1977 Eldorado noise from exhaust header
 

Hi,
im owning a 1977 Eldorado Biarritz. Bought the car from LA and it arrived here in Germany some days ago. I drove the car in LA for 10 days and eveything was fine, but sinde its here (much colder) its making some strange whisteling noise.

The noise is located at the end of the right side exhaust header. Thought its a blown gasget where it goes in the exhaust, but ist seems to be another broken part. There is a stange part with vacuum lines at the end of the exhaust header, if the car runs for 3-5 minutes, the strange whistleing noise is gone.

This is my first cadillac, and as im more from the supra, nissan and datsun turbo world, i have no clue what this part might be. Lokks like some kind of valve??

Thanks for your help!

Header
 

The part that you are mentioning is the heat riser valve. The purpose of this part is to give the engine a faster warm-up time. It has a big spring that will allow the valve to open more as it gets hotter and it also has a vacuum line that goes to it. Maybe the vacuum line is off or broken and that will cause the whistle that you hear. It is very important that this valve moves freely, they do tend to rust up from condensation. Lube it up good at the pivot points and make sure the vacuum line is connected and not leaking. If you want to take it out and service it you can disconnect the crossover pipe and pull it out from underneath the car. If you have dual exhaust just drop the tailpipe on that side.
If the valve is in bad condition the part is still available.

Thank you very much!
My guess is that the valve isnt 100% ok, so if its cold and its closed, it will make this blow by of the exhaust pressure. If its warm, its opened and the exhaust pressure will go through. It was warm in LA when i drove it, so the valve didnt close. Here in Gemany with temperatures arround the freezing point, its closing and noisy.

My smog pump is also making some noise. I bought one in LA so i can swap it here.
Does it only have one connection on the top of it? Two small bolts and a rubbe pipe going out?
We dont need a smog pump here in Gemany because its a historical car and it wont need to do any smog tests. Is it worth to swap the smog pump or should i go for a shorter belt and disconnect it? Think it also takes some more fuel for the movement of it...

And a last question: Which engine also fits to this gearbox?
I have the 425 engine, it takes a lot of fuel. Our fuel prices are more than double to yours in the USA.
I knew it would take a lot of fuel, plan was just to drive it on sundays. But since im a big fan of engine swaps (just swapping a RB26 engine in a 1974 Datsun 260Z), i would like to know what is possible.

There should only be the vacuum hose and a linkage between the valve and the actuator. Yes ... you can get rid of the smog pump and the cat. converter too if you like.You will never have great MPG from the big block motors. The Olds 350-5.7l was also used in this car. You may get better gas mileage but will lose some horsepower and torque. Not sure what gearbox you have but it must be the transaxel setup. New injectors or a carb. rebuild, depending on what you have, will help a bit with the gas consumption. I have the 368-6.0l and I get about 16-17mpg... this is a sister to the 425 as they share the same block.