M42 rebuild and future turbo projetc

[Diake]

Hi guys,
I own a 1986 316 E30 but I've bought an M42 and all required parts to swap.
Since the engine has seen better days and I'm not sure about its past history, I was thinking about rebuilding it (It has always been something I wanted to do). I also plan to make it turbo in future, but it's a long term project (no much money and more important time at the moment), and I want to drive it in the while. This obviously means that I will spend more rebuilding it and making it turbo in a second time (I aim at 280ish hp at the end, nothing crazy, but without E85 since it's not available in my country).
That said, what do you think are the upgrades worth doing and what should I just refresh/leave? I read a lot of threads and I've understood that the weak points are the timing chains and gears, tensioner, the oil pump and oil pressure relief valve, head gasket. Moreover I tought about upgrading radiator and fuel pump since I have to swap fuel tank. Which one do you suggest? Any other sugestion?
My general idea was not to replace rings, pistons and main bearings at the moment (just check if within specs), but just what I will need anyway and I won't have to replace once again when I go turbo (Timing, Oil pump, water pump, miscellaneous parts in the head, seals, etc)
I was planning to do a build thread, but this will happen in a while, since I'm abroad for some time.

Thank you all in advance and congrats for the awesome forum :)

Luca

[TobyB]

As far as I've found, the oil pump's pretty tough.
The timing idler gear is the truly weak point.

The thrust bearing on the crank is also less durable-
I'd change that, and the rod bearings, just 'cause.
(and they're cheap)

Devil's advocate here, and I'm NOT in Europe, which may make this impossible:

if you're going to the trouble of an engine swap, why not a 6 cylinder?
Here, the parts for the 6 are cheaper than the M42's timing chains,
and they get almost the same mileage and a LOT more torque. And horsepower.

t

[Diake]

Yea, the problem is exactly that in Europe M20B25 engines are quite expensive, and I wanted to experiment with an engine born to fit the E30. An m50/52 swap may be cheaper, but I've found a good deal on the M42.

Regarding the oil pump, I was actually referring to the bolts coming loose, and maybe replacing the gears if they are worn.
Would you suggest replacing bearing anyway, even if I will later go turbo? (I might have to change rods in future for this reason) I thought I could just see if they are in tollerance, but If you say they are cheap... At this point it might make sense also upgrade to 360 degrees trust bearing (from m20 I think)

[TobyB]

I would at least check #3 rod bearing. If it looks new, yeah,
maybe not do them. I forgot- is the m42 rod bolt a stretch bolt? THOSE are kinda pricey...

t

[Diake]

I would probably upgrade to ARP studs in that case, since it will be a future must anyway. Don't you think?