M20B28 Stroker

[MikeM20]

Hi guys, my M20B28 build is in progress and I've my first problem, sorry for my english, i got to try to be understood

My Stuff:
m20b25 block, m52b28 crankshaft, 9.7 pistons with skirt ablation, OEM 1.75mm head gasket.

The problem is when i measure the valves openning when piston on TDC is not enought only 5.4 & 4.2mm for exaust and intake.
The B28 strocker already know this problem and what the best solution? put a thicker gasket ? i don't want to lost to much VR with a big one but i want my B28 running
Thanks for reading.

[gromgsxr]

i was under the impression that the stack hight with the crank throw the shorter 130mm rod with the b25 piston actually put the piston 0.5mm lower down the bore than a stock m20b25.

[reggid]

Mike,

firstly what cam are you going to run?

secondly are those measurements of 5.4mm and 4.2mm clearance between the valve and piston at TDC?

[MikeM20]

For the moment i don't know wich cams i'm gonna use, all need to be clear in clearance and measurements before ordering camshaft.

For the measurement i've done, it's from the top of the head, by the tail of the valve and the top of the guide. First when valve closed and after valve open in contact with piston at TDC, i do the Subtraction and i found my measurements.

[reggid]

that seems pretty normal, a stock cam when setup with clearance is slightly less than 1mm lift at TDC on both valves. so this would have plenty of clearance. even something like a schrick 288 looks like it would probably fit though this may not be the best choice for what you want.

obviously you need to check with clay with final assembly as the closest point is not at TDC its at just after TDC on inlet (valve chases piston down) and just before TDC on exhaust (piston chases valve up)

[MikeM20]

I don't know why i was thinking the Max lift is in TDC, Thanks for the explaination and forget my question

[reggid]

I don't know why i was thinking the Max lift is in TDC, Thanks for the explaination and forget my question

max valve lift is usually between 105 and 114 ATDC by this time the piston is about 55mm or more down the hole.

between TDC and 20* ATDC is most likely area for inlet valve collision

[MikeM20]

Now i need to find the correct camshaft.

Thanks reggid

[reggid]

what is the engine for Street or track?

[MikeM20]

Principaly street but sometimes on tracks
What do you think about a 284 dbillas ?

[reggid]

enem Z45, schrick 284/272, dbilas 284,

[MikeM20]

Asymmetrical camshaft is more for turbo right ? in my case dbillas 284 or catcams 285 may the better choice for my use.
Never ear about enem z45 but thanks for all your answers

[reggid]

id use schrick 284/272 (works well for NA engine) over the catcams. not seen anyone use the dbilas or ENEM. i like the specs on the ENEM

[HairyScreech]

id use schrick 284/272 (works well for NA engine) over the catcams. not seen anyone use the dbilas or ENEM. i like the specs on the ENEM

Your right, those ENEM profile do look interesting, would be nice to see a cam card or the ramp ratio of those to get some idea of the overall profile and accelerations.

[reggid]

i like it because the LSA is tighter at 108 than other manufacturers with the same sort of duration and the duration appears a little milder and its not a split duration like the Schrick. This is a similar philosophy to what Alpina did with their cam

[HairyScreech]

Yes, agreed, The LSA on some of the aftermarket cams seems very wide, these heads need lift more than duration and the wide LSAs just push the power up the rpm range where most M20s are just running out of steam.

The 264/264 108LSA 11.7mm lift cam seems like a really good idea for a daily/livable engine.
My only concern would be the valve acceleration associated with high lift+short duration.

[reggid]

Yes, agreed, The LSA on some of the aftermarket cams seems very wide, these heads need lift more than duration and the wide LSAs just push the power up the rpm range where most M20s are just running out of steam.

The 264/264 108LSA 11.7mm lift cam seems like a really good idea for a daily/livable engine.
My only concern would be the valve acceleration associated with high lift+short duration.

with good springs (new rockers of course) it wouldnt be hard to make it live, its not pushing the envelope IMO compared to other engines out there

the dbilas 276 has high lift and short duration. i measured one out for a friend who used one in a B28 it made very good torque. it actually had only 5degrees more duration at 1mm yet lifted to 11.7mm. The LSA was same as stock.

with a little more duration and 4 degrees tighter it would be pretty good

[HairyScreech]

It might be worth asking ENEM if they can grind the 11.7mm lift on the 280 duration cam with a touch tighter LSA.

It might not me too tricky, certainly the tighter LSA is possible, the extra lift might be more difficult though.

As the m20 is a 2v it's got large valves, which obviously means lots of lift to get the L/D right.
0.3L/D is 12.6 for the stock valve! The 10.3mm lift of the stock cam leave so much available even with a stock head.

[reggid]

It might be worth asking ENEM if they can grind the 11.7mm lift on the 280 duration cam with a touch tighter LSA.

It might not me too tricky, certainly the tighter LSA is possible, the extra lift might be more difficult though.

As the m20 is a 2v it's got large valves, which obviously means lots of lift to get the L/D right.
0.3L/D is 12.6 for the stock valve! The 10.3mm lift of the stock cam leave so much available even with a stock head.

i asked them for duration at 1.0mm but they were less than helpful!

stock head backs up a bit at high lifts so it might not pay off to go to wild without some basic touchup work to the head

[MikeM20]

Hi all !
After some lot of work on the chassis for eliminate corrosion, i'm back with my b28 ! and with another problem too !

When i tight the rods on crankshaft the engine is impossible to turn and i have no axial clearance on some rods
I think the rods bearing (oemM20b25, 45mm) installed are not in accordance with the M52 crank.
The m52 rod bearing is normaly the same for M20b20-25 rods no ?

The rod bearing installed on m52 engine when i disassemble was pn: 1284849/850 and i don't understand because on bmw fans that's for E28 525e !

I've made some measurements on width rod bearing and i found 15.342mm on my oem m20b25 and 15.283mm with the bearing installed on the m52b28.

What do you think ?

[MikeM20]

Today I disassembled the engine, to know what's going on inside !

The good thing is now I know why the engine was blocked, the bad is now I have more questions !

I found some rods bearings without the grey coating, with a shinny area, they was new so, I don't understand why just by hand turning the crankshaft I have this result on my bearings !
After I took off rods and pistons and number 6 was totaly seized on the axle.

The few questions I have right now:
I should replace the bearings, the pistons axles?

Thanks

[reggid]

p/n for standard size rod shells are same on m20, m52,m50, US S50/S52 etc

you really should be measuring the crankpins and bore size of assembled and torqued rod to get clearances and right bearings, plus plastigauge etc. if you dont know how there are professionals for this as get it wrong and its a catastrophe in the making

[MikeM20]

Ok today i take my time for know exactly what I have !
I have done my crankshaft measurments and I found 44.98 & 59.98, so this is standard size right ?

For my rods bearing attrition, it's probaly some bullshit i've done
During the rods balancing i mix rods and rods end and now without bearings I found them not really flush, after a check I found numbers engraved on them, so my problem come from here right ? Shame on me !!
Now I put correct rods with right ends and everything's flush

Do you think I should replace my shinny rods bearings ?

Thanks

[HairyScreech]

Were those bearings put in dry?

[MikeM20]

No, with oil

[MikeM20]

Back few years later, but engine's running well !!
last week on dyno and i'm really happy for the results !!
But for the last step im starting to look Dbilas or RHD ITB, i dont know wich one are the best ...

So my conf is
2.8 engine 130 rods
11.4vr
299 cat cams aac
Dta s80
228.4 hp @6125
289.6Nm @ 5314

[reggid]

Back few years later, but engine's running well !!
last week on dyno and i'm really happy for the results !!
But for the last step im starting to look Dbilas or RHD ITB, i dont know wich one are the best ...

So my conf is
2.8 engine 130 rods
11.4vr
299 cat cams aac
Dta s80
228.4 hp @6125
289.6Nm @ 5314

RHD ITB are better by along way. Dbilas are rubbish except in the aesthetics department.

Can you post up a sheet i'm interested to see the torque curve with that cam

[MikeM20]

[MikeM20]

OK !
so im gonna search for an RHD !
Do you have any prices wit the forum ?

[reggid]

OK !
so im gonna search for an RHD !
Do you have any prices wit the forum ?

Sorry i dont understand what you mean regarding prices with the forum.

Get the the one with plenum not open stacks

https://racehead.com.au/product/bmw-m20-itb-kit-e30/

its very affordable for a ITB kit as its basically a complete kit (not something where you need a bunch of options ($$$) and do linkages, fuel system and idle control from scratch etc, but it is not cheap in an absolute sense per se. The $$$ per hp is hard to beat for a bolt on item though.

thanks for the dyno sheet. What exhaust setup are you running?

[MikeM20]

what you mean regarding prices with the forum -- Yes

Get the the one with plenum not open stacks -- but behind the plenum there open stacks right ?
"All kits are supplied with polished silver trumpets and polished carbon fiber Plenum/ Air-box. See our other listing if airbox is not required."
It's looks like this on the pictures

Gonna order the 42mm

Exhaust setup:
Hartge Manifold & scopion exausts

[reggid]

what you mean regarding prices with the forum -- Yes

Get the the one with plenum not open stacks -- but behind the plenum there open stacks right ?
"All kits are supplied with polished silver trumpets and polished carbon fiber Plenum/ Air-box. See our other listing if airbox is not required."
It's looks like this on the pictures

Gonna order the 42mm

Exhaust setup:
Hartge Manifold & scopion exausts

have not seen a GB on these forums for it

i just meant get the airbox as well, its the same except for the addition of the composite air box. When you add the air box the stacks are enclosed within the airbox and not considered open.

[MikeM20]

Hi guys,
I've replaced my camshaft for a 302° CatCams and i think my clearance is not enought between pistons and valves.
Engine rotating well by hand but when i look thouhgt the spark hole with a boroscope, it's look around 1mm to the closest point.
What should be the minimum clearance for that kind of M20 ?
Thx

[reggid]

Hi guys,
I've replaced my camshaft for a 302° CatCams and i think my clearance is not enought between pistons and valves.
Engine rotating well by hand but when i look thouhgt the spark hole with a boroscope, it's look around 1mm to the closest point.
What should be the minimum clearance for that kind of M20 ?
Thx

some catcams datasheets say

"distance between valve and piston 1.0mm (pref. 1.5mm). check 5-15° before TDC on exhaust, and after TDC on intake"

http://www.catcams.com/products/camshaf ... ge=english

[flybynite]

If you are down to around 1mm, I would be getting the plasticine out (or nicking it from the kids ) and check it properly.

Also make sure your valve springs are up to it. Schrick say that anything above their 288 must have upgraded valve springs.