ARP Head Stud Torque specs??

[manga_blue]

I guess everyone will have to believe what they like.

G

And it's my belief that Mazda's engineers set the torque at 56-60 lbf after taking full consideration of the structure and metallurgy of the head. There's no way that I'd want to exceed their recommendations by 33%. Tail wagging the dog if the bolt maker tells the engine maker how strong the head is.

[gslender]

And it's my belief that Mazda's engineers set the torque at 56-60 lbf after taking full consideration of the structure and metallurgy of the head. There's no way that I'd want to exceed their recommendations by 33%. Tail wagging the dog if the bolt maker tells the engine maker how strong the head is.

I don't think the engine maker is being told anything. I think the use of the engine is being expanded/extended beyond what Mazda intended, and so the head torque with the stock/less inferior bolts that might stretch/yield under extreme FI conditions might no longer be suitable.

G

[wozzah1975]

I guess everyone will have to believe what they like.

G

And it's my belief that Mazda's engineers set the torque at 56-60 lbf after taking full consideration of the structure and metallurgy of the head. There's no way that I'd want to exceed their recommendations by 33%. Tail wagging the dog if the bolt maker tells the engine maker how strong the head is.

Unfortunatley not that simple. 33% more torque on the bolt DOESN'T mean 33% more clamp on the cylinder head, there is far more to factor in. Changes in material of the bolt, thread pitch etc etc effect the end clamp rate. Manufacturers specs, designs and components serve a purpose, and that is in most instances to be a compromise between cost and the intended outcome. Manufacturers specs are for STD engines, not modified engines.

It has been well documented, in particular with stretch style bolts (as fitted to the MX5) in cylinder heads at a certain point of modification they will allow the cylinder head to move. This is a fact. Following std specs and using std components isn't going to help this, fullstop.

ARP make quality fasteners and spend thousands on research before making components, and I'm yet to have a dud. They also serve a purpose of being specifically designed for a high stress application. I have NEVER had an issue when fitting them to their recommended specs in ANY make of engine whatsoever, so if they tell me to torque a bolt to a given spec in most instances thats where it goes to.

This particular part number is unique, as there seems to be conflict on where it should be, and if it causes issues. I torqued my ARP head bolts in my race engine to 65lbs, as the sheet I got with my studs stated that if the head was alloy thats where they should be. Every Mazda engine built since from me has been the same, however research by gslender seems to indicate they should be 80lbs.

If the high torque is being blamed for cylinder heads and blocks cracking, I am yet to see it. I am not saying it doesn't happen, it may, but I haven't personally seen it. The internet seems to be full of people saying that there is a problem, including specialists, so that should probably heed a bit of a warning.

There was also a reference in here somewhere blaming heavy porting for problems. The cylinder head I have cut up here has water between the head bolt boss and the wall of the port, so I can't see that being an issue. IMO porting shouldn't worry the integrity of the cylinder head in that area. It would certainly be apparent in my current race head if it were the case, as it has had alot of material removed from alot of areas. Accessive removal of material from the cylinder head and block surfaces could cause problems, but having said that my block has had .070" removed, and the head has had around .100" removed and it's yet to be an issue, nor have any of the builds I have done. Usually problems with cracks only occur when the engine has been overheated.

I'm curious to see what ARP say about the spec sheets, keep us posted gslender

Cheers
Woz

[wozzah1975]

http://www.miataturbo.net/engine-perfor ... 746/page2/

Interesting the comments regarding the ARP engineer designing them, then leaving. May explain why my kit had different instructions to the current kit supplied.

Cheers
Woz

[Dweezle]

Could a change in torque fluid goo be the reason for a recommended torque change?

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[wozzah1975]

Could a change in torque fluid goo be the reason for a recommended torque change?

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The goo has always been supplied. The more I think about the torque on these bolts, the more I think that it is very very very tight. I wouldn't be surprised if rumours about crushing the head bolt boss are true. As I stated earlier, a small block chev with a cast head and the same size bolts goes to 70lbs, I don't see why a tighter pattern and alloy head would need to be tighter than that. The load on the alloy head bolt bosses in the mazda must be incredible.

Woz

[Dweezle]

That was the main reason i started this questioning.
I read and reread the ARP spec sheet and it really shocked me at how extreme the torque spec was.

I think i will use your 65ft lb Woz.

do you do 3 even stages?

Say 21ft lb, 43ft lb, 65ft lb??

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[NitroDann]

The friction between the nuts and the washers affects it.

For example if the flared out washer part built into the nut is smaller it wll have higher friction, artificially driving the torque spec higher for the same clamping force.

Dann

[Dweezle]

The washers that come with the studs are smaller than oem.

I assume this would make even higher clamp levels?

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[NitroDann]

Higher pressure over the surface but the clamp force is the same nonetheless.

Things like if the studs threads are rolled and the friction properties of the lube also affect how much torque is required to get the same clamping force.

Dann

[wozzah1975]

That was the main reason i started this questioning.
I read and reread the ARP spec sheet and it really shocked me at how extreme the torque spec was.

I think i will use your 65ft lb Woz.

do you do 3 even stages?

Say 21ft lb, 43ft lb, 65ft lb??

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Yes, always 3 stages, the measurements you listed here look fine,

Woz

[Dweezle]

Cheers!!

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[PhilM]

Interesting topic - I wonder if anyone has done a stretch test of the head bolts at 60 and 80 ft/lbs?

My B6 ARP head bolts purchased in November, info sheet has 80 ft/lbs - I will be using 65ft/lbs with OEM washers.

The ARP main bolts (10mm dia) info sheet has 60ft/lbs and I will use 60ft/lbs (OEM 40-43 ft/lbs) because the caps have been align bored to that clamp load, but I will check crank rotation resistance pressure at 45 and 60 ft/lbs.
The ARP 2000 big end bolts supplied by Manley I will be using are 3/8" (9.53mm), the recommended torque is 60ft/lbs to give a stretch of ~ 0.006". So I will expect some bolt stretch clamping on the main bolts.

Manley doesnt follow ARP instructions either: their installation instruction states - "Use 30 engine oil, Do not use Moly or engine lube (I guess they mean engine assembly lube??) DO NOT OVER TORQUE"
Their torque specs on a 7/16" (11.1mm)dia ARP 2000 big end bolt depending on the application, varies from 90 to 105 ft/lbs giving bolt stretches between 0.0055" -0.007". yes, I realise it does not have an al head or gasket under it.

Off head bolt topic - the OEM flywheel/crank bolts come with a red dry substance on them - presumably a locking material. It must affect the thread friction. I will remove it and use a liquid locktite and 70 ft/lbs. any comments?
Phil

[sailaholic]

Are the oem washers the same thickness as the arp ones?

[timk]

I used 80 foot pounds on the supercharged car and 65 on the turbo one, both with NB heads. Who knows what is "correct" but neither have had any issues so far.