I was wondering what makes a crossover or H pipe work and how do you know where to put it exactly? Also what flowmaster muffler is the loudest and do they decrease back pressure more than a glasspack? Any replies appeciated.Thanks in advance.

 

I have read that to locate where your crossover should be located, make a crayon mark down your pipes from the manifolds to the rear and where the heat stops melting the mark is where you should connect. This is just magazine info I got, I just had a muffler shop tell me they didn't think there was any real worth to a crossover tube. I believe the balance tube is suppose to equalize pressure between the pipes to reduce back pressure.

 

Hi Charles,
I have a 79 w/351m (400), that I have a cross over on the exhaust. The biggest difference is in the noise/note of the exhaust. It really gave it a much mellower and deeper tone. I also run fenderwell exit headers(long tubes) and beleive this has helped the bottem end. Sorry, no dyno runs to prove this! Seat-of-pants only! I had mine placed just behind the transfer case and crosses from outside of frame rail to outside of frame rail, my exhaust exits in front of the rear tires, so this has given me more volume in the system as well as balanced the pulses. This is something that I would not have done except that my exhaust system needed to be replaced anyway. Most will tell you that if you're lookin' for more HP, this will not make a difference worth the money spent. Chuck P.

 

I just put headers on my truck and im getting ready to have the exhaust redone anyway.But if the crossover pipe reduces back pressure I dont know if i should get it or not because ive heard that you want some back pressure but ive also heard you dont.What do you guys think?Thanks to both of you for your replies.

 

Hi Charles,
For what its worth, if your going to have the exhaust redone, I would incorporate the crossover if you have the room. I really don't believe that this has anything much to do with backpressure as such, it's more of a balancing device. It will allow less backpressure than not having one, but, I think this is due to the fact that there is more volume in the system, however, once that space is taken or filled, the backpressure will still be only as much as can flow thru the mufflers. One other thing to keep in mind, tube size has alot to do with backpressure, a large tube will lessen, a small diameter will increase.
Hope this helps alittle bit. Chuck P.
Sorry can't help with muffler choice(I run trapps).

 

Thanks for the info,I guess I'll have a crossover put in when I get the exhaust done.

 

As I understand it, the benifit from an exhaust crossover is not in reducing the backpressure but in the fact that it blends the exhaust flow from the two banks of cylinders, creating a more uniform flow. This helps by increasing the flow velocity improving scavaging of the cylinders. The only recomendation as to where to put the crossover pipe I have ever seen is to put it as far forward in the exhaust system as possible.

 

About crossovers, the biggest thing I have read about them is they equalize backpressure, not neccesarily reduce it. The allows for more low-end torque, but I have heard that it slightly reduces HP (only about 1-3.) Hope that helps. Petersen's Four Wheel and Off Road had a great article about it in the Oct'99 issue.

 

Flowmaster 10 series is the loudest.

 

I RECENTLY BUILT A 300HP 302 FOR MY 70 F100, WELL
LONG STORY SHORT, I WANTED FLOWMASTERS TO REDUCE THE BACK PRESSURE AND INCREASE HP. IT WORKED, I GOT MORE HP, BUT IT WAS SO HIGH IN THE RPM RANGE
(AROUND 5500) THAT IT WASN'T USABLE EXCEPT AT THE TRACK. THREE MONTHS AGO I TRADED THEM FOR SOME TURBO'S AND MY LOW END POWER WAS INCREASED DRAMATICALLY. THEY WERE JUST AS LOUD AS THE FLOWMASTERS TOO. HOPE THIS HELPS.

JEFF

 

A properly installed H-pipe will increase torque and HP in almost any situation for street use without more noise, and with a mellow tone. I have used them going back to early 70's with big block Pontiacs, and later with all my Ford small blocks and have had them run within a tenth compared to open headers. Of course this is all relative to tuning. They just sound better!

Proper installation is as close to the collector as possible with the crossover pipe being 75% the diameter of the exhaust pipe. For example: a 2" exhaust would have a 1 1/2" crossover pipe.

When a cylinder fires on one bank it's exhaust goes through its exhaust pipe until sufficient back pressure is reached to divert some of the exhaust thru the crossover to the other side. The same holds true when the other bank fires. This ballances the exhaust somewhat, and keeps reversion to a minimum.

All of this is dependent on materials used. The more a muffler flows, the less you need H-Pipes, according to muffler installers. This helps them sell Flowmasters, and not have to do labor intensive installation of H-Pipes. With a less costly muffler and H-Pipe you can flow as much as those Hi-Po systems and get a much better sound.