Crankshaft Bolts (2012)

A little update. You can download the spec for MS21250 bolts here

http://www.fastenersetc.com/PDF/MS21250.pdf

No mention of "diffuse nickel" plating. It only mentions cad as a finish, but the listing on ebay says these particular bolts have a special finish, and call out a process spec, so I would assume that is correct. You could probably find the process spec with enough searching, but I doubt it would have much significance for your intended use.

the -06020 designates 3/8" diameter and 1.895" grip length.

Ken

Even more useless info

The plating on the bolts is per AMS 2416 and is a nickel cadmium plating, primarily for corrosion protection.

Ken

is chris large crankshaft using this kind of bolts?
ken you have a lot on info about this, other than unbrako and stock bolts what can suggest i can use for offset cranks like chris large cranks
some of the bolts will be bolt into the plate not through it

Martin,

in the past I've used the NAS 626 bolts, which are 180 KSI tensile strength, in race engines with excellent results. If I were doing it now, I'd probably use either NAS 626 or MS21250 bolts (also180 KSI tensile strength). There are higher tensile strength bolts available, up to 300+ KSI, but I don't think you need them for this application, and you don't see them available very often in the suruplus market. If you want to go with the stronger bolts, I'd suggest you talk to ARP at

http://www.arp-bolts.com/

They have several high strength alloys they use for bolts in the 220 KSI to 310 KSI tensile strength range. They will be more expensive than the surplus aerospace bolts mentioned above. If I were building a short stroke crank for higher rpm, like 9,000 rpm, I'd probably use the ARP bolts just to be sure.

SPS also make the higher strength bolts, but I've found ARP easier to deal with as an individual.

I'd definitely go with either 3/8" or 10 mm bolts, and ream the crankshaft holes to fit.

Ken

i just read over the ARP catalog.. I think i can use either the Head Bolts kit Professional Series that claimed 200.000psi or the Chromolly 5 packs bolts that using 8740 180.000psi.

the problem is i can't find info for the Professional Series Head Bolt Kit that contains 3/8-24 and 5/16-24 bolts inside the kits. a lot of option for cars like buick, chev, ford, mini, BMW, audi, VW but no detail info for bolts size and measurement.

but for the 5 pack chromolly bolts i can find both 3/8-24 and 5/16-24 in different length size.

MARTIN.K said:

i just read over the ARP catalog.. I think i can use either the Head Bolts kit Professional Series that claimed 200.000psi or the Chromolly 5 packs bolts that using 8740 180.000psi.

the problem is i can't find info for the Professional Series Head Bolt Kit that contains 3/8-24 and 5/16-24 bolts inside the kits. a lot of option for cars like buick, chev, ford, mini, BMW, audi, VW but no detail info for bolts size and measurement.

but for the 5 pack chromolly bolts i can find both 3/8-24 and 5/16-24 in different length size.

Click to expand...

That's a problem with trying to use their catalog. Years ago, when I first started using ARP studs in Yamaha singles, they listed their fasteners by size, and you could sort through for what you wanted. Somewhere along the way, they stopped listing them that way. The last time I needed some specific size studs, I went to their plant, which is near me, and told them what I needed, and they showed me the fasteners they had available. At the time, they were very helpful in person. I suggest you contact them (email, phone, mail) with your needs, and see if they can help. For example, tell them you need some 3/8-24 12 point bolts, non-waisted, x.xx inch length under the head, in 200,000 psi or higher tensile strength, and ask what they have available. They are licensed to manufcture a variety of mil-spec fasteners, including MS21250, so you could also tell them you are looking for the equivalent of MS21250-06xxx, where xxx is the grip length in 1/16" increments, wut in 200,000 psi tensile strength or greater. You can look at the spec to see what the grip length numbers are. Just remember that grip length is the unthreaded portion of the shank, not the total lenght under the head. Unless they've changed their attitude since I dealt with them, they should be wlling to help you.

Ken

Yes, i try to contacted them before and a sales representative replied back his name is zac... and his not very helpful on helping me getting off the shelf bolts.. he try to drive me on making a custom one and he said it will cost a U$1,000.

probably i will try to call them on monday... ARP2000 is a good material but in the catalog they only use it for conrod bolts they don't mass produce it for other purpose i think.. but can order a custom one... that is why i minimize my option to Profesional Series Head bolt kit, since most of the bolts are long and the shank diameter is not smaller that the threaded part a non-waisted... with that i can customize it to fit my need.

the nuts do you prefer to use a std 12 point nuts or a 12point self locking nuts

Sorry to hear that. I always had good luck with them, but that was a few years back. It does sound to me like you could find the right size MS21250 or NAS626 bolts somewhere, and they should be strong enough, but if you can find stronger ones, there's no reason not to use them instead.

I used 12 point self locking nuts, and also used red loctite on them. When converting from 5/16" bolts to 3/8" bolts, I did have to turn down the outside diameter of two of the nuts to fit in the spotfacing on the crankshaft halves. I believe there are smaller diamter nuts available that would fit as is, but I have no experience with them.

Ken

Hi Martin, if you succeed to find out the right specs and to buy them at a decent price , that will be nice if you could give us your way, cause I had tried too with ARP and was totally lost in their products, may be i am not the only one.....may be some Norton fans would appreciate to buy something like a kit to refurbish a nice crank (not to say a racing one, that's my case)...

I recently milled out a 750 crank to fit the later, 850 style 3/8" studs. The main issue I ran into was that the recess on the crank at the two upper locating studs was too small for the nut of the larger 3/8" stud to fit, after consulting with some forum members, I decided to shoulder the 4 nuts for those studs just enough to clear the flange on the crank cheek.

In all the reading I did on this upgrade prior to embarking on it, I never came across this particular issue being mentioned.