New onef or me..., Late /4 exhaust Options

[914werke]

So I have a couple of late /4 project cars I need to fix up & off. One is Forrest green survivor, remarkably original for a 50 yr old car.
I started working on fixing what issues it has including pulling & resealing the engine. The cars undercarriage has a LIBERAL coating of a black tar-like undercoating sprayed all over the drivetrain including the heat exchangers.
Interestingly the late forward facing late exhaust collectors still have the OG heat cover attached which I had never see before (IMG:style_emoticons/default/idea.gif)
It took some experimenting to figure out how to remove this hard black undercoating but once I figured it & cleaned them it revealed the most unadulterated set of late HE Ive ever seen (IMG:style_emoticons/default/aktion035.gif)
The collectors looked a little wonky so I removed the jackets to find nice heat/rust cracks in both! !! Danm~ (IMG:style_emoticons/default/WTF.gif)

[JeffBowlsby]

A new one to me. What’s the hole and heat jackets for?

[wonkipop]

A new one to me. What’s the hole and heat jackets for?

stabbing a wild guess at it - i would say the jackets are part of a primitive quasi-thermal reactor role for the exhaust outlets in the late cars. i have read elsewhere in literature that the late exhausts did have this feature. they were not full scale thermal reactors like the USA 911s and 912E had, which were to avoid porsche fitting catalytic converters to those models in 75 and 76. think porsche could not fit cats in those particular 911/912s early on when cats came in. i believe mercedes were similar in approach. fitting thermal reactors for a while in lieu of cats.

not a great idea as it turned out.

i know the 914s had the cats for california at least in 75/76 but the cats were quite small. i believe the quasi thermal reactor exhaust stubs before the heat exchangers did some work getting rid of unburnt hydrocarbons before the remainder was dealt with by the cat.

a further guess. perhaps only the california cars got this jacketed initial exhaust stub outlets? though the PET does not seem to distinguish anything in terms of USA markets.

if you look in the PET there are quite a few variations on this stub exhaust part listed.
i've never really tried to work it out. seems to involve up to and then past certain engine numbers on the late engines.

as to the hole in one of them. no idea on that one! (IMG:style_emoticons/default/smile.gif)

if these things really were intended to act as kind of quasi or part thermal reactors its hardly a surprise they have heat cracks - esp if they were jacketed. i imagine the unjacketed ones might have not gotten quite so hot?