Mystic1688
New Member
Found out today my IMRC's are shot they are leaking very bad out of each ends. What are my options I seen on here some guy selling rebuild kits?
IMRC's Replace/Rebuild?
- Thread starter Mystic1688
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I'm selling a set of good imrcs. Pm me an offer
Rebuilding the aluminum IMRCs is pretty straight forward.
Remove two small screws from each butterfly. Heating each screw up with a small torch makes removal simple. Once the butterflies are off, slide the main shaft out the back of each plate. You will find an o-ring on each end of the shaft that is probably so dried up you will swear that it is something else. Cut it off. Each IMRC plate has a small bearings on each end of the plate where the main shaft goes through. They probably are not rotating well at all. Work them out of the IMRC plate using a small punch from the butterfly opening side. They will come out eventually.
With everything apart you will be able to clean the IMRC easily. I had a local machine shop run mine through an ultrasonic and they looked great. You can get the same effect with brake cleaner and a brush.
Once everything is clean and dry, apply a light coat of oil on your new bearings and tap them into place using a socket the same diameter as the outside of the bearing. Put a new o-ring on butterfly shaft closest to the arm, add a light coat of oil to the o-ring, position the return spring on the shaft and insert the shaft through the rear IMRC bearing. Work the shaft through to the last open butterfly hole, install the forward o-ring with a light coat of oil and slide the butterfly shaft the remaining way into the forward bearing. The butterfly shaft should rotate freely but not be able to slide back out too easily. Reinstall the butterfly plates with two small screws on each. I used red loctite on the threads for peace of mind. Once the butterflies are installed, you are good to go.
Bearings should be a S688-2R and o-rings should be a -008 size (or maybe a -106 for a real tight fit).
Remove two small screws from each butterfly. Heating each screw up with a small torch makes removal simple. Once the butterflies are off, slide the main shaft out the back of each plate. You will find an o-ring on each end of the shaft that is probably so dried up you will swear that it is something else. Cut it off. Each IMRC plate has a small bearings on each end of the plate where the main shaft goes through. They probably are not rotating well at all. Work them out of the IMRC plate using a small punch from the butterfly opening side. They will come out eventually.
With everything apart you will be able to clean the IMRC easily. I had a local machine shop run mine through an ultrasonic and they looked great. You can get the same effect with brake cleaner and a brush.
Once everything is clean and dry, apply a light coat of oil on your new bearings and tap them into place using a socket the same diameter as the outside of the bearing. Put a new o-ring on butterfly shaft closest to the arm, add a light coat of oil to the o-ring, position the return spring on the shaft and insert the shaft through the rear IMRC bearing. Work the shaft through to the last open butterfly hole, install the forward o-ring with a light coat of oil and slide the butterfly shaft the remaining way into the forward bearing. The butterfly shaft should rotate freely but not be able to slide back out too easily. Reinstall the butterfly plates with two small screws on each. I used red loctite on the threads for peace of mind. Once the butterflies are installed, you are good to go.
Bearings should be a S688-2R and o-rings should be a -008 size (or maybe a -106 for a real tight fit).
If you look closely at the ends of the butterfly screws, they are staked to prevent them from falling out into the intake. It looks like they smashed the ends flat with a vice grip. I smashed mine back to near round with vice grips and the screws came right out.
It would be a good idea to stake them again with a vice grip in addition to the locktite.
It would be a good idea to stake them again with a vice grip in addition to the locktite.
Last edited:
Mystic1688
New Member
anyone know the part number for the butterfly bolts?
I'd say just get rid of them my 98 cobra was just a cai and exhaust comparing that to my 96 cobra which is full Bolton with imrc delete and na svt shortrunner the bottom end loss is barely noticeable granted I have 4.10s but I'll never have the issue again
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