The 57 Olds 98 which is the latest project, appeared to have had at one time , a dual exhaust system. Ancient Mfg hangers for pipes and mufflers on both sides still exist . Currently I have single exhaust pipe on passenger side.Exhaust manifold on drivers side ports in the middle, with header under engine joining passenger side exhaust.
It would appear that in order to have dual exhaust, I would need a different left side exhaust manifold!??
Did Olds produce several types of manifolds for the drivers side..????
Any thoughts would be appreciated.
Regards,
Fletch
PS Appears to be no way to route left pipe from exisitng mid port manifold.

 

First what engine are you running? Second if you are saying that you have a crossover pipe from the drivers side manifold into the passenger side manifold, then that's correct. If it's a small block (330, 350, 403) then you have a couple of options.
From the factory all Olds did was to cap off the inlet from the drivers side and just run the single exhaust pipe in the passenger side and run a second pipe on the drivers side.
You can but new dual exhaust manifolds from Thorntons that have eliminated the crossover.
You can also try a set of headers, but I have no clue what you would do for a car that old.
If you have a big block (400, 425, 455) then you can do as was done on the small blocks and cap the port or get factory W/Z manifolds. These were the factory hi perf manifolds.
Then headers, but again I have no clue what will fit.
If you have the older 394, 324, 303 I'm not so knowledgeable about those and someone else will have to speak up for those.

 

If the car still has its 371, 1957-58 LH manifolds are the same for single or dual exhaust per my 1965 chassis parts manual. Plus, dual exhaust was standard on Ninety Eights so someone has changed things around.

57 Chassis Manual shows the DE layout and indicates the LH connection to manifold is very close to the front crossmember, which agrees with your center dump manifold.

 

Randy /Rocketraider: Thanks, the engine is the stock 371. In order to run the L/H exhaust from the manifold, the pipe would go between the idler arm and under the starter. Seems a bit awkward, not mention restricting the steering and heating up the starter. The power brake unit as well as the power steering unit present the problems. I wish the manual showed a picture or lay-out, Hate to screw up this process. Conversion to single exhaust looks correct, as if some one decided not spend the $ for 2 pipes,mufflers and resonators. A dealer early on, could made the retrofit.The car is unmolested save the exhaust,indicates 90K on speedo.
A picture is worth a thousand words,
Thanks again,
Fletch
Flet

 

My 57 when I had the 371 was a factory J2 and had dual exhaust. It was routed as you state. Tight fit but it never overheated the brakes or the starter.

 

Thanks: Let me understand. Header came down from med section of manifold, traveled through upper side of drag link to the left or right of idler arm and ran below starter. Thought is, it would heat starter, and pipe would have to be removed if you had a starter change.
Someone has changed the exhaust to single, with header running under the engine.
Sure would be great if anybody has a picture of a factory DE.
Thanks Citcapp,
Fletch