:. Projects/Mods .:. Kooks 1 3/4" Headers & cats .:
There isn't a whole lot to say about headers that hasn't been said before, so here's the summary:
That said, I wanted to make sure I got the best bang for my buck. As of this writing, in this author's opinion, (which is based on talking to lots of folks and research) that means Kook's headers for the C5. I have seen dyno graphs showing appreciable (10hp or more) improvements on cars moing from TPIS headers to Kooks, from FLP's to Kooks, and from the Dynatech headers to Kooks. Several folks have reported improvements moving from Stainless Works headers to Dynatechs. One fellow on Corvette Forum claims to have tested them back-to-back, and says that the Kooks made more power everywhere in the powerband. But, there are no graphs to show this. So, the only direct comparison I have not seen is Kooks and LGM headers, so I collected as many dynographs as I could of similarly modified Z06's, and placed them all here.
- They will all make more power on your car
- They will all make a little more noise
- More than likely, you will be happy with whatever ones you choose.
The general trend of those cars is that the LGM cars have a few more mods, and make a few more ponies. Draw your conclusions as you will, I chose that to mean that with similar mods, the Kooks would make similar power, and for nearly 40% less than the LGM headers.
The exact variation of the Kooks System I chose to go with was: 3" cats, into a 3" x-pipe, which at its exit necks down to 2.5", and goes back in that fashion to the Z06 mufflers. I guess this is the 'standard' Kooks setup. They can build you a 3" back to the mufflers that necks down juuust before the flange, like the LG setup, and then of course there's the 1 7/8" flavors and whatnot. If I had not found these headers as a deal new for $1,100, I would have bought the 1 7/8" From MTI, on their recommendation.
I've written a number of pretty long articles on Corvette Forum, which I'll copy here. Unfortunately, I don't have any pictures to go with these, but they are floating around on CF and Z06Vette.com if you do some searches.
Kooks Install - Day 1
Man...what a ton of work. I've done a lot of DIY work over the past 3 years, and this amount of R&R sure seems excessive for something like a set of headers. Hopefully my opinion will change once they're in place and I get to hear the car and drive around some.
Things started out going relatively smoothly, around 5:00. I removed the H-pipe the night before - which included breaking off all six header-to-h-pipe bolts, since they were basically rusted in place. No matter - they're never going back on.
I removed the manifolds, alternator, and everything else, no problem there, either. The first snag came when I tried to remove the valve covers - the PVC line going from the driver's side to the passenger side, behind the intake manifold, crumbled in my hand when I tried to remove it. Grr. Replacement part #1 to order today.
Valve covers and coil packs came off fine, but boy are those harnesses crusty and brittle after 85,000 miles of running the car. On the upside, the heads have absolutely no varnishing to them, and look brand new.
The problems started when I tried to get the Kooks in. I pulled the steering shaft nut - easy, and pulled both of the nuts on the engine mounts. Was thinking to myself "What a bunch of weenies these CorvetteForum DIYers are" at this point. So, I started with the passenger side, thinking it was going to be the easy one.
I raised the motor about as high as I could possibly think of doing it - hearing all sorts of bad noises coming from under the firewall as I did it, since I kept needing juuuuust a little more space for the header to *maybe* get in. I kept checking clearances there to make sure stuff was mostly OK, so hopefully nothing back there got too messed up. Isn't there a MAP sensor back there somewhere that gets close to the firewall? I'm worried about something back there having gotten squished or cracked. Unfortunately, there was absolutely no other way to get the passenger side header in - the A/C line that runs by the frame rail there was in the way in too many places....Ugh!!
Finally, after a while, it dropped in. On to the driver's side. Hah - yeah right.
After about an hour of fighting with it - and breaking off the head of that small sensor near the front of the driver's side head - I finally decided there was no way the header was going in without removing the alternator bracket. The brake lines by the brake booster were in the way, and the alternator bracket made it such that there simply wasn't room for the flange to move downward. The motor was jacked up so high it wasn't even on the stud of the motor mount anymore, and the black part of the firewall, up by the windshield wipers was bulging from the bracket of one of my fuel rails.
I'm sure my install was complicated somewhat by the oil cooler and AN lines that I have installed - but I had to remove the oil filter, the filter adapter with the cooler lines running out of it, and finally the alternator bracket, which involves removing the power steering pump for acces to the last alternator bracket bolt.
Finally, after I got all that stuff removed or loosened, the driver's side header slipped in easily enough and then I spent the next hour fighting with the power steering bracket and alternator bracket, trying to get everything properly lined back up again. What a mess. Called it a night at 11:00PM.
So, now I have to re-run my oil cooler lines, since the headers now occupy the space where they went before. I think I'll run one next to the framerail, by that lower brake or clutch line, and the only place I can see for the other one is between the engine mount and the subframe of the car. There's already a wiring harness running through there from GM, so I imagine another -12AN line won't hurt either, as long as I can get everything lined up again.
Then it's time to reattach the steering, starter, plugs, wires, valve covers, coils, alternator, oil filter O2 sensors, dipstick, cats, x-pipe and then replace the broken sensor, AIR tube gaskets, and PCV line.
What could be easier?
Day 2 - Finishing the Install
Yesterday I finished up the install. One expects to encounter problems when installing aftermarket parts, but this install - both related to the header system itself and not - did seem a bit more difficult then the normal rash of problems one encounters.
The day started rather inauspiciously - when I went to replace the starter, the 13mm nut fell off and in between the primaries of the header and got stuck on the back side of the collector. I did a , then a , and then (FIGURES!) . So, we had to jack the motor up again, pull the header, and turn it upside down so the nut would come out, since even my tiny pen magnet couldn't fit in there.
Fortunately, having done it once, it took literally under a minute to get the header in and back out again. I guess it'd go a lot quicker having done it before.
Next big challenge of the day was rerouting the oil cooler lines, which wouldn't have been a problem for most folks, since they wouldn't have them... I ended up running one near the framerail, zip-tied to a brake line, and ran the other in the space between the motor mount and the subframe, where a wiring harness already runs. I had to slightly relocate that harness, but finally everything seemed to be clear of eachother.
Things went together basically smoothly after that. One of the exhaust manifold bolt holes in my head was not wanting to let the bolt thread, so I ran a tap through it to make sure nothing would get stripped.
A few other problems cropped up. First, the fasteners that Kooks sent were incompatible with eachother; the nuts would not thread onto the bolts. So, I took them all to Home Depot and found some matching nuts for the bolts. I never did find a thread pattern that matched the nuts, metric or otherwise. One fellow suggested that the nuts may have a special design to prevent them from working loose - kinda like nylock nuts work - so I will give Kooks a call about that today to check - when I looked a the threads, it just looked like they were stripping *shrug* (thread asking about this: Here )
And, on another note, the hardware they send is SAE, not metric. : "Here, take your entire car that's metric and enjoy scrounging up a 9/16 socket and wrench, just since we didn't want to take the effort to find metric bolts" I'll go find some metric fasteners later at a fasteners place here in town.
After I had the fasteners, courtesy of Home Depot Racing I started putting everything together, which is where I ran into a second snag. A giant chunk of welding slag was blocking one of the O2 sensor bungs, so I had to pull the cats and x-pipe back off, and use my die-grinder to open up the hole so that the O2 could fit in. In the process, that munged the threads pretty bad, so I ran another tap through those to make sure all would be well. Good thing I"ve got my giant Harbor Freight tap-and-die set from working on the Eclipse, or I'd have been screwed on this install.
Got every bolt started, put antiseize on all of it, and started tightening things down until it was all tight. The V bracket to attach the headers to the bell-housing isn't even in the same zip code as far as fitment, so I might re-examine that tonight and see if there's any way of getting that to happen.
The exhaust tips don't currently line up, so I'm going to fiddle with rotation and fitment of stuff until they're all in line again. Predicably enough, about 50% of the bolt holes that were touched by the monkey that installed my gears was pretty cross-threaded or stripped, so I took a bit more time having to clean up threads on those as well.
As far as positives, the AIR tubes and oil dipstick lined up perfectly, and the system went togther with itself perfectly. The O2 sensors and wires had plenty of room to be out of the way, so I dont have any worries about burning wires. Similarly, there is plenty of room for the plug wires. I had bought Koolsox as a precaution, but didn't install them - there is ample clearance to all the plug wires. All the pieces fit well together, and nothing hangs down unduly. The heat shields for the cats hang down just a tiny bit, if I recall correctly, but it is not substantial, and my car is in the weeds.
So, at around 1:00AM, we fired it up just to make sure the freaking car still runs . Sure enough, fired right up, sounded a *little* different at idle, and proceeded to fill the garage with smoke from our greasy handprints burning off. The startup was a nice VAROOM! that I was hoping for, and then settled down to a nice quiet idle thanks to the Ti's. It does sound a bit...hollower, maybe? No ticking or other oddball sounds that I'd been led to expect, just a nice smooth, healthy idle. I let it run a bit - no codes - gave it a few good revs ( I can't wait ), and shut her down for the night, in deference to the rest of the neighborhood.
Today or tomorrow I'll double-check (for the 100th time ) all the fasteners and O2 sensor wires, see if I can work out the alignment issues, and take 'er for a rip. I can't wait to see what it'll be like!
So, in short, (if that is possible, anymore) NOT a job for a beginner DIY'er. Nothing insurmountable if you've been doing this for a while, but a toughie if you don't have the tools, experience, or patience.
Subjectively, the Kooks are not quite as impressive visually as the LGM's (I had a set of those at one point also, but was never able to install them due to needing new Hoosiers at the time...). The metal the cats and X-pipe are made up of is thicker, and I believe a bit heavier (subjectively). Probably a difference between the stainless LG uses, and the Kooks mild steel, I don't know. They looked the same to me, color-wise. The 2.5" intermediate pipe doesn't quite have the cool factor that the mondo 3" intermediate pipe of the LGM's does. The headers themselves look very nice - very comparable - and have a cool "kooks custom headers" plate welded one one primary on each side. Nice touch.
I weighed my stock manifolds and H-pipe on a litlte postal scale I bought for weighing parts:
Stock Manifolds: 12lbs x 2 (all the double walls were cracked and/or gone !!!)
Kooks Headers: 10lbs x2
Cats/X-Pipe/Intermediate Pipe: 29lbs
So, almost 20lbs savings, and the cats weigh the lions share of that 29lbs, I'd say, of the X-pipe. They are heavy. Including the Z06 mufflers, I've cut almost 40lbs from the car in exhaust parts alone!
Final costs, before tuning:
$1,100 - Kooks headers w/ cats, new from CF member
$40 - GM exhaust manifold gaskets, Muffler gaskets, AIR pipe gaskets (didn't want to use the cheesy paper ones from Kooks)
$60 - replacement water temp sensor (oops), replacement PVC hose
$4 - fasteners to replace the mismatched ones from Kooks
When I shopped for LGM's, with my '97, my cost estimates came out as:
$1,900 - headers + cats (new, special price)
$50 - shipping
$60 - exman gaskets, muffler gaskets, AIR gaskets, intake manifold gaskets
$60 - new AIR tube req'd for 97-00 cars
$100 - O2 Sims
For me, with my 97, these Kooks represent a $1000 (or, $1100, without the broken parts by yours truly...) savings over the LGM headers, (recognizing that I saved about $250 by finding them secondhand, versus the $1,350 new cost ) which had been my choice up until now.
In the final analysis, after the last few details (fitment & alignment, mostly) are addressed, we'll see if it turns out to be worth the money saved. For somebody with my relatively (to the rest of this crowd, it seems) meager means, that represents a huge chunk of money, and hopefully it will enable a few other go-fast goodies a bit sooner down the line, or at least, enough Hoosiers for me to be able to compete for a full season this year
Day 3 - Final details + driving impressions:
For those that are still listening ( Day2: Here )
I got home today and finished up the last few details with the Kooks. I was able to get the V-bracket that bolts the header primaries to the bell housing installed with a little bit of effort, and I took a few minute and realigned the tips. [Update: When we tried everything with the bolts tight, the holes were about an inch off on the headers. I loosened the cats, and loosened the V-bracket, and with a bit of slack, it all came together nicely. ] All is good as new, although I left my RHS tip too high, and it's rubbing on my trailer hitch - oops. I'll adjust them backd own after everything cools back off again. [ Update:I did this in 10 minutes - now it's no problem. ]
Sound impressions: Not a heckuva lot different from before, with the stock manifolds and Z06 mufflers. I was surprised at the minimal difference. Then again, my ear isn't real sensitive to those things, I guess. Idle is smooth as ever, and sounds maybe a bit "hollower" but that's about it. It doesn't ping, tick, 'klink' or make any other oddball sounds that might drive one (me) crazy, for which I am grateful.
Cruising around is, to me, indistinguishable from the stock car. No resonance or other negative behaviors.
WOT - wow, a lot more torque. the 2000-4500 band really woke up, which is what I was hoping for. The top end is still limited by the weak-a** stock cam, but even it is clearly better. The car just pulls harder everywhere in the revs, which is different from how I'm used to the DSM's when you turn up the boost. A second gear roll-on from around 3K really gets your attention now, and the car moves with more authority from a low-rev 4th gear stab as well. I am happy. There isn't much more noise evident from the rear of the car, just some beautiful music from the front, that sounds *great*. Very smooth, and it got rid of a 'jingle' I had around 3K RPM - heh.
We'll see how the dyno graph bears out the gains. I have a 'before' of my Z06 Ti, Blackwing, and 3.90's, so I'll be able to get a straight before-and-after. Then I'll have her tuned, allon the same dyno, so it should make for some good A/B/C comparative numbers.
I think that's about it. Other than the muffler adjustment, which I need to tweak (my own fault), I don't have any complaints left with the car. All the brackets and such ended up lining up after a bit of head-scratching, the car sounds just as I'd hoped (I'll have no trouble passing the 93dB limits at SCCA, I think), and I've definitely picked up a few ponies.
The final bonus? After going out and romping on the car for about 10 miles this afternoon, I let everything cool off so I could give it another once over, and noticed that the headers turned a beautiful shade of GOLD! I'd forgotten that stainless does that. How cool!
Final Notes & Observations
A few things bear adding here, which I had mentioned at the bottom of my CF posts:
I think that the only part of the install that was *really* worrisome was raising the motor to actually get the headers in. Not knowing exactly how much it was safe to raise the motor, and hearing the creaks and groans from under the intake manifold made me pretty wary, and I'm not a newbie at this kind of thing. Other than that, the extra step of pulling the steering shaft (one 15mm bolt) and the oil filter (no nut at all) , I hardly even noticed. Plus, having to take my oil cooler lines into account added at least 3-4 hours to the project, with re-routing lines, and removing the large filter adapter.
FWIW, the oil cooler notwithstanding, having done it once, I bet I could complete the job on a full Saturday's effort, and still have time for an afternoon carwash and beer. So, perhaps having an experienced friend is the best way to do this mod.
For doing it at home, I actually liked the capability of installing them from the top - getting the car high enough (on jack stands) to install a header from the bottom seems a bit scary to me.
As far as power, as of this writing (4.11.04), I have not dynoed the car, and I expect I will have it tuned at some point as well, to get the most out of my investment. As well, the car has not thrown any codes, and is not exhibiting any ill behavior. I will drive it for a week, double-check all my fasteners on the install, and then it'll be time to go racing!
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