Hi there,
My first post. I have a 1964 Bonneville 390 and I have already fitted a 21/2" exhaust with Flowmasters and side exit. Sounds pretty good but my partner wants it louder.

I checked with the exhaust shop and the main reason its still pretty quiet is the balance pipe after the manifold where the driver'* side pipe runs under the engine and joins with the other pipe. They then run as a dual exhaust from there.

I've been looking into headers and checking other posts here which pretty much confirms my thoughts that they aren't out there off the shelf. Then I check out RamAir Restorations and they have long branch manifold reproductions. I'm thinking that these could work to allow me to run a complete dual exhaust set-up, with the driver'* side pipe running straight back instead of straight down and under.

Does anyone have any experience with this or any other options?

Many thanks for your help.

If I'm not mistaken, even with true dual exhaust you still need a X pipe to balance out the exhaust gas. Headers will also change the tone of the exhaust. If your looking for true louder exhaust they do have a exhaust cutout valve that when opened gives you full open exhaust.

Thanks for that. I'll check out the x pipe too. It looks like that is also available. I checked with Mad Dog Headers and they have a stock set that will probably fit depending on the power steering. Might still be an option too.

You can run dual exhaust with stock manifolds without a problem. But if you add the factory long branch manifolds, it will really wake the car up.

The only thing I'm not sure about with the long branch manifolds is clearing the oil filter. They look like the down pipe goes back a long way. The Ram Air site mentions an oil filter adaptor so possibly this changes the angle of it or something.

Yes, you must use the oil filter adapter with the long branch manifolds as it does change the mounting angle of the oil filter for clearance. All the High Output cars had them, so if you can find a picture, you'll see what it looks like.

Great, thanks for that. I'll need to factor that in as well.