Which LT1 blocks will fit into a 94 Formula?

[Crazy Canuk]

Hello, as some of you know I lost my engine last week and I thank eveyone for there advice on what I should do. I have a 94 formula firebird that is basicly stock. I have done all the little things, wires plugs, opti, brakes, and the rear was rebuilt 2 years before I got my car (I have had my car ruffly 2.5 years) and has 127k kilometers on it, in the 2.5 years I have had it I used it as my daily driver putting 40k kilometers on it. The body is mint and I don't realy want to get rid of it if it isn't going to make me drown in debt.

One option is to drop a used block into it drive it for 3 more years then park it and use something else as my daily driver. However I know the general differences on the LT1's durring the years I dont know which engine are interchangeable with my engine. If I can get a used engine locally and installed for around 2k I think thats my best option atm.

From what I see the difference between the 94 and 95 is that the 95's have vented optisparks but thats the only real main difference. the blocks that are newer are all OB2 so they have more sensors. Also there are corvette blocks with 4 bolt mains however if I recall right they need a new wireing harness if they are to go into a firebird/camaro.

So if anyone can tell me what would be involved (extra then just dropping it in and hooking what I have on my block to the new one.) with a non 94 LT1 engine that would be awsome.

Again all of your help is appreciated, I am still in the deciding phase but I wan't to make the decision with the most information that I can get.

Thanks again

[Injuneer]

If you are speaking strictly about the block, and not the various accessories and fittings that bolt to it, ALL 1992-1997 LT1 blocks are identical, except for the fact that the Corvette blocks had 4-bolt mains, and the F-Body and B-Body engine had 2-bolt mains. There are NO physical or dimensional differences between any of the LT1 blocks, other than the number of bolts in the 3 center main bearing caps. They are totally interchangeable. They ALL have the exact same casting number and the same "327" cast into the block. Even an LT4 engine will have the same block.

The Opti differences and the CKP sensor addition are covered by the use of three different versions of the timing cover. The block will accomodate any of the three covers.

You can buy any LT1 engine, and swap over your external components - timing cover, front accessory mount, etc., use ONLY the sensors that are already on your 94 engine, use your existing 94 harness and PCM.

Beyond that, there will be differences in the heads - cast iron on the B-Bodys, aluminum on the F-Body and Y-Body. And, in the aluminum heads, there are two different castings used.... 92-95 and 96-97. The appearance of the two aluminum heads is significantly different, with different casting numbers and different flow numbers. The later heads flow better stock, and are lighter. The early heads are heavier and can accept more porting for a larger increase in flow. I can give you a link to a photo comparison of the two aluminum head designs.

http://64.65.63.61/forums/showthread.php?t=427346

If you buy a Corvette engine, you will need to remove the knock sensor from the drivers side and put a block drain plug in it. In any case, you must use the low impedance knock sensor from your 94 in place of the high impedance sensor used in 96-97 for OBD-II. You will also have to swap over the complete from accessory bracket if its a Corvette engine, and swap the harmonic damper from your 94 so it will sit in the correct place for the serpentine belt.

Here's a copy and paste from a couple posts I did on another forum recently on a similar question:

There are a number of "external" differences between the 93-95 engines and the 96-97 engines. I'm assuming you want the 97 engine to work with your 94 PCM.

The 97 will have a vented Optispark, compared to the 94 unvented unit. You need a different harness from the gray connector on the passenger side of the intake manifold to the Opti. You also need to add a nipple to the intake elbow to allow the Opti vent air supply line to connect, and "tee" into the EGR vacuum nipple on the drivers side of the intake to provide a vacuum source for the Opti vent system. And you need the vacuum harness if it didn't come with the 97 engine.

You have to swap the low-impedance (4.5Kohm) knock sensor from your 94 onto the 97 block, in place of the high-impedance (100Kohm) sensor used in 97.

You will have a crank position sensor (CKP) on the 97 engine that you don't connect to anything. Leave the sensor in the hole in the timing cover, or you will have to fabricate a plug for the hole.

The 97 engine will have a vacuum flow switch on the passenger side valve cover for the EVAP system. Remove that switch and discard it. Use the stock plastic and metal lines from your 94 to connect the charcoal canister vent line to the EVAP purge solenoid on the passenger side of the intake manifold.

The 97 will route the vacuum source for the PCV valve from the drivers side of the engine to a small port in the front of the intake, under the throttle body. You can leave that where it is, or swap over the U-shaped hose that routes the PCV vacuum source back to the nipple on the drivers side of the intake, and put the pipe plug from the front of the intake on your 94 into the open hole on the 97.

The AIR system on the 97 is a lot different than the one used in 94. It have a backflow vent system and a vacuum detection switch and a bunch of other crap that was not used in 94. If they had the AIR recall (95-97) done on the 97 engine, that will just add to the clutter. Simplest solution is to swap the rubber hoses that run from the AIR pump to the AIR hard lines from your 94 to the 97 engine.

That's all I can think of off the top of my head.... if there is anything else, I'll add it later.

Another difference I thought of..... the throttle body coolant connection on the passenger side is at a different angle on the 93-94 engines, compared to the 95-97 engines. That's because they rerouted the steam line from the back of the heads so it flows through the coolant connection on the throttle body starting in 1995. You need to use your 94 bottom plate off the throttle body, so it will match the hose angles. You can get a top and bottom throttle body plate gasket kit.... PN 17113074, or AC-Delco # 40-743 $4.87. Or just swap the entire throttle body from your 94 onto the 97 engine. Other than the nipple for the coolant hose, they are identical.

This article will explain a few other subtle differences, like the connecting rods:

http://www.automotiverebuilder.com/ar/ar99928.htm

[Crazy Canuk]

Thanks again Fred,

That was exactly what I was looking for. I read the last linked article last night on the internal differences.

I am glad to hear that there isn't anything major that would prevent any LT1 engine to fit into my car with swapping over parts from my old engine and gives me more options to choose from. I thought the Corvette engine was more trubble to fit in there too, however those blocks are harder to come by and probably wont be an option for me.

I am going to go to my mechanic and see what he's willing to do for me, I like to know the most I can so I can be helpful and actuly understand my problem better.

Thanks again!