Cheap ICM
Thread Starter
Launching!
Joined: Apr 2013
Posts: 225
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HEI ICM on LT1 Awhile ago I posted a thread about using the ICM from a 80s HEI in place of the LT1 ICM, I made a diagram to show what I was thinking.
I deleted that thread, because all I got was flame for "trying to re-invent the wheel"...Well I am now creating this one because it does indeed work.
Using the fair amount of SBC parts floating in my garage (free HEI ICM) and the fact my brother needed a new ICM I told him about my idea. He tried it and I have seen his car running using the HEI ICM with the LT1 FI.
I have not had time to record a video yet.
After the sheer amount of flame I got last time for being willing to try something new I will not re-add the diagram I made until I have a video also.
If a simple video showing the HEI ICM hooked up and running the car is not enough, I don't know what would be.
Diagram
PhotoBucket
PostImages
Alternate
My brother recorded the video.
I deleted that thread, because all I got was flame for "trying to re-invent the wheel"...Well I am now creating this one because it does indeed work.
Using the fair amount of SBC parts floating in my garage (free HEI ICM) and the fact my brother needed a new ICM I told him about my idea. He tried it and I have seen his car running using the HEI ICM with the LT1 FI.
I have not had time to record a video yet.
After the sheer amount of flame I got last time for being willing to try something new I will not re-add the diagram I made until I have a video also.
If a simple video showing the HEI ICM hooked up and running the car is not enough, I don't know what would be.
Diagram
PhotoBucket
Spoiler!
PostImages
Spoiler!
Alternate
Spoiler!
My brother recorded the video.
Last edited by ChevyOwner; Dec 17, 2023 at 04:19 PM.
Thread Starter
Launching!
Joined: Apr 2013
Posts: 225
Likes: 0
IMO the two main advantages are cost and availability.
In my area there are 3 Napa stores, 4 CarQuests, 2 AutoZones, and 2 soon to be 3 O'Reilly Autos. Two chains try to stock the factory part for about 100$, but every part store has the HEI module for $25+ depending on brand and quality.
I can get an AC Delco brand HEI ICM for $50 or an AC Delco brand LT1 ICM for $150.
As for why his car uses so many I think it is more installer error then bad parts, however good luck telling him that.
In my area there are 3 Napa stores, 4 CarQuests, 2 AutoZones, and 2 soon to be 3 O'Reilly Autos. Two chains try to stock the factory part for about 100$, but every part store has the HEI module for $25+ depending on brand and quality.
I can get an AC Delco brand HEI ICM for $50 or an AC Delco brand LT1 ICM for $150.
As for why his car uses so many I think it is more installer error then bad parts, however good luck telling him that.
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TECH Addict
Joined: Dec 2010
Posts: 2,610
Likes: 4
From: Maricopa, AZ
I like this. More testing should be done as far as compatibility with the PCM (resistance, load, etc.) and dyno results to show it doesn't effect power negatively.
Can you get a resistance reading between A-C, B-C and D-C for the HEI ICM and LT1 ICM compare them?
How accurate is the tach signal with this ICM? The LT1 Stock tach is off pretty bad (mine is 200 high at 875 idle and 500 high at 6500 redline).
Also, what's the drivability like? Same, improved, worse?
But, I like how it's no longer mounted on the head, it's cheaper, and it is good fix for a common fail point on LT1's.
Good job ChevyOwner.
One more thing, clean that engine bay yo!
Can you get a resistance reading between A-C, B-C and D-C for the HEI ICM and LT1 ICM compare them?
How accurate is the tach signal with this ICM? The LT1 Stock tach is off pretty bad (mine is 200 high at 875 idle and 500 high at 6500 redline).
Also, what's the drivability like? Same, improved, worse?
But, I like how it's no longer mounted on the head, it's cheaper, and it is good fix for a common fail point on LT1's.
Good job ChevyOwner.
One more thing, clean that engine bay yo!
Thread Starter
Launching!
Joined: Apr 2013
Posts: 225
Likes: 0
I can get the resistance of the HEI ICM but the not LT1 ICM, I don't have any good LT1 ICMs.
As for the rest of that I might be able to, but it is not my car.
After I finish the LS swap I am working on and rebuild my LT1 for a different project I can find more of that out.
As for the rest of that I might be able to, but it is not my car.
After I finish the LS swap I am working on and rebuild my LT1 for a different project I can find more of that out.
TECH Addict
Joined: Dec 2010
Posts: 2,610
Likes: 4
From: Maricopa, AZ
Thread Starter
Launching!
Joined: Apr 2013
Posts: 225
Likes: 0
I guess I picked up all my loose electronic parts and put them in a "safe" place and lost them.
I was able to ohm one at my local parts store and measured two of them wrong. I measured
A-B 160K
A-C 150K
A-D 1688K
I was able to ohm one at my local parts store and measured two of them wrong. I measured
A-B 160K
A-C 150K
A-D 1688K
TECH Addict
Joined: Dec 2010
Posts: 2,610
Likes: 4
From: Maricopa, AZ
I'll post up my results this afternoon. So these are the correct numbers?
Teching In
Joined: Feb 2013
Posts: 33
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From: N. Ky
Nice discovery. Even with it off the head mount I would use an aluminum heat sink and some thermal compound to be sure you pull the heat out of it.
I was going to crack one open at work and get some of the electronic engineers to help me beef one up. Maybe I'll crack open an HEI as well and compare. Anyway, nice find.
I was going to crack one open at work and get some of the electronic engineers to help me beef one up. Maybe I'll crack open an HEI as well and compare. Anyway, nice find.
TECH Addict
Joined: Dec 2010
Posts: 2,610
Likes: 4
From: Maricopa, AZ