Refresh M20B25 or build M20B27 SuperEta on a stand? (Details inside)

[phenryiv1]

I have an /89 325ic that is leaking like mad. Oil pools under the car form somewhere on the front of the motor and the whole thing is the weakest B25 I have ever driven. My '87 had a fresh B25 swap and was much quicker, and my '88 SuperEta with a 2.7i top end was leaps and bounds ahead.

I have several 885 "i" heads at my disposal, but the most likely scenario in either option will be to buy a rebuilt 885 "i" head and use that as the top end of either option below. I also have a complete 1988 SuperEta engine on-hand, though it is of unknown mileage and condition.

Either option will have the same work done to it- refreshed head, new WP, TB, accessory belts, oil pan gasket, thermostat, full gasket set, chipped DME, etc.

While this is a project car (and thus speed v. downtime is not the highest concern), my time is valuable and I have a million other things going, so there is something to be said for speed/ease of the final execution. I don't have ot get max performance out of my e30- this is a weekend cruiser and will never be a high-performing track car so the goal is to balance time/cost/ease with outcome/performance. I want a good return on my resource (time/money/sweat) investment.

Options:

1. Refresh the B25 in the car.

Pros:

• Single mass flywheel already in the car
• Won't have to remove the block, accessories, etc.
• Have a complete 2.5L top end to refresh damaged/missing parts

Cons:

• Unknown if that will stop the leak
• Not sure about the condition of the bottom end, overall
• Pain in the butt to replace the oil pan gasket, clean/paint the block, etc.

2. Build the 1988 2.7L bottom end/B25 885 top end and make a SuperEta 2.7i

Pros:

• Slightly more HP/Torque versus the B25
• Can be built on a stand
• Easier access to oil pan/gasket
• Easier to clean up and paint the block
• Have a complete 2.5L top end to source for parts, so no need to scavenge from the B25 that is in the car

Cons:

• Have to pull the B25 to install this
• Not sure about the condition of the bottom end
• Dual mass flywheel & clutch (unknown commodity, but I have 2 of each)

I may be missing some pros and cons, so feel free to add to my list. But with all of that said, any thoughts on the comparison between the 2? Would things change if I add a BimmerHeads regrind cam to the mix?


Thanks in advance.

[digger]

slightly more torque with SETA bottom end especially if you can hone and use new rings? or are you not looking to go that far into it?

[phenryiv1]

slightly more torque with SETA bottom end especially if you can hone and use new rings? or are you not looking to go that far into it?

I'd prefer to not get that far into it. For that cost I would start thinking M/S swap.

Having driven a strong SETA 2.7i (2 of them, actually) and a strong B25, I like both of them. I liked both 2.7i motors (both had dual mass flywheel setups) for pure powerband and torque, but the rebuild 2.5i was no slouch.

Maybe I am being a wussy about it but I am dreading pulling the motor to swap blocks. At the same time, I am not all that confident in the current clutch and block (I have barely driven the car as I work on other elements of the build) but they could be just fine.

[77320i]

I'd say if you are going to do it use the 2.7 bottom end. It sucks but if you are pulling it out and swapping it you can reseal the oil pan, crank and intermediate shaft seals and KNOW it won't leak again.

As for the dual mass, just take the single mass flywheel and bolt it up. I'm shaving mine down for a turbo ix stroker build and everything I've read is that so long as you have the correct clutch matched with the correct flywheel it will be fine to go from dual mass to single mass. Apparently there is a slight difference in the transmission bell housing size but none of those issues should affect you since your transmission started as a single mass. Though, if you put the dual mass on then you may run into some clearance issues from what I've read.

The 2.7i motor is good but if you drop the 2.5i 885 head on it you get dual valve springs so it can rev higher and get more power and torque, I'm not sure if the cam is different between the two but just add a nice aftermarket cam while the head is off, a good chip and that should be one sweet motor for not a whole lot of money.

[phenryiv1]

I'd say if you are going to do it use the 2.7 bottom end. It sucks but if you are pulling it out and swapping it you can reseal the oil pan, crank and intermediate shaft seals and KNOW it won't leak again.

As for the dual mass, just take the single mass flywheel and bolt it up. I'm shaving mine down for a turbo ix stroker build and everything I've read is that so long as you have the correct clutch matched with the correct flywheel it will be fine to go from dual mass to single mass. Apparently there is a slight difference in the transmission bell housing size but none of those issues should affect you since your transmission started as a single mass. Though, if you put the dual mass on then you may run into some clearance issues from what I've read.

The 2.7i motor is good but if you drop the 2.5i 885 head on it you get dual valve springs so it can rev higher and get more power and torque, I'm not sure if the cam is different between the two but just add a nice aftermarket cam while the head is off, a good chip and that should be one sweet motor for not a whole lot of money.

The SETA cam and the B25 cam are different, and I may go with the BimmerHeads regrind cam at any rate.

The single v. dual mass flywheel issue is not really that big of a deal- just a point to mention in the pros/cons chart.

Resealing the oil pan has been added to the list of to-do steps for either option. It would be easier on the 2.7 but lots of people swap pans on a motor while installed so it will not be a deciding factor but it will be a fixed part of the process.