Leaking head gasket

[jamesw]

I've torqued to 80 with moli-lube (just the cheap kind you get in a grease gun tube at autozone) on a few engines/heads with no problems. But I would try the recommended 50-55 first and use a good beam/pointer type torque wrench in either case.

HTH
James

[Linda]

Keith,
Do you have a ARP link for that info? What size are you referencing?
Thx

Linda

[Gregs672000]

I have broken an ARP head stud in the past using moly lube, I believe at 80lbs. I would stick with what ever ARP recommends on their site.

[Linda]

That is why I was asking for the link being used for the info.Anyone have it?
Linda

[Jujuman]

These are the studs I bought:
Partnumber: 2285
Datsun Roadster High Performance 1600 & Fairlady Head Stud Kit

Kit includes 10 - studs, 10 - washers and 10 - 12 point nuts.These great kits replace factory head bolts and eliminate problems associated with head bolt use as opposed to more reliable studding of block. Common problems include bolt breakage, block thread damage and breakdowns, less clamping force, and bolt stretch. Keep that head from moving around. Racers love this stuff. Manufacturers note: Material - 8740 Chrome moly. Tensile strength 190,000 to 200,000 PSI. U.S. made.General torque spec. 80 FT LBS Ultra torque lube. Be sure to add on Ultra torque lube Part# 2464 when purchasing this kit.

As datsunparts.com is a vendor perhaps he can give some insight? I would assume they are very good studs as he makes a ton of datsun parts.

[JT68]

ARP studs are excellent and very strong in general. They are not made by Datsunparts. Note the wording "general torque value"

The issue is not so much failing the stud, but damaging the block and/or crushing and distorting the head. Lots of AL 1600 heads have the bolt holes through the head distorted by excessive force. Its a non-issue for the iron head. U20 camstands are pretty strong, but can also be deformed if the forces get out of hand.

The R and U blocks are tough and will tolerate high torque values. 80lbs dry is high, 80 lbs with moly lube is vert high. 80lbs cold with moly lube is way up there (because the head expands so much), where as an 80lbs value at temp is pretty reasonable since it corrects for expansion. Thats only 15 over for the U20.

There is a good chance your block will be fine at 75-80 lbs.

There is also a fair chance the threads will begin to distend (volcano) or develop stress cracks on the deck, but you probably won't know it until you disassemble the engine and see it or magnaflux the deck way on down the road. I've thrown away U20 blocks with stress cracks at the bolt holes, so it does happen.

80 is a generic value most likely derived from the stud diameter and recommendations for the Ford SB which has iron heads. I would seriously doubt that ARP ever had a R16 block and did any testing with the R16 head for thermal expansion!

Don't panic if your engine is setup that way and certainly don't loosen the bolts at this point. Just be aware there are many cases that excessive torque values have consequences. As i said in the earlier post, there is no reason an R16 should NEED 80lbs when the stock value is 45. Mid 50's-60 is plenty. J

[keith0alan]

I will stand corrected. These are 7/16" studs and the ARP general torque specs recommends 80 ft/lbs as the optimum clamping force torque. This is 75% of the yield strength of the stud and has nothing to do with what any particular engine requires to seal. The ARP studs use fine threads on the top nut so will provide more clamping force with the same torque. Just as a w.a.g. I would thing the studs would provide at least 50% more clamping force at 50 ft/lbs and double or more than stock at 80 ft/lbs. Given that I would say make your own informed decision about your torque. 14 to 1 CR, I think that I would go high. Stock motor I would be comfortable at 50. Once again, these are strong and can handle 80 ft/lbs of torque but you may not need that much clamping force.

[jamesw]

Exactly Keith - we use LOTS of studs and nuts in my business (pipeline) and the torque or tension value is purely a fraction of the yield strength. Normal service it's usually 50% so the ARP recommended 75% is a bit high but evidently it works because I have not seen a stud snap or fail from fatigue.

James

[Linda]

I was able to find my info on the ARP studs I used, and as mentioned, rated to 80, but a lower torque is recommended as explained here by JT, Keith.

The kit for 7/16-20 studs with washers and12 point nuts is 154-4201 found on ARP website, with specs. Described as for a SB Ford.
Linda

[JT68]

Correct, Im not at all concerned about the stud itself. It is the block and head that will see the damage if anything does. Kind of a bummer if your original 67.5 U20 block cracks, so personally, I'd go a little easy there.

14:1 race engine - why not?

[devo]

You start with both center bolts then move diagonally to the opposite bolts working your way out from the center, so the bolts at the front and rear will be last. There are several bolt patterns that will work equally well.

Do not loosen all the bolts.

You can loosen each one by 1/4 turn then increase in 5-10 lb increments. There is no need to go to 80 pounds cold and several good reasons not to. It should seal at 50lbs. 60-65 is not a problem. Remember AL expands far more than steel so 60-65 cold is way more at temp and significantly more than should be required.

If all this fails, you can add 3-5 lbs to the rear right bolt. You wouldn't do this with a U20, but the R head is far more forgiving.

If you have a cheap click type wrench you might borrow a beam type. If you are careful, one can be quite accurate with a beam. Cheap clickers are notorious for variance and mis-cal.

Did you put any sealants on the gasket? These often create failures.

Best of luck.
J

Just an update on this thread that Jujuman started, and I jumped on with the same problem of an oil leak , between the block and the head at the rear. I have an iron head '66 with ARP studs, rebuilt within the last 1000 miles. I took JT's advice above. I loosened each nut a little, one at a time, put on some ARP Ultra Torque assy lube and retightened to 50 lbs with a beam type torque wrench. Using the torque pattern sequence for these motors. Incidentally, each nut came loose at about 45-50 lbs when taking off. Second round of tightening at 55 Lbs. Third round at 60 Lbs. I ran the car, and voila... no more oil leak! My thanks to a very talented enthusiast!

[Jujuman]

Board Recertification Test complete.
Pulling that valve cover off today. And retorque party tonight because the weather is nice. Wanna run before the cold comes. I have some Lucas assembly lube. Will post with results

[SLOroadster]

Ive been told by a few people who know more about roadster engines than I do tell me not to use studs at all on roadster engines. The reason being, the cast iron is hard, but can "volcano" around the bolt hole lifting the head causing the head gasket to leak. People try to tighten the nuts down, making it worse. For that reason, I will continue to use the factory bolts torqued to the factory settings. I've been doing this since I got a roadster, and 17 years later, never had a head gasket issue, or a head bolt issue. No special head gaskets either, just factory Nissan ones.

Studs have the place, on a mild street engine seems like mega overkill.

Just my $0.02,
Will

[keith0alan]

One of the things you do when you get a block machined is to mill the deck flat. This will get rid of the high areas around the bolt holes. I have decked blocks on my mill and it is surprising how much he metal will raise around the bolt holes.

[jamesw]

Great news Devo! Good luck jujuman.

There is no reason NOT to use studs Will. If you're worried about yielding the cast iron then don't tighten them as much. They are just fasteners - and studs are always superior to 40 year old bolts IMO.

Cheers
James