my IMRC deletes


back in January i attended a dyno day at Brother's Performance here in Florida. i threw my Cobra on the dyno for shits and giggles and it produced a whopping 208rwhp and 257rwtq breaking up at 4200rpm :(


i was told over and over again that the IMRC's were the problem. well i FINALLY decided to get it done, either clean them or delete them.

i went to the track just to practice driving a manual trans at the track and to get a before time to compare to after the deletes.

best time: [email protected] with a 2.1 60 ft. i wanted to cry :cry:

got the plates out and saw instantly why there was a power drop... they were disgusting. absolutely terrible. the driver's side plate was ****ed up. the bracket that holds the cable was bent badly, the cable was kinked and not even connected to the IMRC plate. even if the cable was connected, the butterfly valves were so stuck, it wouldnt have made a difference.

the passenger side wasnt as bad, dirty, but still functional.

since the driver side was so bad, i decided to just delete them.

this is after breaking up most of the Carbon deposits that were caked onto the plates...



after cleaning and removing the buttlerfly valves in the plates, i went to check out the intake valves in the heads and see how nasty they were. they werent too bad considering it is 15 years old and has 106,000 miles except for one thing...

i found this little baby INSIDE the secondary intake port for cylinder #5


yep, a metal EGR gasket from the previous owner's attempt at a delete. i thought it couldve been dropped in there by me, but it was jammed down there pretty good and was, as you can see, torn up by the intake valve. luckily the intake valve looked good (dunno how that didnt get scratched or worse)

so i was left with this


and a messy ass garage



bolted everything together, started her up, and Vacuum leak! furthest back fuel injector on the passenger side would not seat in the IMRC plate. Fuel rail bent somehow during dis-assembly. :mad:



got the rail repaired and went to install. started up great, great idle. man was i happy, until my alternator stopped working. found out a wire was cut when reinstalling the coolant crossover. repaired the wire and what do ya know? it holds voltage again!

what a shitty week it's been. but man it was worth it, car pulls so so so much harder at 3500rpm. currently it is still untuned so under 3500 i get a stumble or two and it doesnt pull as hard as before, but that'll be taken care of soon.

feels like Cobra V-tec :lol:

and to celebrate the deletes...

cant wait to hit the track this friday and really see the difference
Last edited by a moderator:


Car sounds great and I think with the IMRC deletes you should lose some low end but gain much more on your top end. Either way once its tuned you'll be much more happy :thumbup:

Go Down South

South is my last name
How much lost power do you think you'll gain back now that you deleted em? I was very surprised to see your car make such little power.


4 point 6
with his mods if the rest of the motor is strong and good to go I would guess 260-270rwhp just from deleting/fixing those IMRC's. At least that is the range it should be in. The 96-98's do dyno less then the 99/01 just do to differences in heads/cams and a terrible factory tune. But fortunately with a tune and bolt-ons they can make up some good ground. At least that is what I have seen.


Yeah, 260-ish sounds about right, its still 15 years old and has 106k miles on it.

Took two incar videos after the deletes to compare to my first video I took when I got the car.



Last edited by a moderator:


Mellow Yellow
is that you or the IMRC's causing that delayed vtec-like acceleration in the before video?

either way, damn it must be a night and day difference. you were making bolt-on NPI power on the dyno, not 4v power.


New Member
altanticblue98 thanks for the pics, you helped me more that way. my 98 cobra was sat for 2 years. got it out ans ran it for a little bit and found out after 2500rpm i would feel the car want to pull over and kick me out and say this is grannys car and drive me that way. so i read up alot and pulled out my imrcs and found urs to be clean compared to mine. i bought all new gaskets and plugs wires. cleaned the intake and manifold good went threw 8 can of brake clean and 3 tooth brushes later they are clean. the only thing i dont know and if anyone can tell me do i need to leave the cables on and the acutator box on. or can i take it off perm?


I removed the cables off the plates, and removed the actuator box completely. I left the harness tucked away.

Since I didn't want to wait for jb weld to dry, instead of removing the rod that runs through the plate, I just unscrewed the butterflies off the rods

Ted, I didnt go WOT until ~4k rpm in the before video