whats the best way to gain performance out of a 1985 trans am with a 305. by the way it has an LG4 engine code

 

Read this https://www.thirdgen.org/forums/faq-...5-engines.html .

See sig.

 

well what kind of performance are you look for..simple thing would be 350 or just a cam, but if you are looking for something fast and fun look in to a small blower

 

Here is an example of what you can do using the LG4 305 motor as a base:

Because of its small ci and low cr adding a supercharger is a great way to get a lot more power out of a stock 305 lg4. The Weiand/holley 144ci blowers work very well on a 305.
Remove the stock cylinder heads (should be 416 castings) and improve them with home porting and a larger 1.94" intake valve. The more porting and chamber de-shrouding the better. Don't be shy on the porting on these heads. Airflow is power. These heads flow very well when properly ported. Then add some stock diameter performance valve springs.
There are many off the shelf hyd cams that make great blower cams.
EG Crane #113801 or Crane #113941 or Crane #113821 being just a few.
Summit #1103 and 1105 will also work very well for less $$$'s.
1.5:1 rockers are fine. Stock type long slot rockers are fine if you're on a budget. A good Summit aluminum roller rocker is nice (#SUM-G6905).
You'll want to install exhaust headers and a big hi flowing exhaust system.
2.5" head pipes into a big 3.00" or 3.5" main exhaust pipe to the back of the car.
You'll want to change the rear gear ratio to either a 3.73 or 4.10.
If using a auto trans (th350-th700r4) you'll want a high stall torque converter with a actual stall of 3000 to 4000 stall. A 9" or 10" converter will work well.
You can use a GM HEI distributor. You can improve it with a MSD coil and a advance curve kit. Adding a CD spark box with a boost retard function is an option too.
With a 8.5:1 cr you'll be able to run about 7psi of boost on 92 octane fuel with some ignition boost retard. (you'll want to run about 28deg timing under full boost @ wot) If you want to run more boost for more power you'll need to use a higher octane (110) racing fuel or add a water/methanol injection system to suppress detonation while under high boost.
The stock LG4 cast pistons will handle 7 PSI of boost (as long as pinging and detonation is avoided). If you want to run more than this, a low cr forged piston is recommended.
A 750cfm carb is best for this blower. A common Holley #3310 carb with a few mods works very well. Basicly needs .110" high flow needles and seats, the secondary metering block kit, a rejet for the blower (74pri 86-88sec) and a selection of larger accelerator pump squirters and cams. I like to remove the choke horn and choke for more flow. You'll need a fuel pump and fuel lines that can deliver the fuel volume nessessary for a 450HP+ motor. Use a 110+GPH rated fuel pump and 1/2" fuel line from tank to carb.
Another route is to use two 72GPH pumps with 2 3/8" fuel lines from tank to carb. Yes this involves replaceing the whole fuel system including tank pick up tubes, either way..
Engines run on fuel to make power, not wishes. The stock fuel system is barely enough to feed the stock motor @WOT making under 200hp.
A stock short block 305 LG4 supercharged and modified as above would make about 450BHP.
This is not a real radical motor. You can drive it every day. (requires 92 octane fuel) Expect very low 12's drag ET's. 11 second ET's are possible.
As long as your 305 is in good overall condition (oil pressure, ring seal) you can use the bottom end as is. A simple hone/re-ring and bearing rebuild can freshen it up to give you some piece of mind.
I would start by doing a compression test and oil pressure test. @2000 rpm hot you should have about 45 PSI. Compression should be in the 150PSI zone and be fairly even on all the cylinders.

This is just one way to skin the cat using the stock LG4 motor as a base for big power. The street performance return on the $$$'s is very good by going with a supercharger for your 305.