2.7I stroker turbo

[foundation982]

I know I know search search search first!

I have searched and found likes a bits of information that have been helpful but I have a very specific situation.

I bought a 89 325i off craigslist automatic not running, Hauled it home it was a stuck fuel pump. Got it running pretty well, drove it around, it had a few intake leaks with surging idle. Oil pan started leaking oil and the valve cover was leaking, water pump was also leaking. All the belts were also on their last leg.

Engine has 160-170psi compression across all 6.

I also have a 87 5 speed ETA drivetrain from a car I parted out a few years ago.

I'm going to convert the 325i to a 5 speed. I almost have all the parts for it besides the driveshaft. Right now I pulled the 89 325i's motor and transmission, got rid of the slushbox and will tend to all the motors leaks as well as painting the block etc.

Here's the question I know everyone has asked in some shape or form but should I take my ETA crank and pistons and put them in the I engine? or the i head on the ETA block? I Still do not know if the ETA is in good shape.

Would that be a good setup for a small boost application? Planning on a small Garret T3 wanting to get around 250 300 hp and not really push the car to its limits.

Or would I just be better off running a small turbo on the I motor and not even bother with making a hybrid ETA i?

And no I do not want to swap in a m50.

[varg]

I think that you're better off turbocharging a stock M20B25 than an M20B27 with an B25 head. B27 pistons don't match the B25 combustion chamber well, so you wind up with more capacity but a lower compression ratio and worse quench so the engine is less efficient overall. A proper 2.7 stroker with B25 pistons isn't hard to do and avoids these issues though. When you take an engine apart to that extent it should be rebuilt and some machine work is mandatory though, so it depends on your budget.

But, change your timing belt right away if you haven't, if the engine is leaking and the belts were in bad shape the timing belt is probably a time bomb.

[foundation982]

I think that you're better off turbocharging a stock M20B25 than an M20B27 with an B25 head. B27 pistons don't match the B25 combustion chamber well, so you wind up with more capacity but a lower compression ratio and worse quench so the engine is less efficient overall. A proper 2.7 stroker with B25 pistons isn't hard to do and avoids these issues though. When you take an engine apart to that extent it should be rebuilt and some machine work is mandatory though, so it depends on your budget.

But, change your timing belt right away if you haven't, if the engine is leaking and the belts were in bad shape the timing belt is probably a time bomb.

Thanks for the insight, The engine I believe has very little wear. What machine work would you insist on? I'll be doing a leak down test on it to more accurately detect its health and to ensure everything is sealing. Timing belt is obviously a must, This one is terrifyingly worn, its starting to shred on the front side and has cracking everywhere. I wouldn't be surprised if its the original.

won't the B25 pistons hit the head with the eta crank? What machine work gets the b25 pistons to work? I wouldn't mind honing the cylinders I also have access to some good machine shops.

I've owned several of these cars but haven't got far out of the realm in the modifying world. Finally got a rough cheap one I don't mind beating on a bit.

[digger]

Either appear capable to meet your goals so use the one in best condition

[varg]

Thanks for the insight, The engine I believe has very little wear. What machine work would you insist on? I'll be doing a leak down test on it to more accurately detect its health and to ensure everything is sealing. Timing belt is obviously a must, This one is terrifyingly worn, its starting to shred on the front side and has cracking everywhere. I wouldn't be surprised if its the original.

won't the B25 pistons hit the head with the eta crank? What machine work gets the b25 pistons to work? I wouldn't mind honing the cylinders I also have access to some good machine shops.

I've owned several of these cars but haven't got far out of the realm in the modifying world. Finally got a rough cheap one I don't mind beating on a bit.

If an engine is being rebuilt, may as well at the very least surface the block and hone the bores (if necessary). With B25 pistons and a B27 crank the pistons are actually too low. The solutions are to take material off of the block or get custom pistons with the same type of combustion chamber design as stock pistons. SuperETA pistons will also do the trick. In my opinion, neither of these options are necessary with modest power goals. A stock B25 with studs and an MLS gasket/o-rings will easily make the kind of power you're talking about fairly reliably.