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Manifold bolts, switching from steel to bronze.

Weasel

NAXJA Forum User
NAXJA Member
Been reading about switching my manifold bolts over to brass or bronze silicon bolts and nuts when I change my gasket. I've noticed that 5-90 and others are very picky about maintaining the proper torque on these fasteners. The question that has occured to my is if you use a material other then steel, then your torque spec are no longer valid. Brass is softer then steel and will strech more then the steel will, so do you compenstate for this? I realize with this app and only 23 ft-lbs, it probably doesn't make much difference but. I suppose I could refigure the equivelent torque for brass or bronze.
 
Your torque spec will remain valid, go ahead and use (what, 21 pound-feet) the manual listing. Having done this a couple times, I can attest that it will work.

However, replacing your spring washers at the same time will not go amiss, and you can probably get new Bellevilles from the same place you get your bolts. I would like to experiment a bit to find the best configuration, but so far it would seem to be putting the "dish" washer down first (the OEM one,) then put the Belleville on with the open end OUT, and then put a flat washer down as a bearing surface for the bolt head. This will give you maximum use out of the Belleville, and still maintain spreading the clamp load (which is what the OEM dish washer is for.)

Once I come up with a better idea, I will be sure to let everyone know - but that sounds workable so far, based on what I have used Bellevilles for before.

Also, bear in mind that brass & bronze will get incrementally harder, rather than softer, due to repeated heat soaking and gradual cooling. This is opposite of the behaviour you will find in alloy steel, and another good reason to not use steel there. Therefore, the "springiness" you mention will become rather less of an issue over time, which is why I had not mentioned it before (because it eventually will become a non-problem.) If you want to restore them to their original state, next time you pull the manifold, heat the bolts to dull red and drop them in water - this "anneals" the alloy, and lets you work up the hardness curve all over again.

In short, there is no reason to change anything other than the bolts - you are assisted by the fact that this is a "low preload" fastener, and therefore installation torque is not as critical as it could be.

5-90
 
the studs are a fine thread 3/8" correct, I see you can get defromed nuts in both 3/8" threads, wouldn't have to worry about they coming loose.
 
It's funny how ferrous and non-ferrous act differently.
 
Last edited:
Weasel said:
the studs are a fine thread 3/8" correct, I see you can get defromed nuts in both 3/8" threads, wouldn't have to worry about they coming loose.

The "outside" end of the stud is 3/8"-24, the "inside" end is 3/8"-16.

There is a sound engineering reason for the two different threads, but it confuses logistics, and isn't fully necessary in this case. Threads going into a casting are almost invariably coarse - that allows more material at the thread root to resist pullout. Fine threads will typically hold more clamp load - but aren't necessary here, since clamp loads are low to begin with. I tend to replace the OEMR studs with 3/8"-16 studs cut out of a section of brass "allthread" rod, and just use 3/8"-16 machine nuts on them. Problem solved.

Saudade - what did I have backwards? Just wondering - I seem to have missed the edit, but Langer1 quoting you brought it to my attention... I'd just like to check, and make sure I didn't get something reversed (although I don't think I did...)

5-90
 
5-90 said:
Saudade - what did I have backwards? Just wondering - I seem to have missed the edit, but Langer1 quoting you brought it to my attention... I'd just like to check, and make sure I didn't get something reversed (although I don't think I did...)
5-90

Nope. You got it right. I misread your post and thought you were referrring to steel. When I saved my post and reread the thread, I realized my mistake and corrected my post. Langer1 was just a bit quicker on the draw.
 
Saudade said:
Nope. You got it right. I misread your post and thought you were referrring to steel. When I saved my post and reread the thread, I realized my mistake and corrected my post. Langer1 was just a bit quicker on the draw.

No problem - I just wanted to make sure. I do sometimes get things reversed - ask about the time I said that "your front end is probably a Dana 35..."

Needless to say, I was having a bad day - but I'm always willing to admit when I'm wrong! It's agreeably rare, but it does happen, and I like to make sure when it does...

5-90
 
5-90 said:
Your torque spec will remain valid, go ahead and use (what, 21 pound-feet) the manual listing. Having done this a couple times, I can attest that it will work.

However, replacing your spring washers at the same time will not go amiss, and you can probably get new Bellevilles from the same place you get your bolts. I would like to experiment a bit to find the best configuration, but so far it would seem to be putting the "dish" washer down first (the OEM one,) then put the Belleville on with the open end OUT, and then put a flat washer down as a bearing surface for the bolt head. This will give you maximum use out of the Belleville, and still maintain spreading the clamp load (which is what the OEM dish washer is for.)

Once I come up with a better idea, I will be sure to let everyone know - but that sounds workable so far, based on what I have used Bellevilles for before.

Also, bear in mind that brass & bronze will get incrementally harder, rather than softer, due to repeated heat soaking and gradual cooling. This is opposite of the behaviour you will find in alloy steel, and another good reason to not use steel there. Therefore, the "springiness" you mention will become rather less of an issue over time, which is why I had not mentioned it before (because it eventually will become a non-problem.) If you want to restore them to their original state, next time you pull the manifold, heat the bolts to dull red and drop them in water - this "anneals" the alloy, and lets you work up the hardness curve all over again.

In short, there is no reason to change anything other than the bolts - you are assisted by the fact that this is a "low preload" fastener, and therefore installation torque is not as critical as it could be.

5-90

I'm cornfused.
Can you explain the difference between dish-washers and Bellevilles? I'm hoping to be swapping on a APN header before too long. I googled "dish washers" and got nothing but maytag and kemore products.:laugh3: I also googled bellevilles and found what appeared to be dish washers.

Serouisly though, I would like to know what is what.
 
A "dish washer" - also called a "cone washer" - is a largish and sometimes (like ours) fairly thick washer that isn't flat. It's shaped like a dish or a bowl, and is often used to spread loads more effectvely than a regular flat washer.

A "Belleville" (properly, "Belleville Spring Washer") is also a conic or dish-shaped washer, but it's made rather thinner and made from spring-tempered steel. Not only will it help to spread loads (when used as a cone washer,) but it will also allow relative movement between parts without straining the fastener. They can be stacked in various configurations to increase spring power, or to maximise space to move, but that's not necessary here.

A Belleville spring washer is useful in this case because it can be used as a conic washer (which spreads the clamp load of the bolt,) but also because it's springy enough to allow for expansion of the aluminum and steel manifold flanges (which expand at different rates - aluminum at .000012"/"/*F and steel at .000006"/"/*F, which is why our manifold bolts "unscrew" over time,) but they will make room for the differential expansion without putting a "turning" force on the screw, thus ensuring that it stays put.

Why not use them OEM? Because dish washers are cheaper than Bellevilles (mild steel vice spring steel,) and the theory is that dish washers will also flex - but not when they're 1/4" thick!

So, stack them like this"

\\/|B
//\|H

The thick double line is the OEM dish washer, the thinner angled lines represent the new Belleville, and the straight vertical lines are the flat washer. The "BH" is the bolt head.

I'm going to experiment with various ways to stack the Bellevilles, but I just got a batch for myself, and what I've outlined above is just what came to mind first. I'd like to eliminate the OEM "dish" washer - but I haven't gotten that far yet...

5-90
 
OK, that makes since to me.

Thanks!
 
Anyone know off the top of their head what the size the bolts are?



5-90, what's your feelings on using anti-sieze on the header bolts? Just curious....
 
Haleyes said:
Anyone know off the top of their head what the size the bolts are?



5-90, what's your feelings on using anti-sieze on the header bolts? Just curious....

3.8"-16 x 1-1/4", as I recall. You can use 1-1/2" bolts, just have washers handy in case I'm wrong...

You'd be better off trying to keep the bolts put than making them a lot easier to back out - if you're using steel, you can use never-seez and torque to 10 pound-feet (to account for the lubricity of the never-seez,) or use LocTite #272 (and NO other grade - it won't hold up!) and torque to ~21 pound-feet. I also use a THIN layer of RTV copper on both sides of the gasket - it seems to help it seal, and gives it a little more "gap-filling" ability and makes it more tolerant of imperfections. Haven't had one burn out yet - and most inline sixes want just a little help (even those with cross-flow heads...)

Anything else?

5-90
 
5-90 said:
Anything else?

Not that I can think of!

I really apperciate your help.
:thumbsup:

I haven't even ordered the APN header yet! Just want my ducks in a row when the time comes......hopefully in a week or two.
Besides, that'll give me time to find some, Bellevilles in po-dunk USA....:laugh3:

Thanks again!
 
Haleyes said:
Not that I can think of!

I really apperciate your help.
:thumbsup:

I haven't even ordered the APN header yet! Just want my ducks in a row when the time comes......hopefully in a week or two.
Besides, that'll give me time to find some, Bellevilles in po-dunk USA....:laugh3:

Thanks again!

Try Small Parts, Inc. They carry odd stuff like that. Fastenal does as well.

I'm considering starting to carry bolt kits - that way, you can get everything at once. Perhaps once I get more data on common fasteners used...

5-90
 
langer1 said:
Why not just use stainless steel?

CRES is still a ferrous alloy - which would carry the problems of seizing against the iron head and softening due to being annealed over time (and in case you're wondering, "annealing" can happen with heat soaks as low as 400*F, in steels.) Granted, CRES typically carries a higher percentage of chromium (which makes it "stainless,") but most fastener CRES is either 304 or 316 - which will still anneal and has a lower percentage of chromium than, say, 416 (and that makes it softer to begin with - since it has to be run through screw machines for thread rolling and cold-heading.)

I tried CRES years ago on SBChevvy headers - I wasn't overly impressed. That was what prompted my changeover to brasses/bronzes - probably 20 years ago. I had trouble with CRES nuts seizing on exhaust clamps, and don't even talk to me about what they did in the head! I should not need a torch to loosen up bolts in the cylinder head...

You're better off with brass or bronze (pretty much any alloy will work - but I typically use silicon bronze, since it seems to work about the best. Aluminum bronze is also good - but Si bronze is easier to find.)

Answer your question? :lecture:

5-90
 
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