8N - Exhaust Manifold Leak Gasket Questions

All,

I have a 1951 Ford 8N with a side mount distributor. I have an exhaust leak near the front cylinder (I think number 1). About 2 years ago, I had to replace the manifold and gasket. When I did that we noticed a few things:

1) Pitting on the gasket seating surface of the engine block near the cylinder number 1.

2) The front bolt hole was stripped. We re-tapped to the next size larger and used a larger diameter bolt. However, I have some concern about how much torque this will take.

I have purchased new gaskets, but on inspection noticed that they are slightly concave. I have a few questions:

1) Which way does the gasket go? Does the concave side face the engine or the manifold?

2) Could I "double them up" in an attempt to close the pitting/gap? If yes, do I just use gasket sealant to mate the two gaskets?

3) Another idea is to use one gasket with a fair bit of sealant and hope that seals the gap.

4) Is there a better way to repair the engine block pitting (e.g. JB Weld)?

Your assistance is always appreciated.

Thanks

Torque should be 27 ft-lbs. Not much.

Then we achieved the proper torque setting 2 years ago. The pitting is the remaining concern.

Thanks for the specification.

Matt:

I had the exact problem a few years ago except mine was on # 4. Using instructions I got on this forum, I repaired the pitting on the block using JB Weld and it has held up just fine since. The process is to clean the block pitted area with a wire brush and brake cleaner to get it spotless. Then apply the JB weld on the area and mount the manifold without the gasket but with a sheet of wax paper between the manifold and block & tighten it down and let it set up for a couple of hours. Remove the manifold & wax paper and grind off the excess JB Weld that got squished out around the mating surface. Re-install the manifold with the gasket & you should be good to go. Like I said, mine has held up well for the past 2 years with no leakage.

J-B Weld is rated to 500 F- Probably not enough. Loctite makes a high-temp filler rated to 2000 F, though.

You need to look at Bruce(VA)'s thread on block pitting repairs. He likes Thermo-Steel and so do I, used it for many years. He has submitted excellent steps to repair the pitted block. Search archives for "manifold repair" and/or Bruce(VA) and it will come up. Forget the JB junk, it won't cut it. Yes two gaskets can be used and often 2 work but you still should fix the pitted block, its easy.

maybe you already checked, but make sure your manifold is straight. the exhaust gases act like a sand blaster, causing the pitting in the block and can erode the manifold surface. most machine shops can re-surface them, but price it first, alot of shops want $30-$50 for a manifold plain, you can buy a new one for around $60.

(quoted from post at 12:14:34 12/12/09) You need to look at Bruce(VA)'s thread on block pitting repairs. He likes Thermo-Steel and so do I, used it for many years. He has submitted excellent steps to repair the pitted block. Search archives for "manifold repair" and/or Bruce(VA) and it will come up. Forget the JB junk, it won't cut it. Yes two gaskets can be used and often 2 work but you still should fix the pitted block, its easy.

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If I had to do it over, I would also use the "Thermo Seal" as it has a higher temp rating. But since the JB is in there and doing well after 2 years on a hard working tractor, I am hard pressed to agree with its classification as "junk".

Don't have to. I have done several with the JB only to soon repair it again. When the manifold is removed with JB repairs you will have some dust falling off with the gasket and the repaired pits will be clearly visible. The Thermo will be just as when you installed the manifold or even better as it seems to continue to harden and even look more like the block metal. As you can see I am not a big fan of JB, it is great in many applications but especially not for block pits. I get all the JB products from one of our sponsors and I have tried them all as recommended. There are at least 6-7 different JB welds, you may have used something other on your block pits than the original or their Hi-Temp as I have, there is no comparison to the Thermo results.

(quoted from post at 13:36:43 12/12/09) Don't have to. I have done several with the JB only to soon repair it again. When the manifold is removed with JB repairs you will have some dust falling off with the gasket and the repaired pits will be clearly visible. The Thermo will be just as when you installed the manifold or even better as it seems to continue to harden and even look more like the block metal. As you can see I am not a big fan of JB, it is great in many applications but especially not for block pits. I get all the JB products from one of our sponsors and I have tried them all as recommended. There are at least 6-7 different JB welds, you may have used something other on your block pits than the original or their Hi-Temp as I have, there is no comparison to the Thermo results.

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Based on your results, I would assume you did a poor job on the prep. Had my manifold off last year to do a valve clean up and the JB was as good as when I put it on.

If the block is badly pitted, you will have problems; get out the hi-temp metal epoxy. (Not JB Weld) VersaChem's exhaust manifold repair, or ThermoSteel, is said to be good to 2000 degrees. Clean the area real well with brake cleaner, put a little epoxy on it, put some wax paper over it and bolt down the manifold. After it dries take off the manifold and take a die grinder and clean the epoxy that might squish into the port. Look at the manifold. If it’s pitted & burned, it isn’t going to seal. Time to surface it or get a new one.

You said "bolt"; did you actually use a bolt or did you use a stud? If the manifold is attached w/ bolts, somebody someday is going to have a BF problem. The tractor came from the factory w/ brass nuts on studs.

The nuts are brass, 7/16-20 x 5/8, NAPA part number STN104X, 27 lbs of torque. A bag of 10 from Fastenal is less than $8; part number 1175115. OEM studs are 1-5/8 long 7/16-14. NAPA doesn’t stock the 5/8’s length, but part number RFD 86644, 1 ¾ inch, works as does part number 86632, 2 inches. These studs are “Handi-Pack” items. (I’ve used these longer studs on my 50 & 51 N’s, but you should make sure they do not bottom out in the block on your N as they are longer than OEM). If you don’t get them at NAPA, make sure that the stud has an egg-shaped center between the different threads. Use washers under the nuts.

Clean all the threads in the block w/ a thread chaser.

There are two distinctly different recommendations on tightening the studs in the block. Because the stud goes into the water jacket & is constantly undergoing extreme heat & cooling cycles, some folks like to double-nut them & tighten them down at 37 lbs of torque. Others say that it’s a stud & should only be finger tight w/ a good dose of thread sealer or high temp silicone on them.

I’ve replaced the studs on 3 of my 4 N’s w/ no leaks; I finger tighten the studs then take a ¼ turn on them w/ vice grips.

The next thing you need to know is that the method of attaching the exhaust pipe to the manifold was developed for the Model A Ford in 1927. If you pay attention to what you are doing, it will not leak.

Make sure you are using the correct clamp. An automotive muffler c-clamp will not work. You need a clamp made for the N. If you have the correct clamp, it has a top & bottom. Make sure you have the clamp on correctly; check out tip # 8, below.

Slide the tail pipe into the hanger clamp & then place the end of the exhaust pipe against the manifold. Look at it! Remember, the pipe will most always fit snugly to the OEM manifold w/o any problem, but a replacement manifold will likely not be the exact same size as the OEM manifold, so you will have some work to do. If it does not mate all the way around, put a broomstick down the pipe & into the manifold & gently bend the pipe until both surfaces mate snugly. If the exhaust pipe flange is bent, you will never get a good seal; check it out. The clamp is not a gasket; if the pipe & manifold do not mate tightly, it will leak. Do not try & hold the exhaust pipe against the manifold w/ your hand & while you tighten the clamp. Get out your floor jack & a block of wood; put the jack under the pipe to hold it tightly against the manifold. With the pipe jacked snugly and squarely to the manifold use your ¾ lb ball peen hammer and tap the pipe tight to the manifold flange all the way around. Its soft metal and this will only take about a minute. Tighten the clamp. (Don't get carried away w/ the jack or you will bend the pipe. Or, overtighten the clamp & snap it in two. BTDT).

I use Permatex CopperCoat as a sealer. I'd be surprised if you can get 2 gaskets under the manifold & still have enough stud to seat the nuts.......assuming you have studs.
50 Tips

Sorry Dan, that "poor job" assumption is totally incorrect, I always use the utmost care in preparation and application. If you want a lasting repair of block pits under the manifold I again would like to refer you or anyone else interested to Bruce(VA)'s posted procedure. It is great and it works! Once you try it you won't have to assume anything. Can't sell me on JB use for that purpose, I've seen it fail too many times.

Well, I guess we have to agree to disagree about the quality of the product (JB Weld) versus the process in its application. I think we have hijacked this thread enough with the debate. In my opinion, Matt should follow Bruce’s process precisely including the use of high temp filler and his result will be positive. But I continue to believe in the JB product after many applications on the engine block, the air cleaner and on cracked carburetors, I have yet to have it fail except when the surface was improperly prepared.

I had a similar problem with my '41 9n.No block pitting,but severe breakdown of manifold at #4.I welded with 3/32 nickle rods at 45 amps.weld to build up,grind down,over&over until I got it built up,then flattened with 6"x48"belt sander,checking with straightedge and no leaks---lha

Excellent advice here. Thanks, Bruce. I had trouble finding ThermoSteel on the net, but finally got it. Made by Blue Magic, Inc. in Conroe, TX, phone 888-522-2746.

I'm a believer!
Dave Erb
New Holland, PA