Couple of specific head bolt/gasket questions.

[Mart]

Question 1:
If you are using copper type spray on the gasket do you fit it when still wet or let it dry first?

Question 2:
What torque do you guys use if using aftermarket aluminium heads and bolts?

(typical 8BA type setup).

Thanks for any help.

Mart.

[Kube]

Originally Posted by Mart

Question 1:
If you are using copper type spray on the gasket do you fit it when still wet or let it dry first?

Question 2:
What torque do you guys use if using aftermarket aluminium heads and bolts?

(typical 8BA type setup).

Thanks for any help.

Mart.

Mart, I always use spray copper gasket. I wait until it is tacky before I install the head and begin the torque process.

[cas3]

Me too

[rotorwrench]

As long as the paint is still soft, it will stick. Unless the weather is hot, a person has around a 20 minute window. The hotter it is the shorter the window of opportunity.

An old friend who is now in hot rod heaven just used any silver or copper pigmented spray paint to coat metallic gaskets. They all work OK.

[Bored&Stroked]

I just let it tack up for about 20 minutes and then place them on the engine. I hang them outside and spray both sides - usually two thin coats so it doesn't run/sag.

On torque, I usually go to 55 lbs - in a couple increments and then heat-cycle and retorque at least 3 times. A lot of the retorqueing has to do with the quality of the hardware. When I use ARP studs/nuts/bolts (expensive), they don't stretch much, and the second torquing is usually all I need. With most aftermarket hardware (Grade 8 at best) studs/bolts, it usually takes 3 heat cycles for the stretch and torque to settle in.

I usually buy ARP heat-treated washers no matter what - they won't gall and screw up the torque readings like a lot of the aftermarket "stud kit" washers do.

[Mart]

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Dale, is that 55 ft lbs with studs and nuts or specifically with bolts.

In my mind a bolt (coarse thread) would need a higher torque value than a stud/nut (fine thread) to achieve the same clamping pressure.

Thanks for the input.

Mart.

[frnkeore]

The torque is based on the minor diameter of the bolt or stud.

Fine threads have a larger minor diameter so, you can not torque to the fine thread spec or, it over stresses the course thread.

[69a]

Vanpelt website says 65 ft/lb for 8BA bolts on cast iron heads. 40 ft/lb for aftermarket aluminum heads. I have aluminum aftermarket heads, but thought 40 was a bit light. Did mine at 55.

[Mart]

Originally Posted by frnkeore

The torque is based on the minor diameter of the bolt or stud.

Fine threads have a larger minor diameter so, you can not torque to the fine thread spec or, it over stresses the course thread.

Originally Posted by 69a

Vanpelt website says 65 ft/lb for 8BA bolts on cast iron heads. 40 ft/lb for aftermarket aluminum heads. I have aluminum aftermarket heads, but thought 40 was a bit light. Did mine at 55.

frnk: I agree that the max tensile strength of a fine bolt is higher at the limit but we are not approaching that limit here.

69a: I read mac's numbers and was also thinking 40 lbs ft for a aluminium head was light. I believe that number is for a factory aluminium head which only came with studs and fine thread nuts.

I have been using 50 lbs for bolts on an aluminium head but have suffered a head gasket failure.

My thinking is that a coarser thread requires a higher torque to achieve the same clamping load as a fine thread.

I'll give 55 a go.

[Ol' Ron]

I torque to 50lbs for 3 or more heat cycles.

[rotorwrench]

Oldtimers from the model A era like Murray Fahnestock always recommended 50 ft/lbs on studded heads. Put oil or grease in a light coat under the nut to allow for further retorques after heat soak. The final torque up will likely equal 55 Ft/Lbs after the retorques. A bolt won't stretch as much but I'd still keep it around a limit of 55 Ft/Lbs. Make sure and observe the proper sequence under all torque procedures. High compression heads may need more but it gets more risky too.

The model A & B blocks have a fairly solid deck but all flatheads and especially V8s get thinner after decking and heads after planing get thinner too. There is a lot of flexibility there so sneek up on final torques in increments so as lot to warp it up. Also make sure the bolts or studs don't bottom out.

[69a]

Also I've been told "composite head gaskets for aluminum heads, copper for cast iron"

[flatjack9]

I have never used any sealer on a head gasket, I torque to 45 lb. ft. on everything. I have my machinist take a light cut on the block deck and surface the cylinder heads so everything is nice and flat.

[Bored&Stroked]

I use studs on most of my engines - just prefer that approach from a torque "feel" perspective and I think they are better for higher performance engines.

I also use an ARP Teflon stud sealer on the studs when I put them in and let them sit at least overnight before I do the rest. I use ARP assembly lube on the fine threads and both sides of the washers and the bottoms of the nuts - helps ensure an accurate torque reading and makes disassembly and retorque procedures easy. I don't have a problem with bolts, especially of 49-53 engines that came with them (saves a lot of cost) but will stick with studs on my earlier engines and any real performance build..

One last thing is that the ARP studs have an allen/socket receiver on the tops - so I can remove one at a time before I pull the heads - makes disassembly a LOT easier. Also, if I have a leaking stud (Hey, it happens!), can pull just that one, reseal the coarse threads and put it back in. I don't use stock studs on anything (for this reason alone).