Manifold Nut Torque?

J

Jim Kroeger

Member
I'm installing a new manifold on my Model A. I have machined the manifold so everthing lines up and am ready to install. Is there a recommended number that the nuts should be torqued at? Also, do I torque again after the engine is warmed up like you do on the head gasket? And finally, is it better to attatch the manifold to the block first or to the muffler pipe first? Any ideas would be appreciated.
 
Just tight is good, which should be about 35#. And they can be tightened a couple times. Most folks attach the manifolds and then install the muffler.
 
I always start with the 2 nuts on both sides of the carb. and work my way out to the ends .. A little at a time this way you sandwich the gasket from the inside out to the both ends and it does not bunch up .When it feel good STOP ! NOT crank them nuts down YOU WILL crack the ears on the intake manifold. Start the car up and let it get warm ...Let it cool down and check them again[with the muffler on]...... you can fight with the muffler. I work by myself so i have a flat car jack to bring the muffler to the manifold and then install the clamp...Also leave the tail muffler clamp a little loose....
 
Last edited:
Hand tight, not knuckle tight. Recheck every once in a while. Use a box wrench and forget about the torque.

Always bolt to block first, then clamp the exhause pipe. A jack under the pipe holds it tight to the manifold while you position the clamp. The larger lip on the clamp faces down, to clamp the pipe.
 
I torqued mine to 20 ft pounds and seems to be about right had to retorque a few times check it when I check the head ,new engine have about 100 miles on it . I use 20 lbs as that is the spec for morpar flathead sixes that I am use to working on.
 
The instruction sheet that came with the new manifold from Snyder's called for 40 ft-lbs. I got it there without breaking anything, but I admit to hold my breath. Now I know why!
 
go back and check it again, it has been known to "POP" and crack later....whew i can see why you held your breath@!
 
Bratton's new catalog I just got yesterday says 25-30. I think I usually stop at 20 & recheck after it's been run a couple of times.
 
The manifold is on and solid as a rock. I decided to torque to 20 lbs. and then check later after running the engine a few times. That weight seemed like a good snug fit without possibly breaking the ears off the intake manifold. Thanks everyone for the tips.
 
Recently i have seen info based on using anti sieze and torque values. Bolt set for my yblock mentioned if you use anti sieze to be careful of torque values. Now my understanding is model a vehilces did not have factory torque values, but does anyone one consider thread lube a factor in torque settings?

Maybe this is a better question on its own.

From arp:
The following excerpt from ARP (the auto-racing engine fastener manufacturer) clearly indicates that different thread lubricants result in different torque values to attain their 75%-of-tensile-strength desired clamping force. I also provided some of their other notes, just for interest sake.


PART NUMBER / TENSILE STRENGTH / TORQUE-OIL 30 wt / TORQUE-ARP LUBE
Rod Bolts
BEB-08..................220,000 PSI...............65 ft lbs....................45 ft lbs
BEB-09..................220,000 PSI...............65 ft lbs....................45 ft lbs
BEB-1...................190,000 PSI................55 ft lbs....................38 ft lbs



The following notes are important!

* ALWAYS wash the fasteners with cleaning solvent prior to installation. They come coated with a "protective" coating, this is NOT a lubricant.

* Choose correct torque from the chart.

* Note the difference in torque settings depending on the thread lubricant used.

* The method to follow for applying lubricant:

* Coat the fastener with lubricant as evenly as possible (especially important with the L99 lube).

* Pull up the fastener so that it is 'snug'.
Do this three times, on the third time torque in the recommended order to the torque as shown in he chart opposite.

* The above method no doubt seems strange, but does ensure no metal to metal contact that increases friction between the threads.

* The torque figures shown will give a preload equal to 75% of the yield strength of the fastener.

* Use a generous chamfer on all stud holes.

* Screw studs into the block using 4 ft lbs only. (Basically hand tight).

* If you feel you have to use a thread locking compound for studs (not bolts or nuts) then be sure to do the final torque before the compound sets up.

* We do not recommend the use of lock tabs which are made from a material which is too soft, and as it squeezes out, the fastener preload is lost.

* Due to leverage differences a fine thread will produce a greater preload for a given torque than will a coarse thread of the same diameter.

* Tap all female threads before installing bolts or studs. (Best not to use a new tap)

* ARP lube, part number L99 is recommended over 30 wt oil if possible, as its superior lubricating properties produce the correct clamping preload for less torque.

* For all connecting rods check that the chamfer required to clear the bolt under head radius is adequate - this is VERY important.
 
The ARP numbers, or any other "yield" chart tell you the "never exceed" or the "optimum" value for the bolt in question, although the example given by Tinker shows the range of values available. Indeed this is a question to consider.
However, the chart values are not necessarily the best torque for any particular application. For example, a cast iron manifold is not the same material as an ARP bolt, not to mention the give in the gasket, which is what causes the crack or break to happen. To tight for the application, regardless of chart torque values, and you get a failure.
I use ARP studs on my head, but I do not torque it to the ARP maximum for a 7/16" above grade 8 stud, the number of which I do not recall off hand, but is much higher than the 60 I use on my HC aluminum head (and may be different for a cast iron head). Just because a bolt (or stud) will safely take a particular torque does not mean the application should be torqued that much. Lacking charts from Ford, all we have to go on is experience, which this forum has a wealth of.
The pros who do it all the time, and experienced amateurs, can actually "feel" the stretch (spring) of a bolt tighening. When the torque value comes up suddenly, it has lost its spring, and it is time to replace the bolt. I worry every time I tighten rods, which have long ago mostly lost their ability to stretch/spring.
 
Last edited:
Carl: I cant find teh part numbers in my computer. I liked the old Search function but this new program from Bill Gates is automatic and written by some 22 year old genius, so I cant figure out how to do specific searches. But they were longer than stock anyway because I have an HC head. Google ARP Bolts and give them a call. The guy I talked to was not very friendly, so get the specs for the stud sizes and lengths and threads and have them ready. Get some old studs and measure the thread lengths too. Get the nuts, and hard washers and build that into the specs if you want them. They have no idea what a Model A Ford is. Its not in their application book. I think the guy I talked to must have been a 22 year old genius too, or maybe just someone having a bad day.
 
Thanks, PC/SR, I had the same experience when talking to someone at ARP. I finally did get a set of studs, but not sure they are the best fit. Time will tell. I'll do some more research.
 
You must log in or register to reply here.
Back
Top