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I'm running a TCD stage 3 setup with a>w on my bone stock 533i at 10psi. Motor has apx 250k miles & still runs strong as hell! I may be rebuilding a b34 to stock specs. All things being equal, would a b34 easily make much more hp/torque than a b32? How much more or same?

The b34 is lower compression than the b32. I'm sure that has an effect.

My guess is the higher displacement will improve power despite the reduction in CR. The higher compression of the b32 is going to be offset by the requirement to retard combustion phasing to reduce knock more than that of the b34. My guess is that there will also be a slight improvement in boost threshold - ie target boost will be reached at a slightly lower engine speed with the b34 due to more mass flow through the turbine.

I've run about every combination possible and currently run a b32 out of a junkyard.. It came out of a 733, I threw on the manifolds and dropped it in, ran 12psi all season (spewing smoke the whole time) and I didn't do anything whatsoever. It was pretty tired so it came apart and I punched it to b34 specs. Had I been able to find decent oversized b32 pistons I would have left it alone. Thanks to a box of old b34's from Peter Florence, I picked the best of the litter and dropped them in. Aside from rings and bearings the thing's a true junkyard dog. Even with a rebuild I have less than $500 into the thing.

I flogged the living shit out of it last year for well over 1500 miles and it's the best motor I've had to date, bar none. The b32 cam works well. It comes on the pipe a little later than the b35, around 3k, but it'll hold it longer to around 5800. That's the range that I'm geared for so for me it is a much more flexible powerplant that others I've had. I do not notice any deficit of power because the whole package seems to work better.

I broke it in on the dyno at only 5psi and it did around 240 hp and around 285tq.. I ran most of the season between 8 and 12 I'd guess it was in the mid 300's, dunno, don't care.

FWIW, what's done more for this motor than anything is Peter Florence. Good tune makes a world of difference.

Bill in MN wrote:. Even with a rebuild I have less than $500 into the thing.

Did you deck the block and hone the cylinders?

Nebraska_e28 wrote:Did you deck the block and hone the cylinders?

The block got bored, decked etc. etc but I got a great deal on it. My machinist of over 10 years got out of the biz and did it as a favor before he left. The head checked out so new seals went on and that was that.

I wasn't sure if boring the thing out to 3.4 would cause issues since the bores are not as thick on the b32 block. No problems so far and I really don't expect any.

I've never decked an M20 block. Used four or five of them, never had a problem. At least one of them had been overheated in the past but its holding 21psi with a stock HG and studs like the rest of them.

I guess its worth checking the deck for flatness before starting a build but its probably not necessary to just deck it.

Bill in MN wrote: That's the range that I'm geared for so for me it is a much more flexible powerplant that others I've had..

What does your gearing look like? Final ratio? I'm doing the same with a 3.2, and currently looking to replace the open diff 3.25.

Thanks!

Aaron

akluminus wrote:
What does your gearing look like? Final ratio? I'm doing the same with a 3.2, and currently looking to replace the open diff 3.25.

Thanks!

Aaron

3.73 and 45/17 tires.

Bill in MN wrote:

akluminus wrote:
What does your gearing look like? Final ratio? I'm doing the same with a 3.2, and currently looking to replace the open diff 3.25.

Thanks!

Aaron

3.73 and 45/17 tires.

Cool, I was wondering about how short to go. Right now it feels like the 3.25 is too tall, but maybe under boost it'd be better.