Torque setting on manifold

jkeesey said:
Modern Chevy and ford manifolds are cracking in the centers from being too tight and not leaving room for expansion. I run A manifolds at 45ft lbs after the manifolds have been cut together and the block has been checked true. Ive done over 30 of them in the past few years and have never had a problem.
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jkeesy,
"THEY" say, there's exceptions to every rule, except for DEATH & TAXES!
Who's Ceasar?:confused: The Bible says I should pay him too!! Bill W.
 
Hey friends! Thanks for the thread....EVERY time I come on this site I get exactly the needed information. I am restoring my 1930 roadster and have decided to buy both intake and exhaust manifolds due to a crack in the exhaust. Have been told that there is no need to mill the new manifolds if bought together(?). Going to install today and wanted to check the FP of torque. Guess from the tread it is somewhere between 30-55fp. Will definitely comply with the cold to warm redo working up to about 40 or 45 methinks. THANKS AGAIN from one rookie out here!! Dennis
 
I think you are right about the new ones not needing milled. I sold a set and they were perfect. Just run a straight edge across them before throwing them on for shits and giggles.
 
FWIW: The last two new manifolds I purchased from Snyder's had an installation guide with them and it suggested 45#. Probably fine for their new castings. I think 45# is to much with originals. With a freshly surfaced intake and exhaust manifold, I tighten to about 25# and then run the engine for a few heat cycles. Then increase to about 35# as a finish.
 
One more reason not to run them up to tight......I had a number three stud pull the side of the water jacket right out of a fresher rebuild. Yes the block had been magna-fluxed and had no issues before the build. I don't think I made it up to 30Lbs. Crack! bleed bleed bleed, swear curse grumble. Remove and strip the block, and had it "stiched" up. I never tighten more than I need to and do it hot.
Cheers!
 
"Guess from the thread it is somewhere between 30-55fp."

Specs in Bratton's catalogue are 25-30 for manifold nuts....i certainly would not go over 35, and no where near 50
 
You can tighten manifolds with a 3/8" drive ratchet,working out from the center.retighten once or twice more & you will be fine.You only really need a T-wrench on the cyl head & if you have installed as many heads as I have over the years,I would be very close if rechecked with a T-wrench.
 
Napa Skip, in this context doesn't RMS stand for "rough machined surface?"

Surface roughness, often shortened to roughness, is a measure of the texture of a surface. It is quantified by the vertical deviations of a real surface from its ideal form. Roughness is typically measured in "RMS" microinches and is often only measured by manual comparison against a "surface roughness comparator", a sample of known surface roughnesses
 
Greg Jones said:
Napa Skip, in this context doesn't RMS stand for "rough machined surface?"
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In this context I'm fairly certain that "RMS" refers to Root Mean Square, which is one of several approaches to quantifying (in this case) the peaks and valleys of a surface (another approach is Ra, which is the straight mathematical average of the absolute value of the peaks and valleys).

Fwiw, RMS is the [square] Root of the Mean of the sum of the Square of each peak or valley measurement.

As a simplified example [I hope I don't goof this up; I'm typing this reply as I watch "Suddenly, Last Summer" on TCM - fortunately the scene with Elizabeth Taylor in her white bathing suit hasn't come up yet] consider a surface with the following 5 measurements of peaks and valleys (I'll use whole numbers instead of millionths of an inch - or micro inches - to simplify the example): +4, +5, -3, +2, 0.

Ra = 1/5 x (4 + 5 + 3 + 2 +0) = 1/5 x 14 = 2.8. (Remember that the absolute value of the measurement is used, so the "-3" is treated the same as "+3".)

To calculate RMS we use,

RMS = Sqrt (1/5 x (4^2 + 5^2 + -3^2 + 2^2 + 0^2)) = Sqrt (1/5 x (16 + 25 + 9 + 4 + 0) = Sqrt (1/5 x 54) = Sqrt (10.8) = 3.3 (rounded off).

Slow day out here on the left coast...

[I'm certain that if I goofed up anything in the above, those more knowledgeable - or who aren't watching Elizabeth Taylor while trying to type - will jump in.]
 
Well yall' torqueing folks, don't mean to gloat, but just recieved this torkin' goodie from my Son, along with a box FULL of other treasures! He restored it to almost new lookin' condition & The Dog:cool: tested it for akuracy & said, "RIGHT ON"!
Who said, "THERE AIN'T NO SANTA CLAWS"?? Bill W.
 

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O.K. I just installed my freshly resurfaced manifold and torqued to 20 pounds. I am already getting nervous about going any tighter. I just need some reassurance I can continue without breaking the ears.
Thanks
 
41plym said:
O.K. I just installed my freshly resurfaced manifold and torqued to 20 pounds. I am already getting nervous about going any tighter. I just need some reassurance I can continue without breaking the ears.
Thanks
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I can't give it to you.:D I saw someone snap the ears before 35 lbs. was reached. I just use my box wrench and common sense.:) Mine don't come loose.
 
I do mine just like columbiA in post #29 . A few years ago it was recommended to torque 7/16 nuts, including the manifold nuts to 55 ft. lbs.. After warping and cracking several good manifolds I've went back to the common sense approach. I tighten the manifold nuts with a 3/8 ratchet and go by feel. after a few warm and cool cycles the nuts will need to be retightened and rechecked for a few times afterward. Besides warping manifolds, tightening the manifold too tight squishes out and ruins the gaskets, causing exhaust and vacume leaks. Usually the manifold will be found to be warped when removed to replace the squished gaskets after over tightening. A 3/8 ratchet would probably strip before reaching 55 ft. lbs. torque.
 
Tom Wesenberg said:
I never use a torque wrench on manifolds.
Also you must remember that because a certain stud and nut can take some amount of torque, that doesn't mean the part being clamped can take the same amount of torque. Cast iron manifold ears on a soft copper gasket might fit in here.
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I agree with you Tom. I think on some things a good feel is more important.
I do use a torque wrench on rods, mains, head, and things like that

It's all about feel, and common sense.
 
I think it's helpful if the two little bolts joining the exhaust and intake manifolds are only finger tight until AFTER bolting to block. You want each unit to be able to find its own seating, without possibly exerting a stress on the other. Also, be sure that you're using the thick curved washers with the convex side out, against the nut.

With some hesitation about using the "B" word, I'm surprised to see that Fel-pro's recommendations about oiling the threads and torqueing while warm both go against the no-ifs-ands-or-buts instructions given by a certain legendary manufacturer of Model A high compression heads.

Steve
 
Also goes against mgf directions as it relates to torquing modern head gasket stone cold and against the fact that adding oil to the threads require reducing the amount of torque .
 
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