Exhaust thread pitch?
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Postmaster
Joined: Jul 2003
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From: Pittsburgh
Exhaust thread pitch?
What's the thread pitch on the exhaust manifold bolts on a 390? Tomorrow or saturday I'm going to be pulling the manifolds and want to have the tap and bit already there for when I snap a couple off. . .
Justin
Justin
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Joined: Feb 2005
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3/8-16 it is. Even if you don't snap any off I recommend chasing the threads. I've made a habit of chasing all threads before assembly of an engine. It doesn't take much time and elimates the hassles of dealing with all the potential issues you can run into.
Good Luck!
Tracy
Good Luck!
Tracy
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Just an update. I started taking my exhaust manifolds off yesterday and found all the bolts to be 5/8's x 1 1/2 course. I dont know much about the history of this motor but I knew someone had pulled the manifolds before as there are gaskets installed. So looks like they were drilled or 3/8's is not correct. Anyways, good luck. This has proven to be a "*****" of a job with the motor in.
Lead Driver
Joined: Apr 2001
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From: Texas
I doubt very much you have a 5/8" header bolt. the bolt head might be a 5/8" socket. But the bolt size should be a 3/8", 16 pitch bolt. If somebody tried to drill and tap and FE head for 5/8" header bolts, they would most likely get into some of the coolant passages.
I mean, a 5/8" bolt is a big bolt. I think the crank/balancer bolt might be a 5/8", and it's probably the biggest bolt on an FE.
I mean, a 5/8" bolt is a big bolt. I think the crank/balancer bolt might be a 5/8", and it's probably the biggest bolt on an FE.
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yeah, sorry about that post. I was tired. as it turns out they were 3/8's. I was just comparing the ones i had bought to the bolts i had pulled out. as it turns out they sold me 5/16's. but they were labeled 3/8's. but they exchanged them no prob so it worked out. now i just have to drill out the two on top that i broke. previous owners are evil!
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i found the easiset way to deal with the broken off top bolts is to drill em out and just run a 2" bolt through it and put a nut on the back. i did this not 4 days ago. i had the passenger rear and the drivers front break off the rear wasn't that hard becuase the PO had cut out a spot in the fenderwell so i could fit the drill in there pretty good. the front was a PAIN i ended up cutting down drill bits and the only way i could keep them straight in the chuck was with a .30 carbine shell. a 90 degree attachment will be your friend.
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Yeah I ended up breaking 3 total. #3, #4, and #7 cylinder all on the top side. I drilled the #4 easy enough. Borrowing an angle drill to get the others. Any suggestions as to drill bits? It seemed like it took forever to drill #4. Would a cobalt split point make it go a bit faster?
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i started out with like a 1/8" and went up frome there in probably 32nds or 16ths and when you get to the bigger sizes like 1/4"+ i would wobble the drill to help out some once your through. and the best bits i have found are just the regular DeWalt bits.
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Postmaster
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From: Pittsburgh
Even using heat 3 still broke. They were the top front 3 on the drivers side. I've drilled them out in vehicle before on a truck, but there was NO WAY these were getting drilled out in vehicle. I wound up pulling the head off, which was actually kinda good since it gave me a chance to see what kind of condition the motor itself was in.
The ODO on the car reads 99956, and I'm pretty positive that it's an accurate number. I also think that the car has been driven lightly during its lifetime. There were NO wear ridges AT ALL on any of cylinders 5-8, and all of the chambers were pretty carboned up. This tells me it's lead a pretty easy, low RPM life. There was also no buildup under teh valve covers, all it was was that kinda golden brown oil color. I was pure beauty under there.
So anyway, i got them drilled and tapped out and got the manifolds hung no problem. It hasn't run yet as I'm down 2 spark plugs (the two over the exhaust leak shattered as soon as I touched them with a socket) and have a bunch of stuff to do this week. It'll all happen soon enough.
Justin
The ODO on the car reads 99956, and I'm pretty positive that it's an accurate number. I also think that the car has been driven lightly during its lifetime. There were NO wear ridges AT ALL on any of cylinders 5-8, and all of the chambers were pretty carboned up. This tells me it's lead a pretty easy, low RPM life. There was also no buildup under teh valve covers, all it was was that kinda golden brown oil color. I was pure beauty under there.
So anyway, i got them drilled and tapped out and got the manifolds hung no problem. It hasn't run yet as I'm down 2 spark plugs (the two over the exhaust leak shattered as soon as I touched them with a socket) and have a bunch of stuff to do this week. It'll all happen soon enough.
Justin
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