Raceware recommends 65 ft lbs, and no more. For those of you running Raceware studs, let's see what you are torquing to. Anyone have one fail or loose its strength?

 

I am not voting because i dont know. I hope others follow suit and dont vote if they dont know either. Following bad advice on this subject would be dangerous.

 

Just to be clear, I am not suggesting anyone follow what others are doing. My purpose in asking is merely to assess the credibility of Raceware's (somewhat off-hand) advice to me -- specifically that the studs could be compromised if torqued to 90+ ft lbs.

 

I was wrong when I stated that we used 75 the last time. It was 85lb. I wonder if they're just being conservative so as not to invite stripping the thread?

 

Maybe, but when I called Raceware, it came up in a different context. I said I wanted to order a new set because I was trying to fix a head-lift issue. In response, he said he didn't really want me to waste money on a new set because my existing ones are sure to be fine "unless you've been torquing them to 90 ft lbs or something..." He swore 65 ft lbs was "fool-proof" and that anything more just distorts things and causes problems. I know several engine builders who go to 100 or more, so just thought I'd see what others are doing...

 

The studs are fine for higher torque if you wish, the ‘theoretical’ failure point is 110 ft lbs – the aluminum threads I the block will fail (if they are perfect with no damage / wear – failure point will be a little lower for old used threads).

Massive torque is not a good answer. The head will start to deform and create clamping ‘hot spots’. I have tried higher torque on some applications – there is no benefit that I know off unless you like to run your engine into detonation (detonation has higher cylinder pressures and can get into head lift).

 

Chris, what torque do you recommend?

 

Depends…
MLS or stock type head gasket
If stock type – Oring or not
Stock head studs or raceware/ARP
Street or track
Sleeved or Alusil
Previous head gasket problems or not
Boost level

Yeah….it depends on a lot of things

And then we can get into staggered torque patterns….

 

Widefire, no o-ring, Alusil, stock studs, street, lots of boost, no previous HG issues.

 

Ok, Stock torque with 20% less on the end exhaust side studs and 10% less on the end intake side studs.

 

Chris, I also want to play, if you don't mind

Stock headgasket, 1.4mm (skimmed gead)
No O-ring
Raceware
Street
Alusil
No blown headgasket yet
15psi on pump fuel, will try perhaps 20psi on E85
(3.0 8V)

TIA

 

I'd consider keeping the hood closed based on the last part of your sentence.

 

Too late! Motor is already out of the car, and another I'm building right now...

 

Thanks! Can you educate me why less on the end studs?

 

Differential expansion / clamping / loading due to several reasons – the end studs only service one cylinder while the middle studs share cylinders. Also the end cylinders have more of a cooling jacket…there are a couple more reasons.

This concept is based on using a stock type gasket which gets compressed and then relaxed each time the engine goes through a heat cycle. Eventually the gasket gets too compressed and fails. Typically (but of course not always!) the failure starts early in the heat cycle while everything is still expanding.

I will credit Finch for the original idea….one of the few 944 engineering guys that I just don’t question. A link to his engineering firm - http://www.raetech.com/ and the most successful 944 race effort ever - http://www.raetech.com/944_Racing/944.php

This is also one reason why I am not a huge fan of the need for ultra stiff head studs – the rate of expansion is less than aluminum and a stiff stud will exert more clamping force as the bock /head gets hot. If you really crank up the clamping force the head surface will distort. The head gasket (if stock type) will also get crushed further.