New Member - 1989 325ix and Evo

[Wild Ride]

I have the 284/272 schrick cam on a 2.7 stroker with 10.2/1 compression. I lightened the stock flywheel to 13lbs. The car idles around 900 with some lumpiness. Stock new valve springs and rockers have held up for 40k+ miles with frequent redlines. The vibration is ok until you get aftermarket motor mounts, stick with stock.

An engine with slightly less cam and stock compression will be the hot ticket for a daily. It retains the smoothness these engines are famous for.


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[AWDBOB]

It's fine. unless you're building an 8,000rpm, 300bhp race motor, I wouldn't worry about the crank balance or R/S ratio too much. I have an eta take off crank that I just had cleaned up, no idea of mileage but it looked good, and used S52 rods - it turns 7500 without batting an eye - and certainly doesn't vibrate.

and actually I think the lower R/S ratio will help a bit with your lower duration cam, basically increased bottom end torque. the piston will "dwell" longer at the bottom of the intake stroke.

the only thing to watch on the stock M20 harmonic damper is the crank wheel sometimes separates from the damper wheel, but even that is pretty dang rare, and it just means your car won't start since it won't get an RPM signal. :)

What pistons did you use? Your R/S is better than my configuration for high revs (1.67), but I'm assuming you had to move the wrist pin up on the piston a few mm to use those rods?

Good point about piston dwell, also. I doubt I'll notice any difference in bearing wear because I won't be spinning the motor past 7k anyway. It's the over revs that kill the rod bearings.

Seems like the M20, despite the fact that it doesn't make a ton of power, is a very smooth engine through and through.

Any idea what is too much for M52 crank (forged, right?), E rods, and i pistons? I'm assuming the pistons would be the weak point of the build, but am not sure about the integrity of the E rods.

[nando]

It's fine. unless you're building an 8,000rpm, 300bhp race motor, I wouldn't worry about the crank balance or R/S ratio too much. I have an eta take off crank that I just had cleaned up, no idea of mileage but it looked good, and used S52 rods - it turns 7500 without batting an eye - and certainly doesn't vibrate.

and actually I think the lower R/S ratio will help a bit with your lower duration cam, basically increased bottom end torque. the piston will "dwell" longer at the bottom of the intake stroke.

the only thing to watch on the stock M20 harmonic damper is the crank wheel sometimes separates from the damper wheel, but even that is pretty dang rare, and it just means your car won't start since it won't get an RPM signal. :)

[AWDBOB]

both the 272 and 284/272 are pretty streetable. anything more than that, and it will drive you crazy on the street, unless you run a high idle, but that's also annoying.

with the 284/272 I'd target an 800-850rpm idle. stock is ~700-750. a 272 (or 274, if it's similar) is probably a better choice if you don't want it to be too crazy for street use. both will work just fine with stock rockers and valve springs. the IE HD rockers are nice too though.

The cam I was most interested in was the Bimmerheads 274 stock regrind. Looks like it will offer a low/mid range bump in power, while retaining stock drivability. I've had too much cam in pretty much every car I've built thus far, so keeping it moderate and smooth is definitely one of my goals this time around.

How is harmonic vibration/balance on your motor nando?

Rod angle and r/s ratio will obviously be less conducive to high revs and skirt/bearing wear, but I'm wondering if you notice it on the M20 like you do on the 4g63/4g64.

R/S on the 2.5L is 1.8 and R/S on the 2.8L (M52B28 crank [84mm stroke] with the E rods [130mm] is ~1.55. Definitely a significant decrease, enough to notice premature rod bearing wear if you're revving to 7K, I would think.

[nando]

both the 272 and 284/272 are pretty streetable. anything more than that, and it will drive you crazy on the street, unless you run a high idle, but that's also annoying.

with the 284/272 I'd target an 800-850rpm idle. stock is ~700-750. a 272 (or 274, if it's similar) is probably a better choice if you don't want it to be too crazy for street use. both will work just fine with stock rockers and valve springs. the IE HD rockers are nice too though.

[AWDBOB]

Really enjoyed reading the thread. I have a friend with an evo and a couple e30's. Loves them all. You definitely get work done!

Serious question: The 5 speed ix sedan you bought looks like a much better starting point for you as it looks to be much cleaner. I know it's not a coupe and you have time invested in the coupe but why not keep the sedan and sell the coupe?

BTW definitely do the cam, a cammed m20 is a fantastic machine. You should seriously consider replacing the rocker arms as you build the engine anyways, they have a tendency to fail.

Thanks, man. You see, I wrestled with the same thoughts.

First and foremost, I am so ridiculously partial to the coupe it wasn't even an option in my mind. However, I did take some time to consider it, and the car has rust in the same places as mine, specifically above the rear spring perches, which I already repaired on the coupe. Also, the fenders are rusted on the corners, the typical front sunroof drain points, battery box, etc. To boot, there are a TON of imperfections with the sedan on the interior as well that the coupe doesn't have. Basically, the sedan looks good and is PERFECT for a part out, as it's very mechanically sound, but for me to drive the car I would need OCD meds haha. I do want the heated seats, though. Once I put my fresh valance, hood, and fenders on the coupe shell look just as pretty! On and the pitted wheels don't help the case either. I have everything to make the coupe nice, I'm
just waiting for the weather to break. The coupe also runs 10x better than the sedan.

Don't know if you wanted that detailed of an answer, but those around me had the same suggestion, until they sat in/drove it.

you'll want to do the cam if you're doing a stroker.. gotta get more air in there somehow. :p

stock ones will work too. I've had Febi rockers with my 284/272 schrick for years without issues. also using new stock valve springs (they aren't new anymore - that was almost 100,000 miles ago that I built this head!).

True that! Displacement eats up duration like no other. In the Evo my 280s feel like 274s.

How do you like your 284/272? That's incredible that the stock springs hold up so well.

I have been toying with the idea of flipping the RS' to fund more go fast parts.

It's tough already having a built car, as I can't go as in depth with the iX as I did the Evo, even though I would like to. My plan is to make a nice looking daily that is moderately quick, but handles great, aka I have to watch going overboard.

[nando]

Cool, good to know. May not do a cam then if I have to spend $300 in rocker arms.

you'll want to do the cam if you're doing a stroker.. gotta get more air in there somehow. :p

stock ones will work too. I've had Febi rockers with my 284/272 schrick for years without issues. also using new stock valve springs (they aren't new anymore - that was almost 100,000 miles ago that I built this head!).

[Wild Ride]

Really enjoyed reading the thread. I have a friend with an evo and a couple e30's. Loves them all. You definitely get work done!

Serious question: The 5 speed ix sedan you bought looks like a much better starting point for you as it looks to be much cleaner. I know it's not a coupe and you have time invested in the coupe but why not keep the sedan and sell the coupe?

BTW definitely do the cam, a cammed m20 is a fantastic machine. You should seriously consider replacing the rocker arms as you build the engine anyways, they have a tendency to fail.

[AWDBOB]

Don't use old rockers with a new cam..

Cool, good to know. May not do a cam then if I have to spend $300 in rocker arms.

[nando]

Don't use old rockers with a new cam..

[pakc88]

PM sent regarding parts

[AWDBOB]

Front of the car disassembled and getting ready for the part out. Strut housings and front axles are mint, which was a nice plus.

Sending my intake manifold out to Curt Brown so he can work his magic on it.

Hopefully picking up the M52B28 crank and E rods this week. Once some parts are sold I'll send the block and head to the machine shop. Going to deck the block 0.5mm, use a BMW HG, and hopefully that will put me around 9.8:1, which should work nice with the Bimmerheads 274 cam.

It was pleasant to see a brand new clutch in there. One less thing I'll have to buy.

Is it imperative that I get HD rockers, or can I just use my stockers?

[AWDBOB]

Started digging into the new iX tonight. Got the trans setup out, and did a better test on the VC, and it's very tight. I also confirmed that the differentials were 3.91s, which was very relieving. Going to order subframe bushings, trailing arm bushings, and a bushing for the rear diff to tighten up the rear of the car.



Got a bit of a game plan as well. Going to pull the parts car motor, and build a 2.8L using I pistons, e rods, and an m52 crank. Once that's finished, I will drop the motor in the same time as the manual swap. Coilovers and wheels should be on shortly.

I'm getting excited about getting going on this stuff. I foresee a s300sx in the future.

[AWDBOB]

Only use the best ;)

[AWDBOB]

Nice! What did you get it for? Wish I could find iXs that easily around here :hitler:

If you want an iX, follow the snow! [and salt] :)

I got it to use the manual swap out of, and resell with my auto after cleaning it up to result in profit and a free manual swap!