S50B32 Clone

[ForcedFirebird]

To add, if your pistons are 1.2mm below the block deck, then you apply the 1.7mm head gasket, your pistons will theoretically be 2.9mm from the head surface.

When building engines, I aim for .95mm.

To test, put used head gasket, torque with used head bolts, attach cam drive, rotate engine, remove head, measure clay/solder.

For example, when building "budget" m20 2.7l, I use 81mm crank, 135mm rods, stock m20b25 pistons, then shave the block 2mm to get the compression height back.

I suggest your pistons be higher (or block deck lower).

[TobyB]

All the power comes from the head.

unless the bottom end lets it all leak out before it gets to the crank!

heh.

t
if one part doesn't do its ting, de whole ting doesn't do its ting.

[ForcedFirebird]

unless the bottom end lets it all leak out before it gets to the crank!

heh.

t
if one part doesn't do its ting, de whole ting doesn't do its ting.

It would have to be pretty bad...like maybe a hole in the piston, or lacking rings??? lol.

I had a car here at work a few years ago (EDIT: EIGHT + YEARS ALREADY WOW!!!). Compression was at 145psi, 200k mile 2.5 bottom end, dyno'd at 145whp. Refreshed the head, +1mm valves, 272 cam, a little bowl/seat work on the machine, added ITB's with headers, dual 2" exhaust with x-pipe at 3m and that same crank case put down 170whp. Then I added a 2.8 bottom end and it went to 217whp. Long version here: https://www.r3vlimited.com/board/for...-rotating-assy

[digger]

RB26 guys make >1000hp with around 4-5mm wall thickness so it’s plenty unless you get a rare dud or something goes wrong with the “tune” . MM do 87mm on the m20 turd

the engine needs more camshaft

[ForcedFirebird]

RB26 guys make >1000hp with around 4-5mm wall thickness so it’s plenty unless you get a rare dud or something goes wrong with the “tune” . MM do 87mm on the m20 turd

the engine needs more camshaft

Sure, but if the m52 block is thicker, might as well start there. After that block cracked on me, I am now leery about boring the m50 .100". I'd rather play it safe and not worry about the <200cc (84.5mm-87mm is 181cc difference). Use the effort for head work instead IMO.

[esoes06]

Has nothing to do with fuel. The piston to head clearance is to compensate for rod stretch at high RPM, and to accelerate the fuel mixture towards the spark plug.

http://www.theoldone.com/archive/quench-area.htm

https://www.enginelabs.com/engine-tech/quench-unlocking-performance-squished-between-the-piston-and-head/

I don't agree with you. It is directly related to the fuel. High compression engine = high octane fuel.

[esoes06]

Just went to the engine room and took some quick measurements. Measured several through the water jacket with a caliper, this is not a sonic test.

s50us 86mm bore 6.6mm avg wall thickness.
m50nv 84mm bore 6.7mm avg wall thickness
m52 84mm bore 7.4mm avg

Don't have an s52, and didn't check an m50tu

Cylinder that cracked is 5.8mm on that wall.

M52b28 block I'm going to try the 86mm piston. Sleeves

[digger]

Sure, but if the m52 block is thicker, might as well start there. After that block cracked on me, I am now leery about boring the m50 .100". I'd rather play it safe and not worry about the <200cc (84.5mm-87mm is 181cc difference). Use the effort for head work instead IMO.

Not sure what's available in Turkey but M52 may be alloy like here and he wont have S50/52 US unless they are same as m52 iron

[digger]

I don't agree with you. It is directly related to the fuel. High compression engine = high octane fuel.

running the piston to head tighter increases the CR which is worse for knock, except that the additional squish velocity offsets this as to squeezes the end gas towards the plug reducing knock sensitivity. I would run the squish correct and if you need to lower the CR use other means. Its only about 1cc

[ForcedFirebird]

M52b28 block I'm going to try the 86mm piston. Sleeves

If you are happy with 86mm, use the m50 block.

Not sure what's available in Turkey but M52 may be alloy like here and he wont have S50/52 US unless they are same as m52 iron

I always forget that. Here in US, the m52tu is aluminum (m54 construction), the regular m52, that uses the single VANOS, is iron.

I don't agree with you. It is directly related to the fuel. High compression engine = high octane fuel.

High compression is fine.

If distance from head to piston is ideal, you will have LESS knock. I have used 11.5:1 pistons and 93 octane, 3.2l 24v, 1mm squish.

[DesertBMW]

My goal is +300hp
What's your opinion.

After all these years being in BMW community , I have never seen anybody make +300hp on naturally aspirated S52 with any sort of bolt on modification even less with M50 block. But I am sure you just joined the forum two years ago and you will figure it out.

[ForcedFirebird]

After all these years being in BMW community , I have never seen anybody make +300hp on naturally aspirated S52 with any sort of bolt on modification even less with M50 block. But I am sure you just joined the forum two years ago and you will figure it out.

Not as far fetched as you think. Every stock long block s52 at the race track in the GT NASA series is making 250+ whp. m50 manifold, headers and nice exhaust. I just pulled one couple months agop since it started dyno-ing 243.

One of my clients running in SCCA EP series is making 208whp with an m20b25 12.5:1 and my head work, stock intake manifold, 288 camshaft. He's been competing with it for over 4yr, spinning it to 8500rpm. (VIDEO LINK)

Guys at Rabid Race are making 270whp with stock s52's and s54 throttles.

If you want to see what guys are doing to make reliable power, go out to the racing circuit. I've seen some crazy stuff guys do to fit in rule limits. Saw a de-stroked s50b32 to fit in the 2.8 category.

[digger]

We are also taking about 300 flywheel hp,

[ForcedFirebird]

I knew I saw someone break 300. He was making 279whp before the ITB and megasquirt.

https://www.bimmerforums.com/forum/s...5#post29785685

[esoes06]

After all these years being in BMW community , I have never seen anybody make +300hp on naturally aspirated S52 with any sort of bolt on modification even less with M50 block. But I am sure you just joined the forum two years ago and you will figure it out.

I have been working at BMW Mechanics for 25 years. The Camshaft is precise at +350hp with 272 or 284.