340 head torque requirements

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Want to thank everyone for their input so far. Engine building has become a big lesson, to me anyway, since my younger years. Have learned to degree a cam, cc my heads to calculate my compression. Cam selection has been somewhat of a lesson. Not sure where I stand on it. Time will tell. Have checked piston to valve clearance. All that is left are the custom pushrods. Will see how that goes. Again, many thanks to all of you.
 
66fs said:
What fasteners are you using? Did they give you any torque specs? Did you hone your block with torque plates?
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Hughes Engines, If I remember correctly, provided the fasteners. They are 12 pt. hardened steel. Will check my receipts for possible alternate source but believe I'm correct. Came with a butt load of shims as well. Rocker Arms Unlimited bushed the 273 rocker arms. No torque specs provided. Just instructions to clean rocker shafts before assembly. Cleaning means the inside which was very contaminated. Regarding torque plate, Short block machining and assembly was done at machine shop. Doubt torque plate was used. Block deck was surfaced and bored .030 over with sleve in no.1 hole.
 
Clean the rocker shafts, I had thought about that, but did not do it on my stock 318 build, wondering if their are new plugs in the freeze plug set. Do not remember seeing them, will look. Haven't started it yet, wish that I had a dent puller to pull the end plugs, but I know where one is. Other ways to do it too.
 
jawbone said:
Hughes Engines, If I remember correctly, provided the fasteners. They are 12 pt. hardened steel. Will check my receipts for possible alternate source but believe I'm correct. Came with a butt load of shims as well. Rocker Arms Unlimited bushed the 273 rocker arms. No torque specs provided. Just instructions to clean rocker shafts before assembly. Cleaning means the inside which was very contaminated. Regarding torque plate, Short block machining and assembly was done at machine shop. Doubt torque plate was used. Block deck was surfaced and bored .030 over with sleve in no.1 hole.
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You might want to contact Hughes Engines about torque for the head bolts and rocker arm fasteners. We were giving values for stock fasteners. Stock rocker shaft bolts are only grade 5 standard bolts. I only asked about the torque plate as fastener (head bolt) torque has an effect. No worries there. Sounds like your build is similar to the 340 build I'm working on. Do you have an adjustable pushrod to check length?
 
66fs said:
You might want to contact Hughes Engines about torque for the head bolts and rocker arm fasteners. We were giving values for stock fasteners. Stock rocker shaft bolts are only grade 5 standard bolts. I only asked about the torque plate as fastener (head bolt) torque has an effect. No worries there. Sounds like your build is similar to the 340 build I'm working on. Do you have an adjustable pushrod to check length?
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Yes I do. When I was checking piston to valve clearance compared my adj. pushrod against pushrods provided by Rocker Arms Unlimited. Why they provided them do not know but very close to my needs. Do not know the actual effective length at this time. That determination is pending getting the heads on. It's just like many of these suppliers to stipulate consult your service manual for torque specs. The exception so far for me is ARP. Even if the bolts from Hughes are grade 8 vs. stock 5, required torque would be the same would it not.
 
jawbone said:
Yes I do. When I was checking piston to valve clearance compared my adj. pushrod against pushrods provided by Rocker Arms Unlimited. Why they provided them do not know but very close to my needs. Do not know the actual effective length at this time. That determination is pending getting the heads on. It's just like many of these suppliers to stipulate consult your service manual for torque specs. The exception so far for me is ARP. Even if the bolts from Hughes are grade 8 vs. stock 5, required torque would be the same would it not.
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No, probably higher.
 
CRUZE 418 said:
Clean the rocker shafts, I had thought about that, but did not do it on my stock 318 build, wondering if their are new plugs in the freeze plug set. Do not remember seeing them, will look. Haven't started it yet, wish that I had a dent puller to pull the end plugs, but I know where one is. Other ways to do it too.
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The Hughes replacements have pipe taper end plugs to be installed after cleaning. Have read previous post in which someone had horrific time finding stock rocker shaft plugs. Precaution may be necessary before pulling plugs.
 
Preload should be higher due to stronger material of the fastener. Cast Iron is good to at least grade 8. Probably a nit though and I do not know in this instance. I used to have a chart, as torque is a very tricky spec. Depends on things you can not calculate. Stretch is the most accurate.
 
My PRW rockers came with the whole set up for my 418 engine. Got it through Mike at B3 Racing. Your set up sounds similar except you have bolts instead of studs for the rocker arm shafts? I did not clean those shafts, have had them apart and the shafts still look good. Probably got lucky.
Will find plugs for the 318 stock shafts before cleaning!
 
66fs said:
No, probably higher.
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Well I contacted Hughes Engines regarding torque specs on mounting hardware. His comment was 25 ft.lbs for stud style application. Instructions stated 30 ft.lbs. on website for small blocks. He did not want to address my question for bolt applications. It seems they do not offer bolts any more for rocker shaft mounting.
 
66fs said:
Preload should be higher due to stronger material of the fastener. Cast Iron is good to at least grade 8. Probably a nit though and I do not know in this instance. I used to have a chart, as torque is a very tricky spec. Depends on things you can not calculate. Stretch is the most accurate.
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I would agree stretch is the most accurate but is it necessary to consider in this application event though Hughes Engines want to torque rocker shaft hardware to 30 vs. SM 15 ft.lbs. If the fastener does not stretch then it does not hold effectively?
 
CRUZE 418 said:
My PRW rockers came with the whole set up for my 418 engine. Got it through Mike at B3 Racing. Your set up sounds similar except you have bolts instead of studs for the rocker arm shafts? I did not clean those shafts, have had them apart and the shafts still look good. Probably got lucky.
Will find plugs for the 318 stock shafts before cleaning!
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Went to Hughes website. They no longer offer bolt setup, only studs. Think you have the better setup.
 
Back in the very early 1970s I had a '69 340 Swinger that needed a head gasket change. I will always remember that the stock head bolt torque requirement was 95 lbs.
Why do I remember? Because the only way to get to one of the bolts on the rear of the driver-side head was with a 'wobbly-joint' Craftsman socket (we didn't want to have to move the brake master cylinder) and it wouldn't go past 92 lbs. without breaking through the wall of the socket. My buddy and I broke two of them within an hours time.
We took the first broken 'wobbly-joint' to the local Sears store and got the free replacement. We sure got a funny look from the same sales guy when we took the second broken one back an hour later.
We ended up leaving that last head bolt at 92 lbs.
 
ocdart said:
Back in the very early 1970s I had a '69 340 Swinger that needed a head gasket change. I will always remember that the stock head bolt torque requirement was 95 lbs.
Why do I remember? Because the only way to get to one of the bolts on the rear of the driver-side head was with a 'wobbly-joint' Craftsman socket (we didn't want to have to move the brake master cylinder) and it wouldn't go past 92 lbs. without breaking through the wall of the socket. My buddy and I broke two of them within an hours time.
We took the first broken 'wobbly-joint' to the local Sears store and got the free replacement. We sure got a funny look from the same sales guy when we took the second broken one back an hour later.
We ended up leaving that last head bolt at 92 lbs.
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Those were the good old days I remember. Wish it were the same. Afraid to make a mistake that can cost me dearly now.
 
jawbone said:
I would agree stretch is the most accurate but is it necessary to consider in this application event though Hughes Engines want to torque rocker shaft hardware to 30 vs. SM 15 ft.lbs. If the fastener does not stretch then it does not hold effectively?
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30 ft lb sounds like too much. That is the same as 3/8 bolts. You would be safer using the 210/215 inch pounds for factory 5/16 bolts. A certain amount of stretch is optimal, think of a bolt or stud as a very stiff spring that clamps two parts together.
 
Well put and great summary. Every time I ask supplier, with exception of ARP, torque specs; they refer me to OM manual. Had in my possession at one time a generic torque spec chart for different grades of hardware. Granted was not absolute specific but did provide a safe range. From this discussion looks like I need to adopt this philosophy.
 
Per torque tension reference guide grade 8, 1/2 -13 lubricated with oil (K=0.17) recommended torque is 80 ft.lbs. Dry (K=0.20) torque is 106.
 

Attachments

  • Torque-Tension Reference Guide.pdf
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That one is very close to specified. I would agree. I kept pdf. for reference.
 
15 ft/lb on the rocker shaft bolts. Can be grade 5 or 8.
That is because they are not being torqued to the max available for that diam bolt. ARP lists 5/16-18 torque varying from 26 to 32 depending on bolt grade.
Tq is low because you are tightening on a hollow tube that can get squeezed out of shape with excessive tq. Not a problem with stamped rockers, but could bind up other types.
 
Bewy said:
15 ft/lb on the rocker shaft bolts. Can be grade 5 or 8.
That is because they are not being torqued to the max available for that diam bolt. ARP lists 5/16-18 torque varying from 26 to 32 depending on bolt grade.
Tq is low because you are tightening on a hollow tube that can get squeezed out of shape with excessive tq. Not a problem with stamped rockers, but could bind up other types.
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I would agree. Am using Hughes Engines shafts so do not thing deformation is an issue. The debate is what torque value is acceptable for grade 5 vs. grade 8 to achieve the proper stretch and clamping force. I plan on installing my head bolts dry to achieve the 95 ft.lbs requirement (106 max). If oil is used on threads, clamping force is limited to 80 ft.lbs.
 
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