Intake Manifold Install


This is the photo doc of the TPIS intake install on my 86' vette.

The popular talk in the Corvette community regarding the weakest single point in the L98 engine
(used in Corvettes from 1985-1991) is that it is the intake manifold.  I chose to remedy this deficiency
by installing a TPIS's "Big Mouth" intake manifold and their large tube runners.  I also had my Plenum
 ported by TPIS and I had my injectors serviced by "Cruzin' Performance" at the same time.  The new
 intake would change my air/fuel ratio, so an Adjustable Fuel Pressure regulator would be added to
 remedy that situation as well.  The project was actually spurred by the injectors, as they were leaking
and causing a hard "warm start" issue.  I decided to swap the intake since "It was only 12 bolts away,
once the injectors are out!"  I think this "While were in there" mentality is possibly the largest single
contributor to sales in the after market parts industry.

Anyway, we begin our story here:


This is my car before I started the intake work.  As is clearly displayed, it made 213.5HP and 309 lb/ft of torque (I try to use the 2nd pull of all my dyno runs for consistency)
The car had TPIS Long Tube Headers on it (you can read about that install here),  and a high flow cat, otherwise the car was stock (with leaking injectors no less).

So here is the stock intake:


The swap process concept is pretty simple, everything that has a bolt attached to it starting from the top of the plenum down to the intake manifold, must come off the car.
I began by draining about one gallon of coolant from the radiator.  Then I removed the air intake duct and MAF and then the throttle body. That gets us here:

If you are just trying to remove the plenum, you don't have to remove the throttle body, but since I was mailing mine out to get ported, it needed to be separate.

My next step was to go around disconnecting things that were attached to the plenum and intake, such as the brake booster vacuum line at the rear of the plenum:


I labeled everything as I went, and mapped bolt locations as well.  The runners are easier to remove if the plenum is out of the way first.  To remove the plenum,
 I needed to loosen all the bolts on at least one side of the car, and loosening both sides makes things easier.  The lower bolts are difficult to get to and I used this setup to get at them:

The TPIS large tube runners don't even have enough clearance for the stock bolts in the 4 lower bolt points, and so they supply
 four 6mm allen head hex bolts which I had to remove the valve covers to install (more on that later)!  

Once I had the bolts loose, I disconnected the Intake Air Temperature sensor (IAT) located on the bottom of the plenum, and the vacuum lines and removed it.
  Here is a shot with the plenum removed:



And here is a shot of the plenum off the car.  You can see the IAT sensor as well as the 2 vacuum line connections and the brake booster connection as well.
You can also see one of my bolt maps in the background.



With the plenum out of the way I began working on removing the runners.  I had to remove the cold start injector line from the driver's
 side fuel rail.  This is definitely easier with the plenum removed.  I prefer to remove the passenger side runner first
 as each side has 6 bolts holding the bottom of each runner to the intake. 5 on each side are on the outside,  but 1 bolt on each
 side is on the inside, under the plenum.  The passenger side has it's inner bolt at the front of the engine.  The driver's side bolt is
 at the rear of the engine.  Even with the plenum removed, the passenger side is still easier to remove first, and having it out of the
way gave me more room to get at the driver's side interior bolt.  You can see both the interior bolt (under the fuel rail crossover pipe)
and the rear exterior bolt  (and how I got to it) in this pic.  It's tight in there!



With both runners removed I was ready to disconnect and remove the fuel rail.  When I first disconnected the fuel
 supply lines was disturbed by the amount of fuel that was coming out .  I got nervous and sealed the system back up
 before I realized what I had done.  In my infinite wisdom of planning the intake swap I had topped off the gas tank because
 I knew it would be several weeks before the car would be back on the road, and I didn't want to run the risk of condensation
 forming in the fuel tank.  My garage, aside from being unheated, has also settled a bit and has a slight slope to it.  The slope
 was enough to put the top of the fuel tank above the fuel supply line outlet at the engine, and thus gravity was pulling the fuel
out of the pipe.  I remedied this issue by jacking the front of the car up , but  I still made a mess of things, as seen here:



With that little emergency handled, I was able to get back to removing the fuel rail.  The send and return line o-rings were original and looking quite tired:


I got a new set from my local Chevy dealer (I tried the local auto parts stores, but theirs were all black, and I was told that the tan color indicated a different
 heat range or something like that.  At any rate, for less than $5 , I wasn't going to take a chance on a leak or a fire.  Here is a shot of the new and old o-rings together:

With the send and return lines disconnected, I was able to pop the fuel rail assembly out of the intake.  After removing the 4 mounting bolts,
 I used a flat blade screw driver with the blade on the center of the intake to act as a lever to push the fuel rail up and free the injectors.
  It took a decent amount of force, as the injectors did not want to let go of the intake.


The rail comes out as a single piece and you have to spin the retaining clips on each injector and pull them free to get down to just the rail.
I could tell these parts had been together for 20 years!

With the fuel rail removed, I was down to the EGR valve, the EGR pipe, and the distributor as the main items to remove before I could pull the intake.
Since I had never pulled a distributor in a V8 before, I decided to turn the engine by hand to #1 cylinder, Top Dead Center.  If you are unfamiliar with the timing mark on the L98, it looks like this:


I then marked the distributor and took a number of before and after pictures as a reference to where it was and which way it shifted as the gears disengaged.


With the distributor removed I was able to remove the EGR pipe, and then the EGR valve.  That left me with three little connections at the front of the intake:

One is the coolant line to the throttle body, one is a temperature sensor,  and I forget what the third one is.  Luckily, the connectors are all are different,
 so there is no confusion. There are some sensors at the rear of the intake, but they are not actually attached to the intake, so I didn't have to remove them.

At this point I was down to the bare intake!  I really was "only 12 bolts away" from having it off the car!


I think I went through 3 cheap Torx bits before I got smart and bought a decent one (Craftsman).  The bolts that wouldn't budge with the cheap bits came right
 out with the Craftsman bit.  It was a lesson in tools for me!

Once the 12 bolts were removed the intake came free with surprisingly little effort. After that, it was time to clean.


In addition to cleaning the heads, the bolts weren't looking too good


After purchasing a small tap and dye kit, things were looking much better.   I chased the bolt holes as well.


It made an awesome difference in how easy the bolts went back in!


Speaking of getting bolts back in, after I transferred all the sensors, and accessories to the new intake, I laid out the head gaskets, ran a bead of
Permatex's "The Right Stuff" gasket maker along the front and rear channels and dropped the intake in place.  Pucker factor, slightly high!


Even though I had a more experienced friend helping me out with the actual intake install, it was still a dramatic moment for me.  It was the deepest I have ever been in an engine.

Now this should be the part of the story where I sound like a  repair manual and tell you that reassembley is the reverse of removal, but that is not how it worked, and so the story continues!

The intake manifold itself was not a problem, and it went on without a hitch.  The distributor also dropped back in and while I thought I may
 have been slightly off, it turned out that I was dead on.  The fuel rail was the next item on the list, and while the little torx bit that came with the
 AFPR broke during the recheck of the fasteners, it did make it through the installation.  Now, according to the TPIS installation instructions, you
are supposed to install one 1/4" thick washer on  each fuel rail mount stud, and place the fuel rail on top of that.  This is because they claim the
original casting is too short and the little washers will fix it.  Considering the age of the L98, and the amount of time that TPIS' manifold has been available,
 I found this to be strange, and thought  this would have been recognized,  and the casting would have been changed by now (dec 2005).  None the less,
 I dutifully installed the washers and fuel rail assembly as shown below.


Once I had the fuel rail installed, I proceeded to install the new EGR valve, and the intake runners.  While I didn't know it at the time, the EGR
valve base needed to be filed down to fit properly, and not having done this caused a vacuum leak.  This was an after market EGR, however.
  At the time, though, I had more fun things to deal with.  The TPIS big tube runners are larger than the stockers (obviously), but unlike some other manufacturers,
 they did not change the bolt mount on the lower points on the runners.  Thus the factory bolt heads are too large to even fit into the space,
so TPIS provides you with four 6mm hex head bolts.  This is fine except that if the valve cover is in place you cannot get a straight shot at the bolt holes.
 If you have a special Snap-On tool, you can install and remove these bolts without removing the valve covers.  I did not have this tool when I put the
car back together,  but I do now.  Below is a picture of the tool I used (on the left) and the tool that would have made my life easier (on the right).

The ball on the end of the Snap-On tool lets it operate normally at a significant angle.  I tried to buy one at sears, but I was told they do not sell
a ball end hex key tool with a 3/8 drive socket on the end of it.  The socket is nice to have because all of these bolts have a torque requirement.
As I mentioned above, I did NOT have this tool when I put the runners on the car, so I had to remove the valve covers.  This seemingly simple
chore is made more complicated by our friends at General Motors.  As you probably know each valve cover has four bolts that hold it to the
cylinder head.  These four are easily removed, and the valve cover is free to move.  Well, perhaps "free to wiggle" is a better term.  On the drivers side,
the valve cover is bordered by the wiper motor housing in the rear and blocked from any significant movement by an air pump mount bolt sticking just
a couple of millimeters in the way.  The red arrow is pointing at the offending bolt:


Thus to remove the driver's side valve cover you have to remove the air pump assembly.  Technically there are other shortcuts, but I wanted complete
flexibility to help make sure there was as little chance as possible to incur a valve cover gasket leak (since I didn't even want to remove them in the first place!)
Removing the air pump was surprisingly simple.  With the drive belt removed, I disconnected the air hose coming out of the pump, removed the bolt that holds
the bracket to the alternator (the blue arrow), loosened the other bracket bolt so it would swing free of the alternator and then proceeded to remove the one
nut and two bolts that hold the air pump to the motor as shown below.


With this done, the whole pump/bracket assembly lifts off the car and I had plenty of room to maneuver the valve cover.  
This took care of the driver's side, and so it was off to the passenger side where the hilarity continued!

  The 2 main obstacles I found on the passenger's side were the EGR tube and the A/C compressor's metal tube
connection point.  My car did not have any A/C charge it in at the time, so I was free to disconnect it.  As for the EGR tube,
 I  was a bit nervous about pulling the distributor to get a clear shot at the bolts that mount the pipe, so I broke the connection
at the crimp ring. There are also some other small items, but nothing frustrating. Here is a shot of the work in progress.


I have heard that you do not have to break the A/C connection, and I choose the EGR crimp ring because I didn't do a
very good job at reconnecting it when I installed the headers.  This time I had better luck.  The problem with the crimp ring
is that it is in a tight area and you don't have much room for tools.  Here is a shot of the ring:


As you can see, it is not easy to get to.  I found a tool at the local Harbor Freight store that helped out significantly:


Now the technique I used requires two people.  The crimper and the brave assistant.  The crimper slides the ring onto the tube and
with the ring up at the top (where it is easy to work with), uses the above tool to start to compress the ring to make it not so loose
on the pipe.  once this had been started, I moved it down into position.  At this point the brave assistant don's a heavy work glove
and holds the ring in position on the far side of the pipe with one finger while I used two hands to squeeze the mess out of the ring.
I found two hands were necessary and a lot of force was required.  This sows the tool in position:


As you can see the long handle of the tool allowed me to reach the crimp ring and have room to work as well.

This takes care of the runners and valve covers, but there were more obstacles to overcome.  The next main problem was the plenum.
When I tried to install the plenum, I found that it would hit the AFPR body before the bolt holes would line up.  I called TPIS and was told
that "all cars are different" and that some of them do not require the little 1/4" thick washers.  They said to remove the washers, and
if that fixed the problem, then I didn't need them.  Strange that this was not mentioned in the instructions?  I did that and the bolts lined up.
Here is a shot of the plenum installed without the washers, showing how tight the clearance is  between the AFPR and the bottom of the plenum:


As you can see, I don't have an extra 1/4" in there to install the spacers.  The only other major item I found during reassembley
was that the factory thermostat housing had to be filed down to sit flat in the space provided on the TPIS manifold.  I spoke with them later
about this and they  said that was the case in the 85-87 cars (no mention of that in the instructions either).


All of these steps allowed me to get the car back together and  see if it would run without leaking, etc.  I was please that the car started and ran on the
3rd try.  It had been off the road for almost 2 months, so I was impressed.  However, the car would not run well below 2,500RPM, and below about
1,500RPM, it would backfire, buck and die.  I thought I had the timing off, but given the way the engine was running, I didn't have the guts to stick my head
in the front of it to check the timing, so off to the local vette shop it went.  They found that the timing was not an issue but these items were:

I didn't have the cold start injector seated causing an air leak
I didn't tighten the coolant line coming out of the throttle body causing a coolant leak.
The EGR valve needed to be filed down to sit flat on the intake, causing an air leak.
The 4 lower bolts provided by TPIS were 1/4" too long and would bottom out before sealing the lower runners, causing an air leak.

With these items fixed, the car ran, but the injectors were much louder than they were before.  I called Rich at Crusin Performance and asked
about the injector noise.  He asked what else I had done to the car and I told him about the intake swap.  Upon mentioning that, he asked if it was
a Edlebrock or TIPS intake.  I told him it was a TPIS unit and he said that I needed the spacers to allow enough room for the stock injectors.  He
also said that the loud injector noise was caused by the injectors being pressed into the intake, and when they fire the sound resonates through the
intake manifold and causes the increase in volume.  This was annoying, but I had more important things to do, such as find out how much power
 all these changes had gained me.  I went back to the dyno,  but I had forgot that when I dynoed the car after the headers, I still had the original wheels on it.
When I went to the dyno after the intake swap, I had the new AFS ZR-1 wheels, complete with 11" rear rims carrying 315/35-R17 tires.  My friend
pointed out that there is a substantial weight difference between the stock wheel and the new larger after market wheel and that would affect the
dyno run.  I went back to the dyno with the stock rear wheels and made another pass.  Here is a shot of the car on the dyno, and the resulting graph it produced.


And the results:


The blue run was the second run, and so that is what I used.  As you can see the car gained 16.5HP and 17.9LB/FT of torque.

A couple of weeks later I began smelling raw fuel coming from the engine.  I inspected and found that the cold start injector O-ring had torn.
I could have replaced it, but the washers needed to be reinstalled (something else I could do), but that meant the space restriction needed to
be resolved, and it looked like the only way that was going to happen was to shave the bottom of the plenum to gain clearance.  I was NOT
going to try to do that.  So, back to the vette shop it went.  I found out that my mechanic didn't like the idea of shaving the plenum either, and
so while I no longer have a fuel leak, the noise is still there.  I also have a stumble in my idle currently, that I need to resolve.  I hope to resolve
my idle issue, but at this point (feb 2006) for the money spent and gains returned, I think I would have been better off just getting the injectors
 serviced and leaving the rest of the car alone.


Update November 2007: