Exhaust Manifold Rear Bolt

[GhostFish]

I am removing the exhaust manifolds on my 68 Barracuda. It has a 69 HP 383. The manifolds are stock.

This is my first real experience wrenching on my own vehicles and you guys can probably guess what happened. After I was done cleaning up the mess, I started digging and apparently I can't find the right Google search words.

Why is the rear bolt hole for the exhaust manifold inline with the coolant system inside the block? Was there a purpose for doing this?

 

[413]

It's common on many different vehicles. That just how the head needs to be made for it all to fit and function. It really no big deal of you know it ahead of time.

Not just gas cars either, a Detroit diesel 6V92 is like that also.

When porting cylinder heads it's all too easy for newbie to hit the water jacket and need to get the head welded up.

 

[RustyRatRod]

I am removing the exhaust manifolds on my 68 Barracuda. It has a 69 HP 383. The manifolds are stock.

This is my first real experience wrenching on my own vehicles and you guys can probably guess what happened. After I was done cleaning up the mess, I started digging and apparently I can't find the right Google search words.

Why is the rear bolt hole for the exhaust manifold inline with the coolant system inside the block? Was there a purpose for doing this?

I'm not real sure. Maybe something in the production process or the heads required it? All of them both big and small blocks are like that.

 

[Ricks70Duster340]

I'm not real sure. Maybe something in the production process or the heads required it? All of them both big and small blocks are like that.

Many of the aftermarket aluminum heads, such as the Trickflow 240's I have, do not do that. The holes are "blind" and do not go into the water jacket.

 

[GhostFish]

I appreciate the feedback guys. I can't seem to find the logic drilling behind it. There's no channel there so I'm assuming therenis no flow so it's not a cooling purpose. And the heat transfer from the bolt being IN the manifold would negate that inassume. I'm trying to wrap my head around it so I'm going to dig some more. It's an itch I need to scratch

 

[RustyRatRod]

I appreciate the feedback guys. I can't seem to find the logic drilling behind it. There's no channel there so I'm assuming therenis no flow so it's not a cooling purpose. And the heat transfer from the bolt being IN the manifold would negate that inassume. I'm trying to wrap my head around it so I'm going to dig some more. It's an itch I need to scratch

Just know that it needs to be the correct type stud there, or it will never seal properly. There is a "bump" on the stud that separates the threads that go into the head from the threads on the outside of the stud. That "bump" is key to helping the stud seal that hole. Many people have used bolts and almost without fail they have a leak there, however small. I also use red high temp RTV to seal the threads. Regular teflon type thread sealer cannot stand the temperature and will dry out. I don't care how high the label says it will go.

 

[GhostFish]

Just know that it needs to be the correct type stud there, or it will never seal properly. There is a "bump" on the stud that separates the threads that go into the head from the threads on the outside of the stud. That "bump" is key to helping the stud seal that hole. Many people have used bolts and almost without fail they have a leak there, however small. I also use red high temp RTV to seal the threads. Regular teflon type thread sealer cannot stand the temperature and will dry out. I don't care how high the label says it will go.

That is a fantastic tip. Thank you for that! Considering I'm going with aftermarket headers, I'll definitely keep that in mind.

 

[Dana67Dart]

I'm trying to wrap my head around it so I'm going to dig some more. It's an itch I need to scratch

Colorado State University in Fort Collins, Colorado has an extensive " Engines Lab" you could give them a call and see if you can talk to a prof there.

My guess...

The engineers intended for studs on the outside to help during assembly. Knowing that bolts into the water jacket have a tendency to be problematic they went with studs figuring that they would never be removed in the useful life of the engine.

Another thought. Perhaps they were used to secure the head during casting, or a blind hole would have required an additional part to the mold to create inside the head?

Or maybe the water passage inside thee is particularly tight and there was no room for more casting?

 

[GhostFish]

Colorado State University in Fort Collins, Colorado has an extensive " Engines Lab" you could give them a call and see if you can talk to a prof there.

My guess...

The engineers intended for studs on the outside to help during assembly. Knowing that bolts into the water jacket have a tendency to be problematic they went with studs figuring that they would never be removed in the useful life of the engine.

Another thought. Perhaps they were used to secure the head during casting, or a blind hole would have required an additional part to the mold to create inside the head?

Or maybe the water passage inside thee is particularly tight and there was no room for more casting?

Wow! Great thoughts there! I'll see if I can find an email rather than calling for now. Don't want to interrupt the brains there lol

 

[PRH]

All of the exhaust mounting holes on passenger car BBM heads go into the water jacket of the heads.

I’d be surprised if the instructions for installing the headers didn’t call for draining the cooling system as one of the first steps.

 

[Big.J.007]

Non-Hardening thread sealer is your friend if studs are into water jackets.. With or without the thread stop you still need the correct sealer.

 

[RustyRatRod]

Non-Hardening thread sealer is your friend if studs are into water jackets.. With or without the thread stop you still need the correct sealer.

Permatex #2 works well too. Had good luck with it.

 

[GhostFish]

Thanks for all the feedback guys! Great convo and advice here.