I have a 87 Firebird 2.8 5speed and have found a computer controled 305 for sale complete down to the computer. What is the bare minimum that I need to do to make the car drivable. I dont car about having all kinds of sensors to set off the check engine light, etc. I want the motor to go in and make the car go. I know I need the Computer and wiring to make it run, correct? I also need motor mounts, and what else? Will the T5 bolt up? Will the fuel system work? Can I use the V6 harness and plug in the V8 computer or do I have to use the V8 harness? Remember, I want to know the bare minimum I need to do to make the car go.



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Mike D. 87 Firebird 2.8L 5speed with V8 swap in the works.

 

2.8 t-5 bellhousing has a different pattern that the v-8 one. You'll need the correct one.

Is the 305 FI or carbed?

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The motor is fuel injected I believe.

Mike D.

 

There really are plenty of posts dealing with this topic to answer your questions. About the only one specifically that isn't is the bare minimum part. If the 305 is injected, then the answer is "everything". If you go without the fuel injection and computer and go with mechanical carb and distributor, you'll need a lot less (but will need to drop the fuel pressure one way or another). Of course, without the computer, you will always have a check engine light until you take out the bulb.

Look through the posts about V-6 to V-8 for the past few weeks and you'll get an idea what all is involved.

You should be very wary of that "complete" part. It may have all the engine stuff, but how about front springs? Engine mounts? Fuel pump? Regulator? Air cleaner? Tachometer?

See what I mean?

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Its a carburated LG4. Now can you answer the bare minimum question?

Thanks
Mike D

 

Sure. Keeping the computer controlled carb system will require the use of all the sensors, harness, etc. to work properly. However, if you go with a mechanical carb/distributor, then it will be much simplier. You can use the V-6 harness, but it would probably be easier to start with the V-8 harness because wires to things like the alternator and starter, temp and oil pressure senders, and the like will be the right length, go to the right place, have the right type of connector, etc.

In either case, the fuel pressure will need to be dropped to about 6 psi if you keep the in-tank fuel pump the 2.8 now has. There are other posts that deal with how to keep the pump working without the computer (I couldn't tell you that from personal experience since mine had the mechanical pump on the engine).

I'm not sure what you meant by "I dont car(e) about having all kinds of sensors to set off the check engine light, etc." Does that mean you want to avoid the check engine light coming on, or that you don't care that it does?

 

What I meant by the comment "I dont car about having the sensors to set the light off" was that all I want is for the motor to run the car, I want to have the speedo, oil pressure, temp, and volt gauges working. I dont care about having sensors to tell me whats wrong if something does go wrong. The car is being built as an autocross racecar. Ive removed the radio, Im not gonna have AC, smog pump, cats, etc. The car will only have the required equipment for it to be driven. So, all I need to know is how to hook up the motor to make it run.
Thanks for your help, and keep responding, Im soaking this all in for the big swap day.

Mike D

 

Okay, we're getting somewhere. Knowing what you intend to do with the car helps a lot.

The sensors of which you speak are not there to tell you that something isn't working. They are there to provide information to the computer so it can tell the carb and distributor how to feed the engine. When a sensor doesn't do its thing, the computer sets a code in its memory and turns on the SES light.

The V8 harness would be the best way to get the inputs you do want if using the original gages. But, A-pillar mounted pod gages might provide more accurate information, and you'd connect them outside of the vehicle harness anyway. The alternator and starter would still be best connected via the V8 harness, though. You didn't mention tach - factory would work, but if you've really modified the engine and need a more stable and accurate reading, you might want to go aftermarket anyway. The speedometer should be cable driven, so that shouldn't be a problem. You'll need to provide 12volts to the distributor/coil through the ignition switch.

All in all, you might consider just running the wires you need from scratch and forget both the V6 and V8 harnesses. The alternator can be run with a single wire to the battery. The starter needs a cable from the positive battery post to the main terminal on the solenoid, and a wire from the ignition switch start terminal to the solenoid terminal. The ignition switch needs a 12 volt positive wire to the common terminal. The distributor and gages need voltage from the run terminal of the ignition switch. The engine and frame need to be grounded to the negative post of the battery.

How's that?

[This message has been edited by five7kid (edited December 13, 2000).]

 

Ha ha...

We're getting there...
So, do you think it would be easier to run wires from battery to components rather than use the harness and computer? The only factory gauge I want to keep is the speedo. Oil pressure, temp, and tach will be aftermarket bought gauges. The fuel gauge will still work wont it? Anyhow, tell me if I have this right:

Place the motor in the car, attach tranny (need V8 bellhousing), run the wire combo that you mentioned above, attach all hoses, fuel lines, etc., and the car will be ready to drive? I wont be using a cat on the car, or any emissions for that matter, so am I correct in that I wont need headers with air fittings?

Keep the info coming...

Thanks
Mike

 

Hey,

Ive decided to install the motor WITH the harness and computer. That way I can keep all my dash gauge functions, and not have to run wire myself for all the accessories.

My next question is, can I go without the cat, and use headers with no AIR fittings? Will this cause confusion with the computer, and if so, how do I "trick" it?

Mike

 

Here's a piece of info. Use a Mallory fuel pressure regulator to drop your F/P to carb-friendly levels. Get the adjustable 3+ port unit that has a provision for a return line.

 

Me again...

Another question. Ive gotten conflicting anwers on this one. Will my 87 V6 T5 tranny work with the 87 LG4 305 that I bought? People have told me that the have done the swap and it works fine, some people say that it cant be done, so whats the deal?

Mike D.

 

No...cant handle the power from the v8..ppl say it can but for ease of tranny replacement money and headaches get a v8 tranny

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well the 2.8 v6 will NOT work on a LG4 as stated earlier. you can get a v-8 bellhousing for it but i would recommend this only as a temporary measure. the v6 tranny will hold up for a little while but i would find a t5 out of a v8. i have a 86 305 and the smog pump was disconnected before i bought it. Mine throws EGR codes every once in awhile. as far as performance, you can take the AIR tubes and catalytic convertor off without fowling up the computer. you might just want to take out the ses light