1987 325ic engine... head with bent valves

[pe3sko]

Hello sirs,

my friend had his timing belt jump / rocker arms snap on him while driving his 1987 325ic, this resulted in bent intake valves.

I was wondering... what are his options other than straight head swap?
I can source a 325e block & 325e head at good price. I understand the 325e blocks are 2.7L and suppose I could then either find another 325i head to improve on the previous configuration, or use the intake valves from the 325e in the old head... are those the same? Cross-referencing from new parts the numbers match up.

- Using the 325e bottom end with 325i head, what will be the resulting compression and / or exact displacement? Is this recommended?
- Is there another configuration that will allow for improving the block further using a mix of the 325e and 325i parts - like using one's crank and other's pistons / con-rods?
- Is there a cylinder head from any 5-series from the 1980s that would work on the 1987 325i bottom end and be an improvement as well?

Thanks in advance for your input!

[Timmybighands]

Originally posted by pe3sko
Hello sirs,

my friend had his timing belt jump / rocker arms snap on him while driving his 1987 325ic, this resulted in bent intake valves.

I was wondering... what are his options other than straight head swap?
I can source a 325e block & 325e head at good price. I understand the 325e blocks are 2.7L and suppose I could then either find another 325i head to improve on the previous configuration, or use the intake valves from the 325e in the old head... are those the same? Cross-referencing from new parts the numbers match up.

- Using the 325e bottom end with 325i head, what will be the resulting compression and / or exact displacement? Is this recommended?
- Is there another configuration that will allow for improving the block further using a mix of the 325e and 325i parts - like using one's crank and other's pistons / con-rods?
- Is there a cylinder head from any 5-series from the 1980s that would work on the 1987 325i bottom end and be an improvement as well?

Thanks in advance for your input!

You can retain the stock 325i block he has now. More than likely he has NOT damaged the pistons top.

1. If you wish to use the "e" block and use an "i" head, your resulting compression ratio will be very low - 7.9:1. The car will feel less competent even though you will have a larger displacement (2.7) with the better flowing/higher reving head on it.

2. To simply swap heads onto an "e" block, no you wont get more power. If you want more power from by using an "e" block, you'll need to rebuild the entire motor using parts for the 1988 super eta motors. I.E. Rods, pins, and pistons and keep the "i" head, cam, rockers, springs, intake manifold, injectors, wiring harness and ECU.

3. Not that I know of. Obviously the 525i/e have the same motors. However, the "bix six" 535s wont even come close to bolting up.

Good luck man - your best bet is simply finding a new "i" head and make sure to change the timing belt as instructed by BMW. Lesson learned, eh?

[pe3sko]

Thanks for the info!

I believe there is some scoring on the piston tops in the valve relief area... I will tear his engine apart and inspect this more closely.

Just to verify - are the late 325e intake / exhaust valves really the same size as the 325i ones? New parts did seem to cross-reference, but I figured I get it verified from one of you...

[Timmybighands]

Originally posted by pe3sko
Thanks for the info!

I believe there is some scoring on the piston tops in the valve relief area... I will tear his engine apart and inspect this more closely.

Just to verify - are the late 325e intake / exhaust valves really the same size as the 325i ones? New parts did seem to cross-reference, but I figured I get it verified from one of you...

Thats a big negative. The intake/exhaust valves on the "i" heads are larger than the "e" brethren. I'm not certain why they are x-referencing part numbers.