X-pipe for Dual Exhaust

[Haunted Ken]

I'm getting a dual exhaust put on to my 72 Hearse w/ 472, probably 2 1/2" with Flowmaster 40's, should I have an X-pipe installed as well? Or does the 472 like a little back pressure? Also, can anyone recommend a cheap yet decent set of headers? I will eventually be building up the motor with a cam, new valve train, head work, etc... This is my first Cad motor, I've always messed around with Ponchos.... Do the same principles pretty much apply?

Haunted Ken

[STDog]

This is my first Cad motor, I've always messed around with Ponchos.... Do the same principles pretty much apply?

My understanding is they do, but they are applied differently. The 472 is a low RPM, high torque engine. So all those tricks for high RPM, high HP engines are wasted. You never get to those RPMs ( or without mods you break something).

So the mindset is very different. Same principles, but very different application.

[73 Century]

The X will change the sound a bunch. Depending on which mufflers you use it will be good or bad. No O do not have any suggestiond because everybody has a different opinion on the sounds.
I put an X on a borla mufflered car and it sounds much smoother, put an X on a dynomax car and I am not real happy with the sound at cruise.

[Gorf]

Hey Haunted Ken,
I was under the understanding that x-pipes are for high reving high HP applications like STDog said. So on my Caddy I am not going to put it on. However I don't have room to run dual exaust up over the rear axle. Do you? I am trying to find a nice shop that will quietly cut me some exaust so that it dumps in front of the rear wheels. Here is Washington it is illegal to do that for some reasons on passenger cars. :? but most of the Rod guys do anyways. Plus if I do the exaust assembly myself I can accidently "forget" to put the catylitic converter back in. :lol:

[STDog]

I am trying to find a nice shop that will quietly cut me some exaust so that it dumps in front of the rear wheels. Here is Washington it is illegal to do that for some reasons on passenger cars. :?

Really. Is it state law or more local? Still a hearse isn't exactly a "passenger" car is it :)

Plus if I do the exaust assembly myself I can accidently "forget" to put the catylitic converter back in. :lol:

Did it actully come with a CC? I forget when they started showing up.

Luckly mine never had one 8)

[Haunted Ken]

Yes, there is room for duals straight out the back, with a little help from a BFH.... my car is a 1972, so no cats :D I'm not too worried about the sound, my concern is with back pressure; I know that an X-pipe will help engines at higher RPM, but it's been my experience that they can help torque a bit at lower RPM's by relieving some back pressure, but I have heard that Cad engines like a little back pressure, as do the Poncho mills.... but I don't know this to be true.....

And yes, STDog, I understand that Caddy mills don't like the revs without valvetrain mods, (Poncho mills don't really like to spin more than 5500 without modification) but the same ideas apply more or less say than compared to what wakes small block bowties up, eh?

Maybe an H pipe?

Local laws here (Wisconsin) dictates that the exhaust must pass out from behind the rear axle or else I would run the same set-up that you have in mind, Gorf.... :twisted:

Haunted Ken

[STDog]

Yes, there is room for duals straight out the back, with a little help from a BFH.... my car is a 1972, so no cats :D

That was more for Gorf, since he mentioned Cats.

I'm not too worried about the sound, my concern

And yes, STDog, I understand that Caddy mills don't like the revs without valvetrain mods, (Poncho mills don't really like to spin more than 5500 without modification) but the same ideas apply more or less say than compared to what wakes small block bowties up, eh?

What little I've read would point that way. (I didn't get the Poncho reference, nor know much about other engines)

Local laws here (Wisconsin) dictates that the exhaust must pass out from behind the rear axle or else I would run the same set-up that you have in mind, Gorf.... :twisted:

I'm no fan of exhaust changes, but dumping the exhaust anywhere other the the rear bumper is a pet peve. This is a CADILLAC after all. If you want dual, I'd model it after the FWD Eldo dual of the lat 60's early 70's. No cross-over. Follows the frame rail with a sharedd muffler after the rear wheels. It's an interesting muffler, input on both ends and one outlet, an the driver's side. Then a resonator. So for a RWD, I but the mufflers before the axel, and resonators after.