I'm in the process of taking off the manifolds to change the leaking
exhaust manifold gasket. For the first time I notise these two preheat
regulators on the exhaust manifold under the carbs.

Am I correct in asuming that they work basically by diverting more or
less heat to the carbs dependant on the exhaust pressure?

One is frozen, probably causing that carb to be too hot and probably also obstructing the exhaust flow.

Karsten

You are correct, excepting that instead of exhaust pressure, the manifold heat control flaps were worked by thermostatic springs attached between the flap shafts and pins pressed into the manifolds. The springs have probably rusted away by now. You may be able to free up the stuck one and replace the thermostatic springs. Worst-case; You'll have to remove the exhaust manifold to cut out the shaft and flap in order to install new ones, as well as drill out and install new pins if they have rusted away too.
Happy Motoring, Mark

__________________
DrDKW

Thanks Mark,

The springs are still there but the book refers to these as "damper springs" ?

I am in the proces of taking the manifold off right now, but I can't seperate the manifold and the first part of the exhaust....

Karsten

In this case, "damper" may be refering to the heat flap mechanisims themselves. (like as in a 'fireplace damper')

Happy Motoring, Mark

__________________
DrDKW

when all cars had the exhaust diverter to the bottom of the carb to assist in warm up, my dad always checked that first when considering a used car. if it was stuck he would pass on it right away. he said that if stuck it would result in burnt exhaust valves because of the excessive backpressure.

when i went thru my 51 caddy the passage was under the carb in the intake manifold. the passage was about as big as my index finger. it blocked off the driver's side exhaust manifold and diverted it under the carb. i took the spring and damper assembly and "threw it over the hill" and plugged the passage on both sides with jb weld or similar.

it is supposed to help speed smooth running on warmup but i never missed it.

tom w

__________________
[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

I got the manifold off using the "no mercy" approach on the exhaust pipes and cut them off with a bayonet saw. Hope that I will be able to get those little remaining pieces off, they are like welded to the manifold. I might try the Acethylene/oxygen if all other attemps fail.

I guess I could pull off that exhaust diverter and not miss it at all. The car is only driven in the summer anyway. Only issue is that it is a very original unrestored car so somehow it is a shame to mess with it.

One of the problems with this car is that it has not been driven much at all so things get stuck. Total documented milage is 128.000 km.

The reason the manifold was leaking a little exhaust fumes was that a little amount of flake rust had formed on the packing surface. Should I have the entire intake and exhaust manifold planed as an assembly? Actually it does not look too bad after the rust is removed so the gasket might be able to seal anyway.

Karsten

if it doesnt seal.

go for it, imho

tom w

__________________
[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

Or instead of pulling the diverter, hammer it in place so it doesnt divert exhaust and roast the carbs. Nasty device, alleged culprit that warps the Zenith carbs!

And I'd be careful about planing the manifold surfaces, so not to weaken them. Maybe just sand paper them instead but sure as hell get rid of all the dust by washing them in kerosene or something. Ears at/near #6 cylinder have been known to break off. Brand new nuts will make a big difference. Rusty nuts'n bolts will be major problem throughout the car. How are the kingpins?

You can torque manifold nuts in similar pattern to cyl head bolts from the center out when you reinstall it to create an even gasket seal. You want the gasket to crush evenly, a thick asbestos sandwich with metal on both sides - its generally reusable, installed dry naturally. Not sure of the torque, somewhere around 26-28 lbs i think.

Assuming the diverters are very similar to those on my M114 twin carb manifold, I was able to free up the shafts with lots of solvent, replace the (thermo-responsive) springs (17 yrs ago still available) - they produce more backpressure and heat under the carb plate when cold, then "relax" as they heat up, allowing easier deflection of the inner plate by exhaust pressure. Periodic applications of kerosene-type solvents have kept them free, even with long periods of inactivity. Sometimes they do hang up a mite, but can be freed by grabbing and turning the counterweight back and forth (best done when cold)
Since yours are already now history, and given the summer-only usage, it might not matter a lot if they stay open (gone) - but you might consider driving appropriately-sized pins or nails into the old shaft holes, just to get rid of the leaks (whistles?). But leave something protruding, to grab aholt of, in case someone wants to restore them, someday.
Manifold nuts are best if the brass type with a partial horizontal slice near the top - avoids rusting the nuts themselves, the "slice" cuts its way out, on rusty bolt threads, and they act somewhat as an integral tension lockwasher.
Mine are pretty "clean", even after 17 years since changed out.
I have seen sets of them offered on eBay, if you don't find them elsewhere.
If you can't find them, at least consider brass, with brass lockwashers - and don't omit some THICK flat washers, where appropriate, to spread the stress load and avoid cracking off those little ears...
Stan

__________________
stanbabu@3bubbas.com
59 300d
65 250SE/Cpe
70 250/8
72 250C
78 280CE

As to the theoretical operation of the diverters - you're invited to peruse my overly-analytical best guess at their operation on an M130 and M114 -
should be similar on the M180, I 'spect...
See 71 250C exhaust butterfly/pre-heat valves
"71 250C exhaust butterfly/pre-heat valves "
Post #2

Please correct any bum steers I have given, if found to be inapplicable to M180's.

Stan

__________________
stanbabu@3bubbas.com
59 300d
65 250SE/Cpe
70 250/8
72 250C
78 280CE

Thanks for the feedback.

I did purchase new nuts (it looks like they are made from copper), new original washers and new gaskets

This car is one of the few which has been properly lubricated so kingpins etc. seems to be fine.

Karsten