Conflicting torques and defective parts

[Diseazd]

Anyone else notice that the camshaft sprocket bolt torque in the 'How to Modify" book by Frank Honsoweltz on page 86 is 100-108 ft.lbs. and the torque given in the factory manual is 43 ft. lbs.? Which is it? Also......has anyone had any problem with the crank sprocket provided with the Motorsport Japanese timing chain kit. The key slot is too loose allowing the sprocket to rock back and forth?

[geezer]

The Haynes manual says 40 lbs/ft.

[geezer]

Autobooks - 36.2 to 43.4 lbs/ft

Can't help with the keyway Guy...it's always something hey?

Edited August 15, 2008 by geezer

[sblake01]

What was wrong with your original timing kit? I only ask because over the years, I've found that some aftermarket mods create more problems than they solve. I've often said that Nissan did a pretty good job of building these cars and the best parts for them are most often the original ones.

[Diseazd]

I always replace the chain and tensioner when I rebuild old Z engines. The chain kit from Motorsports has tensioner, guides, chain and sprockets. I use Nismo adjustable cam sprockets when I rebuild. This is the first time I've even fitted the crank sprocket.......I certainly agree that you can't trust anything but the real thing. Just a heads up.....don't use the crank sprocket from the timing chain kit.

[xray]

Guy,

My FSM says cam sprocket bolt torque is 86-116 lbft (1973 p. EM-33), similar to the crank pulley bolt torque. So, when I redid the timing components on my engine I didn't run into that conflict.. Not sure why your FSM is different...is it a typo? I elected not to replace the crank sprocket, so I didn't run into the issue you presented.

[JimmyZ]

You can always look up the required torque for that diameter of fastener. The degree of hardness and thread pitch of a fastener also affects torque req's. The engaged length of the threads is great enough to not worry about the female threads. There are torque calculators online but you need to know the tensile strength of the fastener to get a good answer. In this case the lower answer (around 40 ft/lbs) is right if it's a "soft" bolt. It might be as high as 80 ft/lbs for a high grade bolt of this sort. This is an approximation since I don't know the diameter/thread pitch etc...

Here's a link to a good calculator...

http://www.futek.com/boltcalc.aspx For Standard

http://www.futek.com/boltcalc.aspx?mode=metric For metric bolts

This application isn't that critical. (As opposed to a con-rod/main cap) Just use some red loctite after a good cleaning with some acetone or other loctite friendly cleaner.

Carrol Smith's Nut's Bolts Fasteners and Plumbing Handbook is the best! If you're doing anything critical like building a race engine or suspension this book is a must read.

2c

Jim

Edited August 15, 2008 by JimmyZ

[doradox]

You can always look up the required torque for that diameter of fastener. The degree of hardness and thread pitch of a fastener also affects torque req's. The engaged length of the threads is great enough to not worry about the female threads. There are torque calculators online but you need to know the tensile strength of the fastener to get a good answer. In this case the lower answer (around 40 ft/lbs) is right if it's a "soft" bolt. It might be as high as 80 ft/lbs for a high grade bolt of this sort. This is an approximation since I don't know the diameter/thread pitch etc...

Here's a link to a good calculator...

http://www.futek.com/boltcalc.aspx For Standard

http://www.futek.com/boltcalc.aspx?mode=metric For metric bolts

This application isn't that critical. (As opposed to a con-rod/main cap) Just use some red loctite after a good cleaning with some acetone or other loctite friendly cleaner.

Carrol Smith's Nut's Bolts Fasteners and Plumbing Handbook is the best! If you're doing anything critical like building a race engine or suspension this book is a must read.

2c

Jim

The internally threaded part material and hardness will need to be taken into account. Steel grade 8 bolt into aluminum is an example. Also compression of the parts being bolted together. Gasketed joints often can't withstand tightening to full rated bolt torque. Like your Z's valve cover, aluminum internal thread and a gasket. All in all the bolt torque calculators will give you an upper limit that the bolt can withstand.

Steve

[Diseazd]

Steve-It's 43 ftlbs. in the Haynes manual also. The bolt is hardened steel and so is the cam (female threads) so it probably can take a 100 or so ftlbs. ,but it was quite a discrepancy so thought I would bring it up.By the way as soon as they announce dates on the Richmond show I'll post it. Guy

[JimmyZ]

The internally threaded part material and hardness will need to be taken into account. Steel grade 8 bolt into aluminum is an example. All in all the bolt torque calculators will give you an upper limit that the bolt can withstand.

Steve

Absolutley! I agree. The post was meant in the context of the cam bolt problem. A moron might torque a cast oil pan/cork gasket to the bolt's max torque... An ugly surprise when the aluminum cracks.

At 1.5xdia engagement and up the female threads don't matter for aluminum. (it becomes a minor concern) With enough engagement concern shifts more towards getting good preload on the male thread.

Although a cam is casehardened and the female threads are "soft" the length of engagement takes care of worries for the female thd.

I'm not an engineer but have read Charles Taylor's book and others. http://mitpress.mit.edu/catalog/item/default.asp?ttype=2&tid=6993 He has a great breakdown of material selection and fastener design/use in Ch.9.

My intent was to merely offer "D" with a means of researching some reasonable torque values. (put his mind at ease)

2c

Jim

Edited August 15, 2008 by JimmyZ

[doradox]

Absolutley! I agree. The post was meant in the context of the cam bolt problem. A moron might torque a cast oil pan/cork gasket to the bolt's max torque... An ugly surprise when the aluminum cracks.

At 1.5xdia engagement and up the female threads don't matter for aluminum. (it becomes a minor concern) With enough engagement concern shifts more towards getting good preload on the male thread.

Although a cam is casehardened and the female threads are "soft" the length of engagement takes care of worries for the female thd.

I'm not an engineer but have read Charles Taylor's book and others. http://mitpress.mit.edu/catalog/item/default.asp?ttype=2&tid=6993 He has a great breakdown of material selection and fastener design/use in Ch.9.

My intent was to merely offer "D" with a means of researching some reasonable torque values. (put his mind at ease)

2c

Jim

I understand, you were suggesting a way to differentiate between the two torque values to see which one seemed more reasonable. I was just pointing out that it's often a lot more complex than that. Like your 1.5 times diameter for aluminum. If you have control of the processes used to make the internal threads and tighten the joint you may be fine. But once it leaves the plant, well, how many of us have failed to clean, inspect, and properly re-torque every fastener we've ever touched. Fastener theory give us a good place to start, but I've seen plenty of aluminum threads pulled out of holes.

Steve

[John Coffey]

Anyone else notice that the camshaft sprocket bolt torque in the 'How to Modify" book by Frank Honsoweltz on page 86 is 100-108 ft.lbs. and the torque given in the factory manual is 43 ft. lbs.? Which is it?

Didn't anyone think to differentiate between what some racers do (Frank's higher bolt torque number) and what's specified from the factory? Frank maybe had a reason to specify that higher torque number based on the experiences of racers back in the 1970s and early 80s' with the cams, cam gears, and dowels available at that time.

Just a thought...