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Banno

Exhaust Manifold bolts

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If you're using headers with a thinner flange compared to the stock manifold, make sure you use shorter bolts of they'll bottom out before clamping the header flange onto the head. I got a pack of header bolts from rarespares 

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From memory they are 3/8 UNC, try national nuts and bolts on fyans st in sth geelong.

 Thanks mate, Went in today and they helped with what I wanted. Extractors are in and done now. Cheers

 

sorry for the hijack, is it a bad idea to run spring washers? i just stripped a header bolt hole. 

 Don't know if its a bad idea. But a heli-coil be only thing now to fix a stripped hole

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 Auto shops usually sell the bolts behind the counter as "extractor bolts".

 

Spring washer will lose all its tension with the heating/cooling cycles of the engine. Don't reckon they ran them from the factory.

 

Mind you, Clevo's never came out with an exhaust manifold gasket, just metal to metal, so I could be wrong.

 

Also, I drink a lot........... :ph34r:

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Get some long bolts, wind them in till they bottom with some red high temp loctite then cut the heads off and now you have studs. Studs = 100x better then the bolts and it will cost a fraction of getting an actual stud kit.

 

Spring washer should be okay, What temperature does spring metal soften at? I do not think the flange of the manifold will get that hot?

 

Don't over tighten, Torque the bolts/studs. It's alloy it's soft and will expand at a different rate to the 8.8 grade steel bolts so it's best to obey the torque settings.

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the spring washers were all flat when i took them off so i guess they're useless anyway

 

I tightened them to 30 NM but it felt a little excessive, on the last bolt ripped the thread from the head. Next time im going to dial it back to 20-25NM

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hey mate, call ron from kustom bitz  0407818511 he has bolt kits to suit lots of makes and models, they are cheap and cheap postage to, they also have a website hope this helps 

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never thought of the brass nuts - good idea. they use them on turbo stuff from memory.  mind you I've only ever used extractor bolts, cut to size, and never had an issue.  I ordered a set of ARP header studs for the roller cam motor just the other day but that was more for show than anything else. 

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Guest Kode

Does anyone no the sizes of the exhaust manifold bolts for a bf xr6?? Thans

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Sorry dont know about the later model stuff, but would be metric.

 

On a side note I used a 3/8 UNC tap to chase the thread out on my roller cam motor head and when I did it I actually removed metal from the holes. The only explaination for this is the head thread from standard is BSW and the bolt is UNC (I have used a thread pitch gauge to confirm bolt is UNC). If you look at a thread pitch chart the 3/8 UNC and BSW only has a 5 degree thread angle differenc. It has been mentioned else where on this site that by using the different pitch on 3/8 stuff it works as a mechanical lock, fitters that I have spoken to seem to agree with this thought.

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Sorry dont know about the later model stuff, but would be metric.

 

 

On a side note I used a 3/8 UNC tap to chase the thread out on my roller cam motor head and when I did it I actually removed metal from the holes. The only explaination for this is the head thread from standard is BSW and the bolt is UNC (I have used a thread pitch gauge to confirm bolt is UNC). If you look at a thread pitch chart the 3/8 UNC and BSW only has a 5 degree thread angle differenc. It has been mentioned else where on this site that by using the different pitch on 3/8 stuff it works as a mechanical lock, fitters that I have spoken to seem to agree with this thought.

 

That is actually a sound theory, but it could also change slightly during use due to heat

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