Though I'd post up some pic's I took a few weeks ago from the fuel injector swap on my '92 Corvette.  These injectors are the Bosch III design sold as a replacement set of injectors for the '86-'92 L98/LT1 equipped car's.  I purchased them through one of our sponsors (Fuel Injector Connection) last week and they arrived just in time for me to install them over the weekend.  

I figured I'd write up a little "how-to" about the install on an LT1 in case any of you had plans of one day doing the job yourselves.  The entire process really only requires about 20 minutes of actual work.  Some may want to take a bit more time like I did to clean up the fuel rails like I did and snap off a few photo's but all in all, this job can be done in no time.

I went with the Bosch III's  because they come highly recommended by those who've used them and I've read nothing but good comments about the Bosch's performance as well as Jon over at FIC for his great customer service.

Here are the Bosch III's right out of the box as shipped from F.I.C.


I first removed the gas cap to release any built-up pressure and disconnected the battery.  After removing the fuel rail covers, I started off by removing the locking clips that secure the plugs to the injectors.  Each injector has one locking  clip for a total 8 clips all together.  Then I removed the 4 bolts that secure the fuel rail in place with a 10mm socket and finally removed the small vacuum hose connecting the fuel pressure regulator to the intake manifold on the passenger side.

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Very carefully, I pried up on the fuel rail's one side at a time to pull the injectors out of the bungs on the intake manifold and gently flipped the fuel rail backwards towards the windshield leaving the injectors pointing upwards.  (At this point, you're going to want to slide a tray or lay down an old rag underneath the fuel rails for the next step as there will be some fuel leakage from the fuel rail after removing the injectors)




Before you can remove the injectors from the fuel rail, you're going to have to remove the locking clips that are holding them in place.  I used a small flat head screwdriver to carefully pry and slide them out. (The newer style Bosch III's don't require the use of these clips anymore so you won't be needing them any longer)

Keep in mind that there will  still be some pressure left inside the fuel rail, so when you take out the first injector, be sure to have a rag underneath it to catch/absorb and fuel spray that may occur.  Once you've removed all eight injectors, remember, if you're going to turn the fuel rail over to clean/polish it up before it goes back on, keep a rag/tray underneath it to catch whatever fuel that's still inside the rail.  There's not a lot, but you don't want to get any fuel accidentally falling into any electrical connections. - Better safe then sorry...

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These are the old Multec's that you'll be taking out and a shot of them side by side with the new Bosh III's:
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Here's are some shots of the a new Bosch III injector and the old Multec for comparison.  You can clearly see from these photo's that the Bosch's are a lot thinner in shape than the old Multec's and weigh only about half as much as well. :)

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Because the Bosch III's are factory replacements, their connection is identical to the Multec's:
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Bosch III spray nozzle compared to the Multec:
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Side by side comparison from both ends of the injectors:
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After taking some comparison photo's of both injectors, I got back to work. The Bosh's III's come with new o-rings already on the injector.  I used a bit of dielectric grease around the rings on both intake and fuel rail sides of each injector to help them slide into place.  You're going to want to place the injectors in the intake manifold side first by gently rocking them side to side until they slide into place.  DONT try and "twist" them into place!
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The new injectors are in place on the intake manifold side:
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With the injectors in place, you're going to flip the fuel back over and "GENTLY" position it so that the top of each injector fit's snug within the bungs of the fuel rail.  Once all eight are in place, install the 4 bolts back into place and tighten them by hand. Be sure to continuosly check all eight injectors to make sure they're going in straight as your tightening, otherwise you'll run the risk of damaging one if it's not lined up with the fuel rail properly. This is why you tighten them by hand first.  

I started with the front two bolts and worked my way back.  Once I had tightened the bolts as much as I could by hand, and confirmed that all eight had seated properly within the fuel rail, I tightened them the rest of the way with a socket wrench.  Remember, the intake manifold is aluminum, as is the fuel rail.  You don't have to torque the bolts down too hard otherwise you'll dent the fuel rail or even worse, strip the screw threads in the manifold opening.  Just tighten everything nice and snug.

Finally, plug each injector plug back in to their respective injector and reinstall the holding clips.  They simply slide right into place with a push of your finger and lock the plug firmly into place.  Next, remember to attach the small vacuum line back into the fuel pressure regulator and intake manifold.
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That's about it as far as installing the fuel injectors.  At this point, you can throw the fuel rail covers back on and reconnect the battery...
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Now, unless you've changed out your fuel filter recently, odd's are you're going to want to replace it the same time you do your fuel injector swap.  There's not much point in buying and installing new injectors only to foul them up after a couple month's because your filter is allowing contaminants to pass through.

I picked up a replacement fuel filter from Napa.  Cost was only about $10 but in my case, it was definitely worth it.  I didn't take any photo's of the install because there's not that much to photograph.  The filter is located on the passenger side just to the right of the exhaust manifold.  Because I have headers on my car, I had more clearance to work with but it was still a bit of a pain.  You'll need both a 13/16 and a 5/8 wrench to loosen the fittings.  Again, be careful when prying the hard line out of the filter as there is still some pressure left in the line.  Be sure to have a bucket or pail underneath the filter. You way also want to wear a set of safety glasses just to be safe.  Gasoline really stings if it lands in your eyes.  Ask me how I know... :lol:

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Taking the new filter out of its box, I held it to my lips and blew into the end of it.  It required no effort at all and I could feel my breath passing through to the other end of the filter.  

After removing the old filter and trying the same, I was amazed that I had to blow into the end of it as hard as I could, just to feel ANY air passing through it. :eek:  

This was obviously the original 17 year old filter and it showed.  I was surprised the car was even able to run at all.  Just for the hell of it, I decided to cut the filter open to see its condition.  You can see from these pictures that the pleats have basically turned into stiff pieces of cardboard.  I tried to spread them apart and they literally started to crumble in my hands :eek:  




Anyways, by now your injectors should be installed, as well as your new fuel filter.  Double check to make sure all the fittings/plugs/connections/vacuum line are all attached and secure and if you haven't already done so, re-connect the battery.  Before you attempt to start the car, you're going to have to prime the fuel system.  Simply turn the key to the "start" position and wait for the fuel pump to come on.  Wait until it stops, then turn the key off.  

Wait a few seconds and repeat the process.  Do this about 4-5 times to build pressure in the fuel system and then start the car.  It may take 2-3 cranks but it will turn over.  Once again, inspect the injectors and fuel lines for any leaks.  If you're satisfied all is well, take your Vette out for a spin and put some miles on her.  The ECM was erased when you disconnected the battery so you're going to have to drive the car around for a while for the computer to basically "re-learn" everything over again so give it a bit of time.  :)


CONCLUSION:

After driving the car the past few weeks,  I'm happy to say that the car does in fact feel better than before.  How much of this has to do with the fact that the car's got new injectors or the fact that I replaced the fowled up fuel filter remains to be seen.  According to my tach, my idle was pretty solid before I started this project, but like I said, it just didn't "sound" right and I'd hear an occasional "sputter" from the exhaust every now and then while it idle.  That "sputtering" sound is now gone.  The car's throttle response seems more responsive then before and the just feels a lot smoother during acceleration at wide open throttle.  Fuel economy has also seemed to have been improved by about 1 mile per gallon by my calculations.  Nothing huge, but a more than welcome "side-effect" of the new injectors.


Anyways, hope this post helps some of you.  The job isn't very difficult at all and can easily be accomplished by someone with basic hand tools and is not afraid to get their hands dirty.  All in all.   A worth wile upgrade.


Big thanks to Jon at Fuel Injector Connection


LT1*C42009-08-18 10:38:58

Good job and a superior write-up!

thanks....I did the same and was able to chirp tires in 2nd gear.



Jim

Phil that was one great write up, thanks from all of us.  And having pictures for those of us handicapped by lack of comprehension was really helpful  .  I did my fuel filter about a month ago and injectors from FIC are on my winter project list.  Excellent job.

great write up. will be replacing my injectors again when the car comes back from the body shop. replaced once with 24# injectors which said they would not cause any problems as the originals were 22#. jon from fic said that the computer can recalculate at idle to keep levels right but can not when you are driving. said the car would run rich and eventually ruin the cat plus mpg will be lower.

wish mine were as easy to change as yours were.on my 90 you have to remove the plenum and the intake runners. the rest was pretty easy as you described.


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the dynamic duo

c3vr life member #97

I just read your write-up.  EXCELLENT PRESENTATION.  My '91 Z is running good right now, but this info is good for future reference.  This past spring I had replaced my ignition coils because of a "stumbling" issue I was having with the car.  It was my first experience at removing the plenum. Intimidating it was, but I wouldn't hesitate to do it again.  I also have photos of the progress and will have to post them as well. 

Any body give me some pro's and con's about the 1992 ?  I am looking at a primo one owner convertible.  Need something to help me make-up my mind !!  (My wife says I have no mind, but thats besides the point !).