340 head torque requirements

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jawbone

jawbone

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Gentlemen. All reference I can find on forum regarding recommended torque for iron heads is 95 ft. lbs. 1968 service manual specifies 85. My 340 is a 70 model with O heads if that matters. Did Mopar make a change at some point or is the 68 service manual incorrect. Stumbled upon this discrepancy by accident. Will be using stock head bolts with 30wt. oil thread lubrication. Already went round and round with ARP and why not to use their lubricant on stock hardware. Their bolts are shorter than stock so elected not to use them. Always follow service manual guidelines right so why the change.
 
Thanks for the heads up. Would hate to make that mistake. Have spend many hours reading prior to and during this build. Not like in my earlier years where I just was just replacing a discrete part.
 
95lbs on 340/360
85lbs on 318/273
That's what I torqued to since I started.

Check
"how to rebuild small block mopar engines"
"Summit"
and many others...and you will find that some are copying BAD INFO and passing it along further hurting the hobbiest.
For the folks cranking 175+psi.. If you want to up the 'potential' for pushing a head gasket ...go ahead and torque to 85lbs.
As for the why...well i can only imagine its the chambers being larger and so the head becomes that much less integrally rigid and the gap between bore/deck width that much narrower...and so plays in the 10lbs extra clamping force..but I'm just guessing.
All I know is I've never had head gasket issues.
 
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Thanks for the reply. Will follow everyone's lead. Just wanted some confirmation before I proceeded.
 
I sure as hell wouldn't torque rocker shaft bolts at 30 ft lbs. 15 ft lbs on mine. Things are going to start to yield at 30. Like, a cheap torque wrench not clicking when it is supposed to? I have actually been using an inch lb torque wrench on the light stuff.
 
Rockers with stock bolts is 17 IIRC 200 inch pounds

Bolts didn't change size on the heads from 67-72, all are 1/2-13. I do them at 95, 3 steps.
 
I have studs for my rockers, trick flow heads, 180 in lbs. ARP lube. No issues so far.
 
CRUZE 418 said:
I have studs for my rockers, trick flow heads, 180 in lbs. ARP lube. No issues so far.
Click to expand...

jawbone said:
Rocker shaft bracket bolt stated at 15. Believe that to be correct.
Click to expand...

You aren't using stock bolts which are ~17 or 200inch. It isn't 15 for stock bolts with oil.

Also, using the ARP lube reduces the amount of tq required to get appropriate stretch. Whatever ARP suggest for their studs, that's the number to use.
 
jawbone said:
Gentlemen. All reference I can find on forum regarding recommended torque for iron heads is 95 ft. lbs. 1968 service manual specifies 85. My 340 is a 70 model with O heads if that matters. Did Mopar make a change at some point or is the 68 service manual incorrect. Stumbled upon this discrepancy by accident. Will be using stock head bolts with 30wt. oil thread lubrication. Already went round and round with ARP and why not to use their lubricant on stock hardware. Their bolts are shorter than stock so elected not to use them. Always follow service manual guidelines right so why the change.
Click to expand...

From an old motors manual: 85 ft lbs for steel head gaskets ..... 95 ft lbs for composite head gaskets.
I go 90 ft lbs with engine oil --- [not with greases].
 
340's changed head bolts. Same size, same length, better material. Went to 95 ftlb to seal 340 high compression engines. maybe across the board by date? 30 wt oil for lube. Beam torque wrenches stay in calibration. Rocker arm to 210 inch pounds. Using ft lb torque wrench at that low a setting is like using a sledge hammer to do trim finish nailing.
 
pt70 said:
I go 90 ft lbs with engine oil --- [not with greases].
Click to expand...

And don't dip the head bolts in oil. Too much oil on the threads can puddle in the bottom of the hole and hydraulic as the bolt get's to the end of it's travel. It can crack the block. Dip your finger in the oil and brush a little on the threads.
 
CRUZE 418 said:
I have studs for my rockers, trick flow heads, 180 in lbs. ARP lube. No issues so far.
Click to expand...
I am using Hughes Engines rocker arm shafts with brackets (adjustable rockers). Mounting hardware included with what appears to be hardened fasteners. Have contacted ARP regarding using their lube oem head bolts. End result was not to use ARP lube unless using their fasteners. Confusing so I decided to go the old fashion way with 30wt. motor oil. Glad to see you have not had any issues. 180 sounds like a good number.
 
crackedback said:
Rockers with stock bolts is 17 IIRC 200 inch pounds

Bolts didn't change size on the heads from 67-72, all are 1/2-13. I do them at 95, 3 steps.
Click to expand...
This goes back to my Mopar manual again which states 15 ft.lbs. on rocker arm shafts. Will go the 17. Thanks.
 
toolmanmike said:
And don't dip the head bolts in oil. Too much oil on the threads can puddle in the bottom of the hole and hydraulic as the bolt get's to the end of it's travel. It can crack the block. Dip your finger in the oil and brush a little on the threads.
Click to expand...
Thanks, have done just that. Bolts were brushed, inserted, removed and wiped off to remove any excess. Don't want the oil to affect contact surface of head gasket either.
 
pt70 said:
From an old motors manual: 85 ft lbs for steel head gaskets ..... 95 ft lbs for composite head gaskets.
I go 90 ft lbs with engine oil --- [not with greases].
Click to expand...
I like your comment. This makes sense why my book states the lesser torque. I am in agreement with everyone's comments to use 95. Thanks for your input.
 
66fs said:
340's changed head bolts. Same size, same length, better material. Went to 95 ftlb to seal 340 high compression engines. maybe across the board by date? 30 wt oil for lube. Beam torque wrenches stay in calibration. Rocker arm to 210 inch pounds. Using ft lb torque wrench at that low a setting is like using a sledge hammer to do trim finish nailing.
Click to expand...
Between the change to composite head gaskets and better head bolt material will most certainly go with 95. Regarding rocker arm shaft hardware, have seen multiple but slight differences in recommended torques. My fasteners are not stock so the higher range will be used. Have a new 0-600 in.lbs. CDI torque wrench just for such an application.
 
jawbone said:
Between the change to composite head gaskets and better head bolt material will most certainly go with 95. Regarding rocker arm shaft hardware, have seen multiple but slight differences in recommended torques. My fasteners are not stock so the higher range will be used. Have a new 0-600 in.lbs. CDI torque wrench just for such an application.
Click to expand...

What fasteners are you using? Did they give you any torque specs? Did you hone your block with torque plates?
 
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