Head Bolt Torque Question

Duggie

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When I did a valve job 2K miles ago, I torqued my Fel-Pro gasketed head to the FSM spec of 65lbs.

I just had my head cut .075" for a static 8.05:1 compression. My new Dutra /6 Engines book shows Dutra torquing the head bolts to 80lbs.

What to do?
 

Locomotion

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There would be a difference depending if you use regular oil or the special lube like ARP uses regardless of engine or bolts..
 

Duggie

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'64 /6. Bored .030" over and head shaved .075". Stock cam for now. Semi-daily driver.
 

dano

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If you followed the FSM you should be fine at 65 with 30w oil unless Felpro said differently. Are you experiencing any issues?

ARP has different torque specs for fasteners when you use their lube with their fasteners.

upload_2022-3-20_14-51-20.png
 

Duggie

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If you followed the FSM you should be fine at 65 with 30w oil unless Felpro said differently. Are you experiencing any issues?

ARP has different torque specs for fasteners when you use their lube with their fasteners.

View attachment 1715892990
No issues since doing a valve job 2K miles ago. Just wanted to mill the head now along with upgrading the carb and exhaust. I just got Dutra's book as a gift from the little woman. Until then all my specs have been straight out of the Factory Service Manual and info from the gurus on this forum. 65 to 80 lbs torque seams like a big difference to me.
 

pishta

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Was Dutra using studs? If I were him and building a hi performance slant with his clout, Id be using studs. Very hard to determine the proper torque needed (different bolt finish, lubes, strength) unless your using a bolt stretch meter as in good rod bolts. It would have to be measured off the block and not the head as that is moving under the bolts. I never heard of such a setup but Id probably just follow the FSM, or bolt/stud manufacturer (ARP/Pioneer/Etc)
 

volaredon

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yeah, I too, have seen different specs for those, between FSM, Dutra, Chilton's manual from back in the day, various posts here + at the /6 site/// seems the range I see is 65-80 ft/lb,, most say either 65 OR 70. Not a huge difference there, main thing is they are all even and torqued from the center out. Big difference between 65 ft/lb and 80 ft/lb though/ and none of these (that I remember) say whether that is "dry" torque, or "with oil" I can see the same bolt possibly having the same holding power torqued "oiled" at 80 ft/lb, vs 65 ft/lb torqued "dry". I have seen an article that mentioned how much torque is eaten up by friction especially when torqued dry. but I cant remember the percentage mentioned. I've always oiled head bolts, when I assemble an engine before torquing. They always come out oily anyway, when disassembling!!
I have 0.100" shaved, between block and head, thick Aussie head gasket that's at ~0.050" compressed/ that's 2-1/2x the OEM shim steel (o.020")
so add an extra 0.030" in head gasket thickness, off of 0.100" shaved and that's a net of 0.070" total difference from original OEM. so 0.070" more thread engagement than stock. I don't believe that "as is" originally those bolts come anywhere close to using up all the available threads on the head bolts. I ran a couple in on my block before I put the head on, just with my fingers/ I don't think that's enough to have to run hardened washers. The head bolts thread in easy and deeper still, if would have been needed, than where they stand while holding the head and gasket in place. 0.070" would be what... 1 more thread engaged with the block?
Those bolts are 7/16" coarse which is 14 threads per inch. 14 threads per inch x0.070= 0.980" so my head bolts wind up "just over" 1 thread deeper in the block than original. in my case 0.030" of the shave job on my engine was off the clock but the 0.030" thicker head gasket exactly matches that.

Likewise I have seen a few different specs on torquing the intake onto a smallblock, when we redid the motor on my Mom's 5th Avenue I came up with a spec somewhere of 35 ft/lb. the intake face of a smallblock head is 3/8 coarse threaded and thinner than the deck on a /6. I remember going around a few times splitting up the torque spec in 1/2 or 1/3, and when I got to the 35 on the first couple, it felt like I was starting to pull the threads in the head. so I backed em all off and looked in a different book that showed either 25 or 30 and whichever it was, that was where I had left it. every small block I have messed with since has had an aftermarket aluminum intake, on which I couldnt get a torque wrench on the center 4 bolts "if I even wanted to" so I ended up tightening those with a box wrench.
I wouldnt suggest that on a head gasket of any kind!!!!
I just mention that because I remembered a similar experience with different torque specs listed from different sources. That, in and of itself, isn't good.
 

volaredon

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When I did a valve job 2K miles ago, I torqued my Fel-Pro gasketed head to the FSM spec of 65lbs.

I just had my head cut .075" for a static 8.05:1 compression. My new Dutra /6 Engines book shows Dutra torquing the head bolts to 80lbs.

What to do?
yeah that's funny aint it? ("bad" sort of funny) Every Chilton's or Motor's manual, even the FSM say that a slant is "factory stock" at 8.4:1. and with a net of 70 thou milled off my head and deck, when running my numbers thru a Wallace style CR calculator, I come up with "just barely", exactly, that number. I hate to think how little I really started out with.
so/ you had the valve job done, reassembled and then re-disassembled it for a head shave? You should have had that done the 1st go-round. would have saved yourself a redo.
 

RustyRatRod

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Why would you rethink what the factory service manual says?
 

Slantsix64

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ive always used torque specs from the factory, i have probably torqued down 5 slant six heads to 65FT pounds with no issues. But what is more important is is chasing the threads with some penetrating oil.
 

66 Valiant wagon

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If you're asking it's because you are concerned. If you're concerned I'd pony up the money and switch to ARP studs.
I have snapped head bolts off in the past. It doesn't happen often but it does happen. It sounds like you have a lot of money already into this build.
 

CNC-Dude

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Why would you rethink what the factory service manual says?
Correct...! If your using factory components, then use the factory manual! Don't get confused by what other people say or do, they could be wrong, the book could have a misprint or they may not be using factory components.....
 

volaredon

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Not saying I used others' info but I didn't always have fsm's to go by. growing up, all we had around were Chilton manuals..now I have both and we have the internet, plus word of mouth and somebody's uncle Pete, etc.
Just beware of where you get your info
 

Duggie

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Was Dutra using studs? If I were him and building a hi performance slant with his clout, Id be using studs. Very hard to determine the proper torque needed (different bolt finish, lubes, strength) unless your using a bolt stretch meter as in good rod bolts. It would have to be measured off the block and not the head as that is moving under the bolts. I never heard of such a setup but Id probably just follow the FSM, or bolt/stud manufacturer (ARP/Pioneer/Etc)
Dutra wasn't using studs in this book. His example engine was a worn out '70s(?) engine.

Not a huge difference there, main thing is they are all even and torqued from the center out. Big difference between 65 ft/lb and 80 ft/lb though/ and none of these (that I remember) say whether that is "dry" torque, or "with oil"
When I did the valve job 2K miles ago, I found Red Permatex smeared way up the head bolts. I used the same to reassemble. This time, the machine recommended a Permatex Blue #2 non-hardening for the threads.

yeah that's funny aint it? ("bad" sort of funny) Every Chilton's or Motor's manual, even the FSM say that a slant is "factory stock" at 8.4:1. and with a net of 70 thou milled off my head and deck, when running my numbers thru a Wallace style CR calculator, I come up with "just barely", exactly, that number. I hate to think how little I really started out with.
so/ you had the valve job done, reassembled and then re-disassembled it for a head shave? You should have had that done the 1st go-round. would have saved yourself a redo.

Yep - mine too! Before the head shave, I calculated 8.0:1. After removing .750" off the head, I'm at 8.6:1.

When I first got the car two years ago, it had a burnt valve, oil soaked clutch, Swiss cheese radiator and heater core, trashed 4 spd, flat rear springs, worn out front end bushings, rust, yada-yada. Oh did I mention that I paid to have it inspected back in Rhode Island and it has a really pretty interior and paint job? Anyway, I was a bit overwhelmed with getting my honey "the" model car she drove when she was 20 for her birthday and finding sooo much work to do when I naively thought I was going to change the oil and lube the door hinges. Oh if I knew then what I know now... With the long repair road in front of me, I didn't want to shave the head along with the valve job and blow out the unknown piston ring condition. I wanted a break. Recently, I got a cranking compression of 165lbs with a slightly looser valve adjustment and with that am reasonably confident in the rings holding up to the milled head.

This round started with a new exhaust before the old one falls off. Great excuse for some type of header. If I'm going to do that, I may as well upgrade to that 318 two barrel. If I'm going to do that, I should shave the head. So I'm doing all that and that's how far my money's going. Oh and I don't recall who said it but I can scoot the drivers seat closer to the throttle pedal for free. HA!

Why would you rethink what the factory service manual says?

Only because Dutra has such a good rep in the forums.

And thanks to all the rest for your input. You guys bring years and years of valuable experience to babes in the woods like me. I've said it before and will probably say it again sometime; This car wouldn't be a reliable driver without everyone sharing their experience.

I hope to see some of you guys on the road this year! :steering:
 

RustyRatRod

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Only because Dutra has such a good rep in the forums.

I'm going to try and say this as respectfully as I know how. I like Doug. I think he's perhaps a genius. He's given more to the slant 6 community than probably anyone alive. Having said that, and I mean it, he's tore up more chit trying to do stuff different than what Chrysler designed than anyone I can think of.

And yeah, I know this is how you learn and find out what works and what doesn't, which clearly he's done. I had hopes for that aluminum engine he built he tried to put a deck on. I saw the pictures going in. I knew it would fail. He ruined an otherwise good rare aluminum slant 6 block. Gone. Forever. He even admitted it couldn't be salvaged.

Again, I know. This is how you discover new stuff. How you learn. All that said, there's no way I'd jack up the torque on head bolts 20 LB FT on someone's word no matter who they are when the FSM says 65. Ain't happenin.
 

volaredon

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It's possible some of these sources could be *misprints" but tough to know which ones.....
In this case the general consensus is 65-70 on head bolts on these engines.
 

volaredon

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Dutra wasn't using studs in this book. His example engine was a worn out '70s(?) engine.


When I did the valve job 2K miles ago, I found Red Permatex smeared way up the head bolts. I used the same to reassemble. This time, the machine recommended a Permatex Blue #2 non-hardening for the threads.
Yep - mine too! Before the head shave, I calculated 8.0:1. After removing .750" off the head, I'm at 8.6:1.
Dutra shows several engines in various stages in the book.
I'd never put red permatex or #2 on head bolts. Maybe some Teflon paste on applications that call for some kind of sealer. Otherwise just a little bit of engine oil.

3/4" off the head? No way.
 
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Killer6

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When I did a valve job 2K miles ago, I torqued my Fel-Pro gasketed head to the FSM spec of 65lbs.

I just had my head cut .075" for a static 8.05:1 compression. My new Dutra /6 Engines book shows Dutra torquing the head bolts to 80lbs.

What to do?
I know where You got that number, the text accompanying the step by step pic, but the torque chart at the rear of the manual states 70ft./lbs. The +5ft./lbs. is acceptable with lightly oiled threads.
Beware the typo!!!
 

BillGrissom

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Re the effect of oil, I saw an engineering chart from Rocketdyne concerning bolt torques. It said that regular oil does not change the torque to tension relationship, but only makes it more consistent. Apparently because the oil squishes out to give only metal-metal contact at the final torque value. What could affect the relation is using a high-pressure lubricant such as MbS2 ("moly"), which can give twice the tension (stretching force) for the same torque reading. The bolt tension is what is critical and reading torque is just a way to infer it. Some wheel bearing greases have moly, so avoid using any grease on the threads or underside of the bolt head. Also, blow out the holes since you don't want any oil level which could hydro-lock against the bolt to cause you to stop torqueing too early. Rocketdyne (now Aerojet Rocketdyne) made the liquid rocket boosters on the F-1 engine (Saturn V) and Space Shuttle, so everything they do is precise and carefully vetted and checked since a leak in a rocket booster is much worse than in your car.
 

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