Manifold Replacement

[mattgic]

I developed an exhaust leak on the manifold. I am fortunate enough to have a new one available. So it is a complete replacement, intake and exhaust. The studs came out of the block on removal and the intake mounting bolts just sheard off.
I ordered some new studs, but it seems that the vendors sell brass nuts for the studs. Is this necessary being that this car is not a show car and very likely will never be one.
I shouldn't have any issues using grade 8 nuts for the studs and mounting bolts.

[JayJay]

Originally Posted by mattgic

I developed an exhaust leak on the manifold. I am fortunate enough to have a new one available. So it is a complete replacement, intake and exhaust. The studs came out of the block on removal and the intake mounting bolts just sheard off.
I ordered some new studs, but it seems that the vendors sell brass nuts for the studs. Is this necessary being that this car is not a show car and very likely will never be one.
I shouldn't have any issues using grade 8 nuts for the studs and mounting bolts.

The manifold studs are coarse thread for the block side and fine thread for the manifold side. "Conventional" Grade 8 nuts should be fine, but they are not necessary as you only put nominal torque on them (some folks say 25 ft.lb, some say 40 ft.lb, I'm in the "up to 25" camp). More important is that you use the proper dome shaped washers between the nuts and the manifolds, and install them properly (concave side towards the block). This assures that you will not put undue pressure on the outside of the ears of the manifolds, which can break.

Since you are replacing at least one manifold you should evaluate the flatness of the bolted-up assembly (intake and exhaust) before you install it. The intake and exhaust need to be coplanar when bolted together. I (and many others) use 0.002" as tolerance. If your assembly exceeds that you'll need to have the assembly decked at a machine shop.

[johnbuckley]

Originally Posted by mattgic

.... it seems that the vendors sell brass nuts for the studs. Is this necessary being that this car is not a show car ....

I always use brass nuts... they ensure that things can be undone when the need arises. If steel nuts are used they can rust to the stud which in turn can lead to future problems such as the studs breaking rather than the nuts undoing !!!

[nkaminar]

If you use steel nuts use anti seize lubricant. I use 55 foot-pounds torque. But whatever torque you use, re torque after the first heat and cool down and again at 100 and 500 miles.

[alexiskai]

Originally Posted by mattgic

it seems that the vendors sell brass nuts for the studs. Is this necessary being that this car is not a show car and very likely will never be one.

You should know that the correct nuts for a "show" car are actually the steel ones. Vendors sell the brass nuts because those perform better long-term in a high-corrosion environment.

If you have steel nuts available and you have the manifold, they'll get you back on the road. Personally though, I would include the brass nuts with your next order and then swap them out one at a time. Then you can cross that off the list of things you ever have to worry about again.

[mattgic]

Sponsored Links (Register now to hide all advertisements)

Good input. I appreciate you all.

[Joe K]

And - keep in mind that the gasket resilience affords some "localized distortion" of the manifolds. Between the bolt tension and the heat, it is very possible for the manifold to "warp" and the result will be sealed at the center but lift at the front and rear ports.

Another common distortion seen is the weight of the exhaust pipe "pulling down" on it's connection - and pulling the No 4 port manifold connection "out of match." Which is probably the only reason I can give for using "gland rings" which resist this without question.

I think the point I would make is you want the bolts "snug" but not necessarily "compressive." No more than necessary anyway. If yours is such you can use gland rings, I would try to fit them in.

Joe K

[Chuck Sea/Tac]

Funny story, at the 2014 national meet in Puyallup, I was working with the repair tent. We had some guy with a Vicky, that was trying to reinstall his exhaust intake manifolds. I gave him a click torque wrench to use. He got new bolts with the brass nuts from the the model a vendor on site. He evidently did not know how to use a torque wrench, and torque them until something stripped. I didn’t realize they were brass nuts at first, and I thought he had stripped the threads out of the block. Thank God they were brass and that’s what stripped.

[johnbuckley]

Originally Posted by Chuck Sea/Tac

................. click torque wrench to use. He got new bolts with the brass nuts from the the model a vendor on site. He evidently did not know how to use a torque wrench, and torque them until something stripped..... Thank God they were brass and that’s what stripped.

yes, and its not helped by the Les Andrews book stating do them to 45 ft lbs when most people reckon 25 ft lbs is enough

[Bob Bidonde]

There are two joints in the exhaust system. The first joint is the connection of the exhaust-intake manifolds to the engine. This connection uses studs in the block, a metal clad gasket, steel gland rings, special washers and steel nuts.
Noteworthy are the special washers. They are cup (concave) washers, and when installed the cup side goes against the manifolds. The cup washer behaves like a spring to cope with thermal expansion of the studs. Preloading the cup washers takes up the stud expansion that would otherwise loosen the connections. I torque the nuts to 35 lbs-ft at room temperature and tighten them more if there are exhaust leaks wen the engine is hot.
The second joint is the connection of the muffler assembly to the exhaust manifold. This is where some folks use brass nuts so they will not stick to the steel clamp bolts. However, many use carbon steel nuts or stainless steel nuts in this application.

[P.S.]

Originally Posted by johnbuckley

yes, and its not helped by the Les Andrews book stating do them to 45 ft lbs when most people reckon 25 ft lbs is enough

Les' book is correct, on initial torque. I torque up to 45 when installing new gaskets, so they "squish" and seal properly. Then, when checking torque, I only go up to 40 ft/lbs. 25 ft/lbs is not enough. You'll have problems down the road doing that.

[David in San Antonio]

Bob Bibonde - Your diagrams are so helpful! Do you have them collected in one place, such as a website, or available as a PDF to be emailed / downloaded? I would certainly be willing to pay to help cover your time.

[Mike1291]

Great diagrams as always Bob. I'm going to try your sleeve and Permatex method for the flange, though I will probably substitute 26B for ultra copper since I have some from when I did my manifold.

I had to use a double washer on some of my studs after the threads gave way at 45 fl/lbs. I tried 35 ft/lbs and everything is holding for the moment. Perhaps some have said use less torque after having the same issue I did if they didn't replace the studs.

[ursus]

I looked at installing one of the transition pipes sold by the vendors but noted a caution that it could cause overheating or loss of top end power due to the increased restriction. I have a B-engine with the original B exhaust manifold. Is the increased restriction a potential problem?

[psimet]

Originally Posted by Bob Bidonde

There are two joints in the exhaust system. The first joint is the connection of the exhaust-intake manifolds to the engine. This connection uses studs in the block, a metal clad gasket, steel gland rings, special washers and steel nuts.
Noteworthy are the special washers. They are cup (concave) washers, and when installed the cup side goes against the manifolds. The cup washer behaves like a spring to cope with thermal expansion of the studs. Preloading the cup washers takes up the stud expansion that would otherwise loosen the connections. I torque the nuts to 35 lbs-ft at room temperature and tighten them more if there are exhaust leaks wen the engine is hot.
The second joint is the connection of the muffler assembly to the exhaust manifold. This is where some folks use brass nuts so they will not stick to the steel clamp bolts. However, many use carbon steel nuts or stainless steel nuts in this application.

The diagram about the exhaust pipe connection is interesting. Mine had a packing in it (that looked like asbestos) between the manifold and pipe. I found a really nice copper packing/gasket with a small flange on it from some antique parts manufacturer on ebay a few years back and use that. Seems to work great. Ford may not have ever had one there but I remember thinking that old one seemed to be super old and the copper one I found as passed off as OEM so it's interesting to know there wasn't one. I don't see how it hurts to have one though so I will keep using one.

[nkaminar]

If the fit at the exhaust pipe to manifold junction is proper, gaskets, sealants, and pipes are not needed. Holding up the exhaust pipe with a floor jack is fine to fit the clamp in place, but remove the jack when you tighten the clamp and wiggle the exhaust pipe back and forth as you tighten the clamp to make sure the exhaust pipe is lined up correctly.

Yes, the pipe inside the manifold and exhaust pipe will add restriction, but you probably will not notice it except at very high rpm, and then only if you have a high flow carburetor and high flow muffler.

The studs and nuts are the same as used on the head. If the parts are new or in very good shape they should be able to go to 55 foot-pounds. I agree that 25 is too low. And I would say that 35 is too low. If you don't want to go to 55 then at least go to 45. And re torque like you do with the head nuts.

[Joe K]

It has been my experience to consider the manifold to exhaust pipe a flare fitting: the manifold would be the male cone and the pipe the female flare. The clamp serves as the "compression nut" to bring the two parts together supposedly gas-tight.

Tight is not so tight. I found I could work the female flare with a hammer and a piece of railroad track to a better fit. IIRC, I used "layout blue" to show the high and low spots of the joint and worked (and reworked) the joint to a better fit.

I also found that reproduction clamps were decidedly inferior to a single original clamp which seemed to have deeper than the rest "compression surfaces." A couple of the reproduction clamps were decidedly "thin" in comparison with the original clamp.

So at this point I'm at a thin layer of pipe joint compound and the reworked flare/original clamp.

Joe K

[Bob Bidonde]

Thank you all for the compliments about my diagrams. All of the diagrams I have published can be found on the website of the Model A Ford Club of Long Island at https://www.modelalongisland.com/ Look under "Resources."

[katy]

Originally Posted by JayJay

More important is that you use the proper dome shaped washers between the nuts and the manifolds, and install them properly (concave side towards the block).

FWIW, the subject washers are made of spring steel, so don't go making your own out of normal flat washers.

Here's a sample: https://www.bokers.com/washers/custo...ville-washers/

[Bruce of MN]

Our thick ones https://www.snydersantiqueauto.com/p...9407&cat=41733 are spring steel? I'm no expert, but they sure look like more ordinary steel.