[Agugliel72SS]

So, on my 72 SS 402 I have an exhaust which I purchased from ground up back in 2000 which matches the original with the resonators. I notice from time to time I have to tighten the three exhaust manifold bolts that attach to the 2.5 header pipe that leads to the mufflers. Is this common? Also, I noticed something I do not have which is the 2.5 Chevelle Big Block Exhaust Extension? So, the question is does this go on both the driver and passenger side of the exhaust between the packing gasket and exhaust manifold and header pipe? Do donut gaskets tend to fail?

Also confirming the heat riser there is only one on the exhaust, right?

Does anyone have a good layout of the exhaust systems and components as well to confirm I have everything?

 

[69SS454]

I am a little unclear on your 1st paragraph with what you are asking. There is only one heat riser on the passenger side between the exhaust manifold and the down pipe. It uses a flat gasket on the top and a donut gasket on the bottom. If you are using a functional heat riser, you need the crossover open through the intake manifold. Otherwise, you need a spacer block instead of the heat riser to take its place when using factory pipes. I took the butterfly out of mine and welded the shaft so it looks original but doesn't function. I have not had problems with bolts loosening but I will check them. Donut gaskets do fail like any other exhaust component.

 

[mrpaticular]

Donut gaskets always fail sooner than later.
Rick

 

[brown1972]

I have 2 cars. One has headers and the other stock manifolds. The 3 nuts on the manifolds routinely loosen with engine vibration. I just tighten them every once in awhile. As noted in the other reply, the heat riser is only used on the right side.

 

[Agugliel72SS]

I am a little unclear on your 1st paragraph with what you are asking. There is only one heat riser on the passenger side between the exhaust manifold and the down pipe. It uses a flat gasket on the top and a donut gasket on the bottom. If you are using a functional heat riser, you need the crossover open through the intake manifold. Otherwise, you need a spacer block instead of the heat riser to take its place when using factory pipes. I took the butterfly out of mine and welded the shaft so it looks original but doesn't function. I have not had problems with bolts loosening but I will check them. Donut gaskets do fail like any other exhaust component.

Yes I have one heater riser on the passenger exhaust side that I did disable and I think the donut is leaking and I appreciate the clarity. As for the bolts loosening I think it is more the donut is breaking down I have had them on there for 15 years and they have some leaks.

Also are you familiar with a exhaust extension on the driver's side? Do you have one?

 

[123pugsy]

Donut gaskets always fail sooner than later.
Rick

Once. Never again after using steel donuts.

 

[71350SS]

All there is a heat riser on the passenger side of the exhaust manifold no extension on the drivers side.That's big blocks and small blocks,the heat riser system was not only used on the BBC but it was also used on small block Chevy too.
Are you using the brass nuts or regular steel ones ? The brass are designed not to rust up and seeze like the regular steel nuts do,so the price for that is to periodically have to re-tighten them.

 

[Agugliel72SS]

All there is a heat riser on the passenger side of the exhaust manifold no extension on the drivers side.That's big blocks and small blocks,the heat riser system was not only used on the BBC but it was also used on small block Chevy too.
Are you using the brass nuts or regular steel ones ? The brass are designed not to rust up and seeze like the regular steel nuts do,so the price for that is to periodically have to re-tighten them.

I believe i have S/S I have to confirm this weekend and interesting about the brass screws. Also nothing about a coupling on the driver side which I mentioned in the the original post?

 

[69SS454]

What do you mean with a driver's side exhaust extension, coupling? Do you have a picture? My manifold connects directly to the down pipe.

 

[mrpaticular]

Never heard of the steel donuts. I only like donuts with chocolate on them
Any nut that is not the same material is best.
Header bolts always loosen and sometimes fall out.
Rick

 

[123pugsy]

I've never had a header bolt loosen.
I always use stainless Allan socket heads.

Agree with the donut flavors though.

 

[shovelrick]

Specialty lock washer might help with the bolts getting loose, I have an old Harley that before I had the engine rebuilt and balanced would rattle nuts, bolts and False Teeth 😂 loose so Loctite, Safety wire and I can’t remember the name but there’s specialty lock washers that’ll keep things tight

 

[oldguy67]

I think the best brass nuts are twice the length of a standard nut. The extension you mention I think is to center the donut on the down pipe.