Folks...still looking for a more modern 350 for my 68 Project. Found a 94 LT1 from a Buick Roadmaster with computer and wiring. What are the differences between GM models in these later years? Need advice as I need to make a decision sooner than later...thanks

 

I had a 94' Camaro with the LTI and 6 speed. It came with Aluminum heads (275HP). The full size Buick and Chevy LT1's had iron heads and less power (don't recall how much). The only down side is the issues with the Optispark dizzy. The LS1 is capable of building more power than the LT1 if it makes a difference to you. Either one would be great in a vintage Vette.

Gary

 

Are you speaking of the moisture issues in the opti spark? Hasn't there been a fix for that? Have read a few threads about air and moisture in these. Thanks

 

GM moved to a vented Opti in 1995. Also, make sure that it's the 5.7 liter LT1 as there was also a very similar looking 4.3 liter "baby LT1" made for Caprices and Roadmasters as well.

 

Yes, My 94' went through 2 of them in the 10 years I owned it and the car never saw rain. I'm not sure that the replacements were the ones with the 'fix' or not as the dealer installed them under warrentee. Otherwise it was a nice running engine, lots of power.

Gary

 

If you're gonna go thru the trouble of a swap, why not step up to an LS engine? The LT1 won't make any more power than a comparably built engine with Vortec heads but an LS will make a good bit more, plus you have a much better "WOW" factor when you pop the hood.

 

Just an FYI that I just finished both a cosmetic and performance makeover on a 94 Camaro LT1 for a friend using the new Edlebrock LT1 to LT4 conversion kit, some Comp push rods and Roller rockers, and headers, a Holley 52mm, and Bosch 32lb injectors and I have to tell you the thing not only looks mean it sounds mean and runs strong.

Car Craft just did a Dyno test on the same configuration and with tuning (I sent the ECM out to Ed Wright at FastChip.com) it made over 400hp with a nice thumpity thump to it. We threw some 4:10 gears in there with the 6 speed and it really woke that puppy up. I think it would look hot under the hood of a vette. (We used March Style Track Pulley System and Billett Specialty Valve Covers as well).

My 81 has an LS6 in it so yes, I can vouch they make more power, but the LT1 with some goodies for the money is not a bad swap.

Before:


After:

 

I have tons of experience with LT1s, so let me clear up a few things. One, the 94 model year has some plusses and minuses. The minus is that it still uses the non-vented style Opti. You can change it over to the later 95-up style, but this will require a 95-up timing cover and a longer dowel pin in the camshaft (not a big deal if you're changing it anyway). Go with a good AC Delco Opti (I have heard the Accels are junk, and have heard mixed results with the MSD).The plus is that 94 and 95 still have an OBD1 style PCM, which is much easier to tune, and there is less garbage to cut out of the stock harness if you're going to use it. To me, the real downside of any LT1 is the garbage water pumps that GM put on them. I have had 2 failures (not minor leakage from the weep hole, GUSHING all the coolant out of the motor in a matter of minutes) of new GM pumps; one was on a new car, the other was on a low mileage (about 15-totalled press car) takeout motor. The fix? Use one of the Mezeire Electric water pumps in the stock GM housing. Works MUCH better.

The stock cam is weak, so you'll probably want to trash it. The factory iron heads flow better than the aluminum heads supposedly, but if you're doing port work you'll want to get some aluminum ones. You can buy them cheap. usually less than $200. Or. you could go aftermarket; AFR, Trick Flow, Edelbrock, and others make heads.

If you're doing a full performance rebuild on the motor, you can get an honest 430-450hp. The downside is that dollar for dollar, you could probably start with a 5.7 or 6.0 LS motor and make that with boltons. The cost is about the same. The LT1 does have the advantage, though, that it will bolt up to your original mounts with no changes, and you won't have to change your exhaust (regular SBC headers will bolt up). PM me if you have any other specific questions.

 

Great info guys! I'm going to look at the motor today. It has 65-70,000 miles but the plan is to go through it anyway. Did I understand I can tell if it is a smaller 4.3 by a stamp on the back of the block where the tranny mates up? Other quick identifications? It is out of the car. This is a budget build and want something that will bolt right in and up to the Turbo 400 already in the car. I am open to more modification ideas keeping in mind it is a budget build. Thanks

 

keep in mind the LT1 is a reverse-flow engine and any performace parts will have to be specific to the LT1. I loved my 92, 93 and 94 LT1 Corvettes but the aftermarket was limited and about the same price as LS1 components (but with less bang for the buck).

 

Got it for $375. He was asking $500. Open to any and all budget minded upgrades. Lets here em'

 

Rub Cheetah blood on the engine block. It's free if you kill the Cheetah yourself.


Scott

 

First, check to see if it has the aluminum heads or iron. You'll want to start with an LT4 hotcam kit imo. $500 will get you the cam, springs, rockers, and retainers. It's a nice streetable cam with a good lope and pulls all the way to 6k. Check out the C4 section for advice.

 

Congrats on the buy!

If it's out of a Buick it has the iron heads (unless the previous owner swapped them). How much power do you want to make? As said earlier in this thread, 430 HP should be easy. I put down 385 HP NA at the wheels in my Camaro with the LT4 heads, intake, and hotcam as the major adders (full mods in link in sig). Had I done it all over again, I would've gone with a bigger cam and/or stroked it out to a 383.

Search for Lloyd Elliot and Advanced Induction as they are well known for their LT1 work.

 

The GEN II LT1 conversion was popular until the LSx motor came out. U can use the computer or a carb configuration but both take a fair amount of parts and work. If u run a carb the only intake avail is a dual plane from GMPP. And unless u convert to electric fans for cooling u will need a belt asscessory braket to use your centerifical clutch (or fixed fan if u have one) as the LT1's have cam driven water pump w/o belt drive. I believe the Buick had this fan bracket.

Now alot of L98 (3rd gen camaro) TPI types used the LT1 intake with thier L98 ECM by having a machinist drill a hole in the intake for the distributor. Or u can just install the intire LT1 PCM and use the "Opti" dist.
BTW my '94 Z28 is an OBI PCM and when i installed a new LT1 crate i used the later '95-'97 "Opti" that has a bigger hole in the timing cover (still more parts for u though) and is driven by a little different cam (nose). But i like the later vacuum ported "Opti" than the original vented to air "Opti" ('93-'94).
U also need an electric fuel pump and return line to tank.

Easiest conversion is the carb with dual plane and your origianl dist - u will find a dummy dist drive under the LT1 intake.

But for an easy 300hp with good headers u can't beat the price. GMPP was selling brand new LT1's in the crate for only $1540 this spring '09 (had the late large hoe "Opti" dist though). Just incase u need a replacement someday.

Well i hope this helps and good luck,
cardo0

 

Next question guys...wuold you stick with the Multi Port Injection? Or go carburated?

 

No question I would stay fuel injected. Below are a few things to consider for the swap. It is mainly about TPI, but has a last paragraph about LT1.
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You have a unit
First you have to determine whether you want mass air flow or speed density. The C3 is more conducive to speed-density due to space issues. Mass-air flow is easier to make engine changes without PROM changes. If you are technically proficient enough to make a Camaro harness work they can be bought for $100 or less. I have been told that you can also use a 3.1 Corsica or Cavailier harness with a little work, it uses the same 7730 Speed-Density ECM. Aftermarket harnesses range from about $300 for Painless to $500 for Howell to $700 for Street and Performance. Howell makes a great harness, but for a Tuned Port they do not make one that will control the converter lockup on a 200R4/700R4/4L60 transmission. If you are running a manual or non-overdrive-automatic transmission I highly recommend them. I have heard great things about Street and Performance harness, but do not have first hand experience with them. I also have a Fuel Injection Specialties (FIS) harness and it is OK. The ECM can be had used for $10-50. A good external fuel pump will cost at least $100. I use an 88 Ford Truck external pump, $114 from CarQuest, made in Texas by Airtech. If you have a 78-82 you can use your fuel tank with an 82 sending unit and a TPI pump. 68-77 can also use a modified tank or Rock Valley makes a tank for these cars with a baffle and a GM internal fuel pump. Stock 82 tanks do not have a baffle contrary to popular belief. An aftermarket PROM with VATS and Emissions codes removed will be $100-200 depending on source and complexity. You will have to add an oxygen sensor to your exhaust, $20 for the sensor, $5 for the weld-in bung, and say $25 for an exhaust shop to weld it in if you can’t. Some harnesses use VSS and some do not. An auxiliary VSS sensor is around $75. I recommend using VSS to get better drivability. To install a TPI I say figure at least $800 plus the TPI unit and whatever repairs are necessary to bring it up to useable status. I have TPI/700R4 in my 69 Corvette (Howell harness) and an 83 Pickup (FIS harness) and I love it. Starts good, great torque, good fuel mileage, easy to swap onto stock engines (although both of mine are complete engines out of 90/91 ‘Vettes).

Differences in years
All Corvette TPI intake manifolds work with the older (through 86) iron heads and the factory aluminum heads through 91. F-body TPI intakes use the upright center bolts on 87-92 and thus fit all 87-95 iron heads (non LT1). Either can be swapped to fit the other with some drilling. F-body has the fuel lines come out on the drivers side and has a central port for EGR. Corvette has fuel lines that come out on the passenger side and has an external port for EGR. Corvette fuel rails fit F-body intakes and vise-versa. The runners are all the same through the years, but the LH runner has a hole for a 9th injector in the 85-88 runners. This can be plugged off if you get a nice LH runner and don’t want the 9th injector or decide to run speed-density. The plenums all physically interchange, but 90-92 have an extra vacuum port for the MAP sensor used with the speed-density computers and wiring. 89 is an odd year, it is mass-air flow but without the 9th injector. 89 up throttle bodies can be used on all years, but a 85-88 throttle body requires a ½” hole be drilled in the front of a 89-92 Plenum for idle air. 89-92 Throttle bodies have a more desirable cable attachment. The cable attaches around a circular linkage which has a smoother actuation than the straight linkage on the 85-88. The Corvettes have an aluminum plenum extension over the distributor, the F-body extensions are plastic. The Corvettes use an HEI coil-in-cap distributor for 85-91 (Delco 1103680). 85-86 F-body also used a big-cap distributor. 87-92 F-Body used a small cap distributor with an external coil (Delco 1103479). This same distributor is used in the 87-95 5.0/5.7/7.4 TBI injected trucks and pre-LT1 B-body. The F-body intake gets it's exhaust for EGR from the center passages in the heads like most SB Chevys. A Corvette intake gets it's EGR exhaust from the RH exhaust manifold/header through a flex-tube to an opening near the distributor-no center passages in the intake. If you are required to keep EGR and you have a Corvette intake, I recommend getting the C4 exhaust manifolds. They are like mini-headers, and have a 2 1/2" outlet. I have them on my 69 and like them.

As far as a throttle cable to use, on my Vette, I used a TPI Corvette cable, 1990 I think (now discontinued from GM) but you have to cut the end off inside the car and use a hood-release-cable end (Corvette Central 342138 "cable stop") to get it the correct cable length (the housing is OK). You must use a cable from the type car your throttle body came from if you want to have a chance of not cutting it. Again, 85-88 use a straight pull, while 89-92 have a circular attachment for more smooth actuation and so the inner cable is longer. On my 83 truck I used a TPI F-Body cable and it was OK, but I had to coil it up into a loop in the engine compartment because the housing was so long. I also TPI'd a 72 Chevy truck and used a 90 350 TBI truck cable for it. It was 1/2" short outside if anything, but I was pretty pleased with it all told-I didn't have to shorten it. In a Vette it might be about right. In all vehicles I've done you need a die grinder to square the firewall hole off a bit. All vehicles I've done used the late throttle-body.

I would look into a TPI. They start immediately in winter, have great vacuum, and will get great mileage. I can open the headlights and the wiper door at the same time with no hesitation at all-solid wooomp. With 3.70 gears (and a 700R4 overdrive) I get 18mpg city and 22+ highway. With 3.55 or 3.36 it would be even better. You can probably find a used Corvette TPI engine for $1000 and with an $800 harness/computer/fuel pump you would be set. On a 78-82 you can use the stock fuel tank with an 82 sending unit and TPI pump and be in better shape than 68-77 with an external pump. With the Vette TPI you would have aluminum heads that would remove weight. Even with an F-body iron-head TPI 350 it will be less weight than a stock intake. It will bolt up to everything in your car, use stock accessories, use your transmission, and the visual appeal is awesome. Don't be afraid of fuel injection, it really works.

As far as websites see:
www.corvettefaq.com for conversions or more TPI info at www.fuelinjection.com also www.jagsthatrun.com for misc hard to find conversion parts and info.

LT1
Not to get too deep into the differences in LT1s, there are basically 3 variations. There is the C4 ('92-96) and an F-body ('93-97) version which are 5.7L and have aluminum heads. There is a B-body ('94-96) which is 5.7L with iron heads that actually flow better than stock aluminum heads. There is also a 4.3L B-body (L99) version that you want to stay away from. There is an LT4 in '96 that is an upgraded LT1. All are dimensionally the same as far as bolt-ons. Corvette engines have 4-bolt mains, all others have 2-bolt. All are cast iron blocks. An LT1 is a very similar installation to a TPI. As far as the mechanical installation, the 700R4 and 4L60E transmissions are the same (same length, same basic dimension, mounting, yoke, etc.). You have to have a computer to run a 4L60E which you will have for the engine anyway. As far as the engine, an LT1 will bolt in and can use the same exhaust although you may want to use C4 LT1 manifolds to get true 2 1/2" outlets. The biggest difference between a TPI and an LT1 installation is accessories. TPI can use stock C3 accessories. LT1 has to use LT1 accessories and really needs C4 LT1 accessories. Both F-body and B-body put the a/c compressor low on the passenger side. This interferes with the frame and the right motor mount. You have to use electric fans on an LT1, there are no provisions for a mechanical fan (B-body has an optional one, but it is offset and won't work in a C3). The other difference is in air intake, most LT1s are mass air flow. Again, it is difficult to locate the MAF sensor in a C3. You are better to have it set up for speed-density. In a '78-'82 C3 you could still use an '82 sending unit but an LT1 fuel pump instead. You will want to stay with programming for an OBD1 (pre-'96) style setup, without multiple oxygen sensors. '96-'97 OBD2 engines are fine, you just don't use all the sensors. LT1 requires a custom radiator because of how the hoses run. There are differences in the Optispark, later is better and if you swap to a later cam you can add the later vented Optispark setup. The water pumps are bad to fail and wet the Optispark, so always replace the water pump when you do a swap. LT1s have better top end power that TPIs, but all things considered I'd rather stay with TPI for a cruiser or mild build-I just like the look and the low end torque. If you want more power, LT1 is better; or just step up to an LSx.

 

Wow! A whole lot of info! Thank you for taking the time. I already have a 94 vintage 5.7 ltr LT1 with iron heads. I plan on using my existing Hooker Super Comp headers and sidepipes. I was hoping to use my existing Turbo 400 and wasn't sure if I could. Did you say F body accessories will not work on my 68? I would need to get C4 accessories? Knowing my engine and C3 vintage now, how would you proceed? What accessories? I have the original harness and computer from the car I got the engine from. Can it be used? Can the Turbo 400 be used? As I noticed the flywheel bolt pattern for my 327 and this LT1 are different and won't bolt to the Turbo 400 torque converter. Can it still be used with an adapted flywheel? Thanks again for all the info but need info specifically based on my engine and my year C3. Thanks!

 

The new LT1 is a one piece rear seal crank and when You remove the Flexplates on both Engines You will see the diffrence. The Aftermarket should have a Flexplate thats fits the New crank to the Turbo 400 and it should be avalable easy.

 

Cool. Got any leads? Websites? Thanks