BB Exhaust manifold testing revisted

Here is a set. These are a full 2.400" and could be taken to near 2.500".

As you can see, they will have no problem sealing.

 

ooooh.. 67 LH manifold..

Send up a set if you have them available Jim, would love to test as many different ones as possible.

JW

 

I respect your opinions on this. I'm not saying an "X" pipe with manifolds would be better than headers, only closer to them than what your original graph suggests. All I'm saying is that headers have scavenging incorporated into their design, while manifolds do not. If we were to incorporate scavenging to manifolds, we would see how important scavenging effect is to exhaust (headers and manifolds both), and that scavenging added to manifolds ("X" pipe) vs straight headers (scavenging incorporated into them), the results would be much closer together.

It looks like putting on an "X" pipe would be a bit challenging with the cramped setup there, so maybe this comparison will have to be left to conjecture.

I guess I should have been more specific on exhaust pipe size. No one would hook their 3 1/2" big block headers to a 2" system, and to suggest it is silly. Gains would be mitigated even with a 3 1/2" to 2 1/2" reducer, which is probably what most people use for street (some may use 3" which of course wouldn't have as adverse of an effect), and unless you use mandrel bent system with straight through mufflers, you're not going to get the full effect of straight headers. The 'exhaust system' you show in the picture isn't what you'd see under a typical car, hence my statement of 'straight headers' which it essentially is.

Either way, the headers' benefits will be reduced with any exhaust system (or at least one that resembles one that you'd see under a car).

All this isn't even the point I was originally making, which was scavenging on manifolds making them closer in comparison to the headers. That's pretty much it.

No one disputes the fact that headers are superior to manifolds in terms of maximizing power output, but the differences presented here were a bit misleading (in my opinion) to real-world usage with an "X" pipe on manifolds.

Manifolds need that "X" pipe to have a similar effect headers have by their very design (scavenging), so making it a more even comparison.

I noticed also that the peaks and curves on all test models are nearly in line with each other, showing that manifolds do not give the engine those high peaks and low lows like others here have suggested.

Let me reiterate by saying that headers will always give more power than even an "X" pipe on manifolds (but the difference gap will be smaller than dual pipe with no crossover), so as to not offend anyone who is in love with their headers. Afterall, they spent a lot of money on them and time spent putting them in, and who knows what all else headaches accompanying these two facts (ground clearance, anyone?), along with regular required maintenance. To even suggest their decision to do this was less beneficial than they originally thought is likely to ruffle a few feathers, hence the innuendos I'm seeing.

Selling points or not, there is still an agenda here...

Thanks for your response!



Gary

 

Why would you think I have the least bit of a concern over who puts what on their car for exhaust.

I don't.. I only did the testing because I needed a refresher on a question I get asked all the time as an engine builder. The opportunity presented itself, I took it, and reported the results.

Don't beat the messenger over the head with a CS647 cam... :Brow::grin:


Scavenging in an exhaust header cannot be duplicated with a log style manifold, regardless of what you put behind it, because there is no separation of cylinders.

That's why headers work.

Log style manifolds are always backpressure, porting them reduces that backpressure, and thus helps performance.

JW

 

Does that 67 have a modified outlet? Mine has a flat flange where the heat riser valve would join up.

Tommy

 

Well, well, at least I see you read my posts! I'll take that as a compliment.

I appreciate your doing all this, honest. I love reading about testing results!

Please do not misunderstand or take this as any sort of an attack, because that is not my intention.

I understand that the same scavenging effect cannot be duplicated with manifolds, and is (as you said) why headers work! This is not what I was saying though. lol I could have sworn I said that scavenging was incorporated into headers, while it was not in manifolds...but an "X" pipe DOES scavenge, no matter what's in front of it. This is the main point of my entire (original) post. This scavenging effect of the "X" pipe is what will give manifolds the advantage they need, and hence make the comparison more even when considering both evacuation methods use scavenging (incorporated into headers and "X" pipe for manifolds).

Ok, so maybe we can both agree that adding an "X" pipe after the manifolds will reduce the 'backpressure' that the manifolds have and headers do not. :grin: ...and thus making the comparison as mentioned earlier closer.

I'll be following this thread in anticipation of other manifold and pipe style (hopefully an "X" pipe too) testing. Thanks again Jim. :TU:

P.S.--Buick doesn't use 'log style' manifolds, btw...and so is not hindered as badly. (duck and run)


Gary

 

X over And headers:eek2:

 

All things considered--just take a look at the manifolds vs those headers.

The headers are absolutely enormous compared to the stock manifolds. 3 1/2" exit port size vs 2"? Almost twice the size. Let's be honest--the fact that the manifolds, even in untouched factory form, and without an "X" pipe, did as well as they did is impressive.

On stock 350-375 hp engines (which is what the manifolds were designed to evacuate), these differences would be even less.


Gary

 

Cool thread. Seems to prove that headers might not be worth the hassle for the average street car do you have another motor you can test the manifolds on maybe something in the 550 horse range? It would be interesting to see how they perform in a high horse build.

 

Already posted in a recent thread. All the way up to a nearly 800 hp BB Buick.

 

Yes. Nice catch.

 

Link?

 

Your right Gary.

The need for headers decreases as the motor gets closer to stock

Working out in the shop after dinner, I remembered I had run this test on a nearly stock motor, back in about 06.. This was the motor that was in my 89 Suburban for a number of years.

Motor is totally stock but fresh 70 455 small valve deal, with very mild head cleanup and a TA212 cam. 9.2-1 compression.

Here's the numbers

Manifolds



Headers



The graph



There was never any thought of putting headers on this engine, for such minimal gains, and I always recommend that guys don't waste there money on headers, if they are building a motor like this.

This is the power level that the manifolds were designed for, and they do a good job at this level. The need for Ported manifolds, and progressively larger tube headers come in as the power levels increase.

JW

 

Nice! Thanks Jim!

Seems the headers are a bit more 'peaky' than the manifolds, not the other way around as I have heard others suggest. Good to know.

Everything has its pros and cons. It's always nice to have a broader knowledge of something so one can make a more educated decision.


Gary

 

Very nice work....

Tommy

 

Thanks Larry! I saw that in their catalog and was wondering if that was the same as the KB118.

 

This thread seems to have elicited several sets of massaged manifolds now being sold on the board.

 

Be sure to leave at least 3-4" of the 2.5" manifold pipe extending into the 3" X pipe and you should get the best out of this combo. That small pipe extending into a larger pipe is what I was referring to here: http://www.v8buick.com/showthread.php?303847-Exhaust-tricks-big-torque-gains

 

Not because guys are going to headers. I can assure you.