M20 E30 325i engine change advice

[mattrs]

Hi guys,

This is my first post so bear with me.

I am replacing my M20 engine (E30 325i) like for like, as the current one has had it. Any advice on how to check the newer engine is ok, or anything i should consider replacing whilst its out. And or any general hints (i am a novice mechanic).

Thanks in advance,

Matt.

[leeparkes]

whats happened to your old engine?

[mattrs]

It was down on power and not idleing properly, it turned out the valves are letting by on two pot's.

[leeparkes]

if the bottom end is ok just change the head,
have you already purchased the new engine?

[mattrs]

I decided against that as it has coverd 180,000 miles and has been a track day car for ages. I may attempt to rebuild it and keep as a spare. I got a newer one which came out of an auto, with less miles for next to nothing.

[leeparkes]

right,change the cambelt and water pump before you put it in
also sump gasket because these are a pain to do when they are in the car,
you will need to swap the flywheel off your old engine,and while the flywheel is off you can change the rear crank seal,the auto engine wont have a spigot bearing in the crank either
auto throttle position sensor is different too along with this part of the loom,so you could swap the loom,
are these engines from the same year?

[DORAS]

Good advise from Lee! I put them in complete with the box on now, dont forget to line up the gear linkage in the floor though.

[leeparkes]

jack the back of the car up too when the engine/box is going in,
makes it a little easier,

[mattrs]

Not sure if they are the same year. Can i tell by looking at the engine?
Do i have to swap the loom?

[leeparkes]

the reason you need to swap the loom is the plug for the tps is different between manual and auto
you may be able to mate up the loom with the manual plug but im not sure!
there may be other differences with the auto/manual
i had the same issue doing mine so i just swaped the loom over (not a hard job when the engines out of the car)
what year is your car???

[mattrs]

E reg, I think that makes it an 87? not sure.

[mattrs]

Would just swapping the heads get around this Man/auto loom issue? Is the old bottom end likely to still be any good? (given the miles (180)k miles and track abuse). How can i tell?

[Speedtouch]

Early high compression block will have a 25 6E prefix before the engine number, whereas later 1988-on facelift low compression will have 25 6K prefix.

Engine number is located on a machined flat to the right of the inlet side engine mount, just above the block-to-sump interface.

[leeparkes]

My 25 6E number is on the left side of the mount any ideas why maurice?

changing the head will be fine as long as you keep your 'complete' inlet manifold,
the heads are same!
did the old engine smoke knock etc

[Speedtouch]

No idea why Lee! Both of my M20B25s (high and low comp) have had it to the right of the engine mount.

[Brianmoooore]

By far the easiest way to swap an E30 engine is to keep the loom firmly attached to it, but check out my stickied 'wiring warning' in the engine swaps forum.

[leeparkes]

is there a way i can find what car it came from using the full engine number?
sorry for the slight thread highjack!

[e30bmlover]

do yourself a favour and change the oil spray bar.. it costs very little.

[renoops67]

Early high compression block will have a 25 6E prefix before the engine number, whereas later 1988-on facelift low compression will have 25 6K prefix.

Hi what is the difference between the low and high compression engine

[Speedtouch]

Early high compression is around 9.7:1 and knocked out a conservative 171bhp (some say nearer to 180bhp) whereas later low comp is 8.8:1 and generally gives out around 165bhp, though bss325i on here achieved the magic 171bhp with his standard low comp Sport.
http://www.e30zone.net/modules.php?name ... 85&start=0

I've tried both, and the earlier engine definitely felt more perky and responsive and more economical to boot.