I'm having a fellow board member build me a 500+hp big block for my 68 Wildcat and plan to install headers and a mandrel bent exhaust system on my car and have seen several set ups using a crossover pipe. Does this increase horsepower? I may have some space restrictions with my 2 piece driveshaft and am wondering if it's worth installing the crossover pipe. opinions welcome.
Broad brushing, but a V8 that revs lower Max RPMs (Buick) are happy with the H pipe, and higher RPM reving machines are happier with an X. But, as with all things tweaking and performance, there is more to it in the fitness department. H Pipe is a smaller "footprint" installed than an X pipe. I have and H with 3 inch pipes on an A body with a nailhead, and it was simple to fab.
There "is" an optimum point for the exhaust crossover. It will be determined by exhaust pulse resonance in the RPM range you want to enhance. 'Course, then real life intrudes, and the chassis won't permit the thing to be where it would do the most good, so you move on and put the crossover where it fits instead. Part of what makes an exhaust crossover work is the pulse tuning. Part of what makes it work is that you've essentially increased the muffler volume, which decreases back pressure. Settle for the back-pressure reduction. You'll also get some noise reduction, too.
Unless you are racing and looking for every hundredth of a second you can get, I don't think you need one. Now this is just my opinion and others may be different...
Thanks everybody for the input. I now have a better idea of the purpose of the H pipe. The 2dr. Wildcat shares the same chassis as the Electra so a H pipe is probably a bad idea with all the speed bumps recently installed all over the 'hood as it will impact ground clearance significantly. I have no plans to race a 19 1/2 foot long 4,200 Lb. car, but I do want it to have as much grunt as possible. In Montreal, driving seems to be more of a blood sport with people cutting in to the smallest gap. I was back on the West coast (Vancouver) 2 weeks ago and almost fell asleep at the wheel with all the politeness. Budget constraints won't allow for playing with the trans or diff gears at this point as the engine build will likely be 10-15 K.
my 2 cents........ an H pipe, or an X pipe , both are a balance tube, in that they equalize the exhaust resonance, from side to side. are they worth alot of horse power? no, some? yes. every car is different, but. what they will do, is quiet down the exhaust note, and give the exhaust a more mellow note. on some cars they will eliminate the "droning" noise. you will hear that an X is better, or an H is, unless you have a dyno, who knows! on every car I've installed a balance tube ( typically an H pipe) the car seemed to run smoother, and be more pleasant to drive.
Got a photo of the chassis from underneath? Maybe there's some other options for crossover pipe location.
Thanks Cruzn57, I'll see how the exhaust sounds and take it from there. Unfortunately, I have no pics from under the car. It's tucked away in a warehouse for the Winter packed in like a sardine without access. If things go according to plan, The engine will be ready in the Spring and I'm just trying to get all the peripherals taken care if. Engine mounts, Hi torque starter, cooling system etc etc etc. Exhaust was just on the long list.
I should clarify my goal... I love the way 67-68 Wildcat 2 dr's look period and I'm not looking to build the fastest Buick in town, just the fastest 68 Wildcat. Other than an Electra, I can't think of a worse candidate for building a quick Buick, but it takes all kinds and luckily there are some "free thinkers" here to humor me.
Bill, I'm confused. I looked up the difference between the B and C bodies (1966-1970) and the site I was at grouped Lesabre and Wildcats as B bodied cars and the Electras, 98's etc as C bodied cars. I thought I read somewhere that the Wildcat sat on an Electra C body chassis. https://www.opgi.com/blog/2013/05/decoding-general-motors-body-style-designations/
Cat's belly. "DO NOT RUB!!!" (1967) I am thinking H pipe right behind the transmission cross-member is doable.
The back of the transmission at the mount and the cross-member are not going to move. If you stay above plane at the bottom of the exhaust pipes just aft of the cross-member and about an inch or two below the drive shaft just behind the yoke/shaft U-joint(blue), I believe there is ample room for a lateral pipe that would be nearly straight. (red) Even an oval exhaust tubing could be used for lower cross section at the "cost" of more for and aft area. I have seen some pretty wild plumbing in tighter areas with turbos. About the only time it never works 100% of the time is if you never try it any % of the time. Me? Sometimes I have to prove myself I am wrong, and that's about the only time I ever quit. It's genetic.
Seems like a real pain to have if you ever need to work in that area. I have a new cross pipe sitting in my garage because the exhaust company told me they remove a lot of customers cross pipes. For a street machine, mine sounds great without it.
Thanks! If the car sounds good without it, then I'm inclined to leave it out. I will find out in the Spring.
Define "sounds good". If you have a crush-bent exhaust system like in the photos, you DESPERATELY need a crossover tube, as far forward as you can get it. (Ahead of as many of those bends as possible.)
I will be going with Ceramic coated headers and a mandrel bent system front to back. The exhaust pictured isn't from my car, but is pretty much the way the old system looks presently.
