Nice option, but I have enough from the the 2 motors I tore down.

 

As you surely know very well, Flyer (but I'll say it anyway), there's a big problem with cheap, foreign-made fasteners that are manufactured with insufficient attention to QC, and which vary wildly from their nominal specifications (Grade 8, Grade 5, etc.). Depending on what cheap supplier provided the steel, how the threads were rolled, how the heat-treat was done, etc. etc, an individual fastener you get might even exceed the standard, the point being that you can't count on it. This is no problem at all for the big hardware and auto parts chains, but it's a huge problem for manufacturers such as Boeing, which keeps an eagle eye on the suppliers of their AN certified fasteners, and yet they catch runs of junk fasteners from time to time (usually in maintenance operations, occasionally at airlines).

So when I hear someone say, "you should have Grade 8," I'm skeptical because I know that unless the person asserting this is buying certified aircraft fasteners, with a paper trail, or getting them from a stand-up outfit like ARP, he is unlikely to know what his fasteners really are, six stripes on the bolt heads notwithstanding. Neither am I, most of the time, which gets me in trouble because when I started working on cars over fifty years ago, all our fasteners were made in USA with some effort to hold to standards, and I got used to that and sometimes forget.

As to exhaust manifolds breaking (nominal) Grade 5 bolts/studs . . . why? The only such fastener problem I ever had was on a 460 where the manifold got insufficient accommodation for expansion and it pushed the last stud so hard sideways that it broke the head casting around the fastener (which itself did not break)(BTW, this was a frequent occurance with 460s for a while). What's going on here that calls for super-strong fasteners? I'm willing to be wrong (have had some practice) if the thing is explained to me.

 

Exhaust manifolds are subject to extreme temperature changes. Much more than the head that is holding them. It is not uncommon for exhaust manifolds that are heat cycled to snap off the fasteners due to repeated expansion and contraction. So the fasteners are strengthened, leading to cracked exhaust manifolds, leading to strengthened manifolds of better materials, leading to even stronger fasteners - a chicken / egg cycle.

I saw it on dyno durability testing and experienced it first hand on my own vehicles. My RV is used for pulling my race cars and as such the 496 Chevy gets worked pretty hard. One exhaust manifold has sheared the end studs. The other one actually broke apart. I replaced all the sutds. And the replacement exhaust manifold had a list price of $750! It was as hard as stainless steel when I went to grind off the casting flash before installation. And the old one had warped by about 1/2 inch and would have never bolted back on. [Ever wonder why the mounting holes (save one) are way bigger than the stud diameter? To allow for expansion and contraction of the manifolds without breaking anything.]

 

That's also why the flange that bolts to the head is split. It would warp if it wasn't.

 

Wait a minute, trozei, the flange is split because the exhaust manifold and intake manifold fit between each other and each stud simultaneously holds two manifolds, . . . or are you talking about something else?? (hmm, like maybe you mean the two-piece EFI manifolds?).

Anyway, I defer to your wider experience and superior knowledge on this. Flyer, drilling the outer mounting holes of the manifold oversize was the backyard fix for the 460 problem. The center hole where the manifold growth had little effect, was left small to locate the manifold relative to the ports. 460-powered RVs were the chief parts-breaker because of the high underhood temps and marginal airflow. Incidently, on impulse I recently bought an '87 E350 based ambulance with a 460 (now for sale, I changed my mind). Ambulances spend a lot of time sitting with the engine on fast-idle, powering lights, and whatever; this one has the hood full of louvers, Fifties hot-rod style, to vent some of the heat-soaking. Not a bad idea for other vans, maybe . . . .

(EDIT) Here's a related question: Lots of stresses can get locked into welded assemblies; to what extent does ordinary engine hot/cold thermal cycling stress-relieve welded steel-tube and stainless tube headers? Would wrapping them with thermo-tape or coating them with a heat-retaining ceramic like Jet-Hot tend to help the stress-relief process? And with any kind of exhaust manifold, maybe one could pre-empt big problems down the road by removing and re-surfacing the flange after some "break-in" period of stress relieving (yes, a PITA, but this is yet another reason I like simple, stripped-down engines).

 

These are what I used on my engine.

These are simply some of the beefiest washers I've ever been able to find:

https://www.nutty.com/EXTRA-THICK-Gr...ers_c_427.html


I wasn't sure what size I needed so I got 26 * 1/2" and 26 * 9/16".
For $0.25 a piece, I wasn't too concerned about it.
They don't have the springiness of the stock ones, but they've been great.
The problem I had with the stock ones is they were too small of diameter. They did a very poor job of spanning between the EFI manifold tabs and the Offenhauser. I've had to have two ears on my Offy welded back on after they cracked.

These have been on there two years now.

 

Smitty, I have wondered the same thing myself. There are lots of forces on exhaust components - thermal stresses and vibration. Thermal cycling may anneal while mechanical vibrations work harden. That is why I don't use headers on any vehicle that gets lots of miles on it, especially if the exhaust gasses are run through a muffler system. Headers used on production performance cars like Mustang GTs use premium grade materials to aid durability.

When I install cast exhaust manifolds I like to grind off all the casting flash. Often the casting lines are in bad locations that are subject to high temps and high loads. A crack can easily start at a flash line and progress into the thicker sections of the manifold.

I also like to remove the flash lines from head castings and block castings, but that is more for visual cleanliness; I've never seen one crack through the casting flash.

 

One more thing I do:

I rarely use exhaust gaskets. Instead I make sure the surfaces are as flat as possible - often with a belt sander - and assemble without gaskets. All that expansion and contraction can eventually "saw" away the gasket material leading to exhaust leaks and warpage. Ford did not use exhaust gaskets on many late model vehicles but that was also because no gaskets shortened catalyst "light off time" - the warm up time necessary for the catalyst to start functioning.

 

Yup, got a set of new EFI manifolds shipped from Texas, first thing I did was what you describe, followed by a heat-cured high-temp paint. With a similar motivation I take the time (maybe largely wasted) to put chamfers on the sharp edges of all the drilled holes I see; where it looks lie it might actually be important, I'll then do the old edge-peening trick of placing a slightly oversized steel bearing ball over the hole and smacking it a few times with a hammer.

The no-gasket deal is interesting. Used to run cylinder heads without gaskets in outboard racing days. For a sealant (after advice on this) I went to one of the older paint stores, and asked for a small can of silver (aluminum) paint. I specified that I wanted one that had been sitting on the shelf for a long time, and DON'T shake it at all. Opening it at home, it was as I hoped, liquid on top, solids on the bottom. I poured the liquid into a container, then poured a little less than half of that back into the paint can. Stirring up the solids with the small amount of liquid gave me an aluminum paste that would seal well, and probably allow some relative movement of surfaces without losing its ability to seal (and transfer heat). Is it better, or as good as, commercially-made sealants? Don't know, but it has worked for me.

Here's a funny one. Somebody writing in to Hot Rod stated that in the Air Force they use milk of magnesia painted on threads as a high-temp anti-seize . . . hmm, possibly they only do this with Phillips-head screws . . . ??

(EDIT) Flyer, I've been going to ask this for a long time, and you being an engineer who races, maybe you'll know about it. Everybody knows the old racing technique of polishing con-rods and other such parts, followed by sending them out to be shot-peened. I'm wondering first if any worthwhile degree of peening can be done by leaving parts in the local machinist pal's "wheelabrator" cabinet for an extended period. But what I'm really curious about is whether one can significantly affect the fatigue properties of a cast aluminum surface by polishing followed by blasting the surface in my buddy's glass bead-blasting cabinet???? Given how the glass-beader can warp pieces of thin sheet steel (learned this the hard way), I'm guessing it can't hurt, might help. Have you heard anything about this?

You can see what a cheapskate I am; then and now, you can't make a dime in the kind of racing I did. No fame, no glory, no prize money, no long-legged cheer-leaders, no lines of sponsors with suitcases of cash, just lots of evening hours spent in the basement shop with a radio for company. And the company of a lot of fine people at the races, win or lose.

 

Smitty,
Welcome. I have one remaining seat left in my "Lifetime Cheapskate's Club". Being a "cheapskate" has taught me to be innovative, think outside the box, and find low cost alternatives to stuff I can't afford. As a result I've spent a large part of my adulthood acquiring /building/learning/inventing machines, techniques, and tools that allowed me to do much of my gearhead projects without outside help. Your cheapskate merit badge is in the mail.

I'm not familiar with the term "wheelabrator". Is it one of those cabinets with a paddle wheel that flings shot at your parts? If so then yes, it will work to stress relieve parts.

I think in a pinch any concoction with a sugary slurry can be used as a thread locker, but I would worry about getting accurate torque readings, if torqueing to spec is required. With a little heat the sugar will turn to 'taffy' in the threads.

I like to use a film of red hi-temp silicone when I install exhaust manifolds.

I like your technique of prepping bolt holes. I generally be-burr all my head and block castings. If the edge is sharp enough to cut skin it gets chamfered. I'll try the ball bearing technique.

As far as blasting instead of shot peening - I don't know. It may help. I would say glass beading may be a preferred media over more abrasive stuff, but none would be as good as steel shot for work hardening the surface.

 

Like many, yet not all, early Boomers who were born to parents who were formed by the Depression and the rationing of WW2, my brother and sister and I were taught that frugality was one of the cardinal virtues. Typical Smith Christmas morning experience was/is opening a package wrapped maybe with newspaper (but hey, with a ribbon!) while the giver explains, "you won't believe it, I got it for eight bucks at Value Village, and yeah its got a few scratches to polish out, and make a handle to replace the broken one, but it was such a DEAL!," . . . and the receiver of the gift is saying, "Cool, only EIGHT BUCKS?!, all right!!!" None of us can relate to the many ordinary people who would be miffed if a significant amount of money was not spent on their present, and stunned at getting a Christmas present second or third-hand present from a junque store. What we like as much as the present is the DEAL, the bargain. In similar fashion, we learned that any Smith should be able to make things, and do things for themselves. Smiths sewed many of their own clothes, used shop tools, hung wallpaper and laid linoleum, cut firewood, hunted and fished for the freezer, canned or smoked salmon, preserved berries and veggies we grew . . . and fixed our own cars.

So we grew up imagining that this was standard behavior. But it wasn't necessarily. Many others of my parents age came through the depression years and the war fed up with scrimping and determined to live it up once they had good jobs and cash in hand, and they were NOT going to waste their time fixing old things and I suppose that their kids picked up that that point of view. To this day I can walk through a wrecking yard or recycle center and see all kinds of Perfectly Good Stuff that people just throw away . . . which is good, I can bargain for it!

Steel shot seems a little much for most aluminum, but maybe it's just a matter of re-setting the pressure.. In fact, about 1973 I was on a crew that sent several sets of rods to be shot-peened and evidently the pressure through the gun was way too high because rather than the usual sort of matte shot-peened finish, these rod beams were deeply blasted by the media. We ran 'em and had no rod beam failures, but they sure didn't look very good.