91 Firebird 305 Replacement (Page 1/2)
Phirewire MAR 16, 01:06 AM
Need to replace the engine in this 91 Firebird I am getting, Just gonna throw another 305 in, does it need to be from same car or similar car close to same year, or any 305 TBI will work?

Also what trans would be mated to the 305, is it a good engine? I want something that can get up and go but cruise when not.

(I'd ask on thirdgen but you guys are like family when it comes to this stuff)
Racing_Master MAR 16, 06:31 AM
Any old 305 will work, however a 305 isn't something that has a lot of pep to it. I would say get a 350, they are cheap, plentiful, and have a cheaper aftermarket (only slightly since 350 and 305 parts are interchangeable, however any 305 specific stuff is more expensive due to less interest), and with a 350 you can get more power. You can swap the TBI setup from your current engine to your new engine, or you can switch it to a carb, or switch it to TPI (I have a 305 TPI in my camaro, little torque monster).

As for the transmission, the automatics in Third Gens are TH700-R4 transmissions, while the manuals are Borg Warner T-5 transmissions. With the T-5 the transmission is at a 17 degree canter, so if you want to upgrade to a different manual, you will need a different bellhousing if you have a T-5.
Phirewire MAR 16, 10:26 AM
Well, I wanted to keep the 305 due to simplicity of swap, and Fuel Economy. I'm looking to get it swapped within 3 days. So I can swap a 305 from a 79 malibu and it will fit in, and use stock wiring?

Also, if i pick up a 305 with TPI from a third gen camaro, would I also need the wiring from it and the computer or ?
Racing_Master MAR 17, 10:19 AM

quote
Originally posted by Phirewire:

Well, I wanted to keep the 305 due to simplicity of swap, and Fuel Economy. I'm looking to get it swapped within 3 days. So I can swap a 305 from a 79 malibu and it will fit in, and use stock wiring?

Also, if i pick up a 305 with TPI from a third gen camaro, would I also need the wiring from it and the computer or ?



a 305 TPI will require you to swap the harness and computer, yes. TPIs are MPFI systems, while TBI has only two injectors. TPI systems are also more advanced, and most junk yards sell just the TPI intake for $300 or so I have found, due to hot-rodders loving their look.

as for the 79 malibu, the cam profiles may be different. in 91 they had roller cams, while in 79 they were using flat tappets. I'd look for a 305 from around 91. wikipedia has a good list of changes to the small block chevy, and should help with picking the one that will go in your car. if you want to keep the TBI, you SHOULD retain the TBI from your car, just swap it onto the new engine, and it should work.

a good way to find direct swappable engines is http://car-part.com it's a database of junkyards, enter in your vehicle info, and what you want, and it will bring up a list of stuff that will work.
ARFiero MAR 19, 09:52 AM
You cano go to the salvage yard and pull a computer off a 90s model Chevy or GMC TBI 5.7 Liter pick-up and its injectors from the Throttle Body Injection system. then get you a mild built 350 and do the engine swap. And swap out the computer and injectors and you are done. It really is that easy!

Shelby

[This message has been edited by ARFiero (edited 03-19-2013).]

Raydar MAR 19, 10:57 PM
The 79 may present some problems.
In 86 or so, GM switched to a one piece crank seal and a different crank and flywheel.
IIRC, the earlier engines were externally balanced. Had a weight on the flywheel of flexplate, where the later engines were internally balanced.
(Similar to the 85-87 vs 88 V6. Unlike the V6, however, I believe the bolt pattern is different. May help to reduce the chances of installing the wrong flywheel. Don't hold me to this. I could be mistaken.)
Also, the intake manifold center bolts changed at about the same time. The angle of the bolts changed.

I'm with the others. I would be tempted to grab a TBI 350.
Khw MAR 19, 11:01 PM
My parents have a 89 Camaro with the TBI 305 in it. When they first bought it, my highschool graduation year, the occasional drive I got to take in it was a blast. In 89 the 305 had 230 hp and the 350 had 240 so if your not planning to mod the engine, I don't know how much of a difference that 10ish hp is really going to make. Did a litle checking and the 350 TPI in 91+ went to 245 hp, so it'd be 15 hp difference for a 91+ setup.

[This message has been edited by Khw (edited 03-20-2013).]

Lou6t4gto MAR 20, 05:29 PM
a NON roller motor is a Big drop in performance, better with a 87 up engine, all 8 cyl engines will "bolt" to the trans. when changing the INTAKE, check the bolt pattern and intake gaskets" before" you try, just go into a parts store and look ate the gaskets in the performance isle. the reg 1955-80s heads will bolt up all the same, but when you get to Vortec, it's a whole different thing. also the 305 heads have small Valves due to the small cylinder bore.You'll be alot happier if you get a direct swap, Unless you are into alot of "inovation".
rogergarrison MAR 22, 09:35 AM
My 92 Firebird 305 got worse gas mileage (maybe 18 on a good day) than my 350 Corvettes (25+). Id put in a 350 if I was replacing it. If you want more power, modify the 350 to a 383 stroker...still a drop in. I still havent figured out how V6s of the same vintage get worse than V8s. My 302 Mustangs (even GTs) got much better mileage than one I had with 3.8 V6. My Astro with 4.3 runs like brand new and its lucky to get 16 mpg.
weaselbeak MAR 22, 11:43 PM

quote
Originally posted by rogergarrison:

My 92 Firebird 305 got worse gas mileage (maybe 18 on a good day) than my 350 Corvettes (25+). Id put in a 350 if I was replacing it. If you want more power, modify the 350 to a 383 stroker...still a drop in. I still havent figured out how V6s of the same vintage get worse than V8s. My 302 Mustangs (even GTs) got much better mileage than one I had with 3.8 V6. My Astro with 4.3 runs like brand new and its lucky to get 16 mpg.



I've seen really good mileage from both the 3.8 Ford and the 4.3, both Vortec and earlier. Depends on the setup, I guess. I remember the 300 Ford six in pickups getting as bad as 14 mpg, and as good as 22. Go figure.