Hello Everyone
I recently picked up a 1983 Firebird T/A for $500 with a LG4 305 and a 4 bbl computer assised carb. After i got the car home and got it running I went to put it in gear and it didnt move so i pulled my trans dipstick and there was steele filings all in the tranny so I figured while im changing my transmission Id like to put a chevy 350 carbed.


I browsed through the engine swap fourm and I found lots of 305 to 350 TPI and TBI or TPI to carbed forums but I couldnt find the 305 carbed to 350 carbed.

I am going to assume that you can swap the 305 to 350 but since i have a computer assised carb I should keep the carb+ intake from the 305 and put on the 350. Will my stock wiring work with a 350 and its sensors or will have t otake the computer from the 350 donar vehicle. What years 350 will fit?


Sorry for all the rookie questions this is my first built.

Alex

 

Welcome aboard thirdgen.org.

It's pretty much as simple as pulling the 305, putting all the "stuff" on the 350, and installing the 350.

Check out my vBGarage (linked in my sig). Although I've done some modifications to the intake and exhaust, the computer stuff is completely stock.

Assuming your engine is an LG4 (8th character of the VIN = "H"), the exhaust is very restrictive. The only real "fix" is to replace it all.

 

Thanks for the reply, im glad to hear that it will not be a big job to swap the motors, my TA has the LG4 in it right now and ive been told i wont be all that happy with the power it will make even if it could breath (intake + exhaust) the car has a terrible exhaust on it now..i plan on cutting it out and purchasing a set of headers and a magnaflow kit sooner or later.


What 350 should i be looking for. From what ive read on here one out of a camaro or a corvette is ideal. Ive also herd 350s out of the old half ton chevys arent as good but im not sure.

 

It doesn't really matter what the 350 short block comes from. It's the heads and cam that make the big difference, and to a smaller extent, the pistons (dished vs. flat top). You can make really decent power with a truck 350 short block, your 305 heads, an upgraded cam, and the exhaust you have planned. The dished pistons of the truck short block coupled with the smaller chambers of the 305 heads puts you back in good compression ratio territory.

The 305 heads should be assumed to need upgraded valve springs - but that would be the case regardless if you go with a decent aftermarket cam. The heads also benefit from 1.94" intake valves (vs. the 1.84" stock), but that isn't as big a player as cam and exhaust.

Another really good choice is a 350 long block from 1996-1999 light trucks. They have the famed "Vortec" heads, which really flow nicely. The caveats with them are you need a different intake manifold, and the stock valve springs are really poor.

As for complete crate engines, that's pretty wide open. Your budget is about the only limit there.

 

high happy new years im doing this same thing with a 1983 lg4 t-5 z28 and am looking for assurance that this is so simple im also new to third gens but thanks to websites like this one im becoming more familiar with them every day,

okay my questions are about spark and fuel to the engine, is it as simple as tuning to a stock 305 or is the timing different and the airtofuel ratio different being the bigger bore, i guess it seems its easy from the previous posts but am curious about the computer controlled parts of the car (the hei and the carb) sorry if these questions seem elementary but im a rookie to this area

 

As long as it is a computer controlled carb, you don't have to worry about tuning differently except for the secondary rods/hanger. The rest of the carb and timing settings are pretty much what it would be with the 305. Most people advance the timing a little from factory to see if it helps (regardless of 305 or 350).