Looking at M42 or M44 + some mods for twisties, advice needed

[Gruelius]

Hi All,

Considering a m42 or m44 setup for my M40 e30. I would want to do the equivalent of a m50 manifold on a m52 + S50 cams and chip in terms of effort and bang for buck.

What i want to use the car for is daily driving but also taking it on the twisties so the ability to run high rpms through corners would be really good.

So with M42 vs M44 which is better for sustained higher RPM? I would not want to look at solid lifters. Then again if the m44 has significantly more torque/power down low it wouldn't be as bad but on the last run i was constantly changing between 2nd and 3rd.

another benefit of the m42 is i would  assume i could save myself from having to get the ps pump and AC pump to fit.

Ideally i would not be rebuilding the head/block.


The plan would be:
Replace all significant wear items and gaskets
Cams
Chip
Maybe valve springs
maybe injectors
maybe aftermarket ECU if needed (if m44 is the schiznit)


Please let me know what the  best base and common upgrade paths are for motors with these requirements.

Cheers

[wazzu70]

The M42 is better suited for sustained revs due to the cams pushing directly on the lifters. For a street car though the M44 valve train is probably just fine.

Cams and tuning are going to make the biggest improvements for you. I think the M42 would be easier to get a tuning solution for, unless you wanted to keep the late M42/M44 long intake manifold.

Hopefully that helps a bit. Its hard to answer a wide question more precisely!

[Gruelius]

Yeah i think the m42 will be the go, will just need to make an effort to finder a lower KM one and fit the updated timing parts. Will make it easier for fitment in terms of accessories too i assume.

What cams and chip packages are there? i would like to avoid an aftermarket ECU. If there are large gains to be had from larger cams without headwork ill go for it.



Are there any reccomended updated wear items e.g. stronger lifters

[DesktopDave]

I'd be looking for a late-model M42 myself.  Improved cam chain guides, lower-maintenance serpentine accessory belts.  The later DISA manifold won't fit under the E30 hood, from what I've heard.  Not sure if your oil pan would swap over either - it might - but later M42s got the E36 single-piece rear sump setup.

I'd have a custom exhaust made up - the manifold looks great but IMHO the M42 cat-back is a bit stuffy.

As for handling, I wouldn't go larger than 15" wheels.  Five nice light rims with small tires can save a lot of weight.  IMHO larger wheels look a bit too modern.

I'd tune the diff ratio to the speeds you'll be driving.  My 3.73 is good for highway; perhaps a 4.1 or even a 4.27 to improve acceleration if you do urban drives.  Late model Z3s came with a torsen geared diff that might be a good upgrade.  If you can find a small-case diff it'll save you 20 pounds.  A smaller battery might help - those lithium starter batts are coming down in price and they're a whole lot lighter.

A light single-mass clutch would help.

I'd also optimize the motor with mild upgrades.  Do the hose mod (delete the TB heater), upgrade the injectors to 22# 4-hole disc-type, delete P/S & A/C.  Biggest efficiency differences I saw was a solid 2.4 MPG improvement after upgrading to 19# 4-hole injectors and the hose mod.  I added another 1.1 MPG with really thin oil - synthetic 0w20.  I wouldn't recommend oil that thin, however.  Used oil analysis reported uncomfortable amounts of iron, lead, aluminum and chromium (cams, bearings, pistons, rings).  I run 15w50 now, it brought the wear metals back down.

Install an electric fan to replace the engine-driven one.  All synthetic lubes, dilute the coolant as far as you feel comfortable (I run 66% distilled water).  I'd also run a higher-temp thermostat.  A MarkD chip would finish off the package nicely.

[thebrelon]

regarding the intended use of the car I would also consider an E36 gearbox with the right (to your need) diff ratio with a short shift and new bushings on the linkages

[Gruelius]

Yeah the rest of my e30 came from a turbo 323 (cept i have redone the spring/shock package and have the 1.4 diff) so the rest of the car is pretty right.

If i go the rebuild path, have you guys heard anything about using m52b28 rods and pistons? And is the single row timing chain conversion worth it?

[thebrelon]

you can't use M52B28 rods and pistons. rods are 5mm shorter than M42 rods, pistons have a 0.15mm taller comp height, so using both in a M42 would end with the pistons being more than 4mm below deck.
actually you can use M52B28 pistons with stock crank/rods and stock or thinner head gasket depending on the CR you're aiming for. you end up with a high CR M42 anyway.


 

[Gruelius]

I heard the pistons are better in terms of weight and friction, how far would it push the CR? i wouldnt want to go for a thinner HG.

Right now as im looking for a tinker project its looking like if the messing with parts will yield a big enough gain it will get:

whatever cheap (i.e. non aftermarket) rods + pistons, whichever is the bomb

Light on rebuild (checking of clearances and replacement of thrust bearing

Single row timing chain

Cams maybe.


But if all that will give incredibly little gain, will likely just inspect timing gear, check the thrust bearing, put in new seals and maybe replace some timing components. And ill do the rest of the good upgrades.

[thebrelon]

I honestly don't know the gains to expect. CR with a thinner HG would be in the 12s and with a stock HG in the 11s, whichever you go you may gain 10-15hp, may be another 10-15hp with cams, may be...

I don't know what is the minimum gain you're are expecting...

along with single row timing chain you can look for M50TUB25 rods (140mm) which are lighter than stock rods, underdrive alternator pulley, fan clutch delete, lighter flywheel and crank balance. it may not yield much HP but all in all this is not hardcore nor expansive...

you may also have a look at totalseal piston rings.

little by little....

[wazzu70]

I think someone needs to build one of these motors and test it so we know the results

[Gruelius]

going to be a wuss with this one, will just do some common wear repairs, leave it stock internally

Do the cams wear much?

[wazzu70]

Cams aren't really a wear item unless they have unusual scoring. If they look fine and don't have any weird marks/gouges you should be good to go

[the white guy]

I'd be looking for a late-model M42 myself.  Improved cam chain guides, lower-maintenance serpentine accessory belts.  The later DISA manifold won't fit under the E30 hood, from what I've heard.  Not sure if your oil pan would swap over either - it might - but later M42s got the E36 single-piece rear sump setup.

I'd have a custom exhaust made up - the manifold looks great but IMHO the M42 cat-back is a bit stuffy.

As for handling, I wouldn't go larger than 15" wheels.  Five nice light rims with small tires can save a lot of weight.  IMHO larger wheels look a bit too modern.

I'd tune the diff ratio to the speeds you'll be driving.  My 3.73 is good for highway; perhaps a 4.1 or even a 4.27 to improve acceleration if you do urban drives.  Late model Z3s came with a torsen geared diff that might be a good upgrade.  If you can find a small-case diff it'll save you 20 pounds.  A smaller battery might help - those lithium starter batts are coming down in price and they're a whole lot lighter.

A light single-mass clutch would help.

I'd also optimize the motor with mild upgrades.  Do the hose mod (delete the TB heater), upgrade the injectors to 22# 4-hole disc-type, delete P/S & A/C.  Biggest efficiency differences I saw was a solid 2.4 MPG improvement after upgrading to 19# 4-hole injectors and the hose mod.  I added another 1.1 MPG with really thin oil - synthetic 0w20.  I wouldn't recommend oil that thin, however.  Used oil analysis reported uncomfortable amounts of iron, lead, aluminum and chromium (cams, bearings, pistons, rings).  I run 15w50 now, it brought the wear metals back down.

Install an electric fan to replace the engine-driven one.  All synthetic lubes, dilute the coolant as far as you feel comfortable (I run 66% distilled water).  I'd also run a higher-temp thermostat.  A MarkD chip would finish off the package nicely.

Great information Dave!  I vote we sticky this.
Thanks for the great info.
  Stan