head bolt dilemma

[bones]

just did a valve job on a 525I and orderd a new set of head bolts to use on installation.im trying to be a good newbie and did a search on the subject and now under stand the whole expand/contract issues on aluminum heads and iron blocks.the new bolts are torx head with a tapered shank and a different torque value and method than the hex head bolts that i removed.can i or should i reuse the original hex heads bolts?,they have no taper to the bolt shank and seem much more sturdy. thanks bones.

[Ferret]

just did a valve job on a 525I and orderd a new set of head bolts to use on installation.im trying to be a good newbie and did a search on the subject and now under stand the whole expand/contract issues on aluminum heads and iron blocks.the new bolts are torx head with a tapered shank and a different torque value and method than the hex head bolts that i removed.can i or should i reuse the original hex heads bolts?,they have no taper to the bolt shank and seem much more sturdy. thanks bones.

You sure you've got the right spec bolts? From what I remember the M20/30 used hex bolts, but the later 2.0 and 2.5 M50 engines used torx?

Whoever's supplied em hasnt got the year/engine mixed up have they?

[bones]

ferret,im honored,thanks for the response.bavarian autosport did the parts,bolts are the right thread and length.can i use the torx? can i reuse the hex's,or should i be patient and go through the hassle of returning and reordering the hardware.

[whiskychaser]

ferret,im honored,thanks for the response.bavarian autosport did the parts,bolts are the right thread and length.can i use the torx? can i reuse the hex's,or should i be patient and go through the hassle of returning and reordering the hardware.

The standard bolt is torx. You normally torque to 30-32nm, then quarter turn, then quarter turn in the 'star' pattern. Cant remember the manuf of the other bolt but I think its ARP or something. Pretty sure they specify tightening in 3 torque stages. I wouldnt re-use the old bolts but see no reason why you cant use your new torx ones.

[Zeuk in Oz]

Some M20 motors have hex head bolts and some have Torx head bolts.
Whichever, replace them with new Torx head bolts and don't forget to use the old washers ( ask me how I know ).

Apparently hex bolts can be re-used but the tightening procedure is much more complicated, so just get new Torx head bolts.

Also make sure you clean out the bolt holes on the block completely.

[bones]

Whiskeychaser thanks for the info,im gonna use the new torx bolts i ordered and now fell confident that they are the correct hardware. bones

[bones]

Zeuk in oz,gonna use the torx and follow the prescribed tightening and torque instructions,thanks for the input. bones

[winfred]

the original m20 hex bolts can and do break, i've seen the broken bolt head pop out and wedge under the cam destroying the head, the torx bolts are the new style and the torque is simple, 22 foot pounds, then 90 degree turn (1/4 turn) then the last stage is another 90 degree turn, the only reusable bmw head bolts are the ones on the m30 and i replace them anyway