460 Exhaust Manifold bolts - Change now before they break?
 

With an '87 460 with 26,000 miles, I'm considering replacing the problematic factory exhaust manifold bolts. Reviewing the archives, it seems to be a choice of grade 8 or stainless. My experience is that stainless has some stretch in it but not very strong [would guess that 316 SS is about grade 3]. I use a lot of Cat[erpillar] bolts with great success so would probably use them with copper based anti-seize.
Am I wasting my time?

IMO grade 8 is overkill, but they don't cost much more, so what the heck. I like to use stainless steel as much as possible on my trucks, but I wouldn't use it on exhaust manifolds. With a vehicle that old, I think it makes sense to replace both the head to manifold and manifold to exhaust gaskets, plus use new bolts. It all depends on how you view the motor/vehicle. If it's a nice vehicle that you really like, little upgrades like that are worthwhile IMO, and help keep the vehicle nice.

No you are not. This issue is a very popular topic on the RV forums. The opinion of most of the experienced guys there is it is not a question of if but when they will break. Sometimes they will also break off the back corner of the head also-big buck repair. A bigger consideration is whether to stay with the stock manifolds which frequently warp and crack. On my 95 Jayco, the right rear bolt broke off so i put a Banks system on it and picked up 1.4 mpg in the process. Dont use stainless. Use grade 8 with the copper like you said but also chase the threads with a tap first then blow out with compressed air. Thorleys are also good headers and not as pricey as the Banks.

Stainless can be had in all degrees of hardness. I use stainless studs with large brass nuts and hardened manifold washers. Anti sieze in the threads in the head, not needed between the brass and stainless. 100% success.

I used stainless bolts on my 390 installed in my 77 F150 with no problems.

Just wanted to echo the comments above: Doing it before they break is smart! AND, while you're at it, think long and hard about replacing the manifolds. I "waited" until both my manifold was cracked and a bolt was broken off -- not sure which happened first and/or caused the other, but I suspect the stock manifolds expanding and contracting snapped the bolt. That was a major pain in the you-know-what getting everything ready for the new parts. I also went with Banks despite the high cost, but I'm very happy. I've had 2 trouble free years now. My most recent fill-up after 70% highway driving was 13.3mpg, and I ran a 15.58sec qtr at the dragstrip last night! I can't complain considering it's 12 yrs old w/98k miles. . .

I will second or is it third the thumbs up for the banks headers, My 93 460 warped and snapped two bolts off, so I went with the headers, Gained quite a bit of low end torque and a little gas mileage.

Don't wait, you chance stripping out the threads in the head...

I like the studs and brass nuts. I also use the manifolds. Whenever I have a set of used manifolds I have them machined to level them out and reinstall with new bolts or studs and a torque wrench. 30fp works well.

Hardness of stainless is one issue.

The more important issue (IMHO) is galling. Stainless galls iron and mild steel, therefore you run the risk if struggling to get them out down the road, as well as stripping the threads putting them in.

Stainless is pretty - but grade 8 works just fine.

I think I'll go with the Cat grade 8's and do it one at a time so as to not upset the gaskets/fit.
Frederic, I'm curious to know more about the SS galling. Also, does anyone know why many, [but not all], Ford bolts have those grooves in the bolt head?

Stainless Bolts
 

I know this is an old thread but someone may need to know. You can search the tensile strength of bolts and while searching ( I really wanted to used stainless) I found they are not as strong and have a chance of gaulding. Stainless Steel Galling / Locking Up / Freezing Up I decided to stick with good old grade 8 bolts, lots of high temp anti-sieze and brass nuts on studs. If you are afraid of brass nuts coming loose, use two nuts - one as a lock nut. Still looking for a picture and potential problems before I tackle mine. A fastener kit comes with 6 bolts, one smaller than the other 5 and five studs with nuts. That doesn't seem to be correct for my truck. It appears to have 8 bolts of the same size... Man! I'm dreading this job.:( I want to buy new bolts before I start so I don't have to take a taxi to get them once it's apart. ... Danny

It depends on the year, the EFI engines have 4 long and 4 short on each side, some have studs on the end for the heat shields, dipstick tube and brackets for solenoids, coil and air check valves as needed. If you want non-stainless bolts, you want ASTM A193 Gr B7, it is a high temperature bolt, normal Gr 8 is not a high temperature service bolt. On stainless, 304 or 316, cond B is a whole lot stronger than cond A. On the fastener kits, I bought 2 sets for mine when I put it together, I will probably do the same on the new engine, mine were Dorman.

FWIW, I made my living for almost 30 years in materials testing, so I am very conversant with fastener material and strengths. As for stainless (actually CRES for Corrosion REsistant Steel) I use a nickel based anti-seize on all my exhaust fasteners, never had a problem taking them apart later.

Thank you for weighing in on this Bill.

People don't seem to understand that in most cases 'harder' means higher carbon steel.
(carbon is the most cathodic element found in common steel)
Carbon = corrosion

Harder is NOT better.
Stronger is not better.... hell, you're only torquing the bolts to 30 ft lbs!
Tougher is what you want, and most stainless is tough.

316 is probably the better choice if exposed to salt or other chlorides.
I have 316 bolts in my truck more than a decade with no galling issues.
Stainless-on- stainless is likely to gall if you don't use a proper anti-seize.

Jim, every time this comes up I try to set things straight. There is a whole lot of misinformation out there. One of the issues, if you go to a hardware store and buy stainless steel fasteners, you are probably getting 304 cond A stuff, which is soft and will gall even with proper anti seize. You need to go to a source like Fastenal to get the correct material. One of the big issues, most hardware store stuff is Chinese and they are one of the biggest source of counterfeit fasteners.

I bought mine at a chandlery.
Not sure if it is A or B, but it is 316, for use in a marine environment.
I thought B was work hardened, as would happen while rolling threads?