Does anyone out there in Corvette land make their own headers?

If so do you have any sage advice?

I'm about to buy parts from "Headers by Ed", probably monday or so...

 

I have never built my own headers but have read a little on the subject.
David Vizard says equal length is a waste of time. On dyno tests he found no hp advantage and showed they actually made the power band smaller. His reasoning was that at every rpm there is a optimum primary length and by having different primary lengths the power band is lengthened. " Dyno tests with headers having primary lengths adjustable in 3 inch increments show that lengths between 24 and 36 inches have only a minor effect on the power curve, although the longer pipes favor the lower end". I would build whatever primary length that would fit the best. Minimum 1.75" diameter if you are making more than 375 hp.
Collector length is more important. Short large diameters favor top end and long small diameters favor low end. Most headers sold are too large in diameter and too short to be 100% effective in anything short of a full race engine. A 7500 rpm race cammed small block needs a collector length of 18-24 inches long. 3 inch dia. collectors only above 375 hp. In a high horse situation, the collector size should be 1.75 times the primary pipe dia.
Make sure the rest of your exhaust system is up to the task. Mufflers should flow 2.2 cfm/hp. (400 hp needs 880 cfm, so two 440 cfm mufflers required). Add a balance pipe (quieter, possible hp/torque gain)there is no downside.
Tig welds look nice!

 

Also, a 2.5 dia exhaust pipe will flow 560 cfm (up to 254 hp) so a 2.5" dual exhaust will support 500 hp (assuming mandrel bends), muffler shop type bends can restrict up to 10 %

 

Well said, VERY interesting.........

 

Vizard says that equal length is unimportant for 'performance'
No one EVER that I know of has made the performance claim for equal length.
The reason you want equal length is tuneability. If all clyinders are scavanging the same then they all get the same fuel / air mixture...

The reason Vizard saw a broadened torque curve is because different clyinders were contributing differing amounts depending on RPM. Because they are all running at peak performance at different RPM.

Besides, If I could get aftermarket headers that are within 3" of equal length I would buy them. Well, no I wouldn't, they'd have to drop the O-ring seal and merge their collectors, Oh and no more of that different depth into the collector BS to get closer to EQ, Oh and there should be spark plug access, and maybe even fit(?)

 

I can see your point on tuneability, however, that would be assuming that your intake would distribute the air fuel mixture perfectly.
What type of headers are you running on your car now? Doesn't sound like they are working as well as you would like.
I am building a 400ci+ small block engine and am considering Hooker Super comps. I think they come with 1.75" diameter 25" long primaries and a 10" long 3" diameter collector. They also sell collector extensions to tune your engine (they are 18" long and can be cut to length) that bolt on to your collector. Any experience with the hooker brand anyone?

 

LOLRight now I have Hedman Sideexhaust headers, The 'long' tubes are 18" and there is 6" difference in length!
It uses 1 5/8" tubes which was fine for a 350 but way too small for a 434.

The reason that headers matter is that a properly designed header contributes 100 times more to intake flow than the intake manifold, Vizards words not mine

The exaust port shap on my existing header is round and on the head is square, there is about 1/16" of the gasket sealing on the corners of the port, so I blow them all the time.

Collector extensions are great if you are running open headers, but I almost never get to do that, so it's a moot point.

If the hooker primaries are 25" long they are 10" too short, THAT is significant!

 

The only problem with longer primaries is getting them to fit in the confines of the engine compartment and leaving room for the collectors. You can use the collector extensions on a muffled car by welding a reducer into the system (say 3"-2.5"). If you are planning to make more than 500hp (which you may), you would need to run 3" exhaust anyways to prevent hp losses through your exhaust.
To prevent header-head leaks have you tried copper gaskets?

 

I haven't built my own headers yet but I did get the stuff from Ed for my 73 Mustang. He's a pretty good guy. I guess you've probably got to actual do business with him in person. Ed has some pretty convincing dyno tests on the advantages of equal length.

I checked out your website or your Mistress. She's hot. :crazy: Car's not too bad either. Yes, you are one lucky guy.

 

I placed an order for a kit from Ed, should be here soon

Thanks for the 'hot' comment says Patti :D :bb

 

I am wondering if Vizard has any takes on a designing a tubo exhuast system?

 

If it was "ME" i might try to buy an unwelded set from Stahl he has built some of the best Corvette race car headers EVER! ...redvetracr

 

Back to the original question, I built one set of "header" for my '32 Ford (see the post "Other Hot Rods" in C3). I pretty much had to, as there are no sources for turbo-4 headers in '32 Fords ... and I thought it would be a nice experiment. On a nice open engine access like that it was fairly easy, just bought a flange and bunches of 180 degree bent tubing. Took about a week of evenings fitting, triming, welding, and just staring at where I wanted things to go. A mig or tig welder is a must.

Would I do it again? If I could buy a reasonably close factory set to my needs probably not. But, since I'm planning a rather unusual routing for side exhaust for the '65 (no inner fenders and a set-back motor), which means I'll probably end up doing another set.

Be sure to spring for having them ceramic coated when your done, best money I've spent on exhaust stuff.
-Greg


[Modified by GregP, 3:00 PM 8/8/2001]