Hey guys. I haven't posted on the forum in a few years and just traded my 69 427/400 for a 67 L-79 so moving over to C2 section. Its all stock and local NCRS Top Flight 4x and has the off-road exhaust which sounds great. I don't plan to or care about getting it judged anymore and want to get a set of headers on it to make it even louder Are there any long tube header kits that I can bolt on without welding, or do I need to get a set and weld to the existing system. Any insights and header recommendations would be appreciated. Its got PS/PB but no AC. Thanks

 

Hedman makes a nice ceramic coated header for our cars but you will need to have your pipes cut and a collector welded on.

 

I have had Hedman's on mine for years and have had zero trouble with them. I really like the ball at the end versus the flat flange. Love them coated too.

 

Headers won't make it any louder, but they can cause plenty of problems - loose bolts, more heat radiated to the engine compartment, poorly designed alternator brackets, burned spark plug wires...

You can improve performance simply by replacing the stiff springs in the centrifugal advance to bring it all in by 3000-3500 instead of the lazy OE 5000.

There's a lot you can do to improve handling, like precision alignment and sticky tires. You're better of spending the money on these and other small items that will improve the car. Most vintage Corvettes will drive much better if attention is paid to "tuning" the little things.

Duke

 

I would stick with the 2 1/2" cast iron that were on 327 engines and avoid
problems. They do a good job.

Dom

 

If you're shopping for stainless headers make sure you ask for the grade of stainless. A three-digit system is used to identify stainless steel but you need to focus on what is called the 300 series. Type 304 is a popular choice for exhaust systems. It’s also the least expensive. Another good choice is stainless 321.

Avoid any stainless in the 400 series.

The really trick headers are made from Inconel 625. They're also the most expensive.




Richard Newton
Exhaust Headers 101

 

I've been running Hedmans on my 65 L79 for decades and have never encountered any of the problems noted above. Love the sound too!

 

I installed a set of Dougs headers on my 327/350 65 vette .. They are beautiful.. Work very well also 16 gauge not 18 like the rest .. Check them out .. You will be glad you did Joe

 

I respect SWCDuke's words, but! I have Hedman headers coated by Jet Hot attached to my side exhaust. I don't know if my engine performance was increased, but the exhaust note is more tuned and very noticable. I bought ARP bolts for attaching and used quality gaskets. The alternator mount is a high quality piece with SS bolts. Use quality wires and separators. Don't tie them together. This does require the removal of the factory shielding. The alternator mount has never loosened or created any alignment problem. In 23 years of these headers I can say that on only three occasions have I had a very slightly lose single bolt at number 7 exhaust. Heat displacment may be an issue. It's your car, enjoy it as you please. Dennis

 

 

Another vote for Headman headers. I cut the ball and socket off and put vband clamps on to connect to my GNM 3" side pipes. I used Earl's gaskets and stage 8 header bolts. I've had them on my car for almost five years now and no header leaks, no header bolts loosening and nothing but sweet music.

It was cold that day so the puffs of white were H20... now to be totally transparent the compression is 10.5:1 and the cam has .510/.520 lift and a duration of .230/.236 on 110 LSA...

 

Thanks guys for all the feedback. If I go with the stock style 2.5 inch cast manifolds that were on the earlier HP C2's, would I need a complete new 2.5 inch exhaust system?

 

Thanks Duke. Are there any threads on how to change the springs?

 

Try this site or just send it to Lars
http://www.lbfun.com/warehouse/tech_...t%20Timing.pdf

 

Please don't use my articles posted by that website - they are grossly outdated and obsolete, and should not be used. Drop me an e-mail request for a current and valid version of the timing article - Duke, John Z and I have jointly contributed to the article to make sure the techniques described will provide excellent performance and drivability for your Vette. You'll get a better performance increase by setting up your timing correctly than you will by installing headers. And it won't cost you anything...

...and headers won't make your car any louder. That's a function of your mufflers.

Lars
V8FastCars@msn.com

 

Thanks Lars E-mail sent.

 

Doug Thorley headers made my '64 quieter than the stock manifolds. Boy were we suprised!

BTW, if you can find a set of the old Doug Thorley chrome headers for midyears, they are an excellent fit and cleared everything without the need for denting them. A bit tight at the drivers footwell, but I think that is more due to body sag. Note the quality of the welds around the head pipe (you don't see any!) and the thickness of the flanges. The tubing is also thick which is why they are so quiet.

I later had them dechromed and ceramic coated.




And don't forget the Header Power Bracket to hold your alternator.

 

For 1966-67, GM changed the cast iron manifolds to 2" outlets instead of the 2.5" outlets used for 1963-1965. The 66-67 manual transmission cars still used a 2.5" exhaust system, but the head pipe that connected to the exhaust manifold necked down to 2" just before it mated with the manifold. This seems like a stupid idea, but my guess is that GM decided they could save money by using the 2" passenger car exhaust manifolds on Corvettes.

If you are starting with the factory exhaust configuration for a '67 manual transmission, you can easily upgrade to a full 2.5" system by changing the exhaust manifolds and the head pipes. The head pipes are just the piece that goes from the exhaust manifold to the junction at the rear of the transmission.

I have made this conversion on my '67 and it's a simple bolt-in task. I'm away from home right now, but when I get back I can provide the casting numbers for the 2.5" manifolds that are otherwise exactly correct for a '67. You want the correct configuration for the driver-side alternator.

Rather than looking for original, expensive (and rusty) original manifolds, I suggest buying the very good reproduction manifolds from Paragon. Then, send the manifolds out for one of the available high temperature coatings before you install them.

Converting to the 2.5" cast iron manifolds will keep the stock appearance while providing a slight increase in flow. However, if you want maximum power, a set of long-tube headers and low-restiction mufflers will yield more power. I have dyno tested both combinations (2.5" iron manifolds with high-flow mufflers versus long-tube headers with the same high flow mufflers), and the long-tube headers provide about 10 HP more up to 4000 rpm, increasing to about 25 HP at 5500 rpm.

So, long-tube headers provide a tangible benefit above 4000 rpm, but under 4000 rpm the difference is negligible. For regular street driving, most of the time the engine is running under 4000 rpm.

I think the choice of original-style cast iron manifolds versus headers is just a personal preference of original appearance versus maximum peak power. For normal street driving, the difference is negligible.

 

AR Headers provides pipes to connect to your stock system with no welding....unless your stock system is already welded...

 

Yes, noise control is in the muffler and volume is in the exit pipe. If you want loud use the largest diameter pipes and exit pipes you can find and afford. The 2 1/2" cast manifolds are good idea but you will spend just as much as a good header and won't have the cylinder scavenging. Hedman, Doug Thourley are great headers but be sure to get them ceramic coated if you choose to swap to headers.

As for loud mufflers I have a Spintech on my Camaro and hate the noise level it makes because of close neighbors. You have to size the Spintech mufflers because they don't sell them car specific. But they are a designed full race muffler and used in competition classes that use mufflers.

Good luck and let us know what works for you.