C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

Story time- Removed my exhaust (including headers and TWC braces) today for 2151's...

Old 06-04-2007, 12:53 AM
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LouisvilleLT4
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Default Story time- Removed my exhaust (including headers and TWC braces) for 2151's...

You'll notice that this is a pretty long explanation of what I did, and that's because there are simply a lot of steps involved in this job. Definitely a lot more than I thought there would be. It's important that I list them all out, if for nothing else than to warn all beginners of what a daunting challenge it is to prepare for a header install.

My newbie self decided to buy a $400 set of Hooker 2151 Longtubes and connect them to my LT4 in place of my ruined catalytic converters. Despite having never done any work in an engine bay, I managed to remove my whole exhaust all the way to the manifolds, including the evil catalytic converter braces. Moreover, all this was done with the front end 6 inches off the ground and the back end 0 inches off the ground. I simply drove the front tires up on 4 stacked 2x12s and went to work with a set of wal-mart deep sockets and a fairly limited set of tools. Here is how I did it.

Starting in the engine bay...the manifold bolts weren't bad at all, once enough stuff was out of the way that is. First step was to say goodbye to the AIR injection system that heats up the cats when the car is started. It blocked my access, and additionally I decided it was not worth keeping this system so the removal was to be permanent. I unplugged all its associated hoses and pried off their clamps. I unbolted the AIR pump and removed its brace and the attached electronics, unplugged the metal AIR pipe's connection to the intake (I will need a block-off plate here), and removed that pipe completely from the passenger exhaust manifold for better access (but I had to saw it off when its bolt deformed).

I then pulled off my brake booster hose and unbolted the ASR and the cumbersome brace it was attached to for better driver's-side access. By the way, as you unbolt parts it's a great idea to remove bolts and nuts only long enough to get the part out and then return the bolts and nuts to where they came from, so you remember where each one goes.

I detached my intake snorkel from the throttle body and unplugged everything nearby to remove my airbox, which made way for a serpentine belt tool to pry my tensioner away from the belt until I could slip the belt off of the A/C compressor and unbolt four long bolts from its side. The compressor then sagged down out of the way, making all the alternator and A/C support brackets' bolts accessible, which were removed with deep sockets. If the compressor doesn't sag down far enough you can remove the center section of your wheel well - and this also makes a good place to let the ASR box hang - but be sure to put it all back where it was before you attempt to close your hood.

I unbolted and then wiggled my dipstick tube from the bottom until it yanked out, labeled my plug wires and yanked them out by their boots mostly by hand, unscrewed all the spark plugs with a deep socket to give the manifolds room to move, and at this point all the manifold bolts could be got at with a deep socket (although I think I used a shallow socket for the rearmost bolts). These bolts were not frozen in place badly, and a hammer striking the ratchet was enough to pop them all loose. After all, I had sprayed every exhaust-related bolt with WD-40 the night before.

Lots of tedious steps so far, some of which were frustrating and awkward, but not terrible. The terrible part came next, for I had freed up the manifolds from the engine bay but they were still attached from underneath. Dealing with this was to become the biggest test of my patience since ever working on a car.

The flanges between the manifolds and the cats were inaccessible completely at this point. The only way to remedy this was to first detach the cats from the catback, and the only way to do that was to pull the whole catback off of the car. The passenger side only had a one-bolt clamp securing it, which was easily loosened. On the driver's side, however, Satan himself was holding the cat and the catback pipe together. The flange here had three Allen-head bolts, and these bolts were stuck. No amount of torque that I could apply with a mere 6 inches of extra ground clearance could break them loose. I gave them all an extra spray of WD-40 and hammered the hell out of them and they still would not budge. The one on top was not even within reach and it was also just as stuck. Seriously, it was on top of the pipe with frame on either side of it, ensuring that no tool could be turned or even fit into that space. I worked at these bolts until frustration made me quit until the next day, for three days in a row. And then, with the reverberating groan of rusty metal on metal, they budged. And with patience, they loosened.

After that step completely kicked my ***, it was time to re-evaluate whether or not I could do this, and whether it was worth my time. But before I got too discouraged, I removed my O2 sensors (a job I was already familiar with, and already had the proper tools and extensions for) and then I found that luckily, the muffler bolts were easy, as were the exhaust hanger bolts once I figured out it was safe to detach the bolts connecting the hanger springs to the exhaust pipes. The cat-back was now hanging loose. A little wiggle and the only thing holding it was the passenger-side cat's exit pipe, which fit snugly inside of the catback's pipe, so snugly that the pipes had rust-welded themselves together. Several minutes later of two people violently twisting and pulling the catback by the mufflers, and we noticed that we had made progress - a little line we had marked where the two pipes had connected now showed that the pipes had moved about an inch farther apart. Several more minutes of yanking, checking the line, and yanking some more, and the cat-back fell down softly to the ground. It weighed 70 pounds but we already had the heaviest part in our hands.

The passenger side cat still had a brace holding it up, and one of its bolt locations looked impossible to get at but luckily the bolt was missing there. The other bolt came out easily, and now the manifold/cat pairs were loose and free to move. I lifted them both up above their ports, letting the gaskets fall out, and tied them in place with rope in this lifted position. This gave me a little - very little - access to the cat-to-manifold bolts, and it was enough. Once separated, the 13-lbs-each cats fell down out the bottom and the 15-lbs-each manifolds lifted out through the top. Whew.

With the old manifolds off, the new 10-lbs-each headers were now ready to go in anytime, since I had already paid an exhaust shop $50 to weld O2 bungs on the collectors and plug up the existing O2 hole. I still had neglected to order the necessary reducer pipes and decent gaskets, but that wouldn't stop me from at least trying to see how the headers fit.

I looked around for things that would get in the way of putting my new headers in place. I tried to fit them in from the top but quickly realized that this was not the way to go, as the brake lines going to the master cylinder and the fuel lines were in the way on their respective sides. So the next step was to drop the starter in preparation for going in from the bottom. After all I had gone through so far, the starter was a piece of cake. Here's a little tip, unbolt the two electrical cables BEFORE you unbolt the two long bolts holding the starter to the engine; I did not do this and was forced to rest the 9 lb monster on my chest to prevent it from falling and ripping free of the wires.

The catalytic converter braces/"TWC" braces were still hanging down from the transmission, clearly in the way of where my headers would end up. A little searching on here revealed that these were stupidly hard to remove and that most people just cut them - and after looking at how thick the metal was on these, it made me appreciate how hard they must be to unbolt. I knew I had a tough job ahead of me.

The passenger side only had one bolt left so I started on that. It was way up high, practically backed up against the firewall so I had no hope of getting a ratchet up there. I ended up using a borrowed ratcheting wrench to turn it, but it might as well have been a regular box wrench because there was not enough turning room to make the ratchet click once - I had to remove the wrench and manually click it once each time I turned. It seemed like I did this a hundred times, until finally.... the wrench wouldn't go back on. The bolt had backed up too close to the firewall. I suddenly realized that perhaps this bolt was not intended to be removed with the transmission in the car. Disheartened, I gave up for the day.

The next day I reached up to that bolt with needle-nosed pliers and it wiggled and fell right out. It had already backed up just enough to disengage. The passenger brace came out with it, and I felt empowered knowing that others had simply given up on removing this thing. Once it was out, I put it aside and returned its bolts to their position, since they looked pretty important in holding the transmission to the engine block. On to the driver's side.

Two bolts secured the driver's side cat brace to the transmission bellhousing. The lower one was obscured from underneath by the bellhousing but there was barely enough room to fit a ratchet and deep-socket. One nut came off, which had held two ground wires onto the stud that held the brace on. I wiggled these ground wires relentlessly and they would not slide off the stud, but needle-nosed pliers once again came to my rescue and I was able to back them out. I got the stud out with the deep socket.

The brace's upper bolt was even harder to get to than on the passenger's side, and I was forced to try my luck from above. I got out from under the car and, after unbolting a bracket that held the battery cables in place, was able to slide enough wiring harnesses out of the way to give me access. I slid a closed end box wrench down there and found that the bolt turned quite easily. Too easily. It backed up into the firewall again, only this time, the wrench was stuck on the bolt head and would not free itself. Great.
I sighed, and proceeded to yank the wrench back and forth, twisting this way and that, for no less than five minutes. To my amazement, this eventually worked, and I found myself standing there with a freed wrench in my hands. The flange and its bolt came out easily after that. Mission accomplished. I couldn't believe what I had just succeeded in: both of the infamous cat braces were off my car.

My 6-inch-tall homemade ramps under the front wheels had served me well. They allowed me to remove the entire exhaust, but unfortunately they did not give me the ground clearance to feed in the new headers from the bottom; the headers would have to be tilted nearly vertically to slide up into place. Hesitantly, I decided to get over my fear of using jackstands. I would need them to get the extra height I needed.

I jacked the front up by the frame right underneath the engine, high enough to pull my homemade ramps out from underneath, and set the car down. I went around to the side and reluctantly jacked the car up on the metal rocker-panel flange halfway in between the two recommended points, which everyone insists is safe despite my fears of it not being as reinforced as the recommended points. All went well, the whole left side of the car lifted up at once, allowing me to place jack stands at both recommended points, and things went equally well on the right side. Four jack stands were in place but the car was clearly resting on three; I could see daylight above the fourth stand, as is often attributed to the stiffness of the Corvette.

Not about to be crushed by the car's four-inch ground clearance should it fall, I had many backup plans in place. I stacked up concrete blocks all the way to some front and rear frame members, used two extra jack stands under the rocker panels, wedged each wheel against a ramp, and set up my floor jack to catch the car should its weight shift. The last thing I need is, as someone else worded it, an "LT1-shaped imprint on my forehead."

I haven't gotten around to sliding those headers into place yet. The stands aren't quite at their tallest level yet and I know they will need to be to make this work, but that's all a matter of jacking up each side a little higher. Mostly I've just been busy redoing my interior - completely. The car has been down for weeks and this has been a good time to strip out the interior to the frame. What a piece of cake compared to exhaust work! The doors are emptied out, and the cabin is now nothing but an empty polo-green fiberglass tub with some wires running across. Everything is getting cleaned, detailed, and resurfaced, or in a few cases removed permanently if I decide it's too worthless and heavy to stay. It may look like a parts car right now but it will become a truly great car... someday.

I hope someone who is installing 2151's to their LTx engine finds this through the search feature, reads over the step that they're on, and gets at least something out of it that helps them in the process. And I hope this story serves as an example to everyone of what a daunting challenge even the first steps of a header installation entail. Let me know if I've left anything out, because I am keenly aware that it's the little things nobody thinks to mention that cause the most trouble. If you have any questions at all about the process, up to the point where I stopped, then ask away.

Last edited by LouisvilleLT4; 06-05-2007 at 06:21 PM.
Old 06-04-2007, 08:34 AM
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RacerX70CC
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Default Good post...

Excellent post... hopefully this is very enlightening for those who think "ahh, I'll just throw headers on it" without thinking the matter through...

Good luck!
Old 06-04-2007, 01:51 PM
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Good read,hope you get it all done. I might start on this project next week.
Old 06-04-2007, 02:22 PM
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Nice writeup!!
Old 06-04-2007, 02:26 PM
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Nice book, good read
Old 06-05-2007, 09:53 AM
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LouisvilleLT4
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I know a lot of folks are in the middle of this project, so I'll give this one last bump before I let it go into archives.
Old 06-05-2007, 03:19 PM
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I have the 2151 on my LT-1.

They are a great header for the money.

Good write-up. I have one in tech tips thats a couple years old.
Old 06-05-2007, 06:04 PM
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LouisvilleLT4
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Originally Posted by VR'92
I have the 2151 on my LT-1.

They are a great header for the money.

Good write-up. I have one in tech tips thats a couple years old.
They may indeed be a good deal, but I may not have gone this route if I had known some things about the headers beforehand.... the fact that they aren't exactly made for the LT1 corvettes and will hit things like motor mounts and have all sorts of fitment issues, and that they don't accommodate the stock alternator and A/C braces, and that their flange at the ports seems too thin and structurally prone to warping, etc...

Plus, this install has taken me weeks of being stuffed uncomfortably under the car, getting bruised up, and I'm not even close to being done yet.... although on the other hand, if I had been given the opportunity to read my own write-up prior to starting, I could have gotten this far in a day. It would have saved me a lot of trial and error...each one of those hundred steps I listed above required making a lot of mistakes before I figured out the right order to do things in and the right way to do them.

Last edited by LouisvilleLT4; 06-05-2007 at 06:19 PM.
Old 06-05-2007, 06:13 PM
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You did a yeoman's job with limited tools and experience, you are to be commended. Getting the stock cats and their brackets off of an LTx car is a challenge under the best of conditions. The good news is that many things in the future will now be easier such as, changing the fuel filter, the starter and plug changes (w/o the A.I.R. crap on there) should all be less hassle now.
Old 06-05-2007, 06:27 PM
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Originally Posted by LouisvilleLT4
They may indeed be a good deal, but I may not have gone this route if I had known some things about the headers beforehand.... the fact that they aren't exactly made for the LT1 corvettes and will hit things like motor mounts and have all sorts of fitment issues, and that they don't accommodate the stock alternator and A/C braces, and that their flange at the ports seems too thin and structurally prone to warping, etc...

Plus, this install has taken me weeks of being stuffed uncomfortably under the car, getting bruised up, and I'm not even close to being done yet.... although on the other hand, if I had been given the opportunity to read my own write-up prior to starting, I could have gotten this far in a day. It would have saved me a lot of trial and error...each one of those hundred steps I listed above required making a lot of mistakes before I figured out the right order to do things in and the right way to do them.
Although I don't have experience with the Hookers on a C4, I do have other experiences with them that makes me not a fan. I can offer some assistance when it comes to accessory brackets and other misc. BS when it comes to headers on these cars though. I've had three different brands on my '95 plus have fooled with a couple of other kinds on C4s. PM me if I can help and I'll give you a phone number.
Old 06-05-2007, 06:30 PM
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Congratulations! You not only found good ways to accomplish this job, you stuck with the job. I am sure there are many of us who would have quit about your third paragraph!
Old 06-05-2007, 08:12 PM
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Great read...nice detail. A very encouraging write up for people who lack the confidence to tackle their own repairs or mods. Makes me want to put headers on my vette
Old 06-06-2007, 12:44 AM
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Oh yeah, let me know if there are any corrections or inaccuracies with anything I said, or if anything was unclear... my memory is kind of fuzzy and I want this to be an accurate walkthrough.
Old 06-06-2007, 10:10 AM
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Originally Posted by LouisvilleLT4
They may indeed be a good deal, but I may not have gone this route if I had known some things about the headers beforehand.... the fact that they aren't exactly made for the LT1 corvettes and will hit things like motor mounts and have all sorts of fitment issues, and that they don't accommodate the stock alternator and A/C braces, and that their flange at the ports seems too thin and structurally prone to warping, etc...

Plus, this install has taken me weeks of being stuffed uncomfortably under the car, getting bruised up, and I'm not even close to being done yet.... although on the other hand, if I had been given the opportunity to read my own write-up prior to starting, I could have gotten this far in a day. It would have saved me a lot of trial and error...each one of those hundred steps I listed above required making a lot of mistakes before I figured out the right order to do things in and the right way to do them.
The motor mount issue is easily solved by flipping the direction of the motor mount bolts. Fits fine then.

The Alternator brackets aren't a problem limited to the hookers. All you need is a homemade bolt spacer and you can make 2 of the brackets fit fine.

My flanges certainly have held up well. I have removed them and reinstalled them more times than I can count and they are certainly not warped. I did infact learn that you need damn good gaskets to make them fit well though. I use those perceys insert able gaskets.

Last edited by VR'92; 06-06-2007 at 10:14 AM.
Old 06-06-2007, 04:24 PM
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Originally Posted by VR'92
The motor mount issue is easily solved by flipping the direction of the motor mount bolts. Fits fine then.
You're calling something that requires you to own an engine hoist "easy."

Can you tell me more about those gaskets?
Old 06-06-2007, 04:29 PM
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Originally Posted by LouisvilleLT4
You're calling something that requires you to own an engine hoist "easy."
You only need a piece of wood and a floor jack. Place the wood evenly on the oill pan and put just a bit of tension with the floor jack. Remove the engine mount bolt, flip it over and retighten. It's as easy as that.
Old 06-06-2007, 04:31 PM
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Originally Posted by STL94LT1
You only need a piece of wood and a floor jack. Place the wood evenly on the oill pan and put just a bit of tension with the floor jack. Remove the engine mount bolt, flip it over and retighten. It's as easy as that.
This is correctamundo.

What up STL94?
Old 06-06-2007, 04:32 PM
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I stand corrected. Thanks guys.
Old 06-06-2007, 04:41 PM
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Originally Posted by LouisvilleLT4
Can you tell me more about those gaskets?
You know, I said Percys but they are the Earls with the inserts. Best gasket I've ever owned. I love them:

Summit Part number: EAR-29DD3BERL

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