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88 Chevy 305 into my 1991 Pontiac Firebird

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88 Chevy 305 into my 1991 Pontiac Firebird

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Old 08-09-2015, 05:48 PM
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88 Chevy 305 into my 1991 Pontiac Firebird

I have a 1991 Pontiac Firebird, and the engine is giving me ****, I'm not looking for a ton of power, or any extra power. I also have an engine from a 1988 Monte Carlo, that I'm looking to possibly put into the Pontiac to get it back on the road right. What I need to know is, am I going to have to mod the firebird to make this happen, is it worth doing this to make it happen?

About the car/engine

It's a 1991 Pontiac Firebird with a 3.1L V6 fuel injected motor on a manual 5-Speed transmission, which just has a lot of problems with it

The motor is currently in my 1984 Chevy C-10, and the transmission gave out on me, so it doesn't have a transmission to go with it.

The motor is a 1988 Small Block 305 that came out of a Monte Carlo originally, it's carbeurated, and currently connected to a (non running) automatic transmission that came with the truck originally, and I really don't know what other information would be needed for you guys to give me some kind of answer.

I'm wondering what I'm going to need to do to mount the 305 in the firebird, and hook it up to the manual transmission currently in it. Along with what else I'm going to need to be able to switch to a V8 carbeurator from a V6 Throttle Body. Any information, or advice would be great, thank you all in advance.
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Old 08-09-2015, 06:54 PM
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Re: 88 Chevy 305 into my 1991 Pontiac Firebird

Check the sticky thread at the top of this forum section for more detailed info on doing the V6 to V8 swap. It'll have more info than I can provide you, as I'm in the process of a swap w/my bird, but it's just a 305 to 350 swap. Going from V6 to V8 will likely require swapping motor mounts, among other things, IIRC.

The T5 transmission in the V6 cars used a different bellhousing than V8 cars, and also used a lower spline input shaft (10 count, vs 27), so you will need to take that into consideration (the rest of the trans should be the same/very similar internally). You will have to address this in order to successfully use it with the V8 (i.e - get the proper bellhousing/swap the input shafts).

The 305 you have is one of the better versions of the 305 to come from the factory, so if it runs well, and you're not after gobs and gobs of power (stock, it was rated around 180 HP/225 TQ), it is certainly a route you could go for getting the bird back on the road. Some headers and a good exhaust system would do a good job of waking it up if you decided you do want some more power.

Speaking of exhaust, you will need to get ahold of a proper V8 exhaust/manifold set-up anyway. And also, you will need the ECM/wiring for the 305 to run properly, unless you want to run a different induction setup on it than what it came with.

Overall, there will be some work involved to make the V6 to V8 swap a success, but more than likely, you'll love driving the 'bird that much more in the end.
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Old 08-09-2015, 09:07 PM
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Re: 88 Chevy 305 into my 1991 Pontiac Firebird

My truck currently has a glasspack exhaust on it but I don't know if that exhaust will just be able to bolt up. What would I have to do to the transmission to get it to mount up with the 305? And do you know what all will need to be changed to go from Fuel Injected to a Carbeurator? The 305, as far as I know, is fully mechanical. I don't recall it having an ECM. It's in my 1984 Chevrolet. Before the 88 305, it had a 76 305 in it, for whatever reason that's what the previous owner had. However, the engine runs like a dream, and has done so since I put it in the truck four years ago, I got it used with only 28,000 miles on it, and haven't had an issue since then.
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Old 08-10-2015, 12:35 AM
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Re: 88 Chevy 305 into my 1991 Pontiac Firebird

Ditch the 6 cyl 5 speed idea. It's not going to work. Even if you did get it to fit, it would not last long...


You need a transmission for a V8.. Can be auto, manual, 2 speed, 3 speed, 4 speed, 5 speed or 6 speed but it needs to be a V8 trans.

You will need V8 engine mounts to put on the K member of your car. Can buy new at part store for $35

V8 rad. and hoses

V8 Y pipe and exhaust, no the exhaust you have on the truck will not even start to fit under one of these cars

For the carb'ed engine you will need a $115 mallory adjustable fuel pressure reg. and use stock in tank elec. pump. Or drop the tank and remove pump and replace with length of line or non elec. pump sender
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Old 08-10-2015, 04:21 PM
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Re: 88 Chevy 305 into my 1991 Pontiac Firebird

Okay, thank you
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