Project Z06: An Exhausting Weekend in the Shop

As we delve deeper into some horsepower improvements for our C5 Z06 project, the next logical step was exhaust headers. “Logical” is kind of a loaded word here, though, because anyone who has ever installed long-tube headers on a C5 knows that the process can be frustrating and make you quickly question the actual logic of your decision. 

We …

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peripherally related, but can you tell me:

• your rear ride height
• where you measure it
• what are your rear alignment specs
• were / are aftermarket or modified OE parts required to achieve those specs.

your answers may or may not influence monZora's performance.

Says to take the plugs out and then doesn’t take the plugs out.  4th photo from bottom. :-)

A 401 CJ said:

Says to take the plugs out and then doesn’t take the plugs out.  4th photo from bottom. :-)

How else do you think they scientifically verified the nonzeroness of the chance of breakage? Otherwise it would've just been conjecture... 

Ransom said:

A 401 CJ said:

Says to take the plugs out and then doesn’t take the plugs out.  4th photo from bottom. :-)

How else do you think they scientifically verified the nonzeroness of the chance of breakage? Otherwise it would've just been conjecture... 

JG speak for "learn from my mistakes."

The easiest solution to installing headers is obviously to remove the whole engine, put it in another car entirely, cut the headers in half, put them into the car sideways, weld them back together in place, and then install the Vette bodywork over top of the new donor chassis 

Ransom said:

A 401 CJ said:

Says to take the plugs out and then doesn’t take the plugs out.  4th photo from bottom. :-)

How else do you think they scientifically verified the nonzeroness of the chance of breakage? Otherwise it would've just been conjecture... 

This guy gets it

slowbird said:

The easiest solution to installing headers is obviously to remove the whole engine, put it in another car entirely, cut the headers in half, put them into the car sideways, weld them back together in place, and then install the Vette bodywork over top of the new donor chassis 

I see you've read the Haynes Manual version

AngryCorvair said:

peripherally related, but can you tell me:

• your rear ride height
• where you measure it
• what are your rear alignment specs
• were / are aftermarket or modified OE parts required to achieve those specs.

your answers may or may not influence monZora's performance.

• your rear ride height

Starting point roughly where the lower control arms were level at rest. Then I added some rear ride height at Daytona because we were bottoming on the banking. Then I added a little more at Sebring because of bumps. I can get you actual numbers if you want. Just let me know what reference point you want measure from. But most of the adjustments have been judged by tire temps, butt-dyno and lap times rather than absolute measurements.

• where you measure it

Technically I didn't, but if I were going to I'd probably use the four jack points with pucks installed. They would make nice reference points.

• what are your rear alignment specs

Straight ahead toe, plus about a quarter turn of toe-in on each side because it rained once and I got scared. -2.1 camber both sides.

• were / are aftermarket or modified OE parts required to achieve those specs.

Yes. AMT camber kit.

I remember reading many years ago that the length of the exhaust affects the power band.    Short-high pm.  Long-lower rpm.    Truth ?

iceracer said:

I remember reading many years ago that the length of the exhaust affects the power band.    Short-high pm.  Long-lower rpm.    Truth ?

Well, the truth is far more complex than that really.

So, a lot of header design is about scavenging and wave reversion (actually, anti-reversion). Basically, if you think about each exhaust pulse coming out of a cylinder as a wave, you want those waves to hit the common tube where they all join at somewhat regular intervals. You don;t want them bumping into each other, or doubling up. (Actually sometimes you do, but that's a whole other discussion). At the most simple, long tubes give you more control over when those pulses hit the common tube since they join later. With shorties, the individual pipes join way sooner, so it's much harder to control the timing of the pulses entering the collector. 

In general—very, very general—shorties are usually good for a low-end torque bump, but that's where they do most of their good work. Long tubes should see gains all the way across the spectrum, and much higher gains in the mid and high ranges than shorties.