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ARP studs torque and blown headgasket
- Thread starter Morris
- Start date
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the reason for the diferent torque requirements are the LUBRICANT.
The factory torque figures are for motor oil lubricant use.
The ARP figures are for use with the lube they supply with the parts.( high MOS 2 grease).
Use the lube on ALL the threds..studs and nut threads. Also on the washer faces of the nuts and hardened washers. Do NOT exceed the torque figures bu more than 2%. it helps if you have a very accurate torque wrench.
It helps if the case deck and cyl head faces are smoother. Clean the decks with MEK or Acetone. Torque to 20# then go round in 5# increments till you get to where U want to go. Let the motor cycle twice hot to cold then re torque and reset the valves.
The factory torque figures are for motor oil lubricant use.
The ARP figures are for use with the lube they supply with the parts.( high MOS 2 grease).
Use the lube on ALL the threds..studs and nut threads. Also on the washer faces of the nuts and hardened washers. Do NOT exceed the torque figures bu more than 2%. it helps if you have a very accurate torque wrench.
It helps if the case deck and cyl head faces are smoother. Clean the decks with MEK or Acetone. Torque to 20# then go round in 5# increments till you get to where U want to go. Let the motor cycle twice hot to cold then re torque and reset the valves.
Hap Waldrop
Yoda
Offline
I've argued until I was blue in the face with ARP tech advisors, I absolutely refuse to use thier lower torque spec with their assembly lube, on rod bolts and head stud kits, that last time I talked to them, they admitted it really doesn't matter if you use original torque specs or thier reduced torque specs, I still use motor oil and on the head kits, and torque to 50 ft lbs, never, read that again, NEVER blown a head gasket, even on 15 to 1 1275 race motors and 16 to 1 948 race motors. Like I told ARP, why in the world would I ever alter something that has worked so well for so long for me. ON the rod bolt kits I go with their 50 ft. lbs on the 1275 rod bolts, I only use the proper 206-6001 rod bolts, and never had a problem there as well, in fact in the 1275 rod bolts instruction sheet it used to offer a lower torque value years ago with thier assembly lube, but with constant annoyance form builder like me, this is now dropped form the 206-6001 rod bolts instruction sheets. Now if we could just get them to lose the AMC rod bolt head on the MGB application and go with the proper chamfered edge design!!!!!! Sorry I'm not taking advice from some non engine building desk jockey tech guy when it come to my engines!!!!!
racingenglishcars
Darth Vader
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I must say here that torque readings are given by the manufacturer to do several things. First anf formost, to provide a force holding the machine parts together with the necessary pressure. Secondly, the bolts are dimensioned to hold to the necessary and dimensioned force. The thread angle - incline - along with the diameter of the threads determine a ratio of torque to normal force.
Friction on the threads is calculated in with the necessary torque. (Friction between two steel surfaces is well known) A lubricated surface between the threads of the shaft and nut reduce the friction causing a greater normal force for the given torque. If the manual says dry threads, that's what they mean. They have dimensioned the torque reading for dry threads.
As I said, lubricating the threads gives more normal force for the same torque. If you give the spedified torque with lubricated threads, you are moving the bolt / stud further up the elastic area, and closer to the plastic area. This means permanent deformation (elongation) of the bolt / stud. In extreme cases, it can pass the deformation area and enter the break area, where the bolt / stud breaks. Extreme cases come quicker when there is less materal to elongate - short bolts.
Personally I wonder about the statement that ARP wants 37 while the manual says 46 lb*ft. Is this because the ARP bolts / studs are of a finer thread? If they are, this would give the same normal force as the courser thread at higher torque. On this point I agree with JerryB, follow the manufacturers recommendation.
Then comes the question of "WHY use ARP fasteners" if you are only going to achieve the same normal force. I thought the idea of using a stronger steel was to have a greater margin and the ability to use a greater stress within the elastic area. On ths point I agree with Hap. Use the steel properties you have available. Tighten the head at least as tight and maybe tighter than the factory suggested. As long as you don't crush the head (I've seen this on a Chevy 230-6) The higher torque provides a higher pressure on the head gasket and will help prevent leaks.
Friction on the threads is calculated in with the necessary torque. (Friction between two steel surfaces is well known) A lubricated surface between the threads of the shaft and nut reduce the friction causing a greater normal force for the given torque. If the manual says dry threads, that's what they mean. They have dimensioned the torque reading for dry threads.
As I said, lubricating the threads gives more normal force for the same torque. If you give the spedified torque with lubricated threads, you are moving the bolt / stud further up the elastic area, and closer to the plastic area. This means permanent deformation (elongation) of the bolt / stud. In extreme cases, it can pass the deformation area and enter the break area, where the bolt / stud breaks. Extreme cases come quicker when there is less materal to elongate - short bolts.
Personally I wonder about the statement that ARP wants 37 while the manual says 46 lb*ft. Is this because the ARP bolts / studs are of a finer thread? If they are, this would give the same normal force as the courser thread at higher torque. On this point I agree with JerryB, follow the manufacturers recommendation.
Then comes the question of "WHY use ARP fasteners" if you are only going to achieve the same normal force. I thought the idea of using a stronger steel was to have a greater margin and the ability to use a greater stress within the elastic area. On ths point I agree with Hap. Use the steel properties you have available. Tighten the head at least as tight and maybe tighter than the factory suggested. As long as you don't crush the head (I've seen this on a Chevy 230-6) The higher torque provides a higher pressure on the head gasket and will help prevent leaks.
Hap Waldrop
Yoda
Offline
Donn, the reason ARP states lower torque value when using their assembvly lube is in their words "it creates less friction so thereforth require less torque". I think you'll find most racer do exactly as i do, oil threads and 50-52 foot pounds of torque, I normally start out at 50, then on re torques get an additional pound, it's worked for me.
Morris retorqueing is worth a try. If you end up pulling the head you may want to straight edge check both the block and head surfaces to rule them out as being a problem. Morris what head gasket did you use? and did you dress it with anything, the black composite (on both side) head gasket doesn't really require any dressing, but I still dress them, I used to use copper spray years ago, but I now use Permatex Hi Tack spray, no matter what head gasket I'm using.
Morris retorqueing is worth a try. If you end up pulling the head you may want to straight edge check both the block and head surfaces to rule them out as being a problem. Morris what head gasket did you use? and did you dress it with anything, the black composite (on both side) head gasket doesn't really require any dressing, but I still dress them, I used to use copper spray years ago, but I now use Permatex Hi Tack spray, no matter what head gasket I'm using.
texas_bugeye
Jedi Knight
Offline
Many years ago I was working at a heavy macine shop.
we were replacing the transmission deck on a hugh track dozer I was on one side with just plain old motor oil and a torque wrench Bob otheside with a tube of moly. Bob snapped off 4 bolts. The torque wrench went in to be calibrated hmmm. May be I was right after all these years. mind you these were 1"7/8 1 3/4 using a 4X wrench when those poped they ricocheted around the shop like gun fire SCarry!!
we were replacing the transmission deck on a hugh track dozer I was on one side with just plain old motor oil and a torque wrench Bob otheside with a tube of moly. Bob snapped off 4 bolts. The torque wrench went in to be calibrated hmmm. May be I was right after all these years. mind you these were 1"7/8 1 3/4 using a 4X wrench when those poped they ricocheted around the shop like gun fire SCarry!!
OP
Morris
Yoda
Offline
Well I re-torqued to 50#s and that seems to have fixed the problem... for now. Compression has come back up to 165#s on all 4 (was 145-155 before).
This will officially be the first time that the "easy fix" worked for me. /bcforum/images/%%GRAEMLIN_URL%%/smile.gif
And when the "easy fix" craps out on me next week. I have a head gasket on the shelf ready to go. /bcforum/images/%%GRAEMLIN_URL%%/wink.gif
This will officially be the first time that the "easy fix" worked for me. /bcforum/images/%%GRAEMLIN_URL%%/smile.gif
And when the "easy fix" craps out on me next week. I have a head gasket on the shelf ready to go. /bcforum/images/%%GRAEMLIN_URL%%/wink.gif