Engine rebuild time! Any tips / cheats / things to watch out for? 2800cs standard / stock engine.

dj_efk

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Hi all, I searched extensively but couldn't find anything on rebuilding the stock CS engines, so thought I'd start a new thread - My workshop (DS Motorsport in Coventry, UK) has pulled my engine and box to do a complete engine rebuild. They're terrific at what they do but also open to learning: I said I'd put a shout on here to try and scoop up a little of the wealth of knowledge and experience that exists in these hallowed pages.

As per the title above, this is a stock 2800cs rebuild; the car was down on compression on one cylinder, the core plugs were rusting, the whole thing was filthy and needed painting and it also leaked out of pretty much every gasket possible! As I wanted to keep my car's engine number that matches the VIN I decided to have DSM pull it out along with the gearbox (which as per this thread - https://e9coupe.com/forum/threads/5-speed-shift-linkage-bushing-replacement.20602/page-3#post-277349 is getting replaced anyway), to allow them to really tear into it and do the job properly.

As you can see from the pictures it's fully stripped, the block is away as we speak getting dipped and honed (no bore wear which is great). It will get OE or OEM rings, shells, head and rod bolts / nuts, oil pump chain and timing chain, (plus other wearable timing chain components - sprocket, guides, adjuster etc.). The car has a replacement AMC / Spanish copy cylinder head on it and as can be seen, the head has been stripped and inspected and pronounced healthy with the valves & guides within wear limits (also it hasn't been skimmed to death!) - One surprise was someone has smoothed out the intake ports a little, perhaps to match the intake manifolds (TBC when at assembly). Also I have a 123 TUNE ignition kit to go on it once it's back together so hopefully I should be able to get a lovely engine with plenty of power when done.

One upgrade it's getting while it's apart is to relocate the oil temp sensor to the (original / early) filter housing - I know some would say put a later housing on for ease of maintenance, but I have a stack of quality filter elements for the car and can just remove the whole housing / renew the paper gasket where it mounts each time to allow for a "on the bench" filter element replacement.

So for the build, does anyone have any pearls of wisdom to share? I'm just wondering what other potential tips / best practices are out there, plus the potential upgrades it'd be ideal to consider while it's out / all apart?

Thanks!
 

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dj_efk

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In what respect? It holds a good amount of oil and I cruise rather than cornering like a madman, so I don't think I need to baffle it.

Let me know what you're thinking.
 

Drew20

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having just had the alu parts on my intake bead blasted, and the steel parts zinc plated, I can recommend this

do you need any gaskets? I bought a stack of BMW NOS stock from a closing garage, mainly gaskets and oil seals (for carb & injection cars). but also bearings and carb & fuel pump mounting parts
 

dj_efk

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The previous owner told me it's already got a slightly warmer cam in it - In any case I cruise using low-down torque rather than revs and am happy with it how it was in terms of character!
 

jmackro

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Now is your chance to upgrade that oil pan.

I too was curious what sort of oil pan upgrade you recommend, and what benefit it brings to a street-driven car.

sfdon said:
Put a mild Schrick cam in it!

Would such a cam contribute to low-down torque (useful on the street) or top end hp (useful on the track)? And which model Shrick were you thinking?
 

Markos

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I too was curious what sort of oil pan upgrade you recommend, and what benefit it brings to a street-driven car.



Would such a cam contribute to low-down torque (useful on the street) or top end hp (useful on the track)? And which model Shrick were you thinking?

The 2800CS oil pan doesn’t have baffles, so a 3.0CS pan is an upgrade. I can’t recall if we covered this in the “what changed” FAQ. Paging @HB Chris !
 

Honolulu

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Curiosity compels me to ask: if compression was down on one cylinder, but the bores, valves and guides were found good, why was compression down? How much? Bad rings? Head gasket? The cause should drive the result (obviously) and whether non-stock bits might be used this time.
 

sfdon

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In what respect? It holds a good amount of oil and I cruise rather than cornering like a madman, so I don't think I need to baffle it.

Let me know what you're thinking.

If BMW engineers thought it needed improving-
Who am I to argue with them?
 

HB Chris

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Early pan no baffles, it was an early recall by BMW. And oil temp sender was never on the oil housing, it is mounted low on the head on 69/70 only, later cars at top of head.
 

dj_efk

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Oil pan / sump - ah OK, I will look out for one, I assume one from an E12 would fit.

None of our cars had an oil temp gauge from new, the location is recommended in the tech section of this site. The head would be the other ideal location to measure the oil temp once it has made it’s way up there of course.

@Honolulu, one of the valve seats was pitted and this was the cause of the issue - The head gasket had been leaking but interestingly only between an oilway and coolant passage - I assume where the car has stood with a valve open for a long period of time in storage in the past the valve seat corroded.

As new valve seats are going in, I may ask if they can do a five angle job while they’re there.
 
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