TORQUE OF MANIFOLD BOLTS?

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Model T Ford Forum: Forum 2016: TORQUE OF MANIFOLD BOLTS?
Top of pagePrevious messageNext messageBottom of page Link to this message  By ALAN FAIRCLOUGH on Monday, April 04, 2016 - 01:37 pm:

I replaced the exhaust manifold about six months ago. It is about time to re-tighten them.
Do I just re-tighten the bolts until I grunt or is there a recommended toque?
BTW, I have bolts, not studs and nuts. No idea why that happened. It just came that way.


Top of pagePrevious messageNext messageBottom of page Link to this message  By G.R.Cheshire on Monday, April 04, 2016 - 01:50 pm:

I just use this as a guide and make sure the wrench is calibrated I do sometimes go to the low side due to the age of our cars
http://www.engineershandbook.com/Tables/torque.htm


Top of pagePrevious messageNext messageBottom of page Link to this message  By Roger Karlsson, southern Sweden on Monday, April 04, 2016 - 02:14 pm:

Bolts for the manifolds was a late '26-'27 feature, listed as started May 25, 1926 in the encyclopedia: http://www.mtfca.com/encyclo/doc26.htm

Just make sure the bolts are of proper length so they won't bottom out when tightening and so there are enough threads in use. Ford never published any torque specifications back in those days, with some experience you feel when it's tight enough without breaking it (though sometimes it may break anyway with the type of old, sometimes damaged parts we're dealing with)

Going around the car checking all the bolts that may be loose (and that all the visible cotter pins are in place) is a regular ritual with a Model T - might be once a week or once a year depending on how much it's used :-)


Top of pagePrevious messageNext messageBottom of page Link to this message  By Henry Petrino in Modesto, CA on Monday, April 04, 2016 - 02:43 pm:

I may be all wet on this, but when I look at the table in the link G.R. posted the thing that jumps out at me is the second column. It indicates "Coarse Threads/inch". This works fine when using bolts. However, most Ts use a stud and nut. As I recall, the stud has coarse threads on the block end and fine threads on the nut end. So, my questions:

1. Am I correct about the coarse/fine threads?
2. If I am correct, aren't there different torque specs used when the fastener has fine threads?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jerry VanOoteghem - SE Michigan on Monday, April 04, 2016 - 04:24 pm:

Henry,

In answer to #2, yes, the specs would be different for fine versus coarse threads. Fine threads would typically get less torque than the same sized coarse thread.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Henry Petrino in Modesto, CA on Monday, April 04, 2016 - 05:38 pm:

Thanks Jerry. That's what I thought but I couldn't remember for sure.


Top of pagePrevious messageNext messageBottom of page Link to this message  By JD, Wichita, KS on Monday, April 04, 2016 - 05:49 pm:

I believe Jerry said it backwards.

Coarse threads typically get less torque than the same sized fine thread.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Steve Tomaso - Longbranch,WA on Monday, April 04, 2016 - 07:09 pm:

And to answer #1 - both the block & nuts for manifold studs are fine.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Henry Petrino in Modesto, CA on Monday, April 04, 2016 - 07:47 pm:

You guys need to learn to answer in numerical order. :-) :-)

Thanks Steve. I'm sure you're correct, but somewhere I've seen studs with coarse on one end and fine on the other. Oh well, I can't remember what I had for lunch either.

JD, I do believe you are correct. Thanks!


Top of pagePrevious messageNext messageBottom of page Link to this message  By Roar Sand on Monday, April 04, 2016 - 08:10 pm:

If the goal is equal clamping load, Jerry is correct.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Tony Bowker, Ramona, CA on Tuesday, April 05, 2016 - 12:59 am:

The studs with coarse threads on end and fine on the other are for the front wishbone mounting....


Top of pagePrevious messageNext messageBottom of page Link to this message  By Dave Wells, Hamilton Ontario on Tuesday, April 05, 2016 - 08:40 am:

I torque to 30 ft lbs. I know how these manifolds can warp and leak so, I use the copper rings and retorque at least once a week. No problems ever since.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Dave Wells, Hamilton Ontario on Tuesday, April 05, 2016 - 08:44 am:

I torque to 30 ft lbs. I know how these manifolds can warp and leak so, I use the copper rings and retorque at least once a week. No problems ever since.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jerry VanOoteghem - SE Michigan on Tuesday, April 05, 2016 - 08:59 am:

Roar,

Thanks much.


Top of pagePrevious messageNext messageBottom of page Link to this message  By ALAN FAIRCLOUGH on Tuesday, April 05, 2016 - 11:45 am:

Yes, studs are usually made with the coarse thread for the fixed end and the fine threads for the nuts. The pitch of the thread allows for the nut to come loose before the stud does as the nut will require less torque to provide higher pressure at the face.
This is in theory of course and we all know the stud in the hardest to reach location will be the one that comes out before the nut comes off. Specially on exhaust manifolds where extreme heat causes the nut and stud to rust. Use of a graphite or copper based seizing compound provides some help but only on the nuts that are easiest to reach. Murphy was heavily into mechanics.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jerry VanOoteghem - SE Michigan on Tuesday, April 05, 2016 - 11:47 am:

Aren't manifold clamp nuts supposed to be brass?


Top of pagePrevious messageNext messageBottom of page Link to this message  By G.R.Cheshire on Tuesday, April 05, 2016 - 11:57 am:

Alan: you reminded me of one of my favourite quotes from Yogi Berra "In theory there is no difference between theory and practice. In practice there is."


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