Using 12 point ARP style rod and main bolts

[Fred_Maves]

I am reassembling a 1098 cc engine for my Sprite. During a previous rebuild I installed 12 point ARP stye rod and and main bolts. I discovered the remnants of blue Loctite thread sealer. Since, I have been given several opinions regarding the use of this product. The fact that typical tab locks will not match with the facets lead me to be somewhat concerned. Some say:
Torque the bolts dry w/o sealer
Use light oil
Use the higher heat rated red Loctite
Is there a consensus on this topic out there?

 

[racingenglishcars]

...Some say:
Torque the bolts dry w/o sealer
Use light oil
Use the higher heat rated red Loctite

Is there a consensus on this topic out there?

Apparently there isn't a consensus. I personally use blue Loctite. Maybe I should use red ??

Welcome to the forum.

 

[Scott_Hower]

"ARP style"?

I know ARP specifically recommends using their assembly lube, or alternately, some flavor of Loctite during assembly to achieve the proper torque preload.

I would not assemble these dry, but that's just my opinion.

 

[MichiganTed]

Torque specifications are developed for fasteners as received from their manufacture with some torque tension residual fluid on them. The fluid might be cutting fluid, rust preventative, etc. But either way, it isn't removed to develop torque specifications. Doesn't matter if it's a rod bolt, an intake support bracket bolt, or a tie-rod end. So in general, torque specifications are "wet". Remember that what maintains bolt tension is the amount the bolt stretches as the threads try to pull away from the head of the bolt during run down. That's why long bolts have a better torque retention (and lower torque spec) than short bolts: longer = more stretch.

If you use dry bolts with dry threads (which is almost impossible to achieve) a significant amount of your torque measurement will go into friction, up to say 40%. The result will be a under-torque condition.

Blue vs Red loctite really comes down to if you want to be able to service the joint in the future (generally a blue formulation) or if you never ever want to have the joint come apart again (generally a red formulation). Critical fasteners like rod and main bolts won't ever get hotter than your peak oil temperature. And with tab locks, you really don't need any loctite but if you must - I'd go with blue. The tab locks only need grab a small bit of the hex to be effective.

 

[Hap Waldrop]

Loose the locking tabs, use the supplied with part ARP assembly lube, motor oil if you don't have that, you always want to lube these sort of high torque internal engine fastners to get a true torque, so never dry and never with loctite. Fred this advice come from a professional MG street and race engine builder with over 25 years of experience, and I don't build any of my engines, street or race with out ARP fastners, so a product I use very often.

 

[Fred_Maves]

Hap,

Thanks, when I picked up my reworked cylinder head at my area machine shop the "head" shop guy concurs with your opinion. He even gave me enough ARP to use free of charge.

Being a Freshman member, I was pleasantly surprised by the quick, helpful responses to my first post. My next one concerns the correct piston alignment given no obvious front/back markings.

Thanks again,
Fred

 

[Trevor Jessie]

The rod numbers are stamped to help to orient them. (check the manual I do not remember which side they point to).

 

[Hap Waldrop]

The ARP rod bolt used in a 948/1098 engines isn't actually listed as such in the ARP catalog, or website but rather on thier universal rod bolts listed as 1.5" 3/8" univeral part number, they are perfect for the 948/1098 connecting rod as for lenght, shoulder length and such, many of us A series race engine builders have been using this part number for many years with these rods.

 

[BlueMax]

I’ll share a personal word of caution using ARP fasteners. Something you will discover that your main and rod housing will have dimensional change, in my case over a thousandth of an inch. So if you go the ARP rout do a mock build with the ARP torques then take your measurements of your housings. If any change, hone rods and mains for the correct tolerances’ that you’ll need to be applied in your engine build for the proper clearances!

 

[Hap Waldrop]

I’ll share a personal word of caution using ARP fasteners. Something you will discover that your main and rod housing will have dimensional change, in my case over a thousandth of an inch. So if you go the ARP rout do a mock build with the ARP torques then take your measurements of your housings. If any change, hone rods and mains for the correct tolerances’ that you’ll need to be applied in your engine build for the proper clearances!

Yep, thats correct, you don't change the fastner type and not resize (ARP or otherwise) thats engine building 101, meaning resize the big end of the rods, and line bore/hone the mains. Also you should never replace rod bolts, even stock type and not resize your rod's big ends. In fact I think no bottom end rebuild should be done without, at minimum, the rod's big end sizing being checked.