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F-Body FLP Long Tubes Install

Begin the night before by soaking down all the bolts that are coming out with the PB blaster or equivalent.  This will include y-pipe to manifold, y-pipe to catalytic converter, converter/y-pipe assembly to intermediate-pipe, etc.  You might also want to go ahead and remove the alternator since you can’t get to the passenger’s side manifold without doing so.

by Chris 96 WS6

What we needed:

  • FLP header kit—includes drivers and passenger’s side headers, 2 catalytic converters, 2 off road pipes, down pipes, y-pipe, band clamps and V-flange clamps, header gaskets and bolts.
  • Taylor LT1 pre-cut wires (or wires of your choice)
  • Set of 8 Spark Plugs (I used NGK TR55s)
  • Stage 8 locking header bolts
  • O2 wire extender
  • Assortment of Zip-ties
  • 1 Pair of O2 Sensor Simulators
  • 1 can of PB Blaster (or equivalent, e.g. Liquid Wrench, etc.)
  • Assortment of sockets, extensions, and boxed and open-ended wrenches
  • Safety Goggles (ask me what happens when you don’t wear them!)
  • Lots of patience and an extra set of hands


Before you do anything, disconnect the negative battery cable.  You’re going to be removing the starter and wrenching away, you don’t need errant sparks and you certainly don’t need to risk blowing fuses, etc.   No need to make this job more of a pain than it is already!

Jack the car and support with ramps or jack stands.  Try to get the car as high as you can safely, the headers are sort of tall and you’ll need all the room you can get.

Begin the night before by soaking down all the bolts that are coming out with the PB blaster or equivalent.  This will include y-pipe to manifold, y-pipe to catalytic converter, converter/y-pipe assembly to intermediate-pipe, etc.  You might also want to go ahead and remove the alternator since you can’t get to the passenger’s side manifold without doing so. 


Figure 1.  The TA is up on ramps and ready for surgery.


I was assisted by Brian Patterson, a fellow member of the Middle Tennessee F-body Association (www.mtfba.com).  I actually got started Friday night, getting the car jacked up and spraying down all the exhaust bolts with PB Blaster.  I had the driver’s side cat/down-pipe off the car a few months earlier and had chased the threads and anti-seized all the bolts at that time, so I was able to remove it with relative ease.   I also took a couple of minutes to disconnect the battery and then remove the alternator for access to the front bolts of the passenger side manifold. 

Figure 2.  The driver’s side converter assembly removed.



Early Saturday morning I got started again with Brian’s help.  He began removing the driver’s side exhaust manifold with an assortment of three different 3/8ths drive ratchets (one standard, two with various swivel handles) and a deep-well socket.  While he handled that, I worked on removing the remainder of the y-pipe assembly.  The bolts holding the pipe to the manifolds are 15mm and a deep well with at least a 12” extension and a ½ inch drive breaker bar is needed to break the bolts loose.  Throughout the install we used liberal amounts of PB Blaster, hands down the best penetrating oil/catalyst for loosening rusty bolts, etc.

In a little under an hour and a half, we had the driver’s side manifold off and the entire y-pipe and catalytic converter assembly removed.  After routing new driver’s side plug wires, we snaked the driver’s side header in from the bottom.  This header will go in from the top, but the steering linkage must be removed first.  I tried to break two different linkage bolts loose with no success and nearly began to strip one of them before we decided to install the header from under the car. 

Putting the header in from the bottom revealed yet another small problem.  The “quart and a half” size Mobil 1 oil filter I was using would not clear the header collector.  I removed the filter so we could get the header installed.  We took a break shortly thereafter and hit AutoZone for a new standard sized filter and 5 quarts of Mobil 1 5W-30 oil (I figured might as well go ahead and change it while I’m down there). 

I fed the header in from the bottom while Brian guided it from the top with the gasket in hand and a header bolt to hold the header in place.  Once you get the header supported by a bolt (probably one of the middle bolts is easiest), grab another bolt and work on the #1 primary.  Due mostly to the large 1 3/4ths primary tube size, some of the bolts are difficult to line up with their respective holes. 

The rear flange bolt hole on the number 1 primary tube is slotted.  To fit the bolt in, you have to hold the header out away from the head while inserting the bolt at an angle in the slot.  One you have the bolt, thread it in while continuing to hold the header away from the head until you have run the threads in a bit.  For this reason, this bolt needs to be the first one to be run in—the bolt used simply to hold the header up while working needs not to be threaded in very far.


Figure 3.  The driver’s side manifold is outta there!  The extra-large oil filter had to go for clearance reasons.


We finished installing the bolts, threw in the NGK plugs and wires.   At this point it was time to transfer the A.I.R. fitting from the manifold to the header.  We had the foresight to hit the fitting with PB Blaster after we removed the manifold.  When we came back to it, removal of the fitting was a breeze.   Make sure the threads are free from any dirt or rust and apply anti-seize liberally (meaning lots of it, not with a bent toward massive government programs and increased spending).

Once we installed the fitting, we realized the header basically relocates the output of the tube lower and to the right of the original position.  A quick trip to Lowe’s netted us two copper 90 degree elbows and some small hose clamps.  With a couple of short pieces of heater hose I was able to fabricate an adapter to get the A.I.R. pump output tube re-connected to the tube now mounted on the header. 


Figure 4.   The driver’s side header is in. Note the fabricated adapter for the AIR fitting.


Then it was on to the passenger side manifold.  This is where a 4th gen header install gets really nasty.  The front four bolts can be accessed from the top.  The fifth bolt is better accessed from the bottom while the 6th is blind and should be reached by leaning over the fender and using you’re left arm to access with a deep-well socket.  With one of us under the car and the other above, we tried to remove the manifold but kept getting hung on something.  Yes, we had the O2 sensor disconnected; OHHHHHHH, the EGR tube!  The EGR tube connects to the back of the manifold and should be easier to reach once the manifold is free from the head, just don’t forget like we did and tug on it for 10 minutes before figuring out the problem. 


Figure 5.  The passenger side manifold is finally out!  Can you see me in this picture?


The passenger side header also went in from the bottom, but it took a little more finesse to slide it through.  After we got the header in and secured with a couple of bolts, we had to loosen the power steering pump and the bracket that holds its and the AC compressor.  Two bolts hold the power steering pump to the bracket and four bolts hold the bracket to the block/head and one more at the rear of the AC compressor connects to the bracket.  All of this had to be loosened to get enough room to fit a tool to tighten the front header bolt. 

I recommend the Stage 8 header bolts for their Allen wrench compatibility.  We did use the Stage 8’s, but I didn’t have an Allen wrench that would fit.  I ended up using a 7/16th inch crow’s foot on a 1/4in. drive ratchet.  Subsequently I purchased a new set of Allen wrenches and can now access that bolt to tighten without removing all the accessory junk. 

Further complication set in at this point.  After tightening the passenger’s side header, it hit us that we hadn’t hooked the EGR tube back up.  That’s twice that the EGR tube would bite us.  It took over 30 minutes to actually get the bolt threaded into the EGR fitting on the rear primary of the header—its location is awkwardly close to the engine.

Next up was routing the new passenger side plug wires and installing the plugs.  Its best to install the plugs before tightening the header down, the number 8 plug is a particularly tight fit and it helps to be able to move the header a little.  I ended up purchasing an offset boxed end wrench to tighten plug #6.  For #2, I used the 3/8ths drive plug socket with an open-ended wrench to turn it.   Plug routing on the LT1 is no cakewalk, particularly on the passenger side of the engine.  The Taylor wires are close enough to the stock wires’ diameter that they will fit in the OEM looms, which made routing easier than if we had to route huge 10MM wires.   Next time I think I’ll route them over the valve covers!

After we got the topside taken care of, it was time to assemble the Y-pipe.  I had installed the driver’s side pre-cat O2 sensor before we put the header because the vertical position of the bung on the collector would have made installation of the sensor difficult.  On the passenger’s side O2, however, the bung is located horizontally to the ground, so I was able to put the sensor in after the header was in place.

This is also the time to install the oxygen sensor simulators to replace the post-cat O2 sensors if your car requires them (OBDII).  The use of at least a couple of wire ties for each simm is recommended to prevent them from coming loose and getting burned or melted by a primary tube or the y-pipe. 

We began installing the cats by firmly clamping them to the collectors. This proved to be a mistake, yet it was easily correctable.  It is important to remember to place the cats with the heat shields up (the side with the air-gap) or be prepared for hot footed driving. 

After sliding the three y-pipe pieces together  we had problems getting the y-pipe flanges to mate up evenly with the rear cat flanges and sliding that assembly onto the stock intermediate pipe we had problems getting the y-pipe flanges to mate up evenly with the rear cat flanges.  The stock 2.75 inch 1996 I-pipe was actually a good fit.  Since it was intended to slip fit over the OEM y-pipe it was actually nearly 3in. O.D. at its opening.

After an hour or more of fighting the tubing and beating on the clamps with a rubber mallet, I found a solution.  The key is to not clamp the cats to the collectors tightly at all.  Instead, I removed the nut from the clamp bolt, so that each cat was barely hanging there.   With the extra play, I was able to then put the clamps on the y-pipe to the cats, starting the clamp nut only a little bit without tightening at all.  Once those clamps were on, I went back to the front clamps and was able to squeeze them enough to get the nuts on.  With all four clamps threaded, I was able to tighten them all down and then install the three band clamps on the various joints of the y-pipe.


Figure 6.  Brian fights with the driver’s side converter.  Note the excellent ground clearance.


The stock intermediate pipe ended up being not quite so perfect after all. It was a little bit too long, maybe 1-2 inches.  As a result, it pushed the muffler and tailpipes backward and the tailpipes were periodically hitting the rear bumper.  I am convinced this is what made the y-pipe and converters install such a hassle. 

A trip to the muffler shop solved the I-pipe problem.  I had a cutout installed behind the y-pipe on the intermediate pipe, just before the over-axle bend.  The shop, Comprehensive Auto Repair Service in Hendersonville, Tennessee, cut an approximately 18-inch section from the I-pipe, which was replaced with a length of 3 inch aluminized pipe and the cutout.  Enough was removed from the I-pipe to drop the tailpipes into their normal position.

All together this install took nearly 20 hours, only 8-10 more than FLP suggests for an automatic car (stop laughing!).   If I subtract lunch at Arby’s, a break for supper, three trips to AutoZone for tools and oil & filter, and one trip to Lowe’s to get parts for the AIR fitting dilemma, it really only took about 16 hours! 

We did re-learn a valuable lesson that weekend:  Anytime you start a weekend project and your wife or girlfriend asks you about how long it will take, always multiply how long you think it will take by 1.5.

Power with the FLP headers is unbelievable; the car does feel much more like an LS1.  I’ve driven the car with both the catalytic converters and the supplied off-road pipes in place and cannot feel a power difference between the two.  FLP says they have observed several stock LT1s produce more power with the cats in place. 

Placing the car on a Dynojet chassis dynamometer provided us with new power numbers.  Prior to the headers, the car produced 255 horsepower and 289 ft-lbs of torque to the rear wheels.  With the headers installed, its output swelled to 282 horsepower and 317 ft-lbs, a net gain of 27HP/27FT-LBS.  I wanted to make a pull with the cutout opened but we ran out of time; I know of a similar near-stock LT1 with the FLP’s that picked up 15 horsepower and 15 ft-lbs with the cutout open.

The FLP longtube headers are a great purchase and are becoming a popular choice among the LT1 F-body crowd.  They are not cheap by any means, but they are well constructed and come as a complete bolt-in package.   The system offers long-tube performance with good ground clearance, resulting in a system that is very livable on a daily driver.  To top off the positives, Finish Line Performance offers great customer service.

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