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arp head stud torque


gfallon

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I am working on getting my 83 esprit turbo engine back together

I bought the arp head studs from jae and arp said to torque them to 110 foot pounds

that seems like a lot for an aluminum block

I know lotus is 75 on the center and 70 on the outer studs but I also know everyone always said to go with the arp spec when using there studs

so what is your thoughts?

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Use the ARP/JAE spec that you have. The stud is a very different alloy and needs a higher torque value to reach the load to clamp the gasket properly. Use the proper lubricants as well on threads and underside of the nut. 

Jon - 1984 Esprit Turbo

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I looked up the spec on arp web page for an 11mm stud (like we have here) and it said the max is 92 foot pounds

yet jae has 110 foot pounds

just seems to me like I will pull the threads out of the block with that amount

has anyone here used the arp studs?  how much did you torque them to?

( I have arp studs in my supra, 85 foot pounds, and my z24, 50 foot pounds, so I have some experience with arp)

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I have used them.  The ARP studs have the original Lotus specified coarse threads going into the block. The studs are oiled and lightly torqued "27 - 30lbf-ft" into the block.

Then the ARP head studs have a finer pitch thread on the end that clamps the head. Since the thread pitch is different, the actual bolt extension axial load is different than it would have been with coarse threads.

The bullet point on the end of the head studs prevents the stud from turning, so you are clamping the head without putting extra stress on the block threads.

You cannot use the old torque spec with the ARP studs, you also cannot use the later '94+ torque angle spec.

Travis

Vulcan Grey 89SE

My Lotus Photo and Projects Album

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Bear in mind that the original Lotus torque setting of 70 lbs-ft for the front & rear pairs and 75 lbs-ft for the three middle pairs is for the old specification studs and the asbestos head gasket. The later, stronger specification studs required an increased torque setting to ensure adequate clamping of the later Goetze composite head gasket.

Also, the head studs are listed in the parts manual as M12.

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I have both types of head gaskets, bought an engine kit with the goetze and in with all the parts that came with the car is an original type asbestos head gasket.  not sure which is better but was thinking of using the goetze.

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As Derek says, the studs are different, so if you mix & match gaskets, studs or torque vs an angle gauge you are in slightly uncharted territory (although a number of people sem to do it).   I would personally use a Goetze gasket, with later dimpled head studs torqued down using the angle gauge spec, cos as far as I am aware that was the latest Lotus provided spec   Goetze also has the side benefit of counteracting a skimmed head as its slightly thicker than a Coopers.

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  • 2 years later...

I was also concerned about the 110 ftlbs figure from JAE, as I had pulled a stud from the block before at 75-80 ftlbs. But I put a head gasket in with only 90 ftlbs and the ARP Ultra Lube, and on later disassembly it only took 40-50 ftlbs to break the head nuts loose, so something loosened up over time.  I guess I'll be sweating it out as I try 100+ ftlbs this time 😰

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6 hours ago, snowrx said:

it only took 40-50 ftlbs to break the head nuts loose, so something loosened up over time.  I guess I'll be sweating it out as I try 100+ ftlbs this time 😰

Maybe the liners sank into the block (happened on an S3 of mine) or the studs stretch? 😯

Cheers,

John W

http://jonwatkins.co.uk

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On 09/06/2017 at 02:17, gfallon said:

I looked up the spec on arp web page for an 11mm stud (like we have here) and it said the max is 92 foot pounds

yet jae has 110 foot pounds

just seems to me like I will pull the threads out of the block with that amount

has anyone here used the arp studs?  how much did you torque them to?

( I have arp studs in my supra, 85 foot pounds, and my z24, 50 foot pounds, so I have some experience with arp)

I thought they were M12 studs for the 912 and 910 engines

Edited by ekwan
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13 hours ago, ekwan said:

I thought they were M12 studs for the 912 and 910 engines

The ARP studs provided by JAE measure just under 11mm at the unthreaded portion,  insert with them asks for 110 ftlbs. They weren't marked with a tensile psi or an ARP part number .

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32 minutes ago, snowrx said:

The ARP studs provided by JAE measure just under 11mm at the unthreaded portion,  insert with them asks for 110 ftlbs. They weren't marked with a tensile psi or an ARP part number .

Therefore, would it not be prudent to drop ARP an email

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On 25/12/2019 at 01:41, snowrx said:

I was also concerned about the 110 ftlbs figure from JAE, as I had pulled a stud from the block before at 75-80 ftlbs...

Hi Thomas, did you repair this successfully? Just asking as I wondered how feasible it is to repair damaged head stud threads recessed so far down in the block.

I recently noticed this insert kit on ebay (in the US).

https://www.ebay.co.uk/itm/LOTUS-ESPRIT-907-910-912-ENGINE-M12X1-75-CYLINDER-HEAD-BOLT-STUD-THREAD-REPAIR/153450133860

- Jeremy

 

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So far so good, holds 90 ftlbs anyway.  I used a Helicoil kit I had on hand for the block, but that kit looks like a better option. I think my drill was long enough, but the tap in my standard kit was too short to reach the bottom of the stud bore, so I took an 8 point socket that fit the tap's square shank, ground down it's outside diameter and used an extension to drive the tap for the insert. Very slowly and carefully. I used high strength thread locker on the outside of the insert.

An engine out job, and make sure the stud seats all the way down after the repair, if it sits high then it will hit the bottom of the cam carrier on assembly.

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Thanks for that description. Wasn’t pictured but that advert said they supply a special extra long tap, your work around sounded good. The last helicoil I did was on a couple of exhaust stud threads. I was hoping to fit longer helicoils than the ones supplied but found the tap couldn’t cut deep enough to the bottom of the hole. I guess at least the head studs have a better chance with the reduced nose where they bottom out.

I have a block which had suffered from the head studs corroding in. Got them all out in the end but I'm going to have to revisit the situation.

Re gasket/head stud issues - I’d noticed the Northstar engines having similar problems and this radical fix using studs with unequal ends. Not sure if this could be possible with the 9xx block though.

https://www.youtube.com/watch?v=wqEj9BKlVEE

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