BB Exhaust manifold testing revisted

I'm not totally sold on headers being more peaky. Look at the 3000-3500 rpm torque difference, in the first tests posted there's a 40ft/lb gain over manifolds. It might not be worth much on an all out track car, but with most buick owners running 2.?? highway gears every gear change will drop the rpm into that area. The average torque gains really outshine the horsepower.

The ported manifolds only gain power and torque after the torque peak. Shorty headers should fall somewhere in between, with the most gains happening after peak torque.

 

People will remember those numbers even after anything else was said about it showing how it was a test favoring headers while the manifolds were disadvantaged.

You'll get more from headers if all you use are two separate exhaust pipes, one for each side, but the game changes when a crossover is used, particularly the "X" pipe. Who knows, it may still be even steven when using an "X" pipe with both, though the headers are already providing scavenging so the addition of an "X" pipe would probably have diminished returns vs one used on manifolds, since those have practically zero scavenging from the start, and would respond well to anything helping the exhaust pull.

My comments about peaks were in relation to the last graph, and I suppose it would really depend on the combination, since no two are exactly the same. Even with all this considered, real dyno results still only give a general idea of how a particular similar combination would behave, and with varying atmospheric conditions changing constantly, an engine will always be gaining/losing power as its being driven from day to day.

Numbers aside, I assert that an "X" pipe would help manifolds better than it would headers, simply by virtue of the fact that headers are already providing good scavenging, while the manifolds are not.

It still all boils down to preference, but it's nice to see effort being put into testing to show real results to back up theories/claims by others. All these tests do is strengthen my resolve. :grin:

I believe in fairness and an even comparison where all sides have equal limelight. This isn't an attempt to bash headers or manifolds, but to stimulate thought and consideration for either one, both pros AND cons. Each have their place, and again, boils down to preference.

When we can understand WHY something works, it makes the decision easier. We know why headers work, and this is something manifolds lack. Add in the "X" pipe, and now the manifolds have something to help replicate the end result of headers, albeit in a different way. Smoothing out some manifolds and putting on an "X" pipe is a hell of a lot cheaper and way less headache than headers, not to mention maintenance free results that won't scrape/rip the bottom half of the system off after repeated encounters with asphalt/concrete on normal American roads. We all know the pros and cons by now surely, after all this.

Let it be known that smoothed manifolds and an "X" pipe WILL NOT give as much power as headers, but it will certainly close the gap shown in the original graph that started this thread, and is the ENTIRE point of my even posting here, all side notes ignored.


Gary

 

The other thing that should be known from this is its simply not worth spending 700 bucks on porting exhaust manifolds. Take that 700 and spend it on a good converter, fuel system or whatever.. its not money well spent.

 

Sehr gut.

Preference again. Hogging out a set of manifolds is a bit risky I'd think, since it thins the material and would make them more prone to cracking than simply hand polishing as far in as you can reach using simple tools on each inlet port and the exit port. Even this may not do jack, seeing the results of this dyno graph, although it would help some by smoothing up the rough casting and leaving as much material behind to keep the manifold as strong as possible.

Simple massaging (cleanup and polish) is probably the best thing for manifolds on mild combinations. We do it to exhaust runners on heads, why would it not benefit manifolds?? Keep velocity high by retaining as much original structure, using an inner diameter pipe the same size as the exit port size, mandrel of course, then up to an "X" pipe and whatever after that. I spoke of this in another thread here recently with zero comments or apparent interest in my idea. I also spoke of coating the manifolds and these mandrel pipes up to "X" pipe inside and out, to retain as much heat as possible up to "X" pipe to maximize scavenging effect.

Manifold porting is probably best left to individuals who wish to maximize power without using headers, for various reasons such as stealth, original appearance, clearance and fit, maintenance free performance upgrade, or whatever the reason. Beware, however, that improper enlarging can actually harm performance, as is evident on some head porting disasters... so then there is THAT to consider.

What would be awesome is if someone would make a casting to make a set of 'shorty manifolds' like we see on some modern engines. They're basically shorty headers (sorta) but made out of iron poured into a mold (cast iron).


Gary

 

Thoughts Gary on BBB, similar build to the dyno specimen, with headers and H pipe....?

 

My thoughts would be to coat the inside and out of headers (then there is the 'which coating is best to use' debate...), reducers, and the mandrel pipe up to "H" pipe, coating that as well inside and out. This maximizes scavenging by retaining as much heat inside the exhaust up to the "H" pipe. While this would aid manifolds better than headers (in my opinion, and using an "X" pipe instead of an "H" pipe), would still benefit headers of course...though how much scavenging is enough? I've heard discussion of having too much scavenging...

Though I think the results would be helpful, effectiveness would probably be lessened by the fact that the headers are already doing a fine job of scavenging, even with no crossover, as long as they're coated inside and out.

IF it were me, I'd use extended collectors, then a gradual reduction 1/2" at a time down to desired exhaust size (from 3 1/2" to 3", then from 3" to 2 1/2", for example) up to an "H" pipe. The rest after that is preference. Remember that extended collectors aid in lower-mid range torque, so this would be ideal for the combination you have in mind.

What someone needs to do is make oval pipe headers for better engine compartment clearance, as well as ground clearance. This would alleviate one of the biggest cons of using headers, in my opinion.


Gary

 

:gp: Jet Hot Coating...let the games begin...:TU:

 

Gary F., with manifolds going to an X-pipe like the other Gary described and with the "X-pipe" redesigned to if the pipe that is 3" then (2) 3" pipes going into an "oval" pipe that is 3" X 6" about 12" to 18" long to 2 exiting pipes that go to the over the axle where typical dual exhaust goes to whatever size that will fit. With an "X-pipe" redesigned that way wouldn't that have a better scavenging effect? Seems like if there was such an "X-pipe" it would be tunable depending on the length of the center section and better than just the crossover in the center. What do you think?




Derek

 

Thanks for the info JW. We'll now that just shows how much a waste of time porting cast iron logs is. The argument becomes exaughst leaks, and how often u like changing gasgets. I have found the best gasget is one u make yourself. I buy some sheet aluminum about thick as a soda can from local scrapyard, make enough for 3 layers each side, they last many times longer than any I have bought over the yrs. So now it's do I like making my own gasgets . So far it's not too much a bother

 

Anyone can throw headers on. The rest of us like a challenge. 11's with manifolds is waaaaaaay more impressive than with headers.

 

I like the way you think, Derek. This has actually been a subject of much interest to me over the past several months, and I have put a lot of thought into it. As we all know, all "X" pipes are not created equal. They have a similar idea, but the way they do it can differ from an "X" shaped "X" pipe to stamped versions with irregularities inside, to having two mandrel bent "S" shaped pipes with a slit or oval cut out and welded together so they join, sort of like a merged system where most gasses flow past the oval part drawing in from the other side.

I have an idea that I have yet to see on the market, and I don't mind sharing it here because I do not intend to try and make money on it.

I've thought of single exhausts where the scavenger series "Y" pipe merges into a single round pipe, but the two inlet pipes are "D" shaped with the straight part of each "D" welded to each other, maximizing surface area from which the pulse flows past and maximizes scavenging.

I've thought about making a similar setup, only have the two lead into a single, large oval pipe, then reversed to flow back out into two. This may at first seem like a 'dual exhaust restricted by a single' but there is a lot of science involved with airflow dynamics. It would probably have to be tuned to each application so as to not have too much volume on the singe part which slows down velocity and hence scavenging, but not too small as to create a restriction. Depending on the length (and width/height) of this 'single cross section' you could call it an "X" pipe of sorts...

I've had some muffler design ideas too, but that's another topic.

Getting to your idea Derek, does it not sound almost identical to the idea I had? I can see the effects in my mind, but to put it on paper or work it out with advanced math that very few would understand, or if it would even matter because the dynamics are so dynamic that the ever changing effect based on varying RPM would fill reams of text to make a full analysis.

Sooo, to keep it short and sweet, I think 'the' idea is sound, as long as the shape of the 'single crosssection' is oval and matches the dimensions of the pipes going in and out of it. One certain advantage of this would be that the pipes behind this "X" pipe wouldn't need to be perfect (press bent), nor would the mufflers or tailpipes since each pulse would be exiting two pipes instead of just one...meaning they would probably need to be smaller in order to maintain velocity. This would be fortunate for pipe benders where over axle clearances and bending machines make better bends with smaller diameter pipe.

I'm sure all this sounds counter-intuitive to some, but they're finally coming around to advanced exhaust designs that used to be laughed at (even by myself). Once we can understand how this stuff works and have it make sense in our minds, we can accept it and create things with it.

Recall the advantages of an oval, or 'tall and narrow' port design on heads, and how it maintains velocity because it's narrow, but has good flow because of its height/width. This would be a similar effect with oval pipe.

Mandrel bent oval pipe can be had, but is expensive right now. Maybe this will change later on as its popularity increases and mass production ensues?

Did I forget anything? I'll edit or come back later if I did.

I'd like to hear others' input too, maybe we can all put our heads together and someone will read this and spark an idea and come up with something really useful to the community.


Gary

 

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:TU: Right on Jim. That about sums it up.

 

The reason I went with an "oval" pipe in the center section is so the pipe wouldn't hang down further than the pipes going into it. But if there is a formula for figuring out the reduction the center pipe would need to be to maintain velocity to increase scavenging then the center can be reduced. Reducing the center section down like an oval funnel from 3" thick and 6" wide to say 2 1/4" thick and 4 1/2" wide in an 12" to 18" distance could possibly increase scavenging further?




Derek

 

Gaskets? You must be referring to header gaskets? For cast iron manifolds I've never run a gasket, ever, in 25+ years of owning my Buick(s). We've never used a gasket in any big block Buick that has ever rolled through our garage and there's never been one with a leak at the manifold to cylinder head connection.

And for headers, I'm not sure why there would be any arguments about the gasket type. We've just used quality gaskets like TA sells and we've NEVER had an exhaust leak any of our Buicks that have headers. Never, not once, and we've never had to replace a gasket unless the engine was pulled out. There's nothing magical about sealing a set of manifolds or headers. If the head is flat and true, and the manifold or header flange is flat and true, it's not a problem. If you are running something that is warped or untrue, it needs to be addressed prior to assembly or you'll have a potential for issues.

I'm with Jim Rodgers about headers vs cast iron manifolds. We have cars with both and while the cars with headers are faster, the cars with cast iron manifolds are ones that really surprise people at the track. I LOVE having a 100% stock appearing Buick GS conv that weighs 4000 lbs, can dip into the 11s on a set of DOT radial tires. Guys are shocked when they see under the hood and just see a bunch of cast iron topped with an old Qjet.

 

It could, though the "D" port inlets on both pipes would be what did the most scavenging, and leaving the dimensions (in oval form) would mimic the pipes sitting side by side, with the center cut out and them joined together.

Reducing this and then widening it immediately afterwards is a trick used on single pipes, as long as the transition is gradual, as in a cone (round or oval, depending on pipe shape), both in and then out. It would look like two cones facing toward each other with the narrowest ends together. It could be implemented on this, only larger and in oval form. The thickness of the pipe wouldn't exceed the two going into it since it's oval, so ground clearance wouldn't be an issue, although placement on various models of cars could be an issue.

My idea was on the G body Regal, and having this in place of where the catalytic converter used to be, so it was going to fit like a glove. Having the two inlet pipes (head pipes) where one crosses under the oil pan (as in single exhaust), then back out under the transmission crossmember and under the driveshaft behind the transmission mount (this is common on Grand Nationals from the factory), then back to the rest of the exhaust, which can consist of two separate mufflers before the axle, or a transverse dual in dual out muffler (they make such a thing specifically for this G body car, since Grand nationals came this way from the factory). Or a two muffler setup in the transverse area behind the axle, one going one way and the other going the opposite way. All sorts of exhaust options for this car.


Gary

 

lol wow there's a lot of Gary's here!

 

Anyone considered these, one 2x3" into 1x4" then 1x4" into 2x3" back out as an X-pipe?

 

I do the same. Any motor I do that the customer is running iron manifolds, I mill the exh side of the head and the exh manifold flat, never a leak w/o gaskets. Isn't this how they came from GM?
gary

 

Yep.

 

This was mentioned in one of my earlier posts.


Gary