I have a 74 Delta 88 Royale with a 350, it came factory with single exhaust. I purchased a dual exhaust from usapartssupply.com. Their exhaust is about 2 1/2 in. The flange on the driver side does not fit, but the one on the passenger side does. Does anyone know where i can get one to fit the driver side? Thanks

 

You will need to find a "W" lh manifold. Same manifold as used with 69-76 A bodied Oldsmobiles. 71-76 B body Olds.

Henry

 

You shouldn't need special manifolds to run true dual exhaust on a 74 B body. By 1974 the steering knuckle was in front of the centerlink. There shouldn't be any interference on the driver's side.

Sounds to me like you might need a reducer or expander for your exhaust. Do you mean that the pipe pictured is just too small to fit on the manifold? I am confused.

 

You'll probably have to get a good exhaust shop to flange and weld in a new section of pipe to mate up with your existing manifold. 350 manifolds are the same for single and dual exhaust cars in those years; the 455 needs the correct W left side manifold to make dual exhaust work properly and get the pipe away from the starter and lower control arm.

Question. Why didn't you just get an exhaust shop to bend you an aluminized dual system? All the good ones will have program cards for their bender and a really good one can duplicate all the flats and radius bends the factory parts had.

BTW, Oldsmobile has always been notorious for using two different size pipes on their dual exhaust systems.

 

This is true. I just got exhaust on my 64 and the guy had to put 2 inch pipes on the manifold then he expanded to a 2.5in about a foot off the manifold.

 

thanks for the help, but down here in shreveport, la the shops are usually putting junk together and i ordered a catalog from usapartssupply.com and i thought they had everything i needed to make true dual exhaust. the pipe in the picture fits fine, i cant slide the piece next to it on there to bolt on the manifold.

 

What did you do with the original crossover pipe???
Hell, even I could cut THAT in half, and get it close to the other pipe.
I think I have 3 extra's in the garage that I could sacrifice.
Jim

 

You'll be hard-pressed to bolt that big block "W" manifold to a 350. Sorry, this isn't the correct application for that manifold.

 

I had to use 2.25" x 8" long reducers to install my 2.5" exhaust system for the same reason. I could not find the flange bracket in any size but 2.25"
max.

 

maybe something like this? http://summitracing.com/parts/CTO-F8/ not sure if the bolt holes are wide enough. The bolt spacing looks something like 3.5 on my 76 350 delta 88 driver side manifold.

 

You just need to reduce the LH inlet to the pipe. Even a hack exhaust shop could do it for you. Just take the old cross over and the new pipe. Tell them you want that end on the new pipe or make a new end with the small size.

 

If it is a 2.5 (there is no frame of reference to size except the stock flange fitting) pipe, pretty as it is, you will HAVE to cut the end off of it, and use the stock crossover end on it.

Face it now, that pipe is too large for the stock exhaust manifold.

I'll bet your shop will be experts at that!
Jim