Thread: ARP Head Studs

I fitted a set of studs to a 4.6 high comp with 10 bolt heads and composite gaskets, torqued to 70 ft-lb. 12 months later one gasket ring migrated towards the water jacket and leaked. I did them up to 80 ft-lb after that based on the recommendations around the net, here included. 12 months further on and the engine is still going strong.

15 or 16 RV8s. 10 or 11 Chevs. 1 Ford. 2 Holdens. A couple of OMC V6 outboards that had been overheated. ARP make good gear, but you have to be sure that the blocks/rods/heads are hard enough after Brinnel testing to hold under the torque loads. You get a feel for the "snugness" of the thread - if it flops about, it's no good! One of the early 3.5 RV8s I did is still running at 300,000 odd km (1986) - a bit sad because it's been thrashed.

4 of the Chevs are in ski boats, the others in Holdens and other GM products. Ford's been in 3 cars and is now in F150. 253 and 304 still in the cars the engines were built for. ARP rules. HTH.

Why 90 lbft? I dunno, it felt right, particularly with composite gaskets, and I trained on diesels!

Pete

I used the ARP studs (10 stud head) and the composite Elrin head gaskets.

I tensioned the studs between 65 and 70 ft lbs....using two different tension wrenches to check the numbers. 5,000km+ later incl a recent 4500 return trip to Melbourne and it's running fine.

I figured that with the greater coefficient of thermal expansion of aluminium vs steel (twice as much), then when at operating temperature the heads will have expanded twice what the steel studs expand thereby increasing the tension on the studs and compressing the gasket further.

That's the theory, seems ok so far.

cheers

EDIT: Forgot to mention: There's another CRITICAL issue... When tensioning the head there are two forces you have to overcome: the clamping force which is trying to "stretch" the stud by pulling the head and block closer together; and friction between the stud and nut threads and the nut -washer friction which increases as the tension wrench effort increases. If you are using engine oil on the stud threads, then you could probably go to 80 ft lbs because there's a higher friction component for a given clamping force.

However, the special ARP lube stuff in the kit significantly reduces the friction on the threads and between the nut and washer. So for a given tension wrench setting the clamping force is greater. By increasing the tension wrench setting you are likely to go outside the recommended clamping force. The added benefit of using the ARP goo is that the clamping tension is achieved first time up and you don't have to retension the heads after x thousand km.

Thanks everyone for the input. As with everything there are many variables and much to consider. No reports so far of pulled threads here and it sounds like plenty of ARP kits, both old and new, used so that's a good thing. Anyway, kit should arrive tomorrow in time to fit over the weekend. Decision time!

Cheers, Pete.

V8 ARP Stud Torque Numbers

I see in my notes from last year's engine build that I used 65 lbs on both mains and head studs. I remember on the mains I went for that setting because I was checking clearances with Plastigage and that's what gave me the clearance I wanted . . . but I don't remember why I chose that for the heads! Probably because I was using ARP lube as well, which is definitely recommended.

Originally Posted by Davo

V8 ARP Stud Torque Numbers

I see in my notes from last year's engine build that I used 65 lbs on both mains and head studs. I remember on the mains I went for that setting because I was checking clearances with Plastigage and that's what gave me the clearance I wanted . . . but I don't remember why I chose that for the heads! Probably because I was using ARP lube as well, which is definitely recommended.

Definitely using the ARP lube. Rang this morning to make sure it is included in kit. You've obviously had no problems so far with the lower torque figure.

Pete

Originally Posted by discopete

Definitely using the ARP lube. Rang this morning to make sure it is included in kit. You've obviously had no problems so far with the lower torque figure.

Pete

Ah . . . I'm sorry. I knew I forgot to add something to that post. I haven't actually started the engine yet!

I only put it in the car last week. I might actually be driving it around next month. This was a new block with new heads, and not rebuilt, and the torque number I decided on was based on all the numbers I found while researching. As you've seen, there are all sorts of opinions based on block age and history, thread condition, tin or composite gasket, different lubes, and so on.