Been working on a few upgrades/changes over this past winter. I had some engine trouble that turned out to be worn valve guides and something got into the cylinder on #6, creating some grooves. So motor was pulled and freshened up, heads are out for rebuild. Should be getting the heads back soon.

Anyway, I have been using a stock 91-92 ECM with 3 bar map sensor running Code $59 for the past few years. Works well but does have some limitations. Timing table control for instance only goes to 4800 rpm and resolution on map table is not as fine as I would like. You have decent enough resolution to make an engine run well but I have noticed limitations on what values I can enter into the table without having tunerpro RT reset the value to a certain number. Like if I wanted 42.85 VE at a spot, tunerpro may not handle that number and force it to something like 42.91 or 42.74. It was always making it a value somewhat close but not exact, and with big injectors, small changes are required. I also had some random ghost ecm issues that didnt go away with new ecms so maybe it was a bad wire somewhere, I just didnt want to mess with it anymore. My chip burners were worn out and no longer working 100% of the time and I just got tired of that too.

Oh well, so I decided to try this LS1 ECM conversion. I have an LS1 trans am, an L9H 6.2L sierra truck, all tuned by a close friend and shop tuner here in PA, so I figured why not add another LS vehicle to the stable.

Following the many threads here on thirdgen, and referencing many others for wiring diagrams, and pin outs such as ls1tech and austin thirdgen wiring section, here's my progress so far. Still got a ways to go and some questions but getting close.


* First off, I am only doing basic engine controls on this build. I have no emissions, no electronic trans, no fan controls. Fans were on switches on separate wiring but I may add one back to ECM control or head switch temp based control. We shall see.
So the only thing I really need is all the old TPI based engine sensors, just the LS1 version. This will be injectors, TPS, IAC, oil pressure sender, knock sensor, IAT, ignition based stuff, o2 sensors, etc. i am using ls1 tb so ls1 iac and tps sensors are required and fit this build perfectly.


I started off by getting a stock 99-02 Fbody harness for a LS1. I needed this to grab a few connectors and pins, and ofcourse the 411 ECM.


Stripped it down and organized


Most of that you will not reuse. I used the injectors harness, ignition common and ground commons. MAP i reused my 3 bar map sensor. Cam sensor and crank sensor are different for the 24X kit that EFI Connection sells, so you have to buy new pig tails there, but can splice in the wires from the LS1 harness so you can reuse the pins for the ecm side. Makes it easier.

Then I tracked down a stock TPI harness, MAF based since my 89 was MAF. I did this to get the rest of the thirdgen engine bay harness, starting with C100 connector at the driver side firewall. I did not want to cut up my stock orignal harness anymore than it already was, figured I'd save that for another thirdgen if I ever get one.


I basically followed Pockets threads on prepping a thirdgen harness for ls1. I kept everything I needed for my engine bay and discarded the rest. Items like wiper motor, wiper washer bottle wiring, fuel pump relay, etc were kept. MAF relays were deleted.



Almost stripped down entirely to basics I needed for my motor/engine bay.


I ordered the EFI connection 24X ring kit with plastic Vortec timing cover and cam/crank sensors/pigtails/etc.
Installed 24X ring on my Rollmaster double roller. Seems to fit fine.


Heres the plastic cover. Needs some silicone around 2 spots, and near the base by the oil pan gasket corners. Other than that, seems to fit fine.
NOTE: you need a very thin harmonic dampner to clear the cover and sensor! I did not shave this dampner down to make up for the ~.093" thick 24x ring! I will space my accessories out instead. My first balancer was a Romac I used for years and I did shave it down, tried to install and it hit the cover before seating all the way. You need a thin balancer shell, the ATI super dampner is very expensive but is 1.200" (aluminum version). My romac was 1.75" and too fat.



Next was basically using the intake manifold and mocking up the sensors and stuff. Running wires back to the ECM. I measured approximately how long the harness needed to be to mount ECM under dash like TPI ecm.


Didnt have my heads back yet, but still got the engine mockup somewhat accurate. I really wanted the heads and exhaust mounted to route the wires better but this works.

 

Most of the sensors are run to the ECM and pinned out.
NOTE: ignition coils 2&3, 4&7 need swapped as do the injectors at those cylinders. Firing order is different between SBC and LS1 so this was corrected at the ECM pin out


Another shot of the rear of motor mock up



I started laying in the new C100 side harness and taping up the wires, and getting an idea where everything will go.


wiper motor connector is in and lower right side mass of wires is for the oil pressure sender and I need to cut and splice in the new sensor connector.


Thats about where I am at now. Need to pull the C100 side and integrate it into the engine harness side. Mock up the starter on the block and connect the wires to that.

Tape it all up and then cover it in the OEM style plastic wiring tubing

 

I'm curious to see how this turns out for you. Everyone I've seen using the 24x doesn't have quite the creature you do. I wonder how much of a difference you'll see between the two operating systems considering how radical your combo is. I'm in the middle of collecting my conversion for my LT1 so I have a sorta vested interest.

 

If this craps out i have my old wiring i can easily swap back in so its all good. I dont expect issues tho. I believe the crank sensor is aligned right since i have a double roller chain thats not a cloyes that efi connection recommends but seems to fit. Also not using vortec dampner but that shouldnt matter, the accessories will fit with spacers. So we shall see. Havent had any updates in awhile but waiting for my heads to come back so the motor can go in and i can finalize wire layout. Thats about all i am waiting for

 

Did you think about cutting down your dampner? I've heard of that being done. Though I guess the spacers are easy enough for your setup. Either way I can't wait to hear your results.

 

I made that mistake on my Romac dampner. I didnt test fit it and had it shaved down the thickness of the 24x ring. Go to install using the vortec dampner only to find it was too thick on the shell and hit the cover/sensor before snugging down all the way. So i have to find a thin dampner which i couldnt find without spending a ton on a ATI super dampner.

Oh well. So now i have a romac paper weight unless someone makes a spacer. Or uses washers behind pulley to space it out. Its only about .093" thick

Did not want to cut down a 375$ balancer so i left the ati alone. If it throws belts i can space my custom brackets out.

 

Thats how i feel, its nice to have only a few accessories with custom brackets, im running alan grove brackets w/ electric wp.

Stoked to see how this turns out for ya man, i just picked up efi connections original 4x kit and im stoked to see how it turns out.

Ill be following this, and good luck!

 

Havent made much progress. I stopped because i was waiting for the heads to get back from the head guy and i was gonna finalize motor assembly and drop into car. Well i ran into issues with the rocker stands so now need to work with the manufacturer on a new stand for the shaft rockers to better fit these heads.

Once all thats done i can get it back in the car and finalize the wiring. I need to mockup the exhaust stuff so i know where to route some of the wires and coil packs. Then need to finish the hydroboost brake system and oil cooler routing. Once thats done its about ready to run.

Plan is to bypass the turbos to simulate all motor to establish a base tune and verify functionality. Break in motor and then reconnect the boost

 

Has ATI offered slotted dampers for CnP or COP conversion?

 

I do not know for sure but i dont think they do currently lol. It be easy cuz they are 2-3 piece design and just need to swap center hub out

 

Awesome. Subscribed.

 

OK month ago or so I finished the harness. Heres updated pics of the progress.

So after the C100 harness side in the engine bay was completed, I took it out of the engine bay and integrated back into the engine side harness.

I measured from about the point where the distributor would sit to the C100 connection and used that dimension to connect the wires to the main harness.



After the main ignition PINK wire was connected, everything else I laid out and taped up



I shortened the starter wires and rerouted on the trans tunnel



AFter it was all taped up, I use electrical conduit to wrap up the wires like a factory harness.

 

Motor is finally back in the car and ready to finish bolting all the parts back together Had a major issue with the solid mounts I tried to use, couldnt get the motor to line up at all. Went back to stock clamshells with poly bushings and it worked fine. So with that done, I can do everything else. Installed hydroboost and working on my oil cooler now. Then its bolting all the exhaust and stuff back in, laying in the wiring harness and finding a place to mount the coil packs.

With my downpipes going over the covers, I cant put the coil packs on the covers. I need to make custom brackets for the coils and find a place to mount them. Perhaps to the fuel rails / intake elbow bolts. That could easily work. We shall see

 

Subscribed!

 

Can't wait to see the results. Glad you found some engine issues. You're going to think I'm nuts, but I always thought this setup had more in it than you were getting from it. Hoping that I'm right, she should be in the 8s.

 

Oh no doubt. I built this combo to be high 8's on pump gas. Last year with the valvetrain issues, it was severely restricted in potential. Short shifting 800 rpm and wrong converter in the car, it still showed some massive top end potential on low boost and no real tuning, at street weight. Hope this efi system allows alittle more control and power upstairs. New trans brake and converter will cut down atleast a second and a half so its gonna fly

 

Looking Great.

 

I like it a lot, I just wasnt going to spring for 24X unless I was going Coil on Plug, other wise the 4X from a vortec is a bole hunkin funch cheaper, just my 2 cents it is a cool setup i gotta admit.

 

Decided to mount coil packs to the fuel rails using custom made aluminum brackets I made. Worked out nicely although abit busy


finished hydroboost install. Mounted the 4th gen master cylinder today


Hotside is bolted back up, exhaust is all in, and tranny/converter are mated to flexplate.

I used LT1 92-96 corvette MSD plug wires for these coil packs and it worked out nicely. The wires were alittle long in some locations but I was able to route them around enough to make up the length.







Motor is together and ready to start, after I bleed brakes and prime oil, fill trans up, few minor wires, etc. Hook up coldside feed pipe and thats it.

 

Another shot of the coil packs mounted to rails





Laid the wiring harness on motor and started routing it, and eventually it fit like a glove Motor pics above were final wiring harness layout



ECM connectors fit through stock hole, with plug removed.

 

Motor is together and running. Wiring is correct and done right lol car fired on second crank after base file was loaded in. My friend is a good tuner

Initial impressjons it is clear that this ecm is superior to the old stock gm with code $59 i used before. I spent alot of time on that code and never could get idle and free revs and cold starts to be perfect. Always left more to be desired. Cold start was never consistant. Free revs were not good either, i played with that map for days and just never could get it smooth.

Within 3-4 reflashes for adjustments the car was running smooth as silk. Maybe its sequential inj or superior modern ecm command, but this motor is a new animal now. Smooth idle at 860-880 rpm, starts instantly, even on cold starts. So far seems to free revs fine but havent went over 2500 yet, just blip throttle.

I have high hopes for this setup. Driveability should greatly be improved. Gotta fix a few things and then it should be ready

 

Good to see it working for you. Never heard any complaints after that PCM upgrade

In hindsight, how difficult did you find the build?

 

Well, i had experience in repinning maf to sd on tpi so i was somewhat familiar with tpi wiring. I also have a ls1 car and ls1 tb in my sbc car anyway, so alot of the sensors and things were somewhat related, and i was familiar with that.

That being said i didnt find this swap totally difficult. The links by you Pocket regarding general lsx wiring stripping and converting helped. It was just a matter of finding good wiring diagrams for the year harnesses you were working with and then labeling wires. Making a mockup of the engine and laying wires out. I soldered everything which was time consuming but easy to do.

Efi connection threads on obdII tpi also were good links after sifting thru all the posts as there were alot of cross talk about various things and questions that didnt help. Other than that it was fairly straight forward, there are only 3 pieces you need. Cam sensor distributor with pigtail, crank 24x ring with sensor/pigtail, and timing cover which i used the vortec factory one.

The difficult and expensive part was finding a balancer to fit. It needs to be very thin on the shell or it will hit sensor before sliding onto crank all the way. Waterpump needed clearanced on the housing to clear the cover as well, the part where it meets the block and bolt hole bosses. Only one i found was ATI super dampner at 1.2" thick i believe. Near $400

Other than that, harness integration and layout was easy just time consuming but thats good. Makes you take your time and make sure all wires go to proper locations. Very nice to not have fans, ac, emissions, etc wired in. Really cuts down on the pin outs lol

 

Glad to hear its working

This is now in the top 3 list of my future mods

 

Finally street tuned and dyno tuned medium high boost.

Street tune went well but i had one dead o2 so closed loop was running amuck. Went open and no issues now. Will fix that later.
Car drives great, had fun working on it. Did have some issues with cam position sensor codes for circuit high and low. Occassionally stumbles on starts. Like it cant find signal and doesnt fire but next crank fires fine? Not sure what that is.

Dyno was fun, started tuning gate spring itself and saw 8psi. Got 500whp out of it and turned to 7100 rpm with good power curve. Cranked it up 4 psi made 621. Another 4.5 since we ran out of wastegate spring, 770whp 700wtq thru this big stalled automatic 400. Thought it would be mid 800's at that boost but oh well. Ignition and fueling worked flawlessly. Now gotta check to see if my alternator is charging and fuel pressure isnt dropping. Going to push another 8 psi or so and shoot for 1000

 

Yee Haw! This is your daily grocery getter, right?

 

Update... See power adder section. Made 1009 whp sae corrected at about 24.5 psi, 270 kpa peak, and still pulled near 7k rpm. System is working well. Every now and then a hiccup on startup with cam sensor i believe. I did get a code for that a few times. Not sure why. But oh well it clears up after a try or two

I plan to drive this alot this summer. As much as possible

 

oh how i love every build youve had so far of this car.

 

Ever figure out why you were throwing the cam position sensor code? I am having the same issue. You try to crank it and it won't fire....turn the key again and it fires right away.

 

Is the vortec distributor cam sensor ring a true 180 degrees? I thought I read someplace that it was something like 165 degrees or so. I'm probably totally wrong about that, but has anybody verified that it is? if its not truly 180 degrees could that be upsetting the computer? Or is the Vortec CMP sensor itself not providing a strong enough signal to the PCM. Do you have much end play on your distributor? I almost always add some more shim to reduce distributor end-play. Since the gear is helical cut your distributor shaft will advance/retard quite a bit if the shaft travels up/down. Just a few thoughts.

My 54 pickup has a 454 that will be getting the 24x and 411 treatment sometime soon (twin turbos too) so I am very interested in following your progress on this.

 

Nope lol havent seen the code in awhile tho. Car sometimes fails to fire on first crank like you describe. Next try fires fine. Dont know

 

i have a couple examples of 24x cars to add-

local friend never got his 24x lt1 to fire. said the cam sensor wasnt picking up. he wound up pulling it all back off and putting the opti back on it after much discussion with the owner of efi connection involving an oscilloscope and stuff. 355 with lotsa nitrous.

the LT1 i've been working on works fine with the 24x. its headed back to its owner now, and hopefully will be getting tuned sometime this year. 388 with a ysi vortech.

 

Thats strange. It does appear to miss timing so to speak on cranking. Like said every now and then it will crank few times and not fire. Sometimes it fires immediately. But if it doesnt fire the next attempt always fires

 

I had the same issue with mine. Ended up being two pins in the connector were not locking properly in the connector pushing the pins out just right to give issues. Put new pins in and its been fine ever since. Mine however would hiccup when driving if the pins got wierd.

 

I assume you are refering to the cam sensor connector? Using eficonnections sensor and pigtail. Looked to be pretty solid but will double check.


Does it matter which way you clock the housing? Once installed in motor?

 

Yes the connector. Im using hp efi, so I oriented the window to hit the sensor at 195 btdc, I believe the ls is a little different. I clocked it so it worked the way I needed it to. Been fine ever since.

 

LSx and vortec cam connectors are different, but the terminals swap over using a pick

 

its been along time, but, howd this turn out? any final updates? still have the car?