Bolt help please

[dooghssr]

I am swapping the headers out for stock exhaust manifolds on my AMC 401. The manifolds have a 3/8" hole in the center and about a 9/16" hole on the outter holes. The threads into the block are all the same. I assume the outter ones have a fatter top and then drop down to the 3/8" threads. Does anyone know the OEM part numbers or actual sizes to these 2 different bolts.

The heads also have an aftermarket bolt kit that has a big hex head on it and the stock manifolds won't clear. What size bolts do I need to replace these so the stock manifolds will clear.

[tufcj]

No special bolts needed. I'm just running 3/8" grade 8 bolts with small grade 8 washers. I've never had a problem with them coming loose. The bigger holes on the ends were to give them some "wiggle room" on the assembly line to make up for manufacturing tolerance differences.

If you have aftermarket BOLTS, you can probably grind a bit off the manifold for clearance, there's a lot of meat at the flange. If you have a STUD kit, you'll probably need to swap the 3 studs under the exhaust ports for factory bolts.

I might have 6 of the factory short bolts around (used). Let me know if you need them.

Bob
tufcj

[dooghssr]

I could definitely use the six bolts that go under the exhaust ports or atleast what size I would need. The headers were ground down to clear the big hex heads, but I prefer to use stock bolts and not have to grind down the stock manifolds.

[kris]

They are probably ARP bolts. I had to grind the stock manifolds to clear the boltheads with mine.

Some people have had luck with removing the washers from the underside of the bolthead and retorqing. If you try this, do one bolt at a time, do not untorque more than one at a time... Re-torque before removing the next... You get the idea...


k.

[dooghssr]

I was told they are 2-3/8" long, 1/2"-13 USS thread, 5/8" hex head. Install them with no washer. Again I just need to change the 3 on each side under the exhaust ports. Can anyone confirm the size is correct.

[tufcj]

Just dug 6 out of the bolt bin. Your measurements are correct.

1/2 - 13, 2 5/8" long.

Since PM is turned off, click on the email icon (lower left) and send me your snail mail address. I'll mail them to you.

Bob
tufcj

[dooghssr]

I am heading out in the morning to a bolt store to try and pick them up. I need the manifold, t-case and air hole bolts as well. If they have the head bolts I will pick them up also. I will let you know. I appreciate all the help. Knowing the size helps out a ton.

[ol' school power]

Is this a later model 360?
They changed the bolt sizes on the outer 2 bolts on each head to 5/16 I believe.

[dooghssr]

It is actually a 74 AMC 401.

[tufcj]

The factory head bolts are kind of specialized. They have a built in wide area around the head, so a washer isn't needed, and a wider shoulder under the head. They are grade 8. I've never used just a standard bolt for a head. You would need a washer on a standard bolt, which may just bring you back to the original problem.

Bob
tufcj

[dooghssr]

I picked up the bolts today. They only had 2/12 w/a 3/4 head. I ended up grinding the manifold a little and it cleared on the existing bolts. Got them mounted. From what I can find online I should torque them to 30-35 ft lbs. What sequence should I torque them.

I got the bolts for the air holes, but was advised that I should use a spark plug washer when installing. Went to 4 places today looking for them and nothing. Can I use a copper washer or what else can I use.

[tufcj]

I did the AIR holes on one set of manifolds with Allen head pipe plugs. They fit a bit loose, so I coated the threads with Permatex Copper RTV. There is a lip at the bottom of the hole, so whatever you use will bottom out and seal, never had the pipe plugs come loose in thousands of miles of driving. I don't think you'll need any type of washer.

Bob
tufcj

[dooghssr]

the bolt I have are the correct 9/16" fine but are about an inch long. Like you said they will bottom out. I was going to cut them to about 1/2" long. Maybe I can just use them and put some sealant on them.