Lets go with a stock L79 and bolt on a pair of long tube headers.
Exhaust out the back.
Would there be a significant HP gain, 20, 30?

 

Still depends a lot on the pipe size and the mufflers used.

 

2.5 inch chambered exhaust, no mufflers.

 

I think you'll realize a fair gain, that you'll feel in the seat of your pants, but if you have increased out flow, you should increase the in flow, with carb and intake to complete the job.

 

I never did a dyno before and after, but I put on a set of Hedman long tubes with polished Edelbrock heads and bumped the cam up. I am sure it is not have a problem breathing anymore and it sure does sound great.
BTW- I put on a 2 1/2" chambered exhaust under the car and put in a crossover pipe. I wouldn't want any other sound. It gets tons of compliments.

 

I predict you'll feel an engine with snappier throttle response and a little better belt in the seat of the pants, especially at low end.

Open them up and you'll think you feel a big difference. How much? Measure it with a stop watch at there are a lot of variables.

 

Around 30 plus hp gain. But will feel faster due to the sound. stewy

 

That's all the good parts. Plan to be torquing the header bolts on a regular basis or use some kind of locking method (locking bolts or safety wire). If the headers have thin flanges, plan on dealing with header gaskets. If the plugs and headers don't go together, plan on plug changes being a bitch. I hope you don't have to deal with steering and/or oil filter clearance issues during installation. Get coated headers or heat, and later, rust issues will surface.

Find someone who has headers that is happy with them, then buy the same headers. That is no guarantee. From experience with headers on other vehicles, the bends may vary some.

Just a bit of reality for you.

 

It would be closer to its advertised base horsepower providing the rest of the engine is in top condition......another point on replacing manifolds to headers is some Vettes have a alternator bracket problem when using headers as most brackets except the OE`s are not very strong/good either or.......

 

Headers will really wake up a true L79. That engine is held back with the intake and stock exhaust. SBC's are just meant to run headers. A jump up in carb size or a one size up on the carb jets would help too. But, the ever present bolt and gasket checks and tightening and then doing it again every few hundred miles is a bit of a pain too. I highly recommend the ball type connector for the header-to-exhaust pipe connection to eliminate the worst leaky trouble spot, instead of using the typical 3-bolt flange connectors. Use a good header to head gasket and follow the instructions of the gasket maker. And, you will still like headers. Ed

 

Regardless of the maintenance issues, headers are well worth the gains. I use Doug Thorley headers (dechromed and ceramic coated) and the fit is good with no interference.

The only bolts that come loose and need regular tightening for me are those on the number 1 cylinder because of the alternator mount. Thorleys have thick tubes and flanges and I've never blown out a gasket.

 

Not meant to high jack, what about shorty headers ?

 

I forgot about my Hedmans having that ball flange. The old flat style just plain sucks compared to the ball style.

 

Thanks for all the replies.

Everything I do to this car can be easily reversed so I am going to give it a shot.
I have a set of ported 2.02 heads that I bought last year.
If I go through the trouble of bolting them on I would think that a set of headers would a good idea.

I ordered a set of Hedman headers from Jegs, looks like I will get them on Friday.

 

Honestly, if you have the 2 1/2" exhaust and fairly free flowing mufflers, reasonably stock engine on you car, I think you will experience very little overall power gain out of a set of tube headers if you run them closed.

If you open them up, expect a some gain. If you never open them up and aren't running in timed competition, you're wasting your money and setting your self up for a little grief with the leaks that will slowly drive you crazy.

I've had them on three different cars.

 

Unless they are long tube? You are wasting your time and money. Don't bother with shorties.

 

I remember way back when, put header on my 427 Camaro (Yenko) and had to re adjust the heads, and carb because of no backpressure when I took the car to the track, otherwise when the collectors were connected to the stock exhuast it ran great, except when I seemed to have lost the gaskets that fit between the collectors and the stock pipe fitting, then is leaked and hissed.

You will really need to watch and torque the head bolts that connect the headders to the heads, on a regular basis. On a 96 Camaro that I built, I switched to ARP locking bolts and never had a problem.

YOU must look out for "channeling" this is cause when you blow out a gasket between the heads and the headers that can actually damage the heads by cutting a small channel in the metal as the hot gases bust through the gasket, it is detectable by a "hissing" sound.

One other thing, I would wrap insulator material around the heads near the plug wires or change the plug wires to high insulation heat wires, the heat dispursed from the headers is much more then your stock exhaust manifolds

Headers wake up the performance, but is only one part of a system that needs to be a whole to get the full benefit of what you are expecting. Carboration, Heads, better ignition system and CAM completes the system. Also a free flowing air cleaner helps....

To be blunt, if you just use headers, and if they are connected to pipes, you might get a 5 HP gain, open headers (if you adjust for no back pressure) maybe 10 at the most. Remember if you got more coming out, you need to get more going in.....

 

My experience with header bolts is to either safety wire them, or use the extra thick lock washers designed for header bolts.

 

You will love the Hedmans. Nice thick flanges. Make sure you get some sleeves for the plug wires. I had to burn a few before I got smart.

 

The Hedmans showed up yesterday, unfortunately they were scratched up.

I thought I had ordered ceramic coated headers but these had some other cheaper coating.
Called Jegs and they were great in helping me get the order sorted out.
The new HTC coated Hedmans are on the way.

I am hoping not to have to use plug wire sleeves.
I bought a set of new Taylor wires and wire loom rails that drop the wires in from the top.
They will run parallel to the valve covers, maybe the wires will have enough clearance?