Exhaust manifold

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Torrance1

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Hello All

I came across something interesting about the exhaust manifold on my 74 Dart
318..
I'm doing some work on the engine, and decided to replace the exhaust
I also took the exhaust manifolds off. Now the exhaust pipe had been cut off
so when I pulled the manifold off the car, the retaining bolts were "carriage"
bolts...
My question is this, are the manifolds suppose to be threaded for exhaust bolts
or is a Nut and bolt used?
hope this makes sense trying to save on typing..
Best
 
I can't say I've ever seen carriage bolts used.

Stock would typically be a stud in the front and back on both sides, as those go into water. Bolts for all others in between.
 
Bad Sport said:
I can't say I've ever seen carriage bolts used.

Stock would typically be a stud in the front and back on both sides, as those go into water. Bolts for all others in between.
Click to expand...
I knew I needed more words..
No water jackets.. this is the exhaust manifold to exhaust pipe
connection.. And I have never seen a carriage bolt used on
an engine...
I would think that the manifold would be threaded
to accept the two bolts coming up from underneath
Thanks for replying
 
Torrance1 said:
I knew I needed more words..
No water jackets.. this is the exhaust manifold to exhaust pipe
connection.. And I have never seen a carriage bolt used on
an engine...
I would think that the manifold would be threaded
to accept the two bolts coming up from underneath
Thanks for replying
Click to expand...
yeah, no carriage bolts, but some of the later 318, I'm talking late 80s, manifolds weren't tapped for threads. They had a bolt/nut combo where the nut was a clip nut that simply clipped onto the manifold's flange
 
dukeboy_318 said:
yeah, no carriage bolts, but some of the later 318, I'm talking late 80s, manifolds weren't tapped for threads. They had a bolt/nut combo where the nut was a clip nut that simply clipped onto the manifold's flange
Click to expand...
IC, this is a 74... I need more info
I was going to thread the manifold bolt holes...
strange someone would use carriage bolts... really strange
 
on the trucks I have there all bolted on with a locking nut on top and bolt coming from under side.
 
Torrance1 said:
I knew I needed more words..
No water jackets.. this is the exhaust manifold to exhaust pipe
connection.. And I have never seen a carriage bolt used on
an engine...
I would think that the manifold would be threaded
to accept the two bolts coming up from underneath
Thanks for replying
Click to expand...
Sounds like someone just used what they had. It doesn't sound like your manifold is threaded so you can't use studs. I would use Grade 5 bolts and nuts.
 
toolmanmike said:
Sounds like someone just used what they had. It doesn't sound like your manifold is threaded so you can't use studs. I would use Grade 5 bolts and nuts.
Click to expand...
I'm going to look into having the threaded... if possible
 
toolmanmike said:
If you thread the holes you will probably have to drill out the exhaust flanges to accept the bigger bolts. Why mess with a simple design?
Click to expand...
I think I'll take the manifold to my Exhaust shop.. see what
he says.. he might have the part...
 
Torrance1 said:
I think I'll take the manifold to my Exhaust shop.. see what
he says.. he might have the part...
Click to expand...


The manifold has an open hole that you drop a bolt with a washer in, then nut and washer on the exhaust pipe flange to hold it all together. This is all self centering so that the cone on the exhaust manifold mates up perfect with the funnel on the exhaust pipe.

If you tap threads into the exhaust manifold you loose some of the ability for the mating surfaces to float to where they seal the exhaust gasses properly.
 
do not use grade 8 bolts and nuts
brass nuts are ok as are the steel nuts with the slotted acorn on top
lock washers do not help and will become just flat washers with heat cycles
keep it simple so you can get it apart again
cheap stainless works
never seize
 
Wyrmrider said:
do not use grade 8 bolts and nuts
brass nuts are ok as are the steel nuts with the slotted acorn on top
lock washers do not help and will become just flat washers with heat cycles
keep it simple so you can get it apart again
cheap stainless works
never seize
Click to expand...
thanks for your input... I was going to use SS bolts anyway..
 
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