i recently bought a 85 z28 with stock tpi 305 engine. im not looking to rebuild it entirely because it was rebuilt not too long ago and doesnt even have 100 k on it.i just wanna put a cam and a few other things on it to start with. any ideas on the best size cam for stock engine . i want it to hit good though without causing problems somewhere else

 

You're going to get more out of a complete headers + cat-back exhaust system than you will from changing the cam (and drivability won't be affected). Exhaust is Job 1 on any 3rd gen. A complete ignition tune-up (plugs, wires, cap, rotor and coil) and bump the base timing up from 6* to 10* is always a good idea, too.

 

85 TPI had a pretty decent Cam in it already. If it was an 86 I'd agree - change the Cam. But; 'cause it's an 85 I agree with Damon,.... install some bolt-on upgrades FIRST because they will benefit you no matter what cam is spinning in the engine.

 

I agree with what the other members have said. Bolting on a full aftermarket exhaust from the headers on back will benefit you the most. The 1986 LB9's got the LG4 cam which really zapped performance - you can thank emissions and fuel economy regulations for that one. The 1985 LB9's have a higher lift cam and perform well. That being said all the changes you make to your car need to be matched. What are your goals for the car? A fast street car will have different requirements for than those for an all out racing car.

If you don't want to modify the intake you can do free intake mods and use an aftermarket air filter. TPI was designed for the 305 so the gains you get from aftermarket intake and runners won't be as substantial as they would be on a 350 - especially if you are still using the stock heads and cam. You can gut the boxes below the air filters and run duct work from behind the fog lights directly up to the bottom of the air boxes. It's a cheap ram air set up that works well.

Look in to getting some sub frame connectors and boxed lower control arms as well. Making power is good but useless if you can't get it down to the ground effectively.

 

I'm with the rest of the guys on this.. Sure I know a big cam sounds cool but at this stage of the game you will pretty much be wasting time and money.

You will get the biggest gains right now from full exhaust.. Headers, aftermarket Y pipe, aftermarket cat back system.. The stock exhaust on these cars are really bad jokes.

Plus any real engine mods you do like cam, heads, etc will move more air in and more air out, if you can't get that air out, you will not benefit from the upgrade.

Deal with exhaust 1st, then maybe intake mods, either mod yours or replace.

Then IMHO address the suspension, chassis, traction, etc.. Every third gen should have sub frame connectors on them!

Next look into aftermarket tubular rear lower control arms and torque arm.

Posi/limit slip rear if yours is open.

Then move into the engine with cam, valve train, heads