Has anybody used a magnaflow, pypes or flowmaster kit, from headers back with crossover. Just wondering how good they fit on 68-72. Also not sure to use the H or X pipe crossover, is there a difference at high and low rpms. Thanks, Rob

 

I just got a new 2.5" exhaust system put on a few month ago. It's a 1972 with a 455. I had a straight dual exhaust with no crossover, and cheap turbo mufflers. I went to an h-pipe and some flowmaster knockoffs. I am extremly happy with it. I did a ton of research before I got it done, about the whole X vs H pipe debate. The bottom line I came to was the H pipe gives you more of a deeper, mellow, muscle car like sound, and depending on how finely tuned your engine is, you MAY get alittle more torque. If you go with the X pipe, it MAY give you alittle bit more RPM, but sounds more like an exotic, high reving racecar. In the end, unless you have a super tight race engine, the difference is really just sound. I perfer, and got, the H Pipe and love the rumble. I open it up going down the street and it sounds, not lying, like a lion roaring. If youtake a look on YouTube, there is a gentleman with a Merc Marauder that videos his car with an Xpipe system, then the next day with an Hpipe system. Of coarse your, my, anyone elses car won't sound he same, but you can at least hear the difference between the 2 onthe same car.

 

Thanks, I am leaning towards the H. I feel you definitely get the equalization with the H without losing top end power. I could be wrong but I feel the X pipe would cause back pressure at high rpm.

 

I have the dual 3" magnaflow with X-pipe going on my 72 cutlass supreme 455 next week. Will report back once it's on.

 

What is the best location for the H crossover to garner the best performance/torque? Does muffler placement matter, in as far as distance from the H pipe?

I will getting new exhaust next week, so I am looking at this with real interest.

d1

 

If you are taking it to any reputable exhaust shop, they will know what to do. In all honesty, the placement/distance of the crossover and mufflers probably are not that relevant. MAYBE putting the crossover alittle closer to the engine MAY give you 2-3 extra horsepower... It's like getting a K & N air filter. On some applications it may give you an extra 10 horsepower, but you would never be able to tell the difference. I had my shop put the h-pipe further back to clear the trans so that in the future, I won't have to hack apart my exhaust to service the trans. But the bottom line is that it really wouldn't be a noticable difference where the componants were placed. It's not like putting a super charger on it and instantly feeling an extra 150 HP. Have it look good, not squeek or rattle, be all solid and welded up, easy to service the engine/trans, and most importantly sound good! Don't worry about the +/- couple of horses or ft lbs of torque.

 

I remember reading something about marking the pipe(s) with a crayon, in a line from front to back, driving around a bit and rechecking mark. The spot where it burnt off the most is where the crossover pipe should go. not entirely sure what if any REAL difference this would make, but just what I read. When I do mine, if it ends up right below the trans, I plan on having them weld on some bolt flanges so I can pull it out easily when I need access to the trans.

 

I just got the 2 1/2" headers back combo from Flowmaster. It sounds really good. I am very satisfied with the fit and finish. I would definitely recommend it. I also put on a ball and flange joint from the header to the pipe instead of the regular three bolt flange. No leaks! This used to drive me nuts! Now everything is heard out the back where it belongs.

 

The 3" H-pipe Flowmaster system on mine fits just fine.

 

OK, so my car is done. I used flowtech (hedman) headers, these are full length with a 3" collector with a 2" primary. Installed a Magnaflow 3" dual exhaust kit.

Drivers side header was a bugger to install, had to relocate the proportioning valve for the brakes, as well as make some clearance on the #3 cylinder tube for the steering shaft. Passenger side needed the trans cooler lines relocated. The drivers side header sits lower installed than the passenger side, partialy to clear the shifter linkage I assume. It made bolting up the exhaust a little weird. I think I am going to try and find a longer stainless reducer and redo the pipes in front of the X and try and push the Xpipe further forward in the frame. Also, because the 3" tube is so large, we had some issues with the rear springs and clearance. Ended up dumping out the side of the car just behind the tire. Would like to try and exit the rear and maybe find a 442 bumper with the cutouts.

Sound, well it's surprisingly quiet at idle. I can hear the exhaust flowing through the headers more than it coming out the back. Under load and accelerating, it's a smile bringer.

Power wise, my engine is stock on the bottom end, with a mondello street/strip cam from about 18 or so years ago with a edelbrock performer intake and edelbrock 600cfm carb. I removed stock manifolds with 2" exhaust and some sort of glasspack muffler off of it.

Feels like I lost 25hp and some torque on the bottom end and picked up about 100hp from 2000rpm up. the rear breaks loose hard under full throttle over 25mph or so. kind of surprised me.

I'd really like to get it on a chassis dyno and see what kind of power it is making.