Question about exhaust manifold heat shields

[eche_bus]

How important is it for the thin metal and asbestos(?) that surround the exhaust manifold pipes to be intact? Here's mine:

Left side

Right side

The pipes and flanges seem good. No exhaust leaks detected before pulling the system apart. How important is the heat shielding? How should I go about restoring or replacing these? Are there new or NOS?

[Wildthings]

They seem to do a good job keeping the pipe from deteriorating from the outside in. Probably keep some heat away from the heads as well. Never heard of a good replacement though.

[aerosurfer]

On my bus and other header pipes i have sold and come across, i have not had any with the asbestos insulation. Even in the classifieds i have rarely ever seen a pipe with them. All else being equal, its the mating surfaces and especially the flanges that are the critical parts of those pipes.

Perhaps a good insulation idea 40 years ago, but IMO the pipes were over engineered and the insulation was underdeveloped.

I have both great heat and excellent head temps and AFRs out if my stock (to the muffler) system
_________________
Rebuild your own FI Harness..My Harness

77 Westy 2.0L Rockin and Rolling Resto!

72 Sportsmobile (sold)
79 Tran$porter... Parts car money machine (gone)

[gliderman]

I have a '79 Calif. emissions westy with the stock exhaust system. The left-side exhaust manifold had a heat shield that was similarly deteriorated. I assume that it is there to keep head temps down since the manifold runs directly below the head on the Calif emissions setup. At rebuild time a few years back, I remove the old heat shield and wrapped the manifold with manifold insulating wrap that you should be able to find at your local auto parts store. I secured this insulation using steel mig-welding wire wrapped around the manifold every inch or so. Many years later, it is still in place and I have some peace-of-mind knowing that I am not frying my heads with a the red-hot manifold an inch or below.

T

'79 westy

[Bleyseng]

It was stock but almost every set of J tubes I have seen its been rusted off. That being said [email protected] had a good complete set a month ago laying there in the garage.
It's not a big deal as hot air is blasting over the J tubes from the heads pushing the heat away. I don't think it does much to keep the heat from the J tubes from heating up the heads
Maybe it was to try and keep the J tubes as hot as possible so the exhaust going into the HE's was Hot Hot Hot.
I switched over to the 72-74 HE setup as it's much simpler and doesn't rob HP like the later setup. ( about 5hp on a 914).
_________________
70 Ghia Black convert-9/69 build date-stock w/133k 1600 SP-barn find now with a rebuilt tranny and engine
77 Westy 2.0L w/Ljet, Camper Special engine-95hp and with LSD!(sold)
76 Porsche 914 2.1L L20c, 120hp Djet (sold)
87 Syncro Westy Titan Red 2.1L 2 knob 100k miles

[aerosurfer]

[eche_bus]

Wouldn't the Exhaust Manifold insulation/shield both keep temps inside the pipe up AND reduce its heat radiation up into the head? At idle, doesn't the EGR valve lean the fuel mixture, raising exhaust temps somewhat in a situation where there is little airflow over the exhaust manifolds?

Also, if the shielding was there to help reduce emissions, couldn't it be argued that removing it would make it harder to pass emission tests? I've never seen anyone say so, just making a logical extension to the original claim.

Still, if many others have run these bare without elevated head temps AND without emission problems, I'm more than willing to consider doing that. I saw one thread here where a guy ceramic coated them, and that could be a good compromise.

gliderman - I've seen a lot of bad comments about wrapping manifolds. Are you certain it's not rusting out the pipes?

[Wildthings]

[PITApan]

[Hoody]

Properly applied ceramic coating inside and outside the pipes is the way to go once the outer shield has been removed. It will reduce the heat much better then the original asbestos and outer sheet metal skin and there won't be a sponge to hold moisture there.

[aerosurfer]

Its the internet, we can argue and hypothesize til someone starts with the cat pictures and the thread gets locked...

The whatever your thoughts on the collars are, the key components of these parts are the ends. Good torque and sealing to the head, which is well documented, and keeping the other flange sealed and preventing the bolts from rusting to them. If all the rest of your tin is in place, the header F-pipe also has the advantage of mostly not being subject to direct weather elements, and because of its job and temperature, if you are using the engine, its gonna be dry on there.

John,

You haven't shown us any pics yet of the U bend pipes. Those were also originally insulated. None of mine or any I have sold or scrapped had anything left of the original. Its gonna be the ends that are the factor if they are scrap or re-usable.

My U-bend pipes and heater boxes are covered in VHT paint and have held up well in the first 4k+ miles and 2 years.
_________________
Rebuild your own FI Harness..My Harness

77 Westy 2.0L Rockin and Rolling Resto!

72 Sportsmobile (sold)
79 Tran$porter... Parts car money machine (gone)

[Amskeptic]

[eche_bus]

Thanks to all for all the very useful input. Colin, I especially thank you for the research-based comment. Catalyst temperature ... now that makes sense.

[Tcash]

A file would work.
If you know someone at a machine shop you could have them milled?

Good Luck
Tcash
P.S. I would ceramic coat.

[SGKent]

a large flat belt sander with aluminum oxide. Used to sand manifolds flat all the time that way. They have heat worked from all the heating and cooling cycles. A file is really hard to work them with compared to a large belt sander with a plate behind it. Sand 30 - 45 degrees to the right, 30 - 45 degrees left rotate 180 and do again.
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“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin

[aerosurfer]

Those ones look in great shape! Lots of metal on the flanges. What they said above.

Mine were thinner, and warped, took a lot of filing and heat and hammering to get them flat. Use the thicker exhaust gaskets, the ones with the little hole perforations, there is more crush to them than the thin Reinz ones. Seal them up with some copper High temp RTV and you are good to go.
_________________
Rebuild your own FI Harness..My Harness

77 Westy 2.0L Rockin and Rolling Resto!

72 Sportsmobile (sold)
79 Tran$porter... Parts car money machine (gone)

[Bleyseng]

I have belt sanded them and then flat sand them by putting a sheet of sandpaper on a piece of glass. Then sand them dead flat which you can use Prussian Blue to check your work.
If you have a soda blaster it works great to clean them up.

I traded out my set of late exchangers to someone who needed a good set.
_________________
70 Ghia Black convert-9/69 build date-stock w/133k 1600 SP-barn find now with a rebuilt tranny and engine
77 Westy 2.0L w/Ljet, Camper Special engine-95hp and with LSD!(sold)
76 Porsche 914 2.1L L20c, 120hp Djet (sold)
87 Syncro Westy Titan Red 2.1L 2 knob 100k miles

[PITApan]

You can scrape any lose gaskets and do nothing else. Skim them with muffler paste and assemble with ordinary gasket (paste on both sides of gasket. Fer crissakes, it's an exhaust system not a head joint!. The thing is dumping into open air 2 feet away.

[eche_bus]

OK, got a good sense for this now. New territory for me, so thanks again to all that helped by sharing their perspectives and opinions.