I had similar experience as Derek. Went from 2 1/4" to 2 1/2" mandrel with no gain. Stockish 350 needs no more than 2 1/4". I went with the 2 1/2" because it was less expensive than 2 or 2 1/4". Although 2" would weight less. Again I am using iron not headers so the smaller opening in the manifold is already the restriction.
I endorse this statement. The super turbos sound better than anything on the market, IMO, and flow way better than regular turbos thanks to the deflectors. Gary
Pretty much all that's available in complete systems is 2 1/2" or 3". Would be nice to see a 2" or 2 1/4" mandrel bent system, but they probably figure size sells so no one would want a sissy 2" system, or most people would just get a press bent system built at a muffler shop instead. My advice would be to customize mandrel bent up to the "X" pipe, then you can have press bent after that if you want. The header pipes are more important to optimize flow before the "X" pipe anyway. As a note, Jones exhaust sells a cheap "X" stamped that looks ok according to the picture, and it's 2 1/4". If you attach to manifolds (preferably polished), use 2 1/8" mandrel pipe up to the "X" pipe, then have the muffler shop put on some press bent 2 1/4" back to mufflers, then 2" tailpipes. The mandrel bent 2 1/8" Inner diameter is 2", about what the press bent 2 1/4" ends up being at the bends. Then the 2 1/4" mufflers and 2" tail pipes for the cooler, denser gasses for better evacuation. Gary
I use the Walker Dynomax. Nice sound if you like quiet. Use flowblasters if you want noise. I also have 2 1/4" press formed from the manifolds to the crossmember where the 2 1/2"starts. no X or H although they are allowed. I've never found them to provide any gains except weight. Does remove some exhaust drone though.
Not all "X" pipes are created equal, and nevermind the "H" pipe. Mandrel bent pipe from manifolds to "X" pipe maximizes its effect, and best to have 2" or 2 1/8", not 2 1/4" for head pipes. The inner diameter of the pipe is larger than the exit port (unless you ported it some to match) and so gasses slow down, decreasing scavenging effect. Then the speeding up and slowing down of exhaust in and out of the restrictive bends harm evacuation too. It's no surprise you saw no gains. There is very little extra weight with an "X" pipe, unlike the "H" pipe. Gary
To the OP... The argument of "will headers help?" has far less to do with flow than other aspects. Headers are tuned,and not necessarily to your combination. The diameter and length of the pipes, along with the collector dimensions and what happens after that directly correlate to an RPM range that the cylinder(s) [and it's size] are effectively scavenged in. Basically you can math out the peak effectivity of the scavenge effect for each combination. Short tube headers often math out to a peak effectivity well above the torque peak, maybe even beyond the hp peak. My opinion is that those types are fairly worthless to a street vehicle, considering the general detriments of headers. Scavenge= a stronger initial pull on the intake charge, said to be as much as 9x greater than the effect of intake manifold inertial "ramming". This should not be ignored. The right headers with a recurved distributor is often the biggest bang for the buck on a stock v8. Instead of guessing and weighing opinions, math out the headers you are considering and put efforts into the learning curve of tuning and hot rodding. Plan your future builds, budget, and and have fun with it. Yes, they are worth it.
Wow !! Look what I started here. Opened a can of worms here, didn't I ? I think the general consensus here is maybe, or not at all. With headers, the egnine compartment will be much warmer, the floorboards hotter, and they will hang down and scrape the pavement in certain cases. So, maybe I should spend my money on making the car lighter and on the mechanicals. I think I'll start with the gears / trans , and with an 11" drum conversion for the rear ( seems to be a bolt-in proposition ) Anyone ever see a lightened flywheel listed for the buick 350 ? Should help with revving, open a light high end up ? Thanks again everyone for all your input..
Not to contribute to the can of worms, but... "one of the cheapest mods and biggest bang for the buck things you can do is add headers and re curve the distributor"
Keep your flexplate it is balanced for your engine. Headers are a pain for sure, even manifolds to a good 2.5" duals sounds great
If you are patient, bored, and have a beer to drink. There is alot that can be done to open up the stock manifolds. For one, the exit can be opend up alot. Like a whole lot. Many of the bumps and turns can be smoothed. The manifolds can be opened up at the entrance and the gasket matched as well. All of that is a mess from the factory. That's what I would do.
X2 I have a free breathing 455 with ported aluminum heads and a mild cam and we dyno'd the motor with both headers and stock manifolds that were well ported out. There was only a 15 HP gain with the headers. I stayed with the stock, ported manifolds. :grin:
rkammer, curious to see the difference from 3000-5000rpm. I'm assuming that tuning changes were made to maximize each combination? Also curious about tube lengths and diameters in the set tried.
This is pretty much what I'm talking about when I refer to 'polished manifolds'. Smoothing with coarse grit then polishing with finer. Even if you do not take out much material, it will be opened up some by simply doing this, and will greatly improve the manifolds over the factory condition. Sure headers add more power. Otherwise, people wouldn't use them...but the tradeoff comes with a hefty price other than simply money. Ground clearance, hassle, and maintenance are all factors when considering the use of headers. For long-term street use (particularly on stock-mild applications), I always highly advise the use of polished manifolds. :TU: Not to mention custom MANDREL bent 2" or 2 1/8" (1 7/8" or 2" inner diameter) pipe up to the "X" pipe, then whatever behind that, as was mentioned by me in a previous post. Basically, match the inner diameter size of the pipe to the exit port size of the manifold, so as to create an even transition to the pipe. This will aid in scavenging a great deal with stock manifolds. Behind the "X" pipe it doesn't matter quite as much as long as the pipe size difference isn't too great, and transition to smaller tailpipes. Gary
