Cirrusly Blue - The Daily Driver E30... now SUPER powered

[AWDBOB]

Shouldve bought it

I wouldve jumped at the chance if that was local. Theres a guy here who was selling all those parts, (probably the same guy) and wanted $300 or something. Shipping all those parts was the killer, so I passed.

Now Im "forced" to find a bottom end to tear down and a M52 (84mm) crank. Im tempted to do something bigger, like a M54/ S50 (89.6mm) crank or even a S52 crank, but those last two force me to get custom pistons. At least I currently can go with the stock 84mm pistons if I want to.

I still have five cars here and two back east (and Linda still isn't drivable) so for my sanity I opted to not put that pressure on myself....for now haha.

Also, check out Top End Performance- they are a JE dealer that sells stroker pistons with the 885 dome shape implemented. With JE it's highly recommended to get them coated which they offer for a fee.

Takes all the guess work out of custom pistons.

https://www.racetep.com/manufacturer/engine-parts-and-performance/pistons-and-rings/jepistons/bmw/m20/je-custom-6cyl-dome-top-pistons-50245.html

Also also, local to me is Zionsville Autosport- Dwight has been building M20s for a long time, and he has been doing quite a few builds lately using a full M54b30 rotating assembly in an M20 (familiarly used as a drop in for an M52). He shaves the M54 piston tops down and coats them- the rest of it drops in (obvious downside is not matching dome shape).

There are 2-3 locals running this setup and all of their cars run very strong.

[2mAn]

I support this! A local guy had a late m20b25 shortblock, crank spacer, and M52b28 crank, windage tray and engine stand for sale for $250 last week. I had to fight myself hard not to buy it.

Shouldve bought it

I wouldve jumped at the chance if that was local. Theres a guy here who was selling all those parts, (probably the same guy) and wanted $300 or something. Shipping all those parts was the killer, so I passed.

Now Im "forced" to find a bottom end to tear down and a M52 (84mm) crank. Im tempted to do something bigger, like a M54/ S50 (89.6mm) crank or even a S52 crank, but those last two force me to get custom pistons. At least I currently can go with the stock 84mm pistons if I want to.

[AWDBOB]

well... I ordered a new CPS to try and deal with a random issue that has popped up. more importantly I also bought the stroker crank spacer that ForcedFirebird made... and now it begins.

The neverending DD "im not modifying it much" project continues

I support this! A local guy had a late m20b25 shortblock, crank spacer, and M52b28 crank, windage tray and engine stand for sale for $250 last week. I had to fight myself hard not to buy it.

[2mAn]

well... I ordered a new CPS to try and deal with a random issue that has popped up. more importantly I also bought the stroker crank spacer that ForcedFirebird made... and now it begins.

The neverending DD "im not modifying it much" project continues

[AWDBOB]

You can't build a 2.8 with ETA parts by the way. Need the M52B28 crank ;)

I strongly considered those pistons, problem was I would be getting a whole 0.1L and 0.2:1 more compression for about $1k extra. If you're smart, the parts cost of my build really isn't that much. Not that it was very cheap overall, just all of the major expenses stay the same no matter what you build. $1200 pistons vs $100 pistons is.. well, $1100 extra. The only thing specific to the 2.8 really is turning down the crankshaft and shortening the piston skirts. Doing that was about $150 or so at a machine shop. But pretty easy to DIY if you have access to a lathe.

Though if you want the longer rods then the Mahle pistons are the way to go. I've always been curious about how my engine would've felt with 135mm rods vs 130mm. I'd imagine the motor would like revs a bit more... but not sure how much of that I would have really felt.



I strongly considered these as well. Very tempting, but my main issue with it was the materials the pistons are made from. Looks great on paper, especially if you're racing, but from what I hear those pistons like to burn oil a lot more when it's cold. The thermal properties are much different from the stock BMW pistons. I think the metric mechanic pistons or the Mahle 2.9 pistons are a much better bet.

All being said I don't think building an M20 would be the best bang for buck in very many situations. The main benefits are just having really cool, strong & unique motor that's still very E30-like, flying under the CA smog radar, and learning a ton of stuff along the way.

I agree with you, and I think everyone's situation is different. I didn't mean for my post to sound condescending towards your build, because I think your route was very logical given your situation (and your build is fantastic)!

My idea of piston cost differences in 2.8 (m52 crank/eta rods/i pistons) and 2.9 (m52 crank/m52 rods/IE pistons) was not based on used stock late 'I' pistons. I was using 84.5mm overbore stockers (~$600) as my guide, plus ~$1-200 for skirt shaving. Thus, taking the jump to the IE Pistons a bit more logical given those numbers (plus compression, plus fresh bore, plus better R/S, deeper valve reliefs, plus not having to shave the block). That's where I was coming from.

It seemed you had fantastic resources for building your motor which helps keep the cost down a lot, so if I were in your shoes I would've done the exact same thing! For most of us though it seems a bit more beneficial to go the other route.

In the end though, I'm sure the HP and cost difference is negligible between both setups. So the only difference in choosing your route is your satisfaction with what you've done at the end of the project :D.

And yes, I've used non-coated JEs in the past and they slap pretty bad, but throwing a thermal coating on there helps with that and also improves longevity and cooling (at a cost of course). I still agree though, in that the IE Mahles are a safer bet.

[2mAn]

All being said I don't think building an M20 would be the best bang for buck in very many situations. The main benefits are just having really cool, strong & unique motor that's still very E30-like, flying under the CA smog radar, and learning a ton of stuff along the way.

Ignoring the cost of all the different options, my main motivator is that building a proper 2.8L M20 with over 9.5:1 CR can get you most of the horsepower and in some cases more torque than a M52 itself, making it a 2.8L vs 2.8L apples to apples comparison. What you give up in peak power you gain in the highlighted stuff in Bens quote.

Also, Ive been annoying both digger and ForcedFirebird with PMs and I think this info digger typed up is worth pasting here for anyone else considering doing something along these lines.

The first thing to note is the stack height of the stock M20B25 is

= rod length + compression height + throw
= 135 + 34.2 + 75/2 = 206.7mm

ETA 81mm CRANK

If you want to use stock 84.5mm pistons with 81mm stroke you need to remove 2mm off the top of the deck.

206.7 – 81/2 – 34.2 – 130 = 2.00mm

You might also need to shave the skirts a bit. This used to be popular configuration in the UK but now most do the 84mm stroke as the cranks there are easier to fit than the US.

M52B28 84mm CRANK

If you want to use stock 84.5mm pistons with 81mm stroke you need to remove 0.5mm off the top of the deck use an oil seal spacer and machine the skirts and counterweights a lot so it is more involved than simply decking the block.

206.7 – 84/2 – 34.2 – 130 = 0.50mm

RM European also has good prices for OE pistons when I looked.

As far as the difference I think hp will be much the same (within 5 or so hp) but the eta will peak very slightly higher rpm but make less torque (5-10 numbers).

With all the effort for the 84 stroke you can see why some just bite the bullet and go for the $1300 mahle MS which has added advantage
- Slightly more CR
- Deeper valve reliefs
- 85mm bore
- Lower friction skirts

[betz]

I think a 2.8L M20 is great- but for the $ I'm not sure keeping standard bore and modifying old parts for clearance is the best bang for your buck.

I still think that building a 2.9L using an M52b28 crank, 135mm rods, and the IE Mahle Ultimate Street/Stroker 85mm pistons is the best way to go, because you gain stroke while keeping a longer rod (better R/S), and you're able to maintain max quench to match the 885. Takes out all of the guesswork, too. Honestly I'd bet all said and done you'll spend the same amount as putting together a 2.8 using ETA parts.

You can't build a 2.8 with ETA parts by the way. Need the M52B28 crank ;)

I strongly considered those pistons, problem was I would be getting a whole 0.1L and 0.2:1 more compression for about $1k extra. If you're smart, the parts cost of my build really isn't that much. Not that it was very cheap overall, just all of the major expenses stay the same no matter what you build. $1200 pistons vs $100 pistons is.. well, $1100 extra. The only thing specific to the 2.8 really is turning down the crankshaft and shortening the piston skirts. Doing that was about $150 or so at a machine shop. But pretty easy to DIY if you have access to a lathe.

Though if you want the longer rods then the Mahle pistons are the way to go. I've always been curious about how my engine would've felt with 135mm rods vs 130mm. I'd imagine the motor would like revs a bit more... but not sure how much of that I would have really felt.

If you want to get fancy, too, it's only a hair more expensive to use an S52 crank, 135mm rods and get custom JE pistons made (~$900) with matching 885 dome profile and have a 3+L.

I strongly considered these as well. Very tempting, but my main issue with it was the materials the pistons are made from. Looks great on paper, especially if you're racing, but from what I hear those pistons like to burn oil a lot more when it's cold. The thermal properties are much different from the stock BMW pistons. I think the metric mechanic pistons or the Mahle 2.9 pistons are a much better bet.

All being said I don't think building an M20 would be the best bang for buck in very many situations. The main benefits are just having really cool, strong & unique motor that's still very E30-like, flying under the CA smog radar, and learning a ton of stuff along the way.

[MR E30 325is]

Nice work!

[2mAn]

Awesome you got the G260 man, the manual transmission really makes these cars.

It really does. The Auto is fine, but the Manual is what makes the cars wonderful. Couple that with my awesome suspension and Im a damn happy E30 Owner.

lol those headrests were so wiggly. Stoked to see what else is in store here.

I thought I was relapsing

The old ones were so bad!.. The leather is tight and dry. Im not sure I can do anything with it yet. Its been removed from the headrests and I will be feeding it some fluids to see if I can soften it up a little to do something with it ;)

For now, Im hoping some old VW parts Ive been trying to sell will go away so I can start the next phase of the car.

[TheWipprSnappr]

Awesome you got the G260 man, the manual transmission really makes these cars.

qft

[MrBurgundy]

lol those headrests were so wiggly.

I thought I was relapsing

[wworm]

lol those headrests were so wiggly. Stoked to see what else is in store here.

[coldweatherblue]

Awesome you got the G260 man, the manual transmission really makes these cars.

[2mAn]

Cirrusly Blue - The Daily Driver E30

Niiiiice mang.

Thanks mang!

Headrests arrive today as well as another little thing I’ve been trying to get done.

Here’s the collection of stuff ready to go in


You can see how bad the old headrests are in the pic, and I’m not worried about the paint on my trunk to throw the stuff on so don’t even give me a hard time about it

Here’s another angle of the headrests


Tan must be the worst color to try and match because I believe these are both Natur leather but the colors aren’t a perfect match, I’ll live with it





The other thing I’ve been working on was the lower dash cover. It was cracked, and the PO had used some random, I don’t even know what it’s called, to hold it on. So I ordered new ones from eBay, they werent exactly what I thought but they work perfect



Here is the old cover, what you can’t see is on the right side of the steering column that whole piece is missing



This new one is almost perfect but has a similar defect...These old parts are becoming pretty damn brittle



And “new” one installed



That’s it for now

[spiDmang]

Niiiiice mang.