ARP head bolts for m20

#1

Hi guys…sorry to post linking to another forum, but your input would be appreciated on this.

http://www.e30tech.com/forum/showthread.php?t=78310

thanks
Matt

#2

I know that you can use the ARP M50 Main Studs and Rod Bolts, as they are interchangeable with the M20 items (same part numbers in ETK/realoem.com). But if we can get Head Studs, that would be awesome - no more stupid Torx head bolts!

Dave.

#3

Sorry, should have added part numbers:
BMW M50, M52, S50US & S52US inline 6 (Main Stud Ki)t: 201-5000 (Page 43 of 2009 ARP Catalog)
BMW 2.5L (M50/M50TU) inline 6 M9 x 53MM UHL E (Rod Bolt Kit): 201-6301 (Page 30 of 2009 ARP Catalog)

#4

So if one switches from head bolts to head studs, what is the torque level? The Bentleys describes a torque + 90 + 90. It does not mention studs. ???

#5

The outfit making the studs should specify their torque.

I bought reusable bolts from Metric Mechanic for $130 or so. ARP is pretty pricey. The MM bolts can be tightened more then OEM bolts.

One of the things that I learned in my engine odyssey is that you can get away with re-using head studs a time or two, but instead of the 22 ft lbs, 90deg, 90deg business (which works out to about 55ftlbs), you use a different protocol of 3 stages to 55ftlbs. So something like 25ftlbs, 45ftlbs, then 55ftlbs. It might have been 52ftlbs, I’d have to check my notes.

You have to make some judgement calls when you re-use stuff. I put on and removed heads > a dozen times when I was testing heads. I just couldn’t bring myself to buy new head gaskets and bolts every darn time.

Like if a headgasket only saw OEM bolts at 55ftlbs, passed a careful visual inspection and had a couple days on it or less, I’d re-use it with MM bolts at 60ftlbs. I reasoned that the tighter torque would further compress the brass rings in the gasket.

Be anal about clean and chased threads in your block so you can trust your torque #'s.

Main bolts can be reused.