I have a 94 honda prelude si H23A1 2.3l... at idle i dont have a grinding noise coming from my car, but when you accelerate there is this grinding noise coming from the engine and as the RPMS get higher the grinding gets louder and when i decelerate the grinding goes away. What could it be?

 

Are you sure it's not the bearings in your hubs? Just a thought...know that makes a grinding sound, just not from the engine.

 

Check your crank pulley bolt. I know it may sound wierd, but I remember that I had a strange grinding sound coming from one of my motors before, and I couldnt figure out what it was. A week or so later the crank pulley bolt shot off, and destroied the crank.

 

wheres the crank pulley bolt located?

 

heres more of a description.... the engine gets louder but not as loud as it used too and the grinding growls at you

 

Do you get the grinding if you rev in neutral?

 

no not while reving in neutral... could it be a cracked exhaust manifold?

 

The problem showed up after redlining my car.

 

Unlikely since your car still produces exhaust while in neutral. It sounds more like a moving part OUTSIDE of the engine. Maybe tranny, flywheel, clutch, etc.

 

i just found a loose screw on the cover of the exhaust manifold.... i don't know if that's it.

 

its the standard control unit located next to the secondary control unit on the left side of the engine bay. Go to an auto parts store and get a new one. They're cheap: $4 and it'll fix your problem.

 

when i press in the clutch and shift the noise goes away. but once i let out the clutch and accelerate the noise comes back

 

Yes it makes the noise when in neutral and i rev.

 

when i press in the clutch and shift the noise goes away. but once i let out the clutch and accelerate the noise comes back

--this makes me believe its a transmission related noise, but a pry bar to the transmission ans the handle part to your ear (this works just like a stethoscope) and have a friend produce the noise as you pin-point the source of the noise.

check ur transmission fluid and tell us what it looks like, or if its low

 

found out that if i rev in neutral to 2500 rpms the noise is there ticking. But it seems to be coming from the direction of the headers.

 

Record an audio or we aren't going to be able to play "name that sound". We hear what sound your hearing we might be able to help you out.

 

Only an opinion -
If it started this after a redline, there is a strong chance the it is bearing issue.

1. If the crank bends it will cause a binding on the main bearing.
2. Any of the tranny bearings prior to the clutch.
3. I believe that the flywheel has balance weights - maybe one was thrown off.
4. Maybe spun a journal bearing in the engine.