and about the same cost)? I used an Autometer gauge but didn't use the stock gauge face. I'm sure it could be done if you really wanted to.

6. I'll need to pass Calif. smog inspections, so I'm interested in talking to anyone who's already been there and done that. I have met with a very competent CARB Referee, Gus Romo, who is also an Auto Technology instructor at Rio Hondo College in Whittier, CA. He seems like a very helpful resource for setting up the LT1 to pass, but he doesn't know 280Z swaps specifically. Does anybody have information to share? Nothing specific, just retain all the emissions from the donor vehicle.

7. I'd like to avoid as many pitfalls as possible, so if I've forgotten something really important regarding an LT1 swap, please educate me. Can't think of anything at this point.

[DavyZ]

Bartman is one of the best sources of information for this swap and was the one that came to mind while I was reading your post. Voila, he answered a little bit down the page!

 

Anyway, my advice is to do the LT1 swap and use the JTR method for doing it--the LT1 was the last of the 5.7L SBCs that worked with the basic JTR mounts; nice and simple.

 

We have some good info on this site that should keep you very busy reading and I'm sure your swap will turn out just fine after reading about your experience in doing swaps. I think your son will have one of the fastest, smog legal cars in the area. Good luck.

 

Davy

[LS1 240Z]

i have an LT1 Caprice and a LT1 swapped malibu wagon. they are nothing but problems. use a later model gen 3/4 motor.. you will be sooo glad you did. put a truck 6.0 in it backed up by an LS1 t56. you will be so glad you did it over an LT1 every time you drive it and expecialy every time you have to work on it.

[Pop N Wood]

I seriously considered the LT1 for awhile. Maybe you have already read all this, but the 94-95 motors had the OBDII type computer which can be reprogrammed with a lap top. The earlier motors had a chip type computer. Apparently it is not an easy task to switch the 93 motors to the later computer.

 

The other issue is how strictly will the referee interpret the OBDII requirements? The 95’s are not required to meet the OBDII requirements whereas the 96 and later are. I have read posts on this site where people failed to get their CARB certificate because the OBDII vehicles actually used signals from the ABS sensors to modify the fuel delivery. Thus to be 100% compliant people were forced to try and swap in brake sensors. Maybe the guys just got a hard ass inspector but it did happen.

 

You have a 77 so cats are a given. That was a deal killer with my 240. O2 sims are not OBDII compliant.

 

Another option on the speedo is an aftermarket T56 or even TKO. Both tranny’s come with electronic and mechanical speedo outputs. New transmissions are expensive, but it seems like T56 rebuilds, especially on the early units, are pretty much the rule and rather than the exception. The price of a new unit doesn’t look so bad when you consider $1500 is typical for a T56 rebuild.

 

I can’t imagine what it would take to fit a late model truck 6.0 motor in and still be smog. First off I don’t think it is legal to swap between cars and trucks (at least in my state), but more importantly the truck intakes have no chance of clearing a Z hood. If you swap out the intakes you are no longer smog legal.

[Z48LT-1]

I wish to humbly correct the revered veteran of this board, Mr. Wood, but the '94-'95 LT1s were OBDI, while the '96-'97 were OBDII. There were other changes but while all '94 up PCMs are flash upgradeable, the diy opportunities are greater for the OBDI models.

 

Cheers -- Gary

 

Not to hijack the thread, but I just found an interesting article on the difference among PCMs here: http://www.gmhightechperformance.com/tech/0704gm_factory_pcms/index.html

[Pop N Wood]

I wish to humbly correct the revered veteran of this board, Mr. Wood, but the '94-'95 LT1s were OBDI, while the '96-'97 were OBDII. There were other changes but while all '94 up PCMs are flash upgradeable, the diy opportunities are greater for the OBDI models.

 

Cheers -- Gary

 

Not to hijack the thread, but I just found an interesting article on the difference among PCMs here: http://www.gmhightechperformance.com/tech/0704gm_factory_pcms/index.html

 

I think we are saying the same thing. The 94-95 vehicles are not subject to OBDII rules. That is why they are easier to smog. But they do have the flash programmable computers that the OBDII cars did. This is a good thing cause they can be programed with software.

 

Right?

 

OBDII did have some good points, and flash programable software was one of them. The other advantage is a common code reader.

 

I think the only person I might be revered by is Mike Kelly. Everyone else just lets me have it.

[sstallings]

Guys,

Thank you for spending the time to answer my initial questions. I contacted Bowers, and will pursue that course for AC brackets. I'll narrow my engine and trans search to 1995 to get the best starting point of LT1 with MAF, OBD1, vented opti-spark, and a 0.5 OD ratio T56. I'm sure I'll have questions along the way, and eventually be contributing to answers as well.

 

Working in the cramped cabin of a Z will not be that much different than my street rod project, but complying with CA smog requirements will be a new experience. Thanks for all of the tips so far.

Steve

[deja]

Guys,

Thank you for spending the time to answer my initial questions. I contacted Bowers, and will pursue that course for AC brackets. I'll narrow my engine and trans search to 1995 to get the best starting point of LT1 with MAF, OBD1, vented opti-spark, and a 0.5 OD ratio T56. I'm sure I'll have questions along the way, and eventually be contributing to answers as well.

 

Working in the cramped cabin of a Z will not be that much different than my street rod project, but complying with CA smog requirements will be a new experience. Thanks for all of the tips so far.

Steve

 

One thing about the Bower setup is space. I too used it and as Bartman told me there was some "tweaking" necessary to use the Bower mount in mt 280Z. I had to not only massage the shock tower and had the massage the Bower mount as well. And even with that there is less than 1/2" clearance on my setup. A lot depends on where your final engine position is. I also had to modify (straighten) the MassAir bracket they provide to use the cold air setup I'm using.

[wheelman]

sstallings,

If you are planning to upgrade the heads and cam you might consider picking up a Caprice 9C1 LT1 instead of one from a Camaro or Vette. It's the same motor but has iron heads and a cam setup for lower end torque. They're cheaper than the more performance oriented version but with a cam and head swap there is no difference.

 

I swapped in a Caprice motor, kept the iron heads, installed an LT4 hot cam, eliminated the emissions stuff, AC, PS and burned a tune to remove those things from the PCM. Dynoed 274 RWHP @ 5800 RPM and 307Ft/Lbs at 3800 RPM. I'm also running a WC T5 instead of the T56, they're much cheaper and lighter but a bit hard to find, at least in my part of the country.

 

Wheelman

[Mikelly]

 

I think the only person I might be revered by is Mike Kelly. Everyone else just lets me have it.

 

 

 

Put the bottle down Sportin' a toothpick, and get back to work!

 

 

Mike

[RTz]

You two should get a room

[sstallings]

Wheelman,

While I like the idea of LT4 level performance, I think I need to keep my priorities straight:

1. Make it run and stop (Toyota calipers, 510 drums, proprtioning valve).

2. Pass CA smog referee inspection.

3. Enjoy it and get the cosmetics to match the new LT1 performance level.

4. Make it go faster.

 

Of cource, if I didn't live in Los Angeles with a '77 Z, priority number 4 would be first. Once I pull this off (learning on my son's 280Z), I'd like to attempt an LSx swap into my non-smog '72 240Z. That should be a rocket.

Thanks,

Steve

[LT1-280z]

Steve,

 

If you want to use your stock speedo you could get one of these:

 

http://www.tciauto.com/Products/Electronics/

 

Speedometer Control Unit (SCU)

 

They're a bit pricey.

 

I made my own - the hardest part is sourcing a drive motor. If you are into electronics I can share the gory details.

 

http://album.hybridz.org/showphoto.php?photo=17063&size=big&cat=500

[gvincent]

I was going to bite the bullet and go for this one here:

http://www.atrol.com/cablex.htm

There is one on Ebay all the time for $299

But I would be interested in your gory details

I am pretty good with a soldering iron. ()

Thanks,

Greg

 

Steve,

 

If you want to use your stock speedo you could get one of these:

 

http://www.tciauto.com/Products/Electronics/

 

Speedometer Control Unit (SCU)

 

They're a bit pricey.

 

I made my own - the hardest part is sourcing a drive motor. If you are into electronics I can share the gory details.

 

http://album.hybridz.org/showphoto.php?photo=17063&size=big&cat=500

[LT1-280z]

Greg,

 

The one from Abbot looks the same as TCI's, Abbot is probably OEM.

 

Here's the beginings: $300 may not seem to bad.

 

This took me months to come up with, I took it on as a challange - more brain than sense I guess. Maybe I could make kits for the electronics part.

 

 

 

First off you will need a motor with tach leads. I found mine at www.meci.com it’s a surplus motor from a very old 8” floppy drive. It was $3.00, its surplus so they don’t have them all the time. Then I used 1/8” aluminum plate, a slot car axle and bushing to make the drive housing for the 2:1 ratio belt drive. I sourced the pulleys and belt from www.sdp-si.com. Then I just cut down the stock cable to mount the drive unit between the clutch and brake pedals (see picture). I kept the cable as straight as possible to avoid any binding since the motor is pretty small. For the electronics, I used two LM2907 frequency to voltage converters http://www.national.com/mpf/LM/LM2907.html one to read the pulse from the PCM and one to read the tach from the motor. Then used the built in comparator to control the charging of a capacitor whose voltage controls the PWM output of a DRV101 PWM driver http://focus.ti.com/docs/prod/folders/print/drv101.html for the motor speed. Since the motor I used is small I was able to drive it directly, a larger motor might need a dedicated driver stage. The only other part is a enable delay (555 timer) of a few seconds to allow the capacitor to charge up before letting the motor turn on since the voltage across the capacitor is inversely proportional to the speed (higher voltage lower speed) the speedo would jump when you powered up. Calibration is done by adjusting the voltage output of the first LM2907 using small tool I built that has a 60Hz pulse (draw down to ground – the same as the PCM). The 95 Camaro has a 4000 pulse per mile output so 60 Hz = 54 MPH. Set in this way all the settings for tire size and gear ratios in the PCM are accurate. I don’t have the PC artwork in a usable form right now. The one in my car is definitely v1.0 but works quite well.

[Danno74Z]

sstallings,

 

The LT1 engine needs the input from the VSS in order to run correctly. A lot of calculations and adjustments are being used by the computer and ALL the sensors - MAF, MAP (yes the LT1 has one) VSS, TPS, knock, Temp, and others to make this swap emission legal (In CA). In CA (please correct me if I'm wrong) don't they put the car on a dyno and put it through its paces while they are sampling exhaust? As they vary loads and SPEED the computer is taking all this into consideration and altering spark and fuel. I would not convert it over to a mechanical speedo. IMO

 

If I'm not mistaken, I think some HybridZ members who went to a mechanical system on the LT1 eventually went back to the original electronic system for better drivability.

 

Danno74Z

[wheelman]

I tried to run mine without a VSS and found it to have a problem with stalling when coming to a stop, especially if I'd shifted down to slow the car.

 

The reason this happens is the PCM is monitoring the VSS to determine what the idle should be. If the car is moving the PCM opens the IAC a small amount to keep the idle at 1500 rpm or so (this is adjustable). When there is no VSS the PCM always thinks the car is stopped so tries to keep the rpm at idle (around 800). To do this it clamps the IAC completely closed, when you release the throttle there is no air flow into the engine and it dies or will stumble real bad.

It's possible to adjsut some parameters to reduce this issue but it never really goes away and would definitely not pass CA emissions.

 

BTW: I created a VSS using a pulse generator inline with my mechanical speedo cable so I was able to retain my stock speedometer and have the VSS.

 

Wheelman

[Danno74Z]

BTW: I created a VSS using a pulse generator inline with my mechanical speedo cable so I was able to retain my stock speedometer and have the VSS.

 

Wheelman

 

 

Wheelman,

 

Did your T5 transmission come with a mechanical speedo cable only? It sounds like it did and then you feed the VSS signal off the cable to the computer. Nice Job! Us T56 guys with trannys from OEM cars don't have the mechanical output so we can't go this route very easily. Sounds like LT1-280Z developed his own VSS generator - a lot of work like he mentioned.

 

How do you know when your going over 140 with the stock speedometer

 

Danno74Z

[wheelman]

Danno74Z,

Yeah, my T5 only had a mechanical output which in a way was nice because I was forced to make it work. You are correct about getting the signal from the cable as well but I bought a 4-pulse square wave generator to do it.

 

My speedo goes up to 160 mph, don't know if the car ever will, at least not with me driving it.

 

Wheelman