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Thorley Headers


Precise1
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Well, if you end up getting bolts, please do post the all the dimensions, in case I change my mind. I won't be doing mine for a couple of weeks either.

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Well, if you end up getting bolts, please do post the all the dimensions, in case I change my mind. I won't be doing mine for a couple of weeks either.

That's going to be a fun job in the cold. Watched magregor do it on his truck and it was a PITA lol. Unless you've got a heater in the garage.

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No they did not come with a clamp and all the sealant just evaporated. :lol:

The shop I did it in was pissed off that they did not have a clamp or anything but those pipes are so thick that screwing on a silly clamp doesn't do anything. Now I do not know what to do with that slip in nonsense... Do not weld it, you will not get that pipe out.

 

BTW, if you have a 90-95, you don't need to touch the EGR tube and the oil filter clears fine. I'm running a stock muffler and cat right now but its probably a good idea to change those.

Edited by Tungsten
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Just so everyone knows. Doug Thorley took these out of production for a long time but recently started making them again. We should expect to see them on the shelf constantly from now on.

 

Free Shipping on DT Headers to the lower 48.

http://ruggedrocksoffroad.com/doug-thorley-m-112.html

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so steevo, you are saying that if i had the 2 piece pipe welded, the flanges on the 2 piece pipe would clear out of the body and not hit anything?? :scratchhead: thats not what i was told so im trying to understand why

Edited by Tungsten
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check for the flange welds...ive seen some dt that has some crappy welds on the pipe to flange.

 

When i did mine i used grade 8 bolts I believe instead of studs and nut...using bolts has the advantage of ease of removal because when it snaps it snaps on the head above the flange

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...using bolts has the advantage of ease of removal because when it snaps it snaps on the head above the flange

Most of the time, of course same goes for the studs also. All but one of my broken studs were broke where the nut was, so the non-threaded part of the stud was still sticking out of the head.

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So, the exhaust stud I pulled from my 95 is M8x1.25, 46.7mm long with about 13mm of thread on one side and 20mm on the other. The 13mm side is what is threaded into the head.

 

I ran across a box of 10.9 grade M8x30 bolts at work and will do a test fit and some additional measurements tonight to see if this is the right size. M8x25 may be more appropriate. I'm going to order a roll tap to clean up the threads and perhaps form them slightly deeper if needed.

 

I'll update as appropriate.

 

B

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I am not sure yet. They are about 1/8" thick and quite small in diameter (and quite ugly). All I can think of is that they are there for some sort of expansion purposes. :shrug:

Any reason you ask??

 

Ok, the stock stud threads into the hole aproximately 14mm (.55") before it bottoms out on the center section. With the stock exhaust manifolds (aprox 13mm (.5") thick), I was able to snug a 30mm long bolt all the way down to the head without any washers. This means there is at least 16mm+ (.65") of thread engagement possible which solves the concern of enough thread engagement with bolts.

 

The Thorley headers are aprox 11mm (.45") thick, this means you can use a thinner flat washer and still have 16mm+ thread engagement (more than stock studs) or reuse the stock spacer/washers (3mm or .125" thick) and have about the same thread engagement as stock studs would have.

 

M8x1.25x30mm bolts seem like the proper length for the headers (should work fine for stock manifolds also but 35mm long should be perfect) and are what I plan to use. I see no advantage to using studs in this application other than for initial alignment and can be hand threaded in for this purpose. The only thing I'm going to do is try to find some stainless or plated bolts instead of the black oxide ones that I aquired.

 

B

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I eliminated the factory stud and nuts and washers..I used a grade 8 bolt (gold in color) ..I just retorque it every year around summer time

 

B dont use stainless because they are not as strong as a zinc plated grade 8 bolts...as per some members and the guys at my local fastener shop

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Thanks for the tip. I know that stainless isn't as strong, but the headers aren't high torque, correct?

(forgot to check the torque spec).

 

I plan to use some blue loctite to help keep them from backing off...

 

B

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Thanks for the tip. I know that stainless isn't as strong, but the headers aren't high torque, correct?

(forgot to check the torque spec).

 

I plan to use some blue loctite to help keep them from backing off...

 

B

13-16 ft.lbs according to the manual..I have not seen or heard anybody here using stainless bolts for them reason why I went with grade 8 zinc plated

 

just a headsup on the bolt removal :D

 

1257357401083023800.jpg

 

Try to use torque extender instead of crowsfeet wrench on them bolts B..itll make your job a heck of a lot easier.I was able to do my wifes pathy without a lift with ease

1257358321029283000.jpg

http://buy1.snapon.com/catalog/item.asp?P65=&tool=hand&item_ID=2219&group_ID=268&store=snapon-store&dir=catalog standard set

http://buy1.snapon.com/catalog/item.asp?P65=&tool=all&item_ID=2221&group_ID=269&store=snapon-store&dir=catalog metric set

Edited by PATHRIDER
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Well, I have a choice between the 10.9 grade bolts I have or A2-70 stainless ones.Ok, here is some stuff I have learned...

 

A metric fastener from a known reliable source which

bears a 10.9 marking should be good stuff; if it's up to

spec for that marking, it will be capable of developing

tensions that would typically shear threads from a tapped

hole in an aluminum part before the bolt would break.

 

Figure 2b, Screw and Bolt Types

 

How Strong is it?

 

One important consideration in applying a bolt is its strength. The bolt material strength is determined by the alloy and processing method (for example, cold working and heat treating.) The two important material properties are the tensile strength and yield strength. The tensile strength, sometimes called the ultimate strength, is the stress level where the material breaks. The yield strength is the stress level where the material yields or permanently deforms. When operating under any normal load fasteners should be below the yield stress. The tensile strength is always higher than the yield strength. Materials with a large difference between the yield and tensile strength are considered ductile, meaning they will stretch substantially before breaking. The load a fastener carries is calculated by multiplying the material strength by the nominal cross-section area of the thread. For inch-size fasteners, the material strength is specified by the "grade." A grade 8 bolt is stronger than a grade 5, which is stronger than a grade 2. The grade is indicated by a series of marks on the bolt’s head. For metric fasteners, the term "property class" is used and is stamped directly on the head. The property class for steel fasteners is given in the form X.Y, where X is 1/100 of the nominal tensile strength in newtons/mm2, and Y is 10 times the ratio between the yield strength and tensile strength. The multiplication of these two numbers gives 1/10 of the yield strength in newtons/mm2 . For example, a fastener with a property class of 8.8 has a nominal tensile strength of 800 newtons/mm2 (116,000 psi) and a yield strength of 640 newtons/mm2 (93,000 psi).

 

There are two common types of stainless steel fasteners: corrosion-resistant stainless steel, ASTM 304 (a.k.a. 18-8) or DIN/ISO A2, and acid-resistant stainless steel, ASTM 316 or DIN/ISO A4. A2 is by far the most prevalent material, and is what is normally supplied for stainless metric fasteners. The BMW OEM Mareg battery comes with A4 screws for improved acid resistance. There are three typical property classes (strengths) for in the metric system: 50, 70, and 80. The class equals the tensile strength divided by 10. The metric property class is a dash (-) number after the alloy designator. For example, a screw marked A2-70 is a 304 stainless steel screw with a 700 N/mm2 tensile strength. Both alloys come in all property classes, but A2-70 and A4-80 are the most common.

 

Table 1b compares the material properties of typical inch and metric fasteners. The inch-size socket-head cap screws (SHCS) are included in the table which have a higher strength than graded fasteners, but no specific markings except for their shape. I have also taken some liberties with the terminology for the sake of simplifying the comparison.

 

Inch Grade Marks on Head Material Tensile Strength Yield Strength

N/mm2 psi N/mm2 psi

2 none Steel 510 74,000 393 57,000

5 3 Steel 827 120,000 634 92,000

8 6 Alloy Steel 1030 150,000 896 130,000

SHCS none Alloy Steel 1240 180,000 965 140,000

18-8 none 302 Stainless 690 100,000 448 65,000

316 none 316 Stainless 690 100,000 448 65,000

 

Metric Class Marks on Head Material Tensile Strength Yield Strength

N/mm2 psi N/mm2 psi

8.8 8.8 Steel 800 116,000 640 93,000

10.9 10.9 Steel 1040 151,000 940 136,000

12.9 12.9 Alloy Steel 1220 177,000 1100 160,000

A2-70 A2-70 302 Stainless 700 102,000 450 65,000

A4-80 A4-80 316 Stainless 800 116,000 600 87,000

 

Table 1b,Fastener Property Comparison

 

Note that the strength class specifies much more than the strength of the fastener and includes properties like the alloy, manufacturing method, hardness, and heat treatment.

 

Handy Tip: When sorting through a mixed pile of inch and metric fasteners the metric ones can always be identified by the marking on the head, that is 8.8, 12.9 A2 etc.

 

So, my A2-70 stainless bolt is almost at grade 5 SAE and should fail before aluminum threads, unlike the 10.9 (grade 9 equivalent). I'd much prefer the bolt to break before it strips out the hole (unlikely at so low of a torque)and the stainless characteristics should lessen the risk of that. $1.40 each so no big deal, I bet they work great!! ;)

 

B

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Stock exhaust manifolds will either have a brun or rust hole or be warped.

 

The major benefit of headers (expecially the kind that I got) is that they are shiney...

 

I kid you. ;) The whole point is increased performance, as I'm sure you have noticed, these trucks are a bit low on power, so if you can get another 15hp from a full exhaust system, thats a 10% gain...

 

B

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