GoolzCutlass

Howdy folks. I stopped by the exhaust shop today to see about getting an appointment to do true duals on my Cutlass. Looks like there are a few questions. First whats the story with the cross ember for the trans? Do you guys safely notch that out on the drivers side? Is there a replacement I should order? Also my exhaust guy couldnt make sense of the manifolds and how the stock pipes go into each other. We didnt have time to put it on the rack. I told him I would ask the pros here so there no surprises. I was hoping to use my stock manifolds for now. Any pointers for the exhaust shop would be much appreciated. Thank you

Fun71

This diagram shows the system without the manifolds. You can see that the right hand manifold has two ports, one for the crossover pipe to the left side manifold and one for the exhaust pipe.

So for duals, you would cap off the crossover port on the right (passenger) side manifold and run a pipe from the rear port. On the left (driver) side, you would run a new pipe from where the crossover port used to connect.

GoolzCutlass

Awesome thanks Kenneth. Is there a part # for the block of cap? Where can I get that? thanks

Fun71

You can buy a reproduction cap from one of the parts vendors or just have the shop cut the pipe short and weld it closed.

http://www.supercarsunlimited.com/Ex...Cap-i2834.aspx

Oldcoyote

On my 1988 RWD, The hot rod muffler shop cut a piece out, reversed it and welded back in. I don't know if that's Kosher but it was done around 1989.

OK so far.

ELY442

Look into ebay about that cross member. Its a custom made cross member for dual exhaust. I remember seeing it in there.

oldcutlass

If your muffler shop is not familiar with old cars find one that is. Get some recommendations from others in your area that have had similar work done.

joe_padavano

The 1973-77 A-body frames are all pretty much the same. The 1973-74 cars came with double hump crossmembers. Get one of those.

brownbomber77

If you can't find one of the 73-75, an early 68-72 stamped piece will work, just have to drill two new holes in the frame for the relocation. If you're going through the trouble of "true duals"...may as well pick up the extra 20hp and put on headers AND the dual exhaust so you only do the exhaust once...

scottv442

^^^^^
agree, worries me to hear your muffler shop couldn't figure out how the pipes were plumbed on a stock single exhaust cutlass

droldsmorland

Headers = leaks, and installation headaches, most of the time, but cool for sure. Manifolds are the way to go unless you have a cam, gears and you're going to the track? If you use the stock iron manifolds and the driver's side has the heat stove flap in it, make sure it's not frozen. If you chose to remove said stove it's doable, contact me for the procedure as there's more to it than just removal.
Consider an X or an H pipe too. They can be installed with manifolds or headers.

brownbomber77

lol...who's installing your headers? I've had a set of long tubes on my truck for 20,000 miles. I installed a set on my brothers cutlass 7 years ago and they're doing just fine. I use copper header and collector gaskets and retighten them after a couple heat cycles. They even increase fuel economy...things to ponder...

brownbomber77

If the exhaust shop is doing the work to modify the crossmember, this might save some money if they're doing it by the hour...


https://www.summitracing.com/parts/sum-770323/overview/

ELY442

X2, I also apply a coat of Permatex High Temp silicone on both sides of the gasket. I never retighten them. Never leaked on me yet.

crimsoncolby

I've read discussions by guys on other forums who build motors for the track agreeing that headers do very little to enhance hp on stock motors.

Another thing to keep in mind if you plan on eliminating the cat is that most all muffler shops will refuse to install a system without them due to legalities. I had to go with a dual exhaust kit purchased online and install it myself.

droldsmorland

Good point as a 77 has an old skool restrictive cat... Depending on the state you may either need to DIY or get a cat back system? If you DIY check the states regs to see if it needs to pass that inspection annually??? And is it a sniff test or a visual test for that model year?

brownbomber77

OOOOR bring it there on a trailer as an "off road use only " vehicle...