engine and drivetrain Best engine block

[alexfl82]

Hi,

I'm going to build a new race engine, and I'm not sure which block ia the best.

Will be 91,5mm bore and 84mm crank.

I have two types of block.

-74' tii block.

-70' ti block. That has more reinforcements along the crank area.

And I'm also thinking in a E30 318 block, that I had read that is around 7kg lighter.

Can you make me some recommendations for select the best block to my rally car?

Thanks in advance.

Alex.

[kbmb02]

Data points:

 

If the early '70 block has a bolt-on oil dipstick base, it likely does not have grooves* cut into the main bearing journal saddles and caps. If that's the case, go with a later model block (*those grooves help with oiling of the journals, an improvement BMW made to the M10 design).

 

Check the internal gusseting of the 318 block 'between' the cylinder bores. 2.0 liter blocks have more gusseting than E21 1.8 blocks (which adds strength, and yes - more weight, too). Not sure about the gusseting of an E30 381 block. -KB

[alexfl82]

Yes, the early ti block I have has a bolt-on oil dipstick base.

I didn't check this grooves. I'll see.

Based on your advertises I think the best option will be go ahead with the 74' tii block.

[Preyupy]

At 91.5mm bore you really should have it sonic tested for cylinder wall thickness.  I have found a few blocks that had enough core shift while being cast that the wall was too thin at that bore.  Most should be fine but I would say 20% of the ones I have tested I choose not to use. 

[TobyB]

Oh, I missed the 91.5mm bore.

 

At that point, too, the E21 block probably doesn't have enough material, so the '74 

would be my first choice.

 

And if it doesn't pass the test, try the other!

 

t

[alexfl82]

That surprise me.

The piston seller told me that with this bore size I will have no problem, that this is a "secure" bore size.

I don't know any engine shop with sonic test.

That surprise me.

The piston seller told me that with this bore size I will have no problem, that this is a "secure" bore size.

I don't know any engine shop with sonic test.

[alexfl82]

Mmm... the tii block has 84 marked on the casting. The last owner before me told me that one of the engines he gave me with the car was purchased new in the BMW when the original broke. Possible this is the spare engine.

This 84' tii engine must to be as the original 70's tii casting or as the later 80's castings?

I was comparing through the side water holes with the earlier ti block and seems the space between cilynders is the same. About 2-3mm.

What do you think about?

[Tommy]

Hard to say about that -84. Old casting has more meat but less ribs. So if it looks same as the old ones...it must be same...if there's more ribs it's the new one.

 

That bore is on the limits. It should be safe as N/A for old block but for e30 318  it may be too much.

 

  Tommy

[alexfl82]

The 70' ti I have has ribs on both sides along the crankshaft area.

The 84' tii hasn't ribs on this zone. Plane.

[Conserv]

Mmm... the tii block has 84 marked on the casting. The last owner before me told me that one of the engines he gave me with the car was purchased new in the BMW when the original broke. Possible this is the spare engine.

This 84' tii engine must to be as the original 70's tii casting or as the later 80's castings?

I was comparing through the side water holes with the earlier ti block and seems the space between cilynders is the same. About 2-3mm.

What do you think about?

The blocks' "VIN bosses" may reveal the blocks' histories. If the VIN boss (the flat boss just above the starter nose) is stamped with a 7-digit VIN flanked on each side by a "+", then the block was likely installed in a car by the factory (photo below). Throwing that VIN into a decent de-coder should reveal something about the car it was installed in:

http://www.bmwclasicos.com/vin.php

If the VIN boss is absolutely blank, it was probably a new short block sold by BMW. If the VIN boss has some indecipherable combination of numbers and/or letters stamped into it, it was probably a factory remanufactured short or long block. And if has a home-made 7-digit stamp -- or etching, or something other than a stamp -- I'd suspect it was a new short block and the installer made an effort to mark it correctly.

The factory was casting E12 and E21 heads well into the '80s, so an '84 tii block sounds reasonable (I presume you're referring to a cast-in "84" towards the front of the block's exhaust side).

Maybe more determinative of the better block would be sonic testing -- as Byran suggests above -- rather than the presence or absence of ribs. Were ribs eliminated because the failures they were planned to prevent never happened? Or did BMW simply eliminate them because they could cast the blocks more cheaply without them? Or did they simply have a better casting process? Who knows? Who will ever know definitively?

Good luck: it sounds like a great project!

Best,

Steve

Edited November 26, 2014 by Conserv

[alexfl82]

No VIN in this place.

I think only has a "+".

Tomorrow I'll try to take some pics.

The best block for do a big bore engine, where exactly has more meat? In the cylinder wall?

Different space between cylinder walls compared to E30 blocks?

Why the E30 is called 'short block'? Can I measure somewhere for check it?

Thanks for all this help.

[Conserv]

No VIN in this place.

I think only has a "+".

Tomorrow I'll try to take some pics.

The best block for do a big bore engine, where exactly has more meat? In the cylinder wall?

Different space between cylinder walls compared to E30 blocks?

Why the E30 is called 'short block'? Can I measure somewhere for check it?

Thanks for all this help.

If no VIN, then it probably was a new replacement block, as a prior owner suggested. I don't know the differences between 2002 and e30 blocks.

A "short block" is a block with crankshaft, rods, pistons, etc. installed (it's basically everything below the head and above the oil pan).

Steve

[alexfl82]

The block is '84'. But is tii model, they purchased the engine complete.

And the block has the pipe for the kugelfischer oil return.

[AlanM]

I have a 318i block M10 out to 92mm with 84mm stroke in a built engine I bought.  I was surprised to find it was out to 92 when I removed the head to try and find some more Hp.  I had thought it was only 90.5 for some reason, and I also think 91.5 is the full limit of our blocks. I saw a 2002 block that had been taken out to 91.5, and after a teardown there was a discolouration on the wall of number 1 cylinder against the water pump.  Seems the wall was so thin that it could be pushed out of shape with your finger. It had a fair bit of blowby on this cylinder.

 

 I did find some more power though, up from 150 to 165 Hp at the wheels on the same dyno. The bores looked OK.

Edited December 1, 2014 by AlanM

[Conserv]

I have a 318i block M10 out to 92mm with 84mm stroke in a built engine I bought.  I was surprised to find it was out to 92 when I removed the head to try and find some more Hp.  I had thought it was only 90.5 for some reason, and I also think 91.5 is the full limit of our blocks. I saw a 2002 block that had been taken out to 91.5, and after a teardown there was a discolouration on the wall of number 1 cylinder against the water pump.  Seems the wall was so thin that it could be pushed out of shape with your finger. It had a fair bit of blowby on this cylinder.

 

 I did find some more power though, up from 150 to 165 Hp at the wheels on the same dyno. The bores looked OK.

Good information!

Steve