They are not metric, no. At least they're not supposed to be; who knows how some idiot in China might have mis-threaded them.
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| Exhaust Flange Bolt Size? https://www.slantsix.org/forum/viewtopic.php?t=50189 |
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| Author: | 63Valiant [ Fri Oct 26, 2012 3:57 pm ] |
| Post subject: | Exhaust Flange Bolt Size? |
I put a newer exhaust manifold in the '63, the kind with the reinforced ribbing. The output flange is threaded instead of using bolts and nuts as in the old style. They 'appear' to be 7/16 course, but a 7/16-14 will only start to thread then stops, (both holes) and a 7/16-20 won't even catch. Are these holes metric? TIA! |
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| Author: | SlantSixDan [ Fri Oct 26, 2012 6:35 pm ] |
| Post subject: | |
They are not metric, no. At least they're not supposed to be; who knows how some idiot in China might have mis-threaded them.
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| Author: | emsvitil [ Fri Oct 26, 2012 11:37 pm ] |
| Post subject: | |
A 7/16 bolt would have to be an 11 mm............ which I've never heard of. You could try a M10 x 1.75 which would be about an 25/64 x 14.5 |
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| Author: | 63Valiant [ Sat Oct 27, 2012 7:16 am ] |
| Post subject: | |
Thanks guys. If I can't figure this out I'll have to drop some 3/8s through the holes and use nuts on the ends. I prefer to do things proper, but sometimes we have to improvise. As far as I know this isn't a Chinese replacement, it looks to be OEM. And I dug around in my spare parts to see if any of the other manifolds I have are threaded. I found one still connected to a super six intake. One of the flange bolts was broken off in the hole, but the other hole was open and it is reacting to the 7/16s bolts the same way as my other manifold. I carefully started a tap in it to see if it was just rust in the threads that was stopping the bolt, but the tap responded the same way, it starts, then stops. If I apply pressure it starts to cut new thread. Very odd.... |
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| Author: | Aggressive Ted [ Sat Oct 27, 2012 8:00 pm ] |
| Post subject: | |
I just drill them out oversize and use a stainless bolt and lock nut and nut. They are much easier to remove when time comes to change gaskets. Especially when you step up to a 2.25" head pipe. Assembly goes much quicker. |
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| Author: | kesteb [ Sun Oct 28, 2012 6:11 pm ] |
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When I need new nut for those bolts. I found that 7/16 lug nuts worked quite nicely. |
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