Another M20 Storker - I'll call it 3.1L+

[Justin B]

I can't spell :P lol

I'll be taking the M20 out of my E30 and transplanting in the stock rebuilt M20 I had sitting in my garage for the 2002. The E30's engine has been burning/leaking oil pretty heavily and I really don't even want to bother with it and it gives me the opportunity to build the stroker I've always wanted for the deuce.

So far, I have bought-
S52 Crank
-Bimmerforums $450
Spec Aluminum Flywheel
-Flying Brick Performance $565
Sachs clutch kit (Stock - I'd rather let it slip than break my diff)
-Flying Brick Performance $189
Upper Gasket Set (Reinz)
-Flying Brick Performance $69

I haven't recieved anything yet though, I just bought the crank yesterday from socal.

I'll continue to update this post and the thread with on going pictures of the removal and build.

Metric Mechanic Sport 3200 (86mm obviously, and deep pockets = no interferencee) Pistons, wrist pins, moly rings, Metric Mechanic "Rally" cam, bee hive springs w/ retainers and base, main bearings w/ 360 degree oil groove, coated rod bearings, oil seal spacer (comes with a longer bolt), and one can of Harley Davidson TEXTURE black engine paint. That's the stuff that looks like sand, and is for the valve cover.

Stock S50 rods, Conti alternator belt, Conti timing belt, intake and exhaust valves.

Upper and lower Reinz gasket set shiz and rocker shafts.

The heart, S52 crank. It's in great condition. Right now there's just a lot of fiberglass packing stuff sticking to it from the crate.

...and weighs about ~48-49 lbs. Does anybody know what the stock M20 crank weighs? I'll know shortly anyway once I take it out and weigh on the same scale though.

[Jon325i]

Quite the project....should be interesting to watch as things progress. What cylinder bore size do you plan to run with that crank to get the desired displacement?

Jon

[Justin B]

+2mm=86mm. I'm going to talk to Jim at MM tomorrow to sort out a few questions I have. It will be over 3.1L, but not quite to 3.15 to round to 3.2. There's that red Groma Fab 02 that has the same stroke crank as I have, but they run 85mm pistons (I read that somewhere) which isn't even quite fully 3.1L and they call it a 3.2 I think. It's as big as I'd want to go, the bore size is like .6mm less than an S52 at a true 3.2L.

[thornado327i]

What about the top? How do you plan to fill that engine? I mean - is stock M20B25 intake manifold and throttle big enough? I'm not asking about the injectors - they don't do a good job even on 2,7...

I'm asking as I'm thinking what else can I do to my engine...

[SamE30e]

Sachs clutch kit (Stock - I'd rather let it slip than break my diff)
-Flying Brick Performance $189

What's more likely to break, a clutch that you installed with the intention to slip, or a diff that might break (but not likely going N/A making less than 250hp)and takes about an hour and a bit to change?

[Jon325i]

What's more likely to break, a clutch that you installed with the intention to slip, or a diff that might break (but not likely going N/A making less than 250hp)and takes about an hour and a bit to change?

I have to agree with this logic. Changing out a diff is much easier to do than changing out a clutch. If the OP is concerned about breaking a diff, just source a second one of the same ratio and keep it tucked under the workbench until you need it. I've changed plenty of diffs in E30s - a few simple hand tools and a floor jack is all you need to remove the 21 bolts holding it in. No need to pull the exhaust either.

Personally, I would reconsider the choice of clutch before the final assembly and install comes around.

Jon

[thornado327i]

I remember changing my first diff... Felt almost like loosing virginity... <sigh>

[Justin B]

Well yeah, I see the logic. I think the stock clutch may be able to hold it though, if not, oh well. I really don't want to stock pile diffs. I'm not going to be making tons of power anyway, (from a VS turbo stand point) so I think I'm safe. From the diff and the clutch. I very well may just get another clutch, as I was going to buy the Spec Stg3 but saw it as an opportunity to cut the initial cost burden a little for a part that may still work okay. Since I do have an E30 obviously, by the time I'm done with the build I may just buy one and leave the Sachs for later on my DD or sell it.

As far as "filling" the engine, of course. The plan is currently to run a dbilas intake manifold and 3 DCOE flange Jenvey throttle body pairs and larger injectors. At least that's the basic version. Something like 24lb? Megasquirt will be controlling everything. The valves will be the +1 oversized ones, with a schrick cam. As far as head porting goes my stock rebuild has a ported head, but I may just leave that because I don't want to take it apart. I'll just have my stocky stock one done up too.

Jim from MM is supposed to call me in a few hours so I can discuss a couple things about his pistons and other bits so I should have more to post later.

[Jon325i]

Just an FYI re: stock clutches. In talking to people more in the know about this stuff (a couple of veteran mechanics too), the consensus seems to be that the stock E30 clutch can cope up to around the 230bhp level. Anything beyond that will reveal its weaknesses. Mention it to Jim at MM and see what he says.

Jon

[Justin B]

Ah well, I just got off the phone with him from a 51 minute call. It might not work, but then again I don't mind doing work on my cars. Realistically, it'll be a year at least till the motor can be in the car and driving, and if that's if I kick ass on everything else. Bodywork, replacing panels, obviously paint work, a half cage with door bars are being thought about, and an entirely new electrical wiring harness throughout the car needs to be fabricated. In that time I'll have a stock Sachs clutch sitting around collecting dust but brand new. There's a good possibility I'll just flip it and go out and buy a better one. The point is though that isn't even technically the motor to me, or this build, so I really don't even need to think about it right now.

Anyway, from the phone call I changed my mind on oversize valves, at least for now, and the schrick cam. He talked me into the Rally cam shaft, for detailed details, seriously if you haven't talked to him, call and ask. He'll talk forever on minimal questions and its really good information. Basically, he said the intake duration is 290 degrees on both the sport and rally cam, and the exhaust duration is where they differ; the sport has less while the rally cam has a longer exhaust duration. I forget the actual figures, but he mentioned that a lot of overlap is an evil thing, and should for the most part be avoided as much as possible for an engine that want's to idle smoothly, especially with a light weight flywheel as I have. Getting off the gas, coming to a stop, the tuning is a nightmare and to keep the engine alive it would either need to idle at 1500 rpm or have a big heavy flywheel on it. He's been in the business for over 30 years, I'll take his word for it. I have megasquirt (If I can fix the damn thing, but I'll be using that system one way or another at this point) so I'd need to tune for all that, and his cams seem a lot more conducive to tune with properly than a big lopey thing.

He said that he doesn't even bother with +1 valves either. Throughout many flow tests over a 9 month period some time ago he said that he found out that the stock valves flow just as good if not better. Sounds a little weird but I'll go along with it. It's cheaper too to avoid buying valves for $$ and the machine work along with them to seat. His reasoning was (cliff notes) through the intake path, the air will want to go around the high side of the port over the top of the valve into the cylinder. It can't do that well because the valve is even so much slightly wider and it starts being blocked by the exhaust valve on the other side of the chamber. The flow then has the option to go around the low side, but that's a very tight radius turn along the bottom of the port flipping over the valve and into the cylinder towards the intake side. It opens up the port larger, but the restrictions in the way level or outweigh the good.

If I could find an early (85-86ish) eta block too that would be golden, as I wouldn't need to have modifications done to it for the main bearings and supposedly there might be enough (he said don't quote him so I'm not. lol) room to not need to clearance anything for the rods, either. I'm going to buy a set of S50 rods for $125 instead of brand new Eagle forged rods too, he said they work perfectly fine and it's rare that he'll need to re-bush or fix them in any way so I'd be safe to do that and it's what he uses anyway.

At the end of the call, I ended up hanging up after >$2k.
3200 Sport Pistons (Deep Pockets, no valve interference) 10:1
Moly Rings
Coated rod bearings
360* oil groove cut main bearings
Rally camshaft w/ associated springs
Crank shaft seal spacer

[CorvallisBMW]

Wow, this is going to be one cool engine!

[BimmerE30]

whats a good aftermarket clutch to use? I am doing a similar stroker right now.. 3.1L with high flow head, 272 cam.... etc. I was going to use my stock clutch because I heard it would hold up.... but I would rather be safe with a beefier setup in there.

[z31maniac]

Awesome, you are building nearly the exact motor that I want to eventually build.

Only I want to use his custom intake manifold and do his 11:1 compression pistons.

Although I will say I find funny that you are going to drop THOUSANDS on the motor but are trying to cheap out on a clutch. He will also tell you that the medium case diff will have no problem handling the amount of power that you are going to put through it, unless its just junk to begin with.

[CorvallisBMW]

Although I will say I find funny that you are going to drop THOUSANDS on the motor but are trying to cheap out on a clutch. He will also tell you that the medium case diff will have no problem handling the amount of power that you are going to put through it, unless its just junk to begin with.

Exactly. Don't skimp on the clutch. I'm sure there are bolt-on OEM clutches that are designed to handle more power if you are concernced with staying OEM....

[Justin B]

Forget about the clutch.

Anyway, about the motor. I spent most of yesterday pulling it out with the tranny. I have a list of things to buy before any of it goes back in though. Somehow we managed to destroy the CSB (it was fine), I need a guibo, the right side motor mount caught up and tore before I got smart and took the mount arms off, and a couple other small things.

But its out. When I get home from work today Im taking the transmission off it, getting it on the hoist again and hooking it up to an engine stand so I can begin cleaning all the parts and transferring them to the stock rebuilt one that's going in.