Greetings,

I own a 1986 Trans AM, stock LG4 carbureted engine. I have been systematically doing the things necessary to get the engine running smoothly while improving horsepower/torque, hopefully while improving fuel economy.

The first thing I decided to do was to replace the carburetor and intake manifold. I had issues with acceleration and bog down. My 25 year old carb was really tired and I was also getting code 32(EGR) Service Engine Soon code. When I initially replaced the EGR valve I found the intake passage completely carbed up so given these variables it just seemed logical to replace both the intake manifold and carburetor with an Edelbrock Performer 600 cfm carb and Performer RPM manifold. In addition, I replaced the valve seals as I was putting out some blue smoke on start-up and my plugs would foul too easily.

So given my attempts to improve the front-end performance of the engine I want to turn my attention to the back end. What i intend on doing at a minimum is to to put a 3" mid pipe to a new cat and Magnaflow muffler/Y-pipe. I hope this will really help the breathing on the back-end.

My dilemma is whether or not to invest in headers. Given the fact that I live in California I am relegated to shorty headers and am not sure the horsepower gain will be worth the $750 - $1000 for good ceramic headers. Let me know your thoughts.

As for other improvements, any other ideas. Anything I can do economically from an air intake perspective, change the cam, adjust the timing, etc.

Also your thought on HP improvement related to each of the improvements?

New Intake Manifold - ?
New Mid/Y-Pipes, Cat and Muffler - ?
Headers - ?
Air Intake - ?
Cam adjustments - ?

What kind of total improvement might I expect.

Please let me know your thoughts.

Big Ed

 

Unless you replace the stock exhaust, no other mods are going to provide any noticeable improvement. Peruse:

https://www.thirdgen.org/forums/carb...tions-lg4.html

 

Are you going to stay SBC? Then yes, you should go ahead and do headers.

With regard to the LG4 factor, I'd try and go for a better flowing overall exhaust.
The L69 cat is an upgrade over the LG4 or the later model dual cats (not legal for an 86 unless you have a later model engine)...

A cam is rewarding but I'd do exhaust first.

 

Being in Cali, how did you managed to put an edelbrock carb on it and keep it legal to run?

Now, as for the headers, I did notice a large power gain when I put headers on the car. It frees up the power of the motor to the tune of 15-30hp between the 305 and 350 and what other stuff you've done to it already. Probably the single most important HP piece you can put on. Just make sure you are running a 3" cat-back. Get the Hooker 2055's to keep it emissions legal in Cali.

 

its not. itll fail the first inspection. to the OP, you need to either get your carb rebuilt, or get another stock style computer controlled carb if you want to be able to drive this car. youll also need an emission legal intake with the egr provision.