Do or Don't re-torque heads

[Tim Kay]

Is it not recommended to re-torque aluminum heads in an aluminum Dart block? ( vs removing and replacing)

Motor has about 7k miles and a "drippy" water leak out one of the lower studs near #2 exhaust port. Nothing serious, yet, just a bit nagging.

And, if it's ok to re-torque, what's the Ft/lb.setting? Oh, and would it be necessary to re-torque all studs, I assume in the required torque pattern, or just the one ailing stud?

I realize it may not solve my "drippy" issue but it's worth a "shot" before taking the head off. (boy, that last sentence could mean something totally different in another forum!)

Thanks guys,:thumbsup:
Tim

 

[Ron Earp]

If you re-torque then you do so just like putting them on. Follow the correct fasterner pattern and torque spec.

Did you put sealant on the lower studs? They go into the water jacket (well, on std block they do, don't know about Dart) and need sealant.

 

[Jac Mac]

Dart Alloy Blocks have blind stud holes, so to leak coolant from one of the lower studs it must either have a porous block / head or be migrating from the head gasket. Re-torque when COLD, if fitted with studs( these should be 1/2" dia ) I hope you have the correct bullet nosed & longer coarse thread version made specifically for these or you will risk destroying the threads in the block. Torque value will depend on whether you have the correct studs or are using head bolts only

As a point of interest I built a 400+ W/C years ago with hi-port plates & the guy that owned it had a very laid back approach to routine maintenance, it always had a pool of coolant under the engine when parked up in the shop & I asked if he had ever retorqued the heads, with a lot of reluctance he did so & found the outer row pulled down approximately a 1/2 turn each, yet it never let a gasket blow in use, the expansion of the alloy port plate was enought to apply the clamp force reqd ( And NO, his name was not Cliff)

 

[Seymour Snerd]

If you re-torque then you do so just like putting them on. Follow the correct fasterner pattern and torque spec.

Just to make sure no one makes the mistake I did as a kid with my first car: don't do it literally like putting them on new, that is don't back all the head nuts or studs out until they're loose. Or if you do, drain the coolant first.....

 

[Tim Kay]

That's great. I'll take these suggestions and resolve this.

Realizing Jac Mac is right about the blind holes gives me some skepticism as to where the waters coming from. I was hoping it was more like Ron's diagnosis and the threads needed sealant. But I'll start with a full pattern torque.

BTW, What is the torque spec for aluminum head and block. It's different than an iron block, no? (And Jac Mac, I will verify the correct studs are used)


Thanks again guys

 

[Jac Mac]

If you go into the Dart Machinery - Cylinder Heads, Engine Blocks and More... site you will find all the spec sheets for the heads & blocks... The head torque specs are in the cyl head info sheets & in your case if they are studs & 1/2" they state 100 ft lbs final torque. Personally with the 1/2" UNF thread on the long ARP studs[by that I mean the bullet nosed ones made specificlly for the Dart Alloy Block] with lube/washers/12 point nuts etc I use 95 ft lbs with MY torque wrench, I also use a composition head gasket made here for my needs in NZ. I believe I read earlier on one of your threads that you use MLS types, In the Dart info you should note that they suggest coating these prior to fitment & I feel this might be where your coolant leak is coming from, If the car is not pushing coolant out of the header tank in use, but the leak is only after cooldown or after sitting overnight I think the leak may be tracking from a water passage hole in the gasket to the head stud hole via the embossed ridges in the MLS gasket, it might be able to be reduced/ stopped by retorque & if this is so shouldnt be a major concern....unfortunately your there & Im here half a planet away..

 

[Tim Kay]

J Mac, you're the best. Thanks.

 

[Rick]

Perhaps a limited amount of some sort of radiator stop leak would work in this instance, something like silver seal???
After a complete retorque however.
I'm thinking that with the amount of expansion with both an aluminum head AND block that the traditional head gasket may lose some of the clamping force imparted upon it and what you are seeing becomes not that unusual, hence the redesigned gaskets JAC MAC speaks of.