What would you do?

[318kid]

I have a spare engine that I'm looking to build up. I don't want to get too crazy as it's a daily driver, but I want to do a small build. (Nothing too complex) So I ask the m42club,

How would you build up an engine to reach 150-160 hp? It shouldn't take much work and probably won't cost much more money than a stock rebuild.

Currently I would do:

Electric Fan Conversion
S52 pistons
Port/Polish Head
Machine Dual Mass Flywheel Down
Balance and Lighten Crank/Rods/Pistons
COP Conversion
(Maybe a bit higher comperession ratio?)

Later would be dblias.

As much as I would like to do cams as well, I would like to increase lower end torque too. This would be my first engine build, but It is definatley something I'd like to learn how to do. I will be reading up on everything I can!

[Hey-u]

M47 crank, stroker.

[318kid]

M47 crank, stroker.

I don't want to swap cranks out though. Its a lot more work than just boreing the block a bit larger. Does anyone know if I could run stock crank and rods and replace the m42 pistions with .5 overbore M44 pistons. That should make the total to 85.5 compared to 84.0. Every little bit helps. I am just wondering if they are a direct trade of if the m44 is a bit lower (to compensate for the 83.5 mm crank). Does anyone know?

[d.hitchcock]

Don't you have to remove the crank to bore the block?

[wazzu70]

Of course you have to remove the crank to bore the block as Doug said. Removing the crank is not hard at all and is a wise thing to do so you can replace the crank main bearings with a new kit that includes a full thrust bearing.

IMO best money spent would be keeping the 81mm crank, add a decent set of cams, ECU tune.

Boring the block and getting appropriate pistons helps too. Most people overlook cams which is the weak part of this motor.

[318kid]

Don't you have to remove the crank to bore the block?

I don't want to have to go through the trouble of removing the vibration dampener on the m44 crank and have it rebalanced and all of the machine work just yet, however I realized that the crank will need to be pulled regardless. I was just looking for a good solution using the least amount of one-off parts available. If I can keep the m42 crank and still get to my goal, why would I want to spend more money?

Wazzu70, why do you think the cams are the weak part of the m42? What would you consider a good setup cam-wise on the m42? I know someone has done 250/250, which seems reasonable. I just don't want to loose all the torque down low.

Considering between my dad and I we have 2 e30's that will need to be rebuilt in the next year or two I think the first motor will be mostly stock, with just a few upgrades on the "weak spots." (Cams(?), Port the head, lighter weight valvetrain, .5mm overbore, machine down the dual mass flywheel, electric pusher fan, mess under the intake, chip) and then the next build will be same but with more displacement. At least that's the idea. I think the first build should be able to hit 150-160 or so. I don't want a huge built motor, just a bit more that stock.

[wazzu70]

Wazzu70, why do you think the cams are the weak part of the m42? What would you consider a good setup cam-wise on the m42? I know someone has done 250/250, which seems reasonable. I just don't want to loose all the torque down low.

Considering between my dad and I we have 2 e30's that will need to be rebuilt in the next year or two I think the first motor will be mostly stock, with just a few upgrades on the "weak spots." (Cams(?), Port the head, lighter weight valvetrain, .5mm overbore, machine down the dual mass flywheel, electric pusher fan, mess under the intake, chip) and then the next build will be same but with more displacement. At least that's the idea. I think the first build should be able to hit 150-160 or so. I don't want a huge built motor, just a bit more that stock.

The M42 was built more as an economy motor than a sport motor and the cams reflect that. If you have ever seen the results of using S50 cams in an M50 engine you would know how much there is to gain by swapping cams.

VAC Motorsports is a US retailer for Catcams cams. With better cams, you will need some ECU tuning though to really get the maximum benefit. Metric Mechanic also sells cams.

[318kid]

The M42 was built more as an economy motor than a sport motor and the cams reflect that. If you have ever seen the results of using S50 cams in an M50 engine you would know how much there is to gain by swapping cams.

VAC Motorsports is a US retailer for Catcams cams. With better cams, you will need some ECU tuning though to really get the maximum benefit. Metric Mechanic also sells cams.

I've been looking around at specs. What would you recommend in terms of the * of cams that wouldn't loose too much low down torque? Something like the 268/267* or something more wild? If you were in there would you bore the block a bit more (86mm) or would you leave it how it is and just do a .5 overbore?

[wazzu70]

It depends on if you want to purchase pistons or not. If you are purchasing pistons, its not much different going 85 or 86. You have to think about the head gasket though. You will probably need a custom gasket with 86.

269/269 or whatever the smaller Catcams cam has is good. PerTore had a thread where he recently put those in his car and they performed well.