ARP Head Stud Torque specs??

[project.r.racing]

56-60ft.lbs is oem spec. 48, 54 or any other suggested amount under 56 is too low.

[gslender]

You have to also wonder why ARP (who's sole business is head stud and fasteners) would bother recommending a torque rating that would only cause problems? If 60 was fine and better, then why advise 80 and risk people coming back with broken/crushed heads?

G

[Dweezle]

I have found 3 different posts with ARP spec sheets suggesting 3 different torque settings??
Flyin miata supposedly change the 80ft lbs on the sheet to a lower spec when they send them out.

I was going to use the indicated 80ft lbs but it sounded really high and got me searching the web.
Never a good idea haha.

Wozz, Terry and sav from mt.net recommend 60ft lbs.

I am also up for a reason to use the 80ft lbs.
I want this to be right!!


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[gslender]

I'm gonna email/contact ARP and see if I can persuade them to explain the situation.

I'll post back here if I get a reply.

G

[wozzah1975]

You have to also wonder why ARP (who's sole business is head stud and fasteners) would bother recommending a torque rating that would only cause problems? If 60 was fine and better, then why advise 80 and risk people coming back with broken/crushed heads?

G

The ARP sets that I have used have a foot note regarding the tension, revised to 65lbs. I have the sheet somewhere, but I can't find it. That is the tension I have used, yet to be an issue.

Will be interesting to see what ARP say about it when you email them, I'm curious about the answer too, because it has caused confusion in the past.

Cheers
Woz

[gslender]

To add further confusion... this is the official ARP instruction sheet that ships in the current head stud kit as posted on their website.

Part No: 218-4701
Item Name: ARP HEAD STUDS KIT MAZDA B6 BP DOHC
Application: MAZDA MX-5 NA NB B6 BP DOHC

http://arpinstructions.com/instructions/218-4701.pdf

It still recommends 80ft-lbs !!

I've fired off a lengthy set of questions, and hope they will respond accordingly.... we'll see hey!

G

[Dweezle]

Thanks G,
Will be very interested to hear their response.

[sailaholic]

Did you all ask them wtf they supply the studs with metric on one end and imperial on the other?

[project.r.racing]

Did you all ask them wtf they supply the studs with metric on one end and imperial on the other?

You dont understand the American psyche do you? What the rest of the world uses is incorrect.

[gslender]

Response was this....

"I assume the part number you are referencing is 218-4701. If so, the correct torque value is 80 ft. lbs. using the ARP ultra torque lube. We have both engineers and metallurgists that test both the fastener and the block/head itself when developing our kits and our instructions to insure that the proper clamp load will be achieved without destroying the block and the head."

If you want the orig emails, PM me your email and I will forward it.

I think that's pretty clear and I tend to trust them rather then "Bob the engine builder" who is a trained mechanic (no offence to people here who are) but lacks any engineering education and/or study in this field. It obviously sounds extreme and I have no doubt many folks who have used ARP products have walked away from engine head damage and never really know why it occurred - eg. Was it the gasket failing? Was the head pre-weakened due to excessive porting? Was the head incorrectly pre-torqued? Was the cooling effective and/or the cause? Was the turbo boost managed correctly?

I think I will see how it goes and hopefully if I never report back here, it means my head has been fine all that time since!

G

[Dweezle]

Great response from ARP.

Thanks for that G!

I now have to source a oem headgasket anyway so will have a think and talk to others before our torque figure is used.

Will post what we went with when done.

Wonder what ARP do if anything if the head cracks when torquing to such a high figure.



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[gslender]

Wonder what ARP do if anything if the head cracks when torquing to such a high figure.

See, that's the thing - I bet nobody has actually done that, and all the talk about cracked or broken heads has probably occurred after the head has been on the engine punished by absurd heat, high comp pressure, amongst all sorts of issues - the head metal fatigue is something that if it did occur, it may not show up until some other factor has stressed it too, so really you'd be hard pressed inspecting by eye any crack or deformation.

As such, if you did want to test what effect a torque up of 80ft lbs has to the head, you'd have to get it X-ray inspected before and after - and again I'd bet nobody has actually done that either (other than ARP).

There is a lot of talk and opinion on the Internet - hard to judge as everyone's an expert !!

G

[wozzah1975]

This topic raises some interesting things.

The picture below I stole from another forum, but is the EXACT sheet supplied with my headbolts from ARP, and I have it documented on my race engine spec and build list of 65ft lbs in the BP/B6 application. It is the figure I have given every engine build with ARP bolts fitted, 0 failure thus far.

It would seem even ARP contradict themselves regarding the topic, 80lbs listed with a footnote at 65lbs for an alloy head. If you consider the bolt spacing on a B6 or BP head, then consider the same on a small block chev which runs the same size head stud and simialr tension. The clamp load required in theory should be less on the Mazda as the load is more evenly spread when the bolt spacing are closer together. Obviously there is other things to factor in, but it doesn't make sense to me.

My thoughs are this. ARP undoubtably make one of the best products on the market. I have no doubt they spent alot of time researching and testing the items they list on their page. However, it is impossible for them to test every block casting and every cylinder head casting. After sonic testing many blocks, hardness testing and porting many cylinder heads there are serious differences in the castings. The other thing to factor in is that the bolts go hand in hand with modifications elsewhere, which will include porting and machining items in the cylinder head, and/or decking of the block. Whilst the fastener may be capable of the torque listed, other factors MAY limit it. (a Falcon xflow engine is a good example, they will crack the block instantly on the front RHS if you go past the 2nd stage torque setting regardless of what the bolt manufacturers say)

I have never personally cracked a block or head with any engine, and I have never seen a B6 or BP head or block crack from anyone else, however I have only ever used the 65lbs ARP listed. Regardless of what ARP say, I would have alarm bells ringing when specialists in Miata and MX5 engines are suggesting lighter tensions.

Very interesting topic

Maybe ask ARP about their footnote gslender?

[gslender]

The picture below I stole from another forum, but is the EXACT sheet supplied with my headbolts from ARP, and I have it documented on my race engine spec and build list of 65ft lbs in the BP/B6 application. It is the figure I have given every engine build with ARP bolts fitted, 0 failure thus far.

Problem with that picture/scan is that it doesn't say what engine or kit it was from - so it could be a valid and true document from ARP, but it might have come from a kit designed for another type of engine. It might have also been before they did their own tests and 10 years old. Who knows? I will follow up and ask them to explain, but I'm sure without any evidence to suggest it is for a B6 engine, that it will be pretty easy to explain away as not related to the B6 ARP head bolt kit.

Fact is they sell the kit today with 80ft lbs as the recommended and advised torque for the head and engine block. If you buy a kit today, it will have the instructions as per the PDF I found online. Others have tried 80ft lbs and had no immediate issues.

ARP have been asked numerous times, and I clearly pointed out to them that others are stating that lesser torque settings were advised due to head damage - their response is fairly clear.

I guess everyone will have to believe what they like.

G

[wozzah1975]

i know the picture doesn't have a part number shown, but i am 100% sure that is what was supplied with my kit, documented in the build sheet for my engine.

does anyone have any hard evidence of cracking things?

woz