Was wondering if anyone out there ever modified a stock 300hp 350 to make it a 350hp engine? I have a very stock 69 coupe and am considering pulling it out for a rebuild and wondered what parts are required to make it 350hp. I'm sure it requires a new cam, probably lifters, valve springs? Are the 300 and 350 hp heads the same? I want it to look like a stock 300 hp engine.

It can certainly be done, it only takes money!   

You have to be aware that your engine is rated at 300 hp gross...todays engine are rated net. Your 300 gross will probably rate at about 250 net by today's way of measuring horsepower.

We talk horsepower, but drive torque. You're probably better off increasing your torque, even at the expense of horsepower at higher rpm's. Decide what you want out of the car...is it strictly a street cruiser, race only or some of each? How to achieve the best for each is different.

To improve that 300 hp will take at least what you mentioned...a cam and matched lifters. You'll also need a better breathing intake manifold, a carburetor matched to the cam profile (or fuel injection), likely headers and a free flowing exhaust.

The heads will likely need work to make them breathe better...or replace them with high performance heads, either aluminum or cast iron.

To do all this, you need to balance the costs of this against buying a crate engine already built to the specs you want. That may be the more cost effective way to go. Also...be advised that the crate engines available are rated at net horsepower so you'll know what you're dealing with.

What I'm in the process of doing is very similar. I have a car (not a Vette) that came with the same engine...an L48 350 300 gross hp engine. I just replaced it with a GM Performance crate engine...a 350 330 net horsepower small block. Instead of a carburetor, it has Edelbrock fuel injection and Sanderson headers and Magnaflow mufflers. It's not up and running yet, but it should be soon.

The cost of all this is less expensive than rebuilding the original engine to the same specs, plus the bonus of the warranty.

How did you hook up the computer for the fuel injection...I've been considering it myeslf?

I have a speed shop doing it. They have the experience and while I can turn a wrench OK, I'm simply not very good at such detail work. An elctric fuel pump has to be installed by the fuel tank, lines run, computer lines run through the firewall for the controller inside the car, etc.

More than once I've committed the sin of "If it ain't broke, fix it 'til it is!" That usually entails paying someone to undo what I did then fix it correctly.

BTW - I may be in Newport News at the end of next month (not sure yet). If I make it, I'll get in touch and maybe we can hook up and toss back a couple of brews.

I'll be here....surgery on the 26th...then I'll be recovering...

This is more cost effective for the total package:

HP LINK

I didn't do mine this way but sure wish I had...

My objectives are: improve the performance of the 350 and not change the stock appearance of the engine. I'm really just trying to determine the difference between a stock 300 hp engine and a stock 350 hp engine. ie, different pistons, cam, etc. I've built and rebuilt many small blocks, and wanted to stay away from any aftermarket parts that would change the look of my stock engine. Thanks for your replies.

Sounds like you want to keep your engine looking stock.  After years of trying to keep my engine looking stock I was tired of my S10 pick up having more horse power then my Vette.  I recently installed a Ram Jet 350 into my 78 Pace Car.  The performance is outstanding and after driving the car I would never want to go back to a carb.   No modifications had to be made other than to the fuel lines and the L82 can be re-installed in a weekend if I wanted to make the car stock again.

Norsky2007-01-03 09:22:32

I had a 300hp 350 in a 69 coupe..  the biggest immprovement you can make to the overall performance is head work.

Have you thought about getting 383 stocker kit for it?  To see what is involved do a google search.