Hi All.
The right hand side exhaust manifold (on 253 and 308 engines) have a heat tube pressed through the middle of it.
This tube connects up to the thermal choke on the carburetor, opening the choke as the engine/manifold warms up.
This tube is supposed to have a spiralled metal strip running through it.
I have a few questions on this topic:

1. What does this spiralled strip do ? My thoughts are that it might slow down the air passing through the tube. It also provides a longer path for the air to travel through the tube. This would allow more heat to transfer from the manifold to the air flow.

2. Is this spiral strip a press fit inside the tube ? Or does it float around in there ?

3. If this spiralled strip is not present, is the choke operation greatly impacted ?

3. Are the connecting pipes coming down from the carburretor a press fit into the manifold ? Should a sealant be used when connecting these pipes ?

Your expert advice on this critical matter would be appreciated .
Rgds,
Andrew.

Thanks HK1837.
I've seen the repro connecting tubes you can get. They do look good to me and I plan to grab a set when I'm ready.
Here's an image I stole off the net showing the spiral strip:


Rgds.

It's at least from an HQ (253&308). Image is stolen off the net, but I have exactly the same image in my HQ parts catalog. One of the connecting pipes does have an insulating wrap on it, but what I'm interested in is the spiral strip inside the manifold itself.
My catalog calls it 'Baffle - Choke heat tube'. Part number is 2805461.
Rgds.

All HT-HJ and LH to 5/76 LX V8 (except 350 and L34) have two pipes. One is heated, the other is the supply air, comes from a barb in the base of the air cleaner.
I’ve always thought those spirals indicated air flow! Never realised they were actually there.

I'm pretty sure the tube inside the manifold is just a straight tube. Inside this straight tube should be a spiraled strip from what I can tell. I am interested to know if this strip just floated around inside the tube, or if it should be a tight fit. If it was just floating around in the tube, I guess it would be very easy to lose as the manifolds get worked on over the years.

Rgds.

I've seen a lot of those spiral things fall out over the years. They just 'push' in, with not much holding them in except for a bit of friction & the two tubes which simply slide in each end.

The idea of the spiral is just to expose the air to more hot metal surface area for quicker warm up of the the air itself.

Dr Terry

I don’t reckon you need it unless you like in a really cold climate. After I put my Premier back together, from dead cold the heat tone into the carb was warm within seconds and the choke started to open after maybe 2 minutes.