M50/M52 Lower Timing Chain Guide Replacement

[wrs 118]

Does anyone know; is it possible to replace the M50/M52 lower timing chain guide (RH one that engages with the tensioner) without removing the head?

We have the cover off but it looks like it's going to be impossible to remove/replace the guide rail because there's no way to get it off the pivot pin due to the top going through the head and not enough room to lift/tip it over to clear. Is it possible to pull the pivot pin out (unscrew, extract) or is the only possibility removing the head? I have the aluminum type guide on the engine and an aluminum type guide to replace it with. I'm guessing we'll have to leave the old guide as-is if it's not too badly worn.

 

[B.M.W Ltd 950]

Short answer... NO , to do it properly, head & sump off and new gaskets seals etc.

[wrs 118]

Thanks, as expected. Sump is off but trying to avoid taking off the head for no good reason. If the rail is still in good shape will leave it in. If not then will revisit taking off the head. Have all new gaskets etc (except for a head gasket kit).

[B.M.W Ltd 950]

What engine ? Alloy block ?

[wrs 118]

No, iron block. Was originally a M50B25nv. Now a M50B30 (M54B30 guts) with Vanos and US S50 cams. Using the nv head with Vanos installed for stronger valves and double valve springs.

I will consider taking the head off but if this has to happen the engine will also come apart to increase compression ratio. May as well go full-hog if I have to go that far...