Author Topic: smoothest BMW DOHC Four you have seen/heard/felt (Read 3815 times)

KyleTaylor · « **on:** December 16, 2008, 08:59:59 PM »

I really like the m42 for it's fuel efficiency, weight, quick revs, blah blah, but mines is not the most smooth.

It is like silk at idle now, but 3000 to 4000, which is highway cruising revs, it is very loud.

I am changing the differential to a 3.73 LSD to make it a little more highway friendly.

The thing I want to explore is what to replace without rebuilding the bottom end...

Already did the tensioner
Thinking about doing the lifters next (think cam grind too)
what else if that does not work.

roundel318 · « **Reply #1 on:** December 16, 2008, 09:33:24 PM »

As far as I know, the M42 isn't known for being smooth, or quiet for that matter

I am also comparing it to other BMW sixes, V8's etc.

twright · « **Reply #2 on:** December 17, 2008, 06:51:23 AM »

Will putting new motor mounts make it more smooth?

HaNasich · « **Reply #3 on:** December 17, 2008, 08:52:03 AM »

Quote from: twright;62997

Will putting new motor mounts make it more smooth?

m-o-s-t probably

Ron.

roundel318 · « **Reply #4 on:** December 17, 2008, 10:12:53 AM »

If your's are worn, it should

KyleTaylor · « **Reply #5 on:** December 17, 2008, 01:58:19 PM »

My engine mounts and transmounts relatively new... I am thinking about adding a torque dampener like the old m10 had...

I may add some sound deadening under the hood as it is gone...

roundel318 · « **Reply #6 on:** December 17, 2008, 02:23:41 PM »

Ohh, no deadening on the underside of your hood?
You should get that, it helps keep the noisy M42 hushed

KyleTaylor · « **Reply #7 on:** December 17, 2008, 03:26:21 PM »

Quote from: roundel318;63032

Ohh, no deadening on the underside of your hood?
You should get that, it helps keep the noisy M42 hushed

I have been putting it off... I have a big dent on the leading edge... but I got my buddy's stud welder/puller so I can fix it.

I wonder if the glue on style is quieter than the one piece one...

roundel318 · « **Reply #8 on:** December 17, 2008, 10:27:09 PM »

There are part numbers on realoem, not sure if they are available anywhere.
I would do the glue on seperates like OE.

KyleTaylor · « **Reply #9 on:** December 23, 2008, 11:04:21 AM »

Quote from: roundel318;63062

There are part numbers on realoem, not sure if they are available anywhere.
I would do the glue on seperates like OE.

I think I had a 325 that had a screw on panel...

Nomadic · « **Reply #10 on:** December 30, 2008, 06:47:52 AM »

Quote from: KyleTaylor;62974

... It is like silk at idle now, but 3000 to 4000, which is highway cruising revs, it is very loud.
...
Already did the tensioner
Thinking about doing the lifters next (think cam grind too)
what else if that does not work.

A racket at 3000-4000 RPM could be timing chain or rails. Is it the same when the motor is cold?

Have you pulled the valve cover to check the Cam Gears for wear? Have you pulled the lower oil pan to check for loose bolts or plastic bits from the timing rails?

Sometimes you can feel a subtle vibration from a waterpump or an accessory that is about to seize up...

E30 are not known as "quiet" cars... especially the 91 318is'.... the last of the classic "raw" BMW's. E36's are more civilized.
Cheers

roundel318 · « **Reply #11 on:** December 30, 2008, 01:31:24 PM »

With already done the tensioner, get after those rails or the chain itself!
The chain isn't that expensive, just spendy laborwise to replace it.