Since these polls seem to be working, i'm gonna get some feedback on my exhaust system which is about to be redone.

 

Since an "X" gives you better flow sharing back through the mufflers, it tends to be a little stronger than an "H". It also sounds different, sort of like the engine is revving higher than what it really is, and loses a lot of the "V8 rumble".

Either is better than no cross-connection at all.

I built what works as an "X" arrangement in the thumbnail car, and my avatar car has an "H". I probably would not fab my own "H" system, but I'm in no hurry to go to the trouble of changing out the "H" in the '08 just for a few more HP.


Norm

 

When I had my exhaust built I had an X-pipe installed for the extra performance and once installed I found I liked the sound better.

 

Jon, whats your set up?

If your running a 289 or a 302 why not just go straight back into some Flow Master 40's (or what ever exhaust you choose)? You will get the best sound and performance our of your engine this way.

 

Yeah my 289 engine is pretty much stock except for the intake and carb, but i heard an H pipe will give it a bit more low end torque? i dont know if thats true or not

to be perfectly honest, at this point im more concerned with sound than performance, however childlike that may be

 

If you build your exhaust correctly (i.e. mandrel bends and large enough pipe), you do not need a cross over. They are useless above about 3000rpm. If they help at all, it is only at low rpms. There is no imperical data that they help any with horsepower or torque. They idea sounds good, but I have read article stating they work and don't work. The working camp never posted any dyno results from their tests. IMO, crossovers are completely a bandaid for poor designed exhaust. When I built my exhaust, I went with 3" pipe and j bends, custom cut the turns, and it is the BEST exhaust I have ever had. I highly recommend trying it if you are up for a first class system. You can then have it ceramic coated and it will last for ever. In short, if the bolt on system you have has it ok, but do not go out of your way to put one on thinking it is going to help any. Also, true duals sound better.

 

From what others have told me in the past, the idea of an h-pipe and a x-pipe makes plenty of sense, but if an exhaust system is built correctly with long tube headers and all the pipes are cut right, there is absolutely no need. The sound will be the best because in theory there would be no restrictions. If you want a bit more rumble for that 289 look into a mild cam.

Good luck

 

yea, just do 2.5" with flowmaster 40s. they will be perfect. i have them on my 289 similar to yours (carb, intake, headers, bit of engine work) and works/sounds great with no h or x pipe.

 

If the exhaust system was optimally built AND your V8 had a flat crank instead of the usual two-plane crank, that might be true. No need does not necessarily mean zero benefit.

With the crank and firing order that we're accustomed to, you have one occasion per engine revolution where two cylinders in the same bank fire consecutively, which means that there are momentary spikes in total exhaust flow and backpressure in each of your two separate pipes (the exhaust pulses overlap to some degree, and tend to get in each other's way). The reason for cross-connecting them is to share the peak flow between the two downstream flow paths, which ultimately improves the engine's VE because the total restriction is reduced. These gains typically are not huge, but they are there, and if anything they tend to be stronger at higher rpms rather than lower at least in the case of the "X".


Norm

 

Norm, I respect what you are saying, but with all due respect, this is exactly what I have seen on both sides of the coin. It works good at high rpm, it works good at low rpm but stops being affective at high ranges, it does not work at all, etc. I understand the theory behind exhaust pulses and collisions of waves on V8s. I also understand why the cross over should work, but I have not seen any data showing power gains (i.e. good proper "tuned" exhaust vs. good exhaust with a cross over). The best performance gain numbers I have seen involve exhaust come from limiting restriction. This ususally comes from installing an optimum size pipe with little restriction (i.e. few turns and good turns but not too large of diameter for the exhaust flow of your engine).

In general, I put cross over pipes in the same bucket at fancy spark plugs. They may or may not really work, but they sell them all day long, so you feel like you did something good. Get you some E3 plugs and a crossover and you may pick up 2-3hp or loose 2-3 hp but you will have spent some money.

Really, I would love to read some more on this, because I am engineer and like to study this stuff. If you have some data or articles, please share them. I cannot find much of anything that is not just hype on crossover pipes.