M42 E21 swap

[OneCleanE30]

hey guys, just picked up an E21 and I'm planning on doing a M42 swap, how hard and pricey would it be to get around 205hp from the m42 engine? Thanks for your help!

[varg]

Not too hard and not very expensive... if you turbo it. Stock internals and low boost on a little turbo would do. I see picking up that extra 60hp NA being pretty expensive though. It's going to have to rev higher and flow better and will probably have to be a stroker build.

[bmwman91]

Getting 205 NA bhp from an M42 is $$$$$.

All said and done, with core refunds and everything, you can get a 205bhp Metric Mechanic M42 for about $12000. The process will take about 9 months from the day you pay a deposit to the day you receive the engine on a pallet.

If you want to try to do it yourself,
- New M47 crank, $1200
- M47 modification labor - $300
- Custom 11.5:1 pistons - $800
- Custom con-rods for 11.5:1 CR and 88mm stroke: $800
- M44 timing case, pol pimp, oil filter housing - $200 (USED)
- Custom crank position sensor bracket (for M44 case) - $120
- Lighter 35mm S50 lifters and springs - $400
- New larger valves w/ 6mm stems - $300
- Titanium valve retainers and spring seats for 6mm stems - $250
- New 24#/hr fuel injectors - $250
- New crank and rod bearings with performance coating - $200
- Bottom-end machine shop labor - $400
- Top-end machine labor (including mild port, polish, multi-angle valve seats, shaped valve guides) - $600
- Custom dyno tune - $1000
- 11lb M20 single mass flywheel conversion - $1000
- Other misc hoses, gaskets, seals, fasteners (inc. head bolts), supplies, tools - $700

That comes out to: $8520

Other optional goodies:
- Metric Mechanic single row timing chain conversion - $700
- Metric Mechanic "Pulse Chamber" intake manifold - $1000

The stock exhaust header and cat-back are fine for this, as is the stock intake air box and AFM. You will want to use the M42 intake parts, assuming you can make them fit. According to Metric Mechanic, you MIGHT see ~5bhp extra from a MAF conversion and 2.5" exhaust after the header (vs. 2.25" stock).

The machine labor guesstimates above might be a little low too since you will need to go to a VERY reputable shop that can hold tolerances well under 0.001" in order to actually get over 200bhp NA and not burn oil or have crazy blow-by with the CR that you need to use. It should all work fine on 91 octane pump gas. Also be aware that it is likely to take 2x as long as you expect if you try to manage the build yourself (if it is your first big build).

You could buy a clean-running stock M42 and turbo it to get the same amount of power for under $4000. I believe that someone on here is selling an M42 turbo kit.

http://www.r3vlimited.com/board/showthread.php?t=259174

[decay]

I've got a bunch of M42 turbo stuffs for sale. Check my threads.

[TobyB]

...or even one of the ole Downing Atlanta superchargers, if you could find one...

t