I'm no expert, but basically they put in a cable driven box under the intake mani that controls when the valves on those plates will fully open. Those plates are in between the intake mani and the heads. They did it to try to boost low rpm torque, which it does a little. For modded cars it's probably best to just delete the whole thing but my car is gonna be pretty stock.

 

Didnt those only come on the 3v 4.6's?

 

4v dohc

 

Ah ok. I knew they were on 3v's but I have never worked on a 4v so I wasnt aware. Good to know.

 

When I did the 4v swap to my 96 GT there was no 'cost effective' way to get the IMRC's to function properly and running with them closed kills any power over 4000 rpm. So I went and did the delete mod to the stock IMRC's. Mine were just as bad with the oil and gunk caked up in them as yours were. Engine had 134k on it and had never been opened up before that.

But in all honestly and not trying to brag or anything. But with 4.10 gears and long tube headers I noticed no loss of low end torque compared to when the engine was in the Cobra with 3.73's. I'm sure some may have been lost. But it was not noticeable by the seat of the pants. What I did notice was that there was no surge at 4500 - 5000 like before when it was in the Cobra. The power came on strong and smooth and pulled good until about 6500 - 6800 right before the shut off. With the IMRC's when they open up at 3000,.. I dont know how fast they open up,.. I suspect on ours because the gunk was so bad they may have been opening slowly and that was why we felt the surge at 4500 - 5000 because they were probably not fully open until that point.

If your planning on making a daily driver out of it I would keep the IMRC's. But if your looking for every last ounce you can get out of it,.. do the delete mod. Also,.. dont be afraid of the gears either. The 4v has enough RPM to put 4.30 gear to very good use.

Hurst

 

Whoa!! Damn, a 4.30 gear? i thought i was pushing it when i put the 3.90 in my coupe. My impala loves 4.11s though, especially with the big wheels.

 

The car is my daily and will be lightly modded eventually. It has 84K on it and the box itself luckily works fine (no broken gears or anything). I will definitely be putting 4.30s in it at some point. It needs gears bad.

 

The 4v engines need alot of gear, they rev high and dont have a lot of low end torque. Alot of people even go 4.56

 

Damn!! So gears really wake them cars up huh?