Head torque
- Thread starter trendkilllx
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EMW150
Founding Member
They'll work fine at 70 (short) / 75 (long). Any more torque than necessary to seal the gasket just causes additional block distortion.
Michael Yount
Mustang Master
According to the torque data that came with my bolts, ARP bolts of that size used on aluminum heads with ARP moly lube/thread sealer require 60 ft-lbs. That's what I torqued mine to. The figure should be about 10-15% higher if oil (not their moly lube) is used to lube the threads. Torque figures are signficantly impacted by how clean the threads are, and what they're lubed with. They make no mention of different values for the longer/shorter bolts. Be sure you use thread sealer on the bolts that enter the water jacket. I used the ARP moly lube/sealer on all of them. It makes for nice, smooth, even pulls.
EMW150
Founding Member
Michael Yount said:
The reason for the higher torque on the long bolts is to counteract the wedging effect of the intake manifold torque to give the head surface equal compression.
Michael Yount
Mustang Master
EMW - Yeah, I've heard all sorts of reasons for different torquings for the long and short bolts, including the one you've given. All I can tell you is that ARP's data sheet with their 5.0L bolts specifies the same torque for all bolts. And the reason you've given seems counterintuitive to me. The manifold bolts TO the head. The only reason that the lower intake should try to 'lift' the head is if the heads or deck have been cut, the manifold hasn't, and the manifold is hitting the top of the block before it contacts the heads. In that case, tightening the manifold against the BLOCK might try to pull heads up to the manifold. Buy my experience with intakes is that those castings are so weak, you're gonna break an intake long before you're gonna do any significant lifting of the head. And all that's based on a geometry mistake anyway. If the manfold/head/block spacings are correct, the manifold port surface simply gets squeezed against the head port surface without contacting the block. No 'lifting' can take place in that configuration.
EMW150
Founding Member
Think, what you want. Every reputable engine builder I know recommends a compensation between the short to long bolts. Bolt an intake sometime on an engine with just the dowels installed in the heads, no bolts or just leave the bolts loose. Guaranteed it'll lift the top of the intake side of the head off the block.
EMW150
Founding Member
Michael Yount said:
The part you're missing is that the intake / head sealing surface is angled. The intake acts as a wedge. So if you tighten the intake, it naturally tries to force the heads apart. Since the heads are anchored by the dowels at the bottom it causes the head to try to lift at the top.
Michael Yount
Mustang Master
Sorry - your logic still doesn't make any sense to me if things are dimensionally correct. I have no doubt that there are engine builders out there that do it religiously. But you also have guys out there that will drain a T5 of fluid and refill it with 90 weight cause that's what transmissions always had in them. Reminds me of the story of the lady who always cut the ends off the ham before she put it in the oven. When asked why she said because her mom did. When her mom was asked why, she said because HER mom did. When great-grandma was asked why, she said it was because the ham wouldn't fit inside the old small oven she cooked on. I suspect it's a holdover from the days when intake manifolds were cast iron, fasteners weren't as high quality as they are today and the manifold might be stiff enough to lift the head. Think about it - for the intake to lift or wedge the head, it has to be stiffer/stronger than the head is. Pull/push one against the other, and which do you think is gonna give - the head or a porous aluminum intake casting? Lastly, I trust the folks at ARP who are one of (if not THE) leading fastener companies on the planet. I've gotta think if it were an issue worth noting, they'd spec it out that way in the literature with their fasteners.
And I'm completely comfortable seeing it differently than someone else. That's what the forums are all about.
And I'm completely comfortable seeing it differently than someone else. That's what the forums are all about.
EMW150
Founding Member
All I can say is try it like I said 2 posts above. You'll see exacly what I mean. I've done it first hand chasing head gasket problems in the past and talking to professional engine builders. ARP is giving you the recommendation for the bolts themselves, not taking other factors into consideration. And no engine builders don't do carryovers, like your grandma's ham story. These guys work with these engines everyday and know from their own experience.
Michael Yount
Mustang Master
Everyone does "carryovers" (I like that term by the way) - including you, me and the engine builders out there. They're blindspots, and we all have them. (Yes, I may have one here, but like Charles Barkley, I don't think so) We'd just like to think that they're not getting in the way of our projects. And, the issue isn't what happens when things are unbolted. The issue is whether a high quality aluminum head being held in place with high quality fasteners is gonna be moved by a relatively weak manifold casting being pulled into place with relatively tiny bolts at 16-18 ft-lbs. Sorry - I don't buy it. I think the manifold and its fasteners are gonna give/move long before the head does.
EMW150
Founding Member
Putting it together unbolted is just to show you where the stress is placed and where the objects will tend to move. You seem like an intelligent individual, I can't believe you can't see the theory behind this.
Michael Yount
Mustang Master
I'm sure we're both reasonably intelligent - no offense taken. I think I understand you and the physics/geometry completely. I just don't agree with your conclusion. Like I said before - that's ok with me. That's what the forums are for. If the world could learn how to disagree with each other without either side having to take exception to it, we'd live on a much more peaceful planet, and we'd learn more. Have a great weekend!
I think where we differ is that I believe for the manifold to move the head in this situation, it has to be stronger than the head. And I don't think it is - I think the manifold will give before the head will.
I think where we differ is that I believe for the manifold to move the head in this situation, it has to be stronger than the head. And I don't think it is - I think the manifold will give before the head will.
EMW150
Founding Member
Michael Yount said:
That was meant as complement, not an offensive remark. The point is not that it will move the head. The point is, if you know the force is there, why not compensate for it? If you have even clamping force on the top and bottom head bolts, you have less chance of head gasket failure. You have a great weekend also.
Michael Yount
Mustang Master
trendkill - now that we've stolen the thread - did you get your answer?
EMW - your combo looks like it totally rocks. Can you give us the highlights of the new combo in the works?
EMW - your combo looks like it totally rocks. Can you give us the highlights of the new combo in the works?
Michael Yount
Mustang Master
If I were in your shoes and still undecided I would contact ARP and AFR. Calling engine builders will likely net you the same result you got here - different people with different opinions. I believe that ARP will tell you exactly the same thing that's on the literature that comes with their bolts - which is where I was pulling my info from.
Quite frankly, despite EMW's/mine difference of opinion, I don't think it makes a huge difference. If you're using moly lube on the threads on an aluminum head - 60-65 ft-lbs will be fine. If you're not using moly lube - 68-75 ft-lbs. will be fine. And if you want to torque the upper bolts (the ones on the intake manifold side) 5-10 lbs. higher, I don't think it will hurt a thing. I just don't think it's necessary. Talk to 10 different people and you'll likely get about 10 different stories - but I'd bet all of them will be in between 60 and 80 ft-lbs on the bolts.
Quite frankly, despite EMW's/mine difference of opinion, I don't think it makes a huge difference. If you're using moly lube on the threads on an aluminum head - 60-65 ft-lbs will be fine. If you're not using moly lube - 68-75 ft-lbs. will be fine. And if you want to torque the upper bolts (the ones on the intake manifold side) 5-10 lbs. higher, I don't think it will hurt a thing. I just don't think it's necessary. Talk to 10 different people and you'll likely get about 10 different stories - but I'd bet all of them will be in between 60 and 80 ft-lbs on the bolts.
sn9550
Founding Member
Use AFR's instructions. I became confused after reading/re-reading the ARP instructions and ended up torquing the heads to 85 lbsft I think. I think AFR says to torque them at 80 for the top and 70 for the bottom.
Michael Yount
Mustang Master
ARP makes stand alone moly lube, as well as the combination moly lube/thread sealer. So it depends on which one you get. I use the lube/sealer on just about anything that needs lube and/or sealer that won't set up. It even works well on the back of disc brake pads.
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