High compression 2.8 stroker options

[CaffeinatedSoul]

I have been reading and reading yet everyou forum shows different configurations and different compression ratios.
I have a m50b25tu motor and a m52b28tu bottom end with these two motors I've heard the following. I have 93 octane (with 10% E) available in my area and want to use what I have to make the best combo. Has anyone run any of these set ups and what was the outcome?
M50tu block
M50tu pistons
M52b28 crank
B52b28 rods
Standard head gasket.

M50tu block
M50tu pistons
M52b28 crank
B52b28 rods
M52b28tu head gasket since it's thinner

M50tu block
M50tu pistons *must* shave pistons
M52b28 crank
B52b28 rods
Standard head gasket.

M50tu block
M52b28 pistons
M52b28 crank
B52b28 rods
M52b28tu head gasket since it's thiner.

[CaffeinatedSoul]

Anyone?

[digger]

you need to find data on

deck height of block (measure yours)
rod length (will be 135mm or 140mm most likely )
piston compression height
gasket thickness
head cc's

this way you can choose the combo that gives the best compromise of CR and squish by looking at how far above the block the piston sits by calculating approximatetly yourself

[CaffeinatedSoul]

Im a bit confused on how you measure deck height. Ive tried googling it and it looks like you measure the distance from TDC to deck? I have found that this combination uses these figures and this CR
M50tu block
M50tu pistons
M52b28 crank
B52b28 rods
Standard head gasket.

Deck height 209.95
Rod length 135
Piston compression height 32.55
Gasket is 1.75
Head 34cc
CR 11.0-11.6 Wide range but this is what ive seen people say. I just cant seem to figure out why people numbers are so wild on this build.
http://www.zealautowerks.com/advance...75,m,7200,1100,

[Northern]

Left: M52b28 84mm crank and 135mm rods, M50tu pistons.
Supposedly in the low 11.x:1

Right: stock M52B28 everything for comparison.

Not the most helpful post, but yay picture.

[CaffeinatedSoul]

That's what I've found as well. Just wanted to make sure my cr wasn't really really high mainly.

[digger]

if i understand you are taking the m50 shortening the rod by 5mm (140mm-135mm)then increasing the crank throw by 4.5mm (84/2-75/2)?

so the piston sits 0.5mm down the bore further? this will be 11.0:1 CR (increased from 10.5 originally)

i would use a thinner gasket or machine some off the block to achieve proper squish if possible

m50b25 piston

https://catalog.mahle-aftermarket.com/eu/modules/motorComponent/specs/detail.xhtml?filterId=966043

m52b28 pistons have shorter KH 31.82mm so would sit lower down the bore

https://catalog.mahle-aftermarket.com/eu/modules/motorComponent/specs/detail.xhtml;jsessionid=D5004DA52C4883545F28AD518F93FF87?filterId=967052

[CaffeinatedSoul]

You are correct. Of hand. Do you know how much I should have taken off the block?

[digger]

You are correct. Of hand. Do you know how much I should have taken off the block?

nominally it is 0.5mm off the block (or 0.5mm thinner gasket) to retain the same piston position with respect to the deck, as this is the delta change in stack height.

ideally for performance engine a piston to head clearance of 1mm to 1.25mm max is ideal to generate the best combustion.

if you took off 0.5mm then youre pistons would sit

42+135+32.55-210+0.5 = 0.05mm above deck and with 1.75mm gasket your clearance is 1.70mm which is same nominally as stock but could be improved with thinner gasket or decking more than 0.5mm. i'm not sure what the knock on issues are with decking the block alot on this engine but for sure you can get a MLS that would work

[CoreyZ]

I've got an M52 with all M52 internals and M50tu pistons.

Estimated compression was at 10.99:1. Piston sits 1.00mm higher.

Car has a Markert tune and runs great! Chirps third on 255 summer stickies. Not sure when it'll get dynod, probably sometime later this year when S52 cams go in.

[Wishno87]

Anyone else ever try this? I’m sure we all have b25tu pistons laying around.

[JadeFossa]

I also messed with this setup and continued to experiment with this. I ultimately built a version using the M50B25TU connecting rods and M54B30 in an aluminum M52B28. I posted about it here. Thanks for the inspiration to do this. It turned out great and runs like a basket of murder hornets!

https://www.r3vlimited.com/board/forum/e30-technical-forums/24v-engine-swaps/m50-52-s50-52/324648-cheap-11-5-cr-on-an-m52b28/page2?view=thread