M20B28 ITB stroker build - H&B 327s head - 195whp

[E30budget]

Writing for the first time in a while here to share my M20 build. In partnership with VAC Motorsport, CP Carillo, Russ at Steves Machine Shop, and Son of Cobra.

The concoction of parts used on this M20 boosts the power to 195whp and 200ftlbs at the rear tires in my 1986 325es. Redline is set to 6600 due to power falling off up to 7k. This engine is tuned using a Kdata MS2 DME with a modified factory harness. Dyno tuned on 3 dyno's (multiple tuners).

The engine is a 2.8L, maybe slightly over.

The top end:
Hard & Beck 731 head originally from 327s - Custom mahined combustion chamber
+2mm intake/exhaust valves
Five angle valve job
Fully ported cold side
885 dual valve springs
Febi rockers
Bimmerheads 284 camshaft
Bimmerheads cam cover

The bottom end:
M20B27 block cleaned & machined
M20B27 crankshaft knife edge
Overbored to 86mm
S52 rods resized
Custom CP domed 10.25:1 pistons 3D modeled from head scan
Rotating assembly balancing
shimed and machined oil pressure relief valve
AAF oil pan baffle
Lightened flywheel

Intake:
RHD ITB 40mm kit sans trumpets and spacers
Custom carbon vaccum rail
GefahreneWelt billet 40mm adapters for filters
Custom fiberglass trumpets

Exhaust:
Vintage mild steel Super Sprint style headers - long tube - cerakoted
Custom 2.5" Y pipe
Custom stainless 2.5" single exhaust - no resonator or cat
Custom magnaflow muffler with fabricated vintage Ansa Maserati baffled tips


We managed to reduce repricoating mass by 15% - paired with a hogged out SMF the engine spins as if it doesnt have the weight of the pistons and rods. The engine spins up very quickly.

The engine now has 17k miles on it in six months!

Currently the engine is receiving a full A/C Solutions kit, as well as adding a Bosch 2 post ICV to assist with idle for A/C. I also plan to switch to the AAF header system to eliminate some rattles caused by the Y-pipe slip fit.


IMG_2850 by Robert Mosca, on Flickr

[AWDBOB]

Great results- do you have photos of the pistons? I did a similar cylinder head build, but with a 3.1L. Curious how your pistons turned out.

[E30budget]

Great results- do you have photos of the pistons? I did a similar cylinder head build, but with a 3.1L. Curious how your pistons turned out.

I have so many photos to add. I spent maybe 2 hours trying to include them in this post. No wonder no one comes on r3v anymore lol. I gave up and posted it with no photos. I’ll try again tonight.

[AWDBOB]

I have so many photos to add. I spent maybe 2 hours trying to include them in this post. No wonder no one comes on r3v anymore lol. I gave up and posted it with no photos. I’ll try again tonight.

That is so frustrating- I host my photos on Flickr- if you have less than 1000 public images you want to host it's free. May be a good option?

You just copy the Flickr BBCode and paste on here and it works like a charm.

If you don't want to copy/paste each one since you've already spent a ton of time trying, you can make a public Flickr album and share the album link for us to click through on our own.

[zaq123]

it's not that complicated. I can see some pictures in your profile under Media. You just load them and insert into your post. Works fine from me
Here is my full restoration plus 2.8 Mahle piston strocker, ITBS and Haltech Nesus S2 I need to make a post about sometime soon.

[TobyB]

mmmmm ...needs moar cammmmmmm....

Nice!

t

[zaq123]

yes we need pics :)

click image, upload, pick the file on your device, send to server. Once uploaded you can select the size etc

[88Sedan]

Do 731 heads start with smaller valves than 885? I ask because I've only heard of +1mm valves on m20s before and I think that's only intake unless I'm mistaken.

I also am wondering head flow numbers if it was flow tested, and I am dying to see the torque curve because it's probably awesome.

For myself it does take forever to upload just a few pictures. I prefer forums 10000% over other formats for car threads. Man I miss free limitless photo hosting. So many old threads with unviewable/removed photos.

Lastly did Carillo save the piston information for others to use? It would be a great resource for other peoples' stroker builds if there was some reference info to go off...then again I'm unsure if the 731's combustion chamber is different than 885's anyway.

[digger]

Do 731 heads start with smaller valves than 885? I ask because I've only heard of +1mm valves on m20s before and I think that's only intake unless I'm mistaken.

I also am wondering head flow numbers if it was flow tested, and I am dying to see the torque curve because it's probably awesome.

For myself it does take forever to upload just a few pictures. I prefer forums 10000% over other formats for car threads. Man I miss free limitless photo hosting. So many old threads with unviewable/removed photos.

Lastly did Carillo save the piston information for others to use? It would be a great resource for other peoples' stroker builds if there was some reference info to go off...then again I'm unsure if the 731's combustion chamber is different than 885's anyway.

731 have 2mm smaller valves (40/34) so going +2mm takes it to 885 sizes (42/36).

i am surprised the 731 needed a dome, normally a 731 (same combustion chamber as 200) engine can use flat tops especially at around 10:1. In any case unlikely these pistons will be matched to a 885

[E30budget]

Do 731 heads start with smaller valves than 885? I ask because I've only heard of +1mm valves on m20s before and I think that's only intake unless I'm mistaken.

I also am wondering head flow numbers if it was flow tested, and I am dying to see the torque curve because it's probably awesome.

For myself it does take forever to upload just a few pictures. I prefer forums 10000% over other formats for car threads. Man I miss free limitless photo hosting. So many old threads with unviewable/removed photos.

Lastly did Carillo save the piston information for others to use? It would be a great resource for other peoples' stroker builds if there was some reference info to go off...then again I'm unsure if the 731's combustion chamber is different than 885's anyway.

Correct! So it has 885 sized valves. Should have specified as it’s misleading. No flow testing on the head, sadly. I had to throw this engine together immediately after getting back from the machine shop and install it. Engine home at midnight, finished assembly and install at 6am lol.

still working on photos!

and I believe we do still have the data. I have all my paperwork from CP. I believe they will work with an 885 head, but keep in mind I am using a 5mm longer rod than the ETA rods. 135mm iirc.

[E30budget]

731 have 2mm smaller valves (40/34) so going +2mm takes it to 885 sizes (42/36).

i am surprised the 731 needed a dome, normally a 731 (same combustion chamber as 200) engine can use flat tops especially at around 10:1. In any case unlikely these pistons will be matched to a 885

You are right! These are same size as 885 now. As for the machined combustion chamber, that was part of the hardy and Beck 327s package. So all we did was the big valves, springs, cam, and normal decking. It was already ported as well!

my original plan was to slap a stock 731 head on my eta bottom end with a cam, and the same intake and exhaust. However, when I bought this head I didn’t know it heavily machined until I owned it lol. Later we found out about the H&B 327s and the head came out of Berkeley so it adds up!

if I ever move out of CA to somewhere with better fuel I will put an 885 head on it with a more closed off combustion chamber thus raising the compression. Unsure if I would see interference but I don’t think so.

[E30budget]

Welp, for some weird reason I cannot add the photos to the original post in any format. But I can comment them in down here. Enjoy!

[varg]

Got any videos? I want to hear it.

[808ETA]

Awesome pics! How much does your flywheel weight now? How does it drive lightened?

[AWDBOB]

Maaaan that’s a good looking setup!

Did you use the 325e water pump pulley to overdrive it?