Torque specs 1980 johnson 25hp

[Shawnfish80]

Im confused...in the pic are they referring to the actual bolt size or the size of the bolt head, meaning the size of wrench needed to tighten or remove it.. Example..where it says 3/8 are they referring to the diameter of the threaded part or the size of wrench needed?

 

[Faztbullet]

Screw size...

 

[Shawnfish80]

Screw size meaning the diameter of the threaded part? Then why do my 1/2 inch head bolt heads and my 7/16 inch bolt heads on my exhaust cover both have a 5/16 diameter screw size that call for 10-12 ft lbs of torque when i know for a fact my head bolts should be torqued at 18-20 ft lbs or 216-240 inch lbs of torque? Makes no sense hence my confusion...

 

[racerone]

Fact.-----The torque values given are for the diameter of standard THREAD sizes.-----Has absolutely nothing to do with the wrench size !!!------And yes for some years they did put 7/16" hex heads on cylinder head bolts that are 5/16-NC threads.----So measure the threads and torque according to the chart !

 

[Shawnfish80]

Fact.-----The torque values given are for the diameter of standard THREAD sizes.-----Has absolutely nothing to do with the wrench size !!!------And yes for some years they did put 7/16" hex heads on cylinder head bolts that are 5/16-NC threads.----So measure the threads and torque according to the chart !

My bolts on my head have 1/2 inch hex heads with 5/16 dia threads wich call for 120-144 in-lbs, i just found my factory service manual and it says 18-20ft-lbs or 216-240 in-lbs. It lists the head bolts as 1/2 inch wich is the head not the threads yet gives 3/8 thread size values for torque when the threads on my 1/2 heads have a 5/16 bolt dia. ? Sooooooo yeah im not sure about your stated "fact" and tbh im more confused now but im going with my manual specs...

 

[Faztbullet]

That screen shot is NOT from a factory manual..it a danged ole Selco. You don't go by what type/size wrench or socket fits the bolt..you go by the screw thread size...
The values posted are correct so get you a screw gauge as head bolts are 5/16 not 3/8...

 

[racerone]

In table 6 what does the top line say ???----Starts with ---" torque should be used ----Time to read and understand what your manuals are explaining to you I say.----At one time I was involved in tightening fairly large fasteners with torque values up to 900 FT-LBS.----And I know that length of fasteners can be used to determine torque.----Ultra--sonic sound can be used to torque stuff up.----Or torque to a low value, then heat the hollow bolt with an electric heater and turn the nut a determined # of flats to achieve torque when it all cools.