m10b20 block with m10b18 head?

[MikeM10]

would these swap right over or not? the m10b20 was carburated as far as i know and i was wondeing if the Ljetronic in the '85 would affect it.

[Hey_You]

Blocks are the same for the most part, I have a b20 block ready to put my b18 head on it. My only concern so far, is if the piano pistons will work without modification, or if I will have to clearance the head for them to work. And...the passenger side motor mount locations are different, so it won't swap right over, it will have to have a little custom work if going into a 318i. But, if your block is okay, you can swap the 2.0l crank/pistons into your 1.8l block as bore is the same between the two, only stroke is increased with the crank/piston combo. From what I have read, 2.0 block (with normal flat pistons) + 318i head will give you a 8.0:1 compression ration which is perfect for boost.
Other differences: Oil pump pickup is different, will have to swap that over as well as the oil pans from the 318i, and the timing chain on the old b20's is a double row chain, single row on the 318i. Not sure if its possible to incorporate the double chain for the 318i head.

[SkiFree]

Other differences: Oil pump pickup is different, will have to swap that over as well as the oil pans from the 318i, and the timing chain on the old b20's is a double row chain, single row on the 318i. Not sure if its possible to incorporate the double chain for the 318i head.

I would actually change the crank nose on the 2002 crank to a single row crank sprocket. Most of the vintage 2002 racers do this as it's less friction loss and reciprocating weight.

[Hey_You]

Thanks for the input. I think I will just do that instead of sourcing up a new cam gear since i can take the single row off my 1.8

[Hey_You]

I will be playing with some clay tonight, and taking some pictures to see if there is any clearance issues between the b20 block (with piano pistons) and b18 head (318i head specifically). Will post up here later tonight after my finding.
Edit: Sadly, I forgot that I need a nut on the crank to rotate the assembly. Pulling my engine/trans tomorrow during my lunch (just sitting on the mounts, everything else is already disconnected) and will snag my crank nut to check. But so far so good, at TDC there is no clearance issues as the head is sitting flush on the block

[MikeM10]

nice. that doesnt sound too bad. now you said the compression would be pretty low, i dont have plans to boost it anytime soon, maybe in the future. so how would it drive NA with low compression? does it have a big effect? Keep me updated on your project hey you. it looks like you got a good project going!

[Hey_You]

Yeah, it's lower compression with the standard flat top pistons. Have you ever driven a non-turbo Volvo from the 80's? That's a perfect example of a low compression engine. You won't notice it too much, but there will be some power missing with the low compression engine. Should inspire you to boost it sooner!
On another note, I brought home some parts to check things for the b20 block w/piano pistons mating with the 318i head.
Boom, TDC with the baby grands sticking above the deck.

Head set on, TDC as well.


I was able to turn it by hand (with ratchet) and did not feel any interference. Just to make sure, I rotated it SEVERAL times.
Then I got bored, and sat some items on to see what it'll look like.

[Smelser]

Just curious about the oil pan, that looks to be a normal one peice pan. the bulkier 2 peice is sitting on the ground. Is this an easy switch to make? whats the differance in the blocks for them?

[Hey_You]

There is no difference. I just haven't taken the oil pickup from the 318i block and put it into the 2002 block yet. The pickup that's in it won't allow me to put the pan on, so I need to switch it over. I have a spare upper and lower so it won't be long before those are put on. But the bolt pattern is the same.

[Jaxx_]

tyvm for doing this. I'm all for more M10 information.

[Hey_You]

No Problem! I wanted to document this as I have not found a definitive answer online whether this setup would work. So far, so good. I am planning on double valve springs, mixed with a 292 cam, so more checking will be in the future. I will for sure be using clay for that, as I have yet redone my head/valves yet. Nothing other than stock sized aftermarket valves, cam, and springs will be changed from original format. I won't be doing anything fancy with my head as far as port/polish/larger valves. I'm hoping it will wake up the engine a little. Something to be happy with for the time being.

[SkiFree]

A lot of the M10 knowledge resides in the ageing brains of people not accustomed to online forums. If you are interested in talking to some good resources just PM me.

[Hey_You]

So I started on trying to find a way to make my mounts work, this is what I am coming up with, I doubt I will run a/c, so I don't need the bracket that usually goes in front (will have to make sure nothing else bolts to it). I'm trying to figure out how thick of a steel plate I will need (was thinking something around 1/4" thick). Haven't looked into the other end of the arm yet, may need to make an adapter plate to go to the motor mount as well depending on how much the adapter plate relocates things.
Mounting spots on b20 block

My Idea

With the mount sitting where it's supposed to be

[SA E30]

I hear you can use an S14b23 crank, m10 rods and m30 pistons to make a 2.2lt... Just not sure how true it is, and what CR it gives

[Hey_You]

m30 pistons are the same as m10 pistons or so I hear. I have heard the same thing as far as making a 2.2L stroker. Good'N'Tight, I believe, used the s14 crank in his m10. Haven't looked at prices for the s14 crank, but I'm pretty sure it would cost as much as my shortblock I picked up.