First off I would like to give a huge thank you to those with intelligent posts insights and responses, they have been invaluable through the course of my build. I know there have been a number of attempts at this chronicled on TGO but this is the story of a completed LT5 IROC build.

I purchased my 1989 IROC vert in 2014 it had been sitting on the side of the road for 6 years and still rust free which was amazing. After having it trucked home we got it running but the 5.0L TPI engine and trans were shot and it did not run very long and leaked like a sieve. As these things tend to snowball, I found a wrecked 1989 IROC with 5.7L TPI with same dove grey interior. I installed the 5.7L engine and trans along with the 9 bolt Borg Warner rear end with discs and PBR calipers. After swapping the engine, trans, 3” exhaust and rear end along with a complete suspension rebuild including all bushings my vert was on the road again. I then picked up off CL a set of 1LE front spindles with brakes and along with new braided SS brake lines and the car was again on the road and but it was not for long before the 2nd trans went out. At this point we located a T-56 from a 97 Camaro SS and the vert was back on the road and a lot more fun to drive. In 2018 after spending 4 months doing body work, swapping a door, a fender, rear bumper cover and the hood my IROC vert was finally painted in a Lexus tri-coat white color. At this time the Hawks 17” IROC 2 vein wheels were installed and we upgraded the rear gears to 3.73 with a stud girdle cover. So finally after 4 years of numerous upgrades, starts and stops my vert was on the road looking great and fun to drive. So the summer of 2018 and 2019 I put some miles on it attended a few car shows here in the PNW. Then in 2019 the upgrade bug hit me once again when I saw a 1990 ZR1 LT5 engine for sale with only 17K miles on it. I gotta tell you this is one of my favorite engines of all time and I had to have it. After a cross state road trip I had a LT5 sitting in my garage and was ready to tear my vert down again. After almost 2 years my vert is on the road again. Installing a LT5 in a 3rd gen takes some ingenuity and creativity. Originally I was going to use all of the stock sensors, ECM, waste fire coils, engine wiring harness etc. After some deliberation we decided to treat it like an LS engine and installed 8 LS coiIs with custom mounting system under the pleneum, removed the vacuum controlled secondary butterflies, ported the intake housing and plenum, deleted the throttle body coolant, built a custom wiring harness, modified the existing 1997 LT1 bell housing and drilling tapping 1 new bolt hole in the block. Machined a custom billet fuel block for the existing fuel rails.

I used the following major components in this build;

UMI K-member (modified)and control arms

Dirty Dingo adjustable LS engine mounts

MegaSquirt MS3 EVOPro ECM with a flying harness

OBX SS ZR1 headers, modified for the 3rd gen cross member

Holley 2.5” true dual SS header back exhaust system

Custom crank trigger based off the Holley kit

Custom dual 3” intake

4th Gen fuel tank with a Aeromotive 340 LPH pump

New 3/8” SS fuel lines from the tank to engine compartment

BMR remote mount battery tray

Fidanza flywheel



Per Marc Haibeck, based on the engine mods I have done this should be putting out 450+ HP at the crank based on his experience with these changes. On my first outing I can tell you this thing is crazy fast with a 7,500 RPM redline compared to the old TPI engine

For those of you not familiar with the engine or need a refresher as there are many incorrect posts about this engine please see the link below;

https://www.lsxmag.com/features/c4-zr-1-lt5-engine/

Cost wise this came out very close to a high end LS swap and parts are plentiful you just need to know where to look.

A big shout out to my son Cody who was with me all the way, my very good friend Soloc4, Bruce and his crew at Hawks, Mario from the Dub Shop for MegaSquirt tuning, Jerry’s gaskets, and Marc Haibeck ZR1 expert extraodinaar.

 

 

1990 LT5

 

 

 

Damn! Now thats a sleeper alright. Reminds me of the GM built 3rd gen back in the day. Love that engine, one of my all time favs. Excellent work, did you do that at home yourself?

 

Thanks, Yes all by myself and the help of a few friends

 

Looks great!

 

That's a cool car in anybody's book. Well done!

What did you do for the wiper motor? Hoping there's something small hidden in there because I could use more room too.

 

Looks better than the GM show car with its Hot Wheels Neon paint-job.

 

The wiper motor is one of my last items to cross off. I am looking at using the Nissan Maxima wiper motor. I have also read that an S10 wiper motor can be used. LSXMatt has the only install I have seen for the Nissan motor.

 

Ive been wanting to find/use one i could hide in the cowl area. Seems to have plenty of space.

 

Looks great. Very neat conversion.

 

I love it!
It is great to see something other than the common swaps!
Honestly awesome!

This makes me want to swap the Very-NEW GM (Cadillac actually) all aluminum 5.5L VVT-DOHC V8 from the new Corvette!
The LT6 (Impressively with a "Flat-Plane" Crankshaft):



Hyper-Link:
CLICK ME!

 

I have an 88 IROC vert Black/Gold like new and a 91 ZR1 Red/Red. Your IROC is amazing. I also collect 3rd gen IROCs and Trans Ams. If you want to sell it, I am very interested.

Joe 2707765512

 

I have an 88 IROC vert Black/Gold like new and a 91 ZR1 Red/Red. Your IROC is amazing. I also collect 3rd gen IROCs and Trans Ams. If you want to sell it, I am very interested.

Joe 2707765512

 

That is amazing and also my favorite V8. Great job more pics = more better

 

I always loved that engine. There was a Nomad featured in Rod and Custom years ago that had a LT5 and C5 rear transaxle. Also liked the one GM stroked and put in an Impala SS for Tim Allen.