Aug 23, 2019 update to the Chevrolet Corvette Z06 project car

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 installed a set of Texas Speed and Performance 1 ¾” diameter long tube headers, along with their 3” catless X-pipe—yeah, we’ve pretty much admitted it’s just a track car now. Shorty headers make for a much simpler installation experience, but long-tubes provide better performance. Pick your compromise.

The install procedure is as follows:

Remove valve cover covers, coil packs, ignition wires and alternator. We’re also going to recommend that you remove the spark plugs, because the likelihood of breaking one off during removal and installation is highly nonzero.

Remove exhaust center section and crossover tube from underneath the car. This requires removing the rear oxygen sensors, and once you get the center section out, it’s pretty easy to remove the front oxygen sensors as well.

Remove dipstick tube. It’s held against the block by a single bolt, and just presses into the oil pan at the bottom.

Remove stock exhaust manifolds. Each is held to the heads with six bolts. When you get the last couple, we recommend you support the manifold by hand while you remove the bolts and don’t let the last bolts bear the weight of the heavy manifold. It can be bad for the threads in the relatively soft aluminum head.

Congratulations, you’ve lulled yourself into a false sense of security thinking you’re “halfway there.”

On our car, the passenger side header dropped right in from above. No fuss, no muss. But we’ve heard horror stories of starter removal, engine mount loosening, heavy object pounding and more. Suffice to say your mileage may vary. Once our passenger side header dropped cleanly in, we installed a new gasket (you need to use header-specific gaskets as you’ve now bypassed the air recirculation system integrated into the stock exhaust manifolds) and hand-tightened our new ARP header bolts.

Our horror story came on the driver’s side, where we spent the better part of the day trying to wrestle the header into place.

We’d struggle for a few minutes, then hit the internet to look for tips and maybe that magic bullet that would help our header slide more freely. It brought no relief. Some folks said their headers slipped neatly up from the bottom, but we couldn’t make any sense of that method. What finally worked for us was loosening both motor mounts and jacking the engine up slightly, removing the steering shaft and a little bit of good old-fashioned hammer beating. Turns out it would have been easier still if we had removed the valve cover, as the header hung up on one of the threaded bosses for the coil packs.

So the real answer here is there’s no magic formula. Each brand of headers makes them challenging in slightly different ways. Just keep removing stuff until they fit, because eventually, they will.

Once our headers were in, and we had tightened down all of our header bolts and exhaust clamps and lowered the engine back onto its mounts, we had only one remaining clearance issue. The steering shaft kissed the #5 header tube ever so slightly. We did a little gentle massaging with an air chisel with a flat anvil, and the wedge end of a porta-power and gained a few thousandths of an inch of space. Enough where we haven’t seen any additional interference after a few events, and you can hardly tell the pipe was “adjusted.” Takeaway message here is that you should be prepared to improvise during this procedure.

Also, the Texas Speed long tube headers come with extensions for the oxygen sensor wiring since your sensors are now relocated a bit. Take some extra time to make sure that the wires are routed away from hot pipes. We spent a few minutes with cable clips and conduit clamps and used some existing bolt holes for the tunnel cover to make sure our wiring had a nice air gap between itself and any hot surface.

We’ve not yet been to the dyno with our headers, but we went to the next best place: Daytona International Speedway. With the headers in place, our top trap speeds were up from 159-160 at a previous event to 164-165 at the same place on track.

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AngryCorvair
AngryCorvair MegaDork
8/23/19 9:48 a.m.

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.

A 401 CJ
A 401 CJ Dork
8/23/19 11:22 a.m.

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

Ransom
Ransom UltimaDork
8/23/19 11:59 a.m.
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... cheeky

Ian F
Ian F MegaDork
8/23/19 12:05 p.m.
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... cheeky

JG speak for "learn from my mistakes."

slowbird
slowbird Reader
8/23/19 12:08 p.m.

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 cheeky

JG Pasterjak
JG Pasterjak Production/Art Director
8/23/19 1:02 p.m.
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... cheeky

This guy gets it

JG Pasterjak
JG Pasterjak Production/Art Director
8/23/19 1:03 p.m.
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 cheeky

I see you've read the Haynes Manual version

JG Pasterjak
JG Pasterjak Production/Art Director
8/23/19 1:09 p.m.
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.

iceracer
iceracer UltimaDork
8/23/19 6:45 p.m.

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

JG Pasterjak
JG Pasterjak Production/Art Director
8/23/19 7:11 p.m.
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.

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