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E34 M5 Discussion 1988-1995 Sedan and Touring

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Old 12th April 2006, 15:53   #1
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Engine Rebuild

Hi guys

My 1995 3.8 m5 I am afraid is in need of a rebuild, in november 2004 my car developed a missfire, which slowly got worse, I traced to N 5 plug, and upon examination I found the extension stem for n 5 coil perished and with signs of tracking to earth.
Replaced the plugs, repaired the stem with insulating tape, whilst I ordered a replacement form the local Bmw agent and the engine apeared to be running ok.

My father borrowed the car for a day trip and returned with the car running on 5 cylinders, I assumed my temp repair on the coil extension stem was the culprit, when I checked, I found that the engine had munched the spark plug on n 5 cylinder, things did not look good.

I replaced the spark plugs again and crossed my fingers hoping the engine had survived unscathed, no such luck, N5 spark plug would oil up at low rpm.

My suspicion was that in digesting the central electrode of the spark plug the piston was damaged in process or perhaps the head damaged, it would require an engine strip down to investigate, as the m5 has really small spark plugs and I could not check the cylinder with an endoscope.

As the saying goes it never rains , it pours, well all this coincided with serious problems with my 2 partners at work, which eventually led to us spliting up, and a huge financial burden, and to top it off, I split up with my other half.

All these problems resulted in the car remaining in the corner of my workshop awaiting for me to have time to strip the engine down and investigate. and the time has finally come,I decided to remove the cylinder with the engine in situ, after 2 days of headscratching the cylinderhead is finally off,(I think its probably quicker to remove engine from car 1st, and then strip engine) and N 5 piston doesnt look pretty, and the bore is scored.

So next question, Can anyone recomend pistons asides from the originals which cost over 2000 , in which case I would try to obtain lighter racing items.

I would also like to get the head gasflowed whilst its off, can anyone recomend a reputable co or person who knows whats he doing, I moved to spain 8 years ago and have lost touch with the uk tuning scene. but I think my best bet is to have the head done in the uk.

lightweight flywheel again any sugestions.

and I might fit schrick cams aswell if the budget allows.

As you can see if am going to rebuild the engine I might aswell try to improve it whilst i am at it, more power please

Next,I will remove the engine and continue with the strip down.


Joe Rubido
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Old 13th April 2006, 14:31   #2
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sorry to hear about your car, and i can't really help with your questions but while rebuilding i would recommend cleaning and testing the injectors.
I've recently undertook a rebuild myself due to #4 piston melting (looked similar to yours) and it turned out to be an overfueling injector.

Good luck
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Old 13th April 2006, 15:01   #3
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sorry to hear about the bad luck Joe. Looking at it the other way - things can only get better.

Schricks are around 1750euro.
VAC motorsport (US) have some fancy stuff they can do to our heads.
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Old 13th April 2006, 15:17   #4
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Anyone who knows their flowbench can do the head and the valves.

Originally Posted by Jahangeer
sorry to hear about the bad luck Joe. Looking at it the other way - things can only get better.

Schricks are around 1750euro.
VAC motorsport (US) have some fancy stuff they can do to our heads.
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Old 13th April 2006, 16:58   #5
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My head guy is near Silverstone, he does pretty much all the head work for big name tuners that say they do it in-house. He is trade only , but I could pass on your details. I've never had an S38 head flowed, but the S14 heads he does are fantastic - suffice to say , he says M- power heads are pretty damn good to start with.

All he does is gas flowing heads, he doesn't need a flow bench, after 30 years of grinding ports , he can 'see' how they will flow !


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Old 13th April 2006, 17:52   #6
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It is said to be done with cigarette fumes as well, but like auditorial Weber adjustment, I prefer the 'official' way, no offense to your undoubted talented contact, 286bhp
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Old 17th April 2006, 16:20   #7
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Hi guys

I have been doing some investigation regarding possible upgrades to the Engine.

1) Gasflowing the cylinder, any tuner who has experience with M3 S14 engines should be able to do a reasonable job, since they are similar designs, I havent striped the head down completely but I suspect most the gains are going to be from radiuosing the valve seat and valves, and cleaning up the casting.

2) Replacement pistons, Asides from OE, or OE altertatives from other piston suppliers, Better pistons would mean ordering lightweight pistons from the states, like CP, JE or wiseco, which are readily available. I think considering the price of fuel I will stick with the original compression ratio 10.5 which will enable me to use 95 octane unleaded.

3) lighter flywheel, means ditching the 3.8 dual mass flywheel and either fitting a 3.6 flywheel (which I would lighten ) or fitting a Speck alloy flywheel which seems to be only aftermarket flywheel available presently again from the States.

Check out the following links: http://www.specclutch.com/


4) Replacing the camshafts, the options from schrick appear to be 272 or 280 duration cams, although there is another company also making cams for the S38 CATCAMS from belgium. (www.catcams.be)

5 ) Plasma Coils, suposedly double the output of the spark, increasing the fuel efficiency of the engine and power output.

Any other sugestions, I would welcome.


Joe Rubido
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