M10 ARP head studs

Found the long ones

Took a while before I found the correct search criteria, but I think I have found the long studs:

http://www.summitracing.com/parts/arp-am4500-1lb

The short studs are still a problem though and the closest I have found are these:

http://www.summitracing.com/parts/arp-am3750-1lb

The top thread is correct at 1.25mm but the base thread is 1.5mm. I can invert them but that means the torqueing of the nuts (which I'll have to buy separately because they are supplied with 1.5mm thread nuts) on the short side will be with more coarse threads than the long side.

Does anyone who has used these see a major problem with this scenario?

Cheers,

Rob
 
I used the inverted studs

rjplenter said:
The top thread is correct at 1.25mm but the base thread is 1.5mm. I can invert them but that means the torqueing of the nuts (which I'll have to buy separately because they are supplied with 1.5mm thread nuts) on the short side will be with more coarse threads than the long side.
Click to expand...

with the 1.5 threads at the top for years on my race car, zero problems. This setup was recommended to me by ARP.

Pete
 
Call the folks at ARP to verify what studs they have in stock that might work. Ideally, they will give you a ARP kit part number which can be ordered from any distributor of ARP.

The difference in thread pitch is due to different materials used.
Ideally, the 1.5mm thread pitch goes into the cast iron which is softer than alloy steel. The deeper threads loads more area within the internally threaded hole resulting in a stronger and more durable joint.

The 1.25 mm thread pitch ideally goes into the alloy nut which benefits from a larger thread root diameter which increases the stressed area. The fine pitch threads have a lower tendency to loosen and can produce more clamp force than corse pitch threads.

Fine pitch threads are not ideal for soft materials like cast iron, yet this is in designed into the Fiat block.

Switching them around, while not ideal or good design practice does function OK and IMO, better than using TTY bolts by far.


Bernice
 
I find the recommendation of the use of a coarse thread at the nut end a bit of an engineering no-no, as generally the coarse thread (1.5) would be in the block and the fine thread (1.25) would be the having the nut tightened against. A fine pitch thread will handle higher torque forces and will generate a higher clamping force, so reverting to a coarse pitch at the nut end is a retrograde step (from an engineering and physics perspective)

On something like a SBC, which also has differing length fasteners, the usual practice is to fit studs that are all the same length, and install additional spacers under the studs which are effectively too long. The reasoning behind this method is to have precisely identical stretch values across the entire set of studs... as in practice a shorter stud will yield marginally less than one that's longer, so the clamping force supplied will be uneven if studs of differing lengths are used.

The other thing with the ARP nuts is ... where are you going to find a retorque tool to fit their funny twelve point nuts? If you use 10 grade 17mm nuts (M10) at 1.25 pitch then the regular Fiat retorque tool can be used.

Definitely use the ARP hardened washers.


SteveC
 
Spacers

Thanks Pete, Bernice and Steve for feedback.

I had thought of spacers, but wondered if that were too agricultural a solution.

McMaster-Carr have the closest thing I can find to what I would need:

92415A464, Zinc-Plated Steel Unthreaded Spacer, 1" OD, 3/4" Length, 1/2" Screw Size
http://www.mcmaster.com/#unthreaded-spacers/=sq6ejz

Having similar stretch on equal length bolts make sense, but then maybe I would need aluminium spacers to achieve similar material compression:

92510A365, Aluminum Unthreaded Spacer, 1" OD, 3/4" Length, 1/2" Screw Size
http://www.mcmaster.com/#unthreaded-spacers/=sq6efh

It seems that if I can find correct length/thread ARP studs, use a 1.5mm top thread, or use spacers, each is a compromise. So which is the lesser of three evils???

I do have a set of TTY bolts, but soon after I got them I decided to use them only for test assembly duties, not for final assembly. I also have a new head gasket I use for test assemblies, and a new-still-in-the-wrapper gasket that will stay that way until the very last minute. Yep, when it comes to engine building I can be a little OCD... :wacko: :mallet: :nuts: :geek:
 
I wouldn't use spacers, something like that could crush or distort... it just introduces another variable.

I was going to use same studs front and rear (it's normally a 105mm bolt and a 95mm bolt from memory) so I was going to use an extra washer (or maybe two) on one side...the thread length at the top is always too long anyway, it just means (at worst) a little more (maybe 5mm) of thread/stud sticking out the top on one side.

I havent searched ARP's catalogue yet, but I think the M10 sized hardened washers might come in various thicknesses too...so ideally if the nut was being tightened on the same effective length of stud, then the preload and twist would be identical.

(whereas using different thread pitches (on each side) would certainly be an UN-even amount of preload across the gasket face)

In my mind this sounds like to most sensible and correct engineering solution... but I'm also open to suggestions.

SteveC
 
Ok, lets do a few measurements to assist anyone going down this path...

OE M12 hardware.

Stud (short fastener side of the engine)
102mm overall length
engaged thread length (part that screws into the block) 12mm
(usual engineering practice would require an engaged length of a minimum equal to the fasteners outside diameter, any more actually presents no more strength)
unthreaded shank 52mm
top threaded portion 38mm

Bolt (long fastener side of engine)
Under head length 105mm
threaded portion 33mm

OE ground flat both sides under nut/bolt washer 5.5mm thickness (powdered metal)

OE nut 12mm thick.

M10 bolts (victor reinz) integral washer under head (not TTY)
long 98mm under head length
threaded portion 49mm
shank is 'waisted' to 9.5mm

short 84.5mm under head length
threaded portion 50mm
shank is 'waisted' to 9.5mm

brand new unmachined cylinder head (Tipo)
thru hole length long 74.75mm
thru hole length short 60.5mm

so from all this what we really want is,

stud M10, = an engaged thread length a minimum of 10mm...

all ten threaded holes in the block have a depth of approx 33mm, all are blind holes (i.e. none present to the water jacket) and all present approx 25mm of thread (by hand) so we could have anywhere up to 20mm of engaged length here without issues of binding. Ideally we want the thread to fully engage with the block, and no additional threaded portion to be exposed above the block surface, so 20mm sounds like a safe threaded length which will be fully used... maybe 19mm would be OK as this corresponds to 3/4" given ARP is American manufactured and seem to center their measurements around imperial values.


Shank length ... short side is 52mm OEM (102mmO/A), however on the 'long' side this would only present approx 13mm for the nut and washer, simply not enough. On the 'short' side there is approx 25mm of thread exposed for the nut and washer combination above the head.

We don't want the shank portion to be too long, to allow for future head skims and thinner gasket variations, so if one threaded fastener is to be used in all ten positions, it should be 55mm in shank length (max) ... 51mm is 2" so probably a suitable number to settle on.

Threaded length for the nut. If we settle on 51mm (2") for the shank length, then this value calculates out to a minimum of 48.75mm (74.75mm [long side thru hole length] + 25mm [minimum thread for nut /washer and clearance]) so again 51mm (2") or at a pinch 45mm (1.75") would be the required top thread length.

This gives us a stud approx 115/121mm overall (19mm engaged thread, 51mm shank length, 51 to 45mm of top thread)

So using these,

http://www.summitracing.com/parts/arp-am4500-1lb

would be pretty spot on for overall length 4.5" (114.3mm) but I would be checking with the manufacturer to confirm the engaged and shank lengths, just to be sure...

The press in inserts I mentioned in another thread would also be a worthwhile improvement, basically a stepped washer (hardened and ground flat all aorund) which would require opening the head bolt thru hole out to 0.529" (13.43mm) (only at the top portion, but I regularly open M10 style heads out to 13mm to provide additional clearnace when used on M12 blocks) and inserting the washer which stays put if you machine the thru hole with a tight clearance. Check page 85 of their catalogue.

Washer, no chamfer 10mm .850 .120˝
(1pk)200-8590
(2pk)200-8591
(10pk)200-8592

would be the ARP washer to use for the head studs, suit M10, OD is 0.850" (21.59mm) almost the same as the stock washer, 0.120" thick (3.05mm) so 1 on the long side, and three stacked on the short side.

The washers being a little thinner than stock would make up for the additional few mm occupied by the stepped inserts.

I would then use High quality 17mm (10 grade) nuts, as if you use the fancy ARP 12 points, where are you going to find a retorque tool! and I can't find any hex M10 x 1.25 nuts in ARP's catalogue, only in 12 point, so I'm guessing they don't manufacture them.

so with a 115m o/a length, 19/20mm engaged thread in the block, 51mm shank length, 45mm top thread, a 2mm stepped insert washer, a 3mm hardened flat washer and a 12mm thick nut, we have 4.25mm of exposed thread (3.5 turns) which is about optimum.

On the 'short' side with 3 x 3mm washers, and everything else the same, we have 12.5mm of exposed threads, which wouldn't look out of place and shouldn't present any clearance issues for retorque tool fitment.

So your job now Rob, is to call ARP and get some exact measurements for these studs ... and if the engaged/shank/top thread lengths are 'within cooee' of these numbers... my order will be...

20 x AM4500-1LB head studs (or if they have them in kits of ten for a better price?)
2 x packs of ten 200-8598 insert washers
4 x packs of ten 200-8592 hardened washers

enough for two engines

:)

SteveC
 
Last edited:
I sure learn a LOT reading Xweb posts.

This one, while informative, is also frustrating.

The M12 info is (essentially) "Use the stock hardware."

I've read and pondered all the info about bolts vs. studs and was completely ready to install ten new ARP studs in my ten-fastener 1500. Boy, I'm going to do this top end modification right! And only once, too! New studs, washers, and nuts. Silver anti-seize. Loctite the studs in using a thread chaser, thorough cleaning, and disposable head gasket. Take my time. Be very thorough. Torque the nuts using even pressure.

And the upshot on the fasteners for my engine is "Use the stock hardware."

Ok, I'm off to clean the threads of the bolts I have ... :sigh:
 
Coooeeee!

fiatfactory said:
So your job now Rob, is to call ARP and get some exact measurements for these studs ...
Click to expand...

I can do better than that. 10 studs and 10 nuts just arrived. :)

Total length is 114.4mm
Top and base threads are both 25mm
Shank is 64.4mm

They can be screwed 33mm into the block on the short side, so say I screw them in 32.5, that essentially leaves 57mm shank clear of the deck. On the short side my head is 58mm thick so after adding head gasket thickness and a washer it will work fine.

On the long side my head is 73mm thick. The ARP nuts are 10mm thick. Screwed 25.5mm (so entire thread still below deck) into the block the studs will sit 15.9mm proud of the head. That leaves 5.9mm for head gasket and washer with a couple of threads clear.

fiatfactory said:
and if the engaged/shank/top thread lengths are 'within cooee' of these numbers... my order will be...

20 x AM4500-1LB head studs (or if they have them in kits of ten for a better price?)
2 x packs of ten 200-8598 insert washers
4 x packs of ten 200-8592 hardened washers
Click to expand...

Steve, I think we are within cooee.

The ARP nuts are 12 point. My plan is buy a good quality 12 point 12mm 1/2" drive socket and a long extension bar and make my own retorque tool. Some heat to bend the extension bar and weld to the side of the socket et voila!

Cheers,

Rob
 
Rob,

Not too sure if the stud will go into the 'back' threaded holes 32.5mm if the thread length is 25mm...the whole idea is to keep the root of the top thread right at the junction (top of the deck)

PM sent.

Tom,

not at all...

ARP part# AU4.900-1LB Stock Stud replacement is M12 x 1.25, but 4.900 inches overall...if you call ARP and discuss the critical dimensions (provided in this thread) there will be a suitable stud with the correct thread at both ends.

SteveC
 
rjplenter said:
My plan is buy a good quality 12 point 12mm 1/2" drive socket and a long extension bar and make my own retorque tool. Some heat to bend the extension bar and weld to the side of the socket et voila!
Click to expand...

nice in theory, but believe me difficult in practice...the problem being with your 'heat to bend the extension bar' part of the plan...

I have tried to make tools by precisely this method (to suit the 15mm uno/tipo head bolts in fact) ... turned out beaut, looked the business... BUT...the application of heat to bend it, softens the metal to the point where there is a visible twist when 69lb/ft is applied, and the tool can not twist AT ALL if the desired torque is to be correctly applied to the fastener.

Good luck trying to bend the extension bar cold unless you have access to a seriously big press... and then I think you might find it cracks in the process.

I don't know enough about heating and re tempering metals to offer any salient advice on how to do this either ... if you made said tool and then went to see an old school blacksmith who could retemper it... it would work, but without it, sorry but it's gonna bend.

SteveC
 
The drive end and socket end must have precise alignment or the actual torque value will be off dependent on how much error in axial alignment. It must be a precision tool.

Tools are heat treated, heat it up enough to bend, the heat treatment will be destroyed leaving a rod of deflecting mush.

Try bend it cold, better have many, many, many TONs of force to try this, beyond that don't be surprised if the extension bar snaps with great violence at modest bend angles.

Your best bet is to weld something up with thick enough steel to strongly resist deflection. The greater the deflection, the greater the torque error as force applied is used up bending the tool and not applying it to turn the threaded fastener.

Start with 1/2" drive raw parts, don't even think about making a torque adapter using 3/8" drive raw parts.

There are torque adapters that maybe a better choice if they can be made up to fit as required.



Bernice


rjplenter said:
The ARP nuts are 12 point. My plan is buy a good quality 12 point 12mm 1/2" drive socket and a long extension bar and make my own retorque tool. Some heat to bend the extension bar and weld to the side of the socket et voila!

Cheers,

Rob
Click to expand...
 
I just found a reference online to an AM4.250-1lb stud ... a little shorter than the AM4.500-1lb, and it seems they might be 1.25 at each end also... the page (to do with buggies, like those polaris things) doesn't want to load up though...and summit racings listing (as usual) is very vauge on information.

http://www.summitracing.com/int/parts/arp-am4250-1lb

They also list another at 4.000, but the cross refence (again a vauge online reference in russian!) I found shows that as 1.25/1.50 thread pitches, but that's not official

http://www.summitracing.com/int/parts/arp-am4-000-1lb

I've shot ARP a tech enquiry... so we will all know in a couple of days...

you might have missed these Rob as they come up as 'main studs' in summits webstore, and I'm guessing you were searching 'head studs'

also found a listing for a complete head stud / nut kit on ebay... for a punto ... but effectively the correct type.

http://www.ebay.com.au/itm/ARP-HSK-...r_Truck_Parts_Accessories&hash=item485b74a2bc

pretty vauge on information though, so there's nothing to say it's not made up with odd thread pitch sizes...plus seeing as the individual studs can be bought for under $7us each from a variety of places (summit being about the most expensive at more then $10us each) and ten 12 point nuts are around the $30 mark... washers are $5 for 10... seems the guy has a too healthy profit margin tacked on for my taste.

If the slightly shorter studs work out... we might be able to do a swap around for short / long...

I keep finding a load of products that are not listed in ARP's catalogue... these are close but no cigar...
301-8352 M10 x 1.25 12pt nut (10 pack) ... to take a 16mm socket (if only this was 17mm!!)

SteveC
 
Last edited:
I just several minutes ago recieved a reply to my tech enquiry from ARP... nice and prompt and polite... I like that! :thumbsup:

So it seems a little digging has turned up gold!

Am4.500-1lb for the longer stud
Am4.250-1lb for the shorter stud

Both have 1.25mm thread pitch at both ends, both are (according to ARP) approx 0.900" of thread at the block end, and approx 1.000" of thread at the nut end, both have the internal hex at the nut end for ease of assembly.

So there's no need for an additional washer at the short side, the 6mm (0.250") shorter stud isn't going to have any real world measureable difference in deflection at the torque values we require, so I think this is a 'goer'

About the only thing I might change (if I could) would be to use two 0.250" longer studs on the outside front holes (where the head locating dowels are) as the thread presented in these two positions is slightly lower (and below the deck height) than all the rest... but that's getting pedantic. :geek:

I'll email the very polite chap at ARP back and thank him for the info... and at the same time I'm going to suggest that they offer a sohc kit made up, ready to go using these already in stock components... and see what he has to say.

Now we just need to convince them to make some M10 x 1.25 12 points in 17mm wrench size (I can dream can't I :) ) and it would be the perfect 'straight fit' replacement kit.

Edit: unfortunately ARP declined the idea of a pre made kit, due to the need for a 17mm wrench size nut which would be required to use the available tooling for head retorques ... but I'm going to visit my local fastener specialist on Monday and see what I can come up with for 10 grade 10 x 1.25 nuts with a 17mm wrench size ... I'm pretty certain they will be available in stainless (316) which should be more than adequate for the job ... and I might even be able to get stainless ground flat machine washers.

either that or find an available retorque tool in 16mm (5/8) wrench size... :hmm:
 
Last edited:
Well the 'ideal kit' would be 2 x 4.500 studs (for the front outer positions where the head dowels are) 3 x 4.250 for the middle three front positions, and 5 x 4.125 or 4.000 for the five 'rear' (manifold side) positions...

but 4.125 and 4.000 studs in M10 are mismatched thread pitches... (1.25/1.50)

so we will have to settle for 5 x 4.500 and 5 x 4.250 in the correct 1.25 thread pitch at each end...

or maybe 2 x 4.500 for the two outer front holes, and 8 x 4.250 for the rest of the kit... and possibly still double washers on the rear studs...I'll need to have a set of studs at hand to check... all good in theory, but nothing beats knowing when you put it together.

a small compromise that I think is acceptable :)

what do you think?

SteveC
 
I'm not so sure

fiatfactory said:
Well the 'ideal kit' would be 2 x 4.500 studs (for the front outer positions where the head dowels are) 3 x 4.250 for the middle three front positions, and 5 x 4.125 or 4.000 for the five 'rear' (manifold side) positions...
Click to expand...

The manifold side of my head is 73mm thick so the 64.4mm shanks of the 4.500 studs would seem to better?

With the overall length of the 4.500s being 114.4mm that allows for 25mm threaded into the block with 16.4mm (minus some for the head gasket) proud of the head. Or is my math off? :confuse2:
 
manifold side is the 'short' side.... which you said your head was 58mm thick, the long side is the 'spark plug' side which is 73mm thick.

SteveC
 
You must log in or register to reply here.
Back
Top