M50 bore tolerances?

[GunMetalGrey]

Ended up cutting my losses with the current m50 block and picked up a ready to swap m50 for $500. I am happy about it, especially because the swap will be done within the next two weeks then.

[GunMetalGrey]

Yeah, that's what I am starting to think. This gets fairly complicated and there is a lot of room for error.

[NbAmTwE]

Alright, so now that the rotating assembly makes sense, what about the head gasket? And will the stock m50b25tu head work?

I'd do an OEM HG w/ M50 2.99l (3.0)

The head will work just fine, however if you want more rev's like an s50/s52 - you should use their cams, lifters, valves and retainers.

In fact, now that you are looking to do all this work I'd just go buy an s52 and obd1 swap with what engine you have, then part whatever you have left over. People have tried the Frankenstein motors and they can be good if you get the parts cheap enough and you want boost due to larger cylinder walls. Otherwise S52s are pretty cheap now. ~$2300 will be enough to the engine and refresh it with obd1 and make more power. From then on s52 with shrick cams/3.5 maf/injectors/tune would be an even bigger improvement.

[GunMetalGrey]

thread bump time

[GunMetalGrey]

Alright, so now that the rotating assembly makes sense, what about the head gasket? And will the stock m50b25tu head work?

[Wanganstyle]

M54b30 is 3000cc. Thus the b30 designation
S52b32 is 3200cc. Thus the b32 designation

S52 uses 86.4mm pistons
M54b30 uses 83.98mm pistons

Both share rods, crankshaft. Piston bore makes up the additional 200cc

Quite a large difference in bore

Pick the head gasket that matches the piston bore.

[Wanganstyle]

So for a 3.2l I would use the m54b30 crank, m54m30 pistons(?) and m54b30 connecting rods? So a whole m54b30 rotating assembly?
I am pretty sure I need to overbore, and I might as well at this point.
Sorry again, it is easy to get lost in all of this, I really do appreciate all of the help.

M54b30 is 3000cc. Thus the b30 designation
S52b32 is 3200cc. Thus the b32 designation

S52 uses 86.4mm pistons
M54b30 uses 83.98mm pistons

Both share rods, crankshaft. Piston bore makes up the additional 200cc

Quite a large difference in bore.

[GunMetalGrey]

New question, headgasket!
I assume I have to run an s50 headgasket now? In order to get the gasket bore to match the cylinder bore. I feel as though I am talking to myself right now lol.

[GunMetalGrey]

Anyone? Just want to make sure before I start dropping cash.

[GunMetalGrey]

Ok, I think I got it,
I want s50/52 pistons (86mm)
M54b30 crank and connecting rods.
this will give me a 10.5:1 compression ratio
it will be 3.2(?) liter

[nando]

So for a 3.2l I would use the m54b30 crank, m54m30 pistons(?) and m54b30 connecting rods? So a whole m54b30 rotating assembly?
I am pretty sure I need to overbore, and I might as well at this point.
Sorry again, it is easy to get lost in all of this, I really do appreciate all of the help.

that would make a... 3 liter. you don't gain displacement by putting those parts in a different block. :p

for a 3.2 you need S52 pistons, the crank and rods are the same. M54B30 uses the same diameter pistons as an M50/M52 (84mm).

you can't gain displacement by changing the rods, either. the pistons, yes, but the difference will be pretty small and the advantages over changing the stroke aren't really there.

[GunMetalGrey]

I lost myself again...
So let's say I don't want to change my crank, different piston/rod combo?

[GunMetalGrey]

it would have compression like a M54b30 or s52b32; m54b30 is a small bore s52. Not very high compression, a S52b32 usa is a low performance engine with relatively low compression.

The 3.0 L crank has a longer stroke, that is why the same 84mm bore (or overbore) can equate a total of 3000cc instead of 2500cc.

If you desired 3200cc you could bore your m50 block to 86.4mm and use the s52 crank and rods in your block.

So for a 3.2l I would use the m54b30 crank, m54m30 pistons(?) and m54b30 connecting rods? So a whole m54b30 rotating assembly?
I am pretty sure I need to overbore, and I might as well at this point.
Sorry again, it is easy to get lost in all of this, I really do appreciate all of the help.

[GunMetalGrey]

So for the bore, hot tank, cleaning, honing, the whole nine yards it would cost about 150-175. They can also do all of the balancing and other small things like that. So I think it is time to go to a 3.0 ;)

[GunMetalGrey]

So just found out a friend of a friend builds race motors and does not charge much for macine work.
Because I do like the idea of a 3.0, if I can keep the cost at a reasonable amount.