So I am looking at a '75 corvette to buy. I know they suck because of emissions but what is the best thing I can do to it for performance. Biggest bang for the buck. I'm looking for around 400 horsepower. It has the 350 in it with 302 heads. It also has cherry bomb glass packs. The guy that owns it now is no mechanic, and has no idea what he's doing, so he doesn't know anything else about the car. The owner before him did all the mods. I'll try to find out more soon. But what are the best upgrades without breaking my account?

 

It would help to know what you want the car to do. And what your budget is. It would be helpful to know what has been done already and how it runs.oh yes and Welcome!

 

Best bank for the buck, and quickest way to 400+ HP are an LS swap. Sad but true. I was going to build a 400 SBC for mine and by the time I figured machine shop, rotating assembly, heads, etc., it was cheaper to pull the motor and sell it and drop in an LS.

No matter what people say, its not that easy to get to 400 hp on a small block with bolt ons unless you are bolting on a power adder like a supercharger.

 

These suggestions will not net you close to 400 hp but you will notice the power increase. Vortec heads with steel shim head gaskets, aluminum intake with a properly working quadrajet, and ceramic coated headers. I know this will help because its exactly what I did to my 76. I did all the work and spent less than $500.00. I got the vortec heads for $100.00, headers for $200.00, and intake for $80.00.

 

Thank you much, can I have more details on the parts and how you got them so cheap. And I plan on putting a turbocharger on it. I don't mind lag time when it makes such a difference that a turbo does.

 

No offense, but if you know enough to be adding a turbo system to the car, you dont need our advice on other bolt on upgrades, unless you are buying a kit, and thats not cheap either and would take major labor to install and tune correctly.

You might want to try and come up with an overall plan first as things all relate. A cam thats good for turbo, is not what you want NA, etc.

 

I'm doing all the installs myself so I won't worry about labor costs, and I want y'alls advice just to see what other people think. Get more opinions and options then find the best combination.

 

I got the $100.00 heads from a friend who had two sets and wanted to get rid of them both. I bought the $2000.00 Hooker ceramic coated headers on e-bay and were advertised as blemished but I have not found the blemish. The $80.00 aluminum intake was another e-bay win. The steel shim head gaskets are only .015 thick giving me maximum compression without machine work. I also bought a Powermaster mini starter to give me plenty of clearance with the headers. At the time I did the work I had a broken collar bone or I would have done a cam swap. The performance increase was really noticeable being the stock 180 hp L-48 350 is a real dog. I can't say for sure but I will guess I'm now anywhere between 250 and 275 hp.

 

78 L-48, 58k miles. Put in a top-end kit from Summit; aluminum heads, intake, cam, headers and Edelbrock 650. Hp at the wheels (my guess) maybe 225? But, after street racing 5-6 times spun a bearing. A costly lesson, should have rebuilt the bottom end.

 

Are not you beeing too much optimistic? That's a lot of extra power....just wondering.

 

Bang for the buck? Hmm. Mine is a 74 L-48. It had the Ford Escort comparable HP rating of around 190, rather embarrassing by any Corvette standards.

Final answer? LS swap. Hands down, MOST enjoyable mod I've done, and pair it with an overdrive and you have the fixing for dependability, HP, fuel mileage and a LOT more fun that Chevrolet ever envisioned




Once you have the LS architecture in place, the sky is pretty much the limit with what you can do....

 

Could be because I'm guessing. The 062 vortec heads really flow and bolting them on with the steel shim gaskets brought the compression up over a point and the aluminum intake and headers can't hurt. I recommend this setup if money is an object as it was for me.

 

It's an air pump. Get more in-out, and you will have more power.


For the record, there are plenty of folks who have done a simple head-swap (2.02 heads, World products makes a nice, cost effective set that won't break the bank, and perform very well), headers, new carb, and free flowing exhaust - producing respectable gains, and an enjoyable drive.


It completely depends on what you want. I am happy with the 195HP rating on my low-mileage 79, because I did not buy it to race, or be the big dog on the block. My focus: get it to run great (done), preserve it, keep it running great. ALL of the "muscle-cars" were slow by today's standards.


If you simply want a car that represents well, looks original, retains the numbers matching drive-train, and can light em up occasionally, and bark a few gears - carb/manifold (E-brock sells several kits) heads - exhaust and maybe a gear swap if you want to move the power band will certainly get you there, and for FAR LESS than any engine swap, or resto-mod/ LS swap will. You are talking maybe $1k-2K (maybe cheaper if you swap meet a few parts) vs thousands, and a ton of work. I have a few friends who attempted LS conversions. All had issues, all had severe cost over-runs, and all ended up with cars that had hiccups, and issues. It's a great idea....., but have the funds, and then some.

 

Duncan, you haven't really told us much about the engine currently in the car. How many miles are on it? Has it been rebuilt at some point (decked)? 4-speed or automatic? Do you have any idea what gears it has in the rear?

When you say 302 heads, are you talking about Z-28, 302 heads with 2.02 intakes? Today a new set of $1200 Dart Iron Eagles will out flow any factory SB heads made in the 60's.

Good luck... GUSTO

 

If it is an L-48, you are talking two bolt main with cast crank and pistons. Adding a turbo to that is just asking for trouble.

I have a '75 as well. Over the last 20+ years.
- Did a top end on the L-48. Headers and dual exhaust.
- Rebuilt the L-48 and swapped to a Tremec 5 speed.
- Did a 496 big block swap and swapped to a T-56 6 speed and EFI

My $0.02 - go with the LS swap. Even a junkyard LS-2/Ls-3 would be a great basis for a turbo swap.

 

I'm working on trying to get more detail. I have to get some phone numbers. I also don't want to do an ls swap. I'd much rather keep this engine and just put aftermarket parts on it.

 

I think what the guys are telling you is the stock L-48 isn't worth building up; the LS swap is cheaper, faster and easier, plus more reliable than anything you can do to that dog L-48

 

Awesome, wish I had the mechanical aptitude for a LS swap. In Hawaii its hard to find a tuner. Figuring out the cam, trans and rear gears in a tune is all a mystery to me, ha ha! Went with an old school 383.

 

How can a 350 block be a bad starting point?

 

Because an L-48 has a two bolt main, cast crank, and cast pistons. By the time you replace the rotating assembly, replace the main bolts with studs (which requires machining) or convert to 4 bolt mains, an LS swap is definitely more economical.