My old 525e had a cracked head, mixing oil and water badly in the cooling system. So I pulled the head off, whipped out the cam and there it was, a dirty great crack in No.5 journal.
I already had a couple of good 325i (885) heads - one had a bit of alloy corrosion in the back waterway but a very new looking cam kit (Febi rockers). The other was corrosion free but had a nasty cam so I stripped both heads, had the best head skimmed as well as a chemical clean. I rebuilt the head Monday night and started putting it back on Tuesday.
By 2pm it was ready - 4 seconds of churning to build up fuel pressure and awaaaay it went. The raggedy idle smoothed out after about 5 mins but it still didn't idle that well. I reckoned the 325i cam profile really didn't agree with the 525e ECU. Because I mislaid the 325i rubber bellows between the throttle body and AFM, I had to refit the Eta thorttle body to the 325i inlet manifold - this alone would knock a load of BHP off.
But it seemed to rev smoothly and over 4000 rpm comes up on the cam and off it goes! You can only do this by manually holding it in 1st and 2nd gear because itÔš's got a 3.07 diff. I only did all this to prepare the engine for removal and putting into an E30. As a conversion on a 525e it's a waste of time because the engine no longer has the low end grunt and struggles a bit with the tall diff.
I replaced the original 17mm head bolts with the newer type Torx, 30lbs ft, 90 degrees twice. I changed the cambelt, water pump, camshaft oil seal and obviously the head gasket. It looks so easy in the Haynes manual but it's a long old job.
To clean out the cooling system I've added 4 litres of Asdas bleach in the cooling system as well as water and anti freeze and ran it for an hour, drained and refilled with proper antifreeze.
Today came round 2. I found the 325i bellows and so fitted the 325i throttle body. I also borrowed an early 325i ECU and reset the tappets from 10 to 12 thou which smoothed out the idle. Now it seems to go a LOT better - it's regained the lost 'urge' low down and it will now go off the rev counter in 2nd gear (5000 rpm on a 525e). Feels very strong low down.
So there it is, an antidote to all those megabucks 2.7Ôš's!
Budget 2.7 motor build
Moderator: martauto
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MaaasterBates
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Martinaston
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Have you done a compression test ?
How high ?
How high ?
There is NO nucleus.
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MaaasterBates
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Compression is 9.4:1. Standard post 8/85 525e is 10:1 with flat top pistons. 325i pistons have a raised front edge to match the pocket in the head but the rest of the piston is quite deeply dished. Eurpean 1987/8 325e's were called "Super Eta' because they had a standard Eta engine and flat tops but with a 325i head as standard. The compression on those is 9.4:1 as well.
All I needed to complete this job was a 325i air flow meter - the eta one is bound to be throwing a spanner in the works but it's good enough. At least I know that it works and that the suggestion that you can only use 2.5 pistons with the 2.5 head is utter bollocks!
All I needed to complete this job was a 325i air flow meter - the eta one is bound to be throwing a spanner in the works but it's good enough. At least I know that it works and that the suggestion that you can only use 2.5 pistons with the 2.5 head is utter bollocks!
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Martinaston
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As long as the valves are OK then i guess it leaves me with a few more options.
I think you may just have increased the value of the 525e's
So did you use the 325 ECU and injectors and at what pressure ?
I think you may just have increased the value of the 525e's
So did you use the 325 ECU and injectors and at what pressure ?
There is NO nucleus.
How does it compare to the other 2.7's youve driven?
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MaaasterBates
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Don't know because it's in an E28 with a 3.07 final drive and an autobox that wants to change up at 2500 rpm. I drove it again tonight to go down the shops - it pulls away very sharply, feels like it's got a lot of low down torque. I don't know how much better it would be with the 325i AFM but it's hardly optimal as it is with the Eta AFM.
Injectors - standard 325i, standard pressure regulator. Not much point in increasing fuel pressure, but another chip in the ECU would help - even with a stock 325i ECU it will still need revised ignition timing and more fuel.
Injectors - standard 325i, standard pressure regulator. Not much point in increasing fuel pressure, but another chip in the ECU would help - even with a stock 325i ECU it will still need revised ignition timing and more fuel.
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MaaasterBates
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I don't (ta!) but Ant will have it because he wants a scrap M20 head for something and I was going to give him mine. 525e heads are worth about Ԛ£3 as scrap! 
