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Discussion Starter · #41 ·
Here’s a few photos of the new manifolds installed on the engine & the exhaust at the rear of the car. I asked the shop to scoot the tips to the outer side of the bumper guards.
The passenger side bracket is still attached to the manifold but it doesn’t stand out or bother me much.
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Discussion Starter · #44 ·
I could be wrong but I think those may be 2”. Your best bet is to pull one & measure it. I didn’t feel like doing it but after a while of guessing I just removed my driver side. Turns out It was a 2”.
 

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Draw a 2" circle on a piece of cardboard. Cut the center out then cut the board in half. Use it as a gauge and slip it over the header pipe. If it fits then it's a 2" if it doesn't then it's a 2-1/2".
 

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Nominally, the 2" is the I.D. of the exhaust manifold; the O.D.of the exhaust pipe. Measuring the O.D. of the exhaust pipe should answer your question.

I'm not a historian but I'm almost certain the exhaust manifolds were 2" on the '70 full size cars.

Pete
 

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1965 to 1970 Chevrolet's used only 2" inch ram horn manifolds for sure. No 2½" were ever used. The driver's side 2" ram horns angles back to clear the steering box on the 1965-70 cars. ALL of the 2½" ram horns point straight down. I was able to fit the 2½" ram horns on my 1967 Impala. It is a tight fit and I had to take it to a muffler shop to have the custom exhaust built.
I'm thinking about going back to the stock 2" ram horns and factory-replicated dual exhaust.
 

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I just had a complete exhaust system installed on my '62 Biscayne wagon and just now measured the outside diameter of the exhaust pipe which is 2.017".
So as I wrote, make a templet out of carboard cutout 2" hole which is close enough to determine whether your exhaust manifold is a 2" or 2--1/2".
Or you could drive to a muffler shop and ask them what size is your pipe.

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Discussion Starter · #50 ·
There’s always the possibility that cliffs ‘70 could have been altered by a previous owner. Unless he knows for a fact that it still has the original equipment I would either pull one off & measure or try the cardboard method suggested.
 
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