HP Manifold Performance

[c00nhunterjoe]

With regards to manifold testing on the dyno ; the testing I've seen or read about usually has a set of straight down pipes attached at the exhaust outlet. It would be interesting to see a test with a nice mandrel bent x-pipe system installed instead of the straight pipes to see how much of a difference it would make. The "X" has a distinct advantage in breathing vs a straight pipe which would help with reduced backpressure and increased scavenging.

How much it would help is an interesting question ? 


Ron

With long tubes, ive generally seen 5-6 hpwith an h pipe over standard pipe and 8-10 with the x. I would make an estimate of half that, respectivly, with hipo manifolds in place of long tubes.

[JR]

The newest episode of Engine Masters tackled this very subject of no crossover vs. X vs H pipe. They dynoed each with a full exhaust the same length and showed each result.

The episode is on Motor Trend On Demand now. It should hit YouTube in a couple of weeks.

[c00nhunterjoe]

But will they do it with manifolds or headers? Will they recalibrate tuning after each change or just slap and go? Im betting it will have long tubes on an ls based or small block chevy and no recal between runs. Still a decent episode to watch no doubt. But we already know the basic differences with headers. The question is, how much difference on restricive manifolds?

[firefighter3931]

With regards to manifold testing on the dyno ; the testing I've seen or read about usually has a set of straight down pipes attached at the exhaust outlet. It would be interesting to see a test with a nice mandrel bent x-pipe system installed instead of the straight pipes to see how much of a difference it would make. The "X" has a distinct advantage in breathing vs a straight pipe which would help with reduced backpressure and increased scavenging.

How much it would help is an interesting question ? 


Ron

With long tubes, ive generally seen 5-6 hpwith an h pipe over standard pipe and 8-10 with the x. I would make an estimate of half that, respectivly, with hipo manifolds in place of long tubes.

I see it differently Joe ; headers by design have excellent scavenging so installing an X-pipe improves something that is already pretty good. On the other hand, a cast iron manifold has poor scavenging which would be significantly improved with the addition of the X-pipe. I bet the chassis dyno numbers would be proportionally better when installed on a set of manifolds vs headers. Just a hypothesis....

Years back I remember reading a chassis dyno test on x-pipes and I remember the details were something like 20-30 increase in HP/Tq but the details of the article are fuzzy. The FAST guys run x-pipe exhaust systems with their manifold builds so they must be worth something.


Ron

[c00nhunterjoe]

Interesting theory. I would love to see it tested. I suppose it will depend on what type of manifolds they are using as a baseline. If they use factory ls manifolds or fox body mustang's, it wont be as drastic as if the used mopar log manifolds. 

[BSB67]

Dwayne, I think we do look at it differently in the 350 to 450 hp range for the typical street guy.  And I think those are the qualifiers that make the difference.

I feel like if you're really after making some power, you're definitely stacking the deck against yourself by not running headers. Sure.  If power is the only goal, no question

..it's all the doors they open up for doing other things that often don't work well with manifolds. Again, sure.  But most "street" guys I know don't actually go down the path of more and more like racers.  In fact, the few that I do know that would like to step it up, usually don't due to cost, time, and other priorities. And if they do, wouldn't adding headers be the great next option for them to step it up? .

I'll say it again........... some of the higher output FAST motors I've tested would have gained 75-100hp by installing headers and then taking advantage of them by installing a cam to exploit the reduction of exhaust back pressure and the addition of proper scavenging. Two changes......headers, cam.......75-100hp. Of course.  It is probably a 625 hp motor, (with manifolds).  I'm sure it will make a another 75 to 100 hp with a change to headers, and a cam change. But the guys asking the question are no where near that power, have no desire to get that power, and would not want that cam in there street car anyways. Certainly there are exceptions. 


I believe that my responses are generally qualified with power goals, cost and owner's overall wants of the car - all three together.  Everyone is different and we never really know what a poster's balance is between these three.  Does making the same power without headers cost more?  Probably in most cases, maybe all cases.   But the details of the situation matter in how much the power difference is or the $ difference.  Usually switching to headers costs money.  That money can be used somewhere else to to recoup some of the power that is being giving up.  

Again, it is balance of what an owner wants with the car.  

[PRH]

If you took my FAST motor example of swapping to headers and then changing the cam, and reversed the order of those two changes, it would illustrate my point about "opening up the doors".

The header friendly cam installed with the manifolds still in place would end up being a reduction in power, in which case the headers alone could show a 100hp improvement from that point.

High cr(needs c16 fuel) 526 FAST 6bbl build(which has so far run better than any other 6bbl build in that class), lots of coatings, windage tricks, really good heads, very aggressive roller cam...... About 630tq/625hp with ported carbs, running extrude honed manifolds and 2.5" mandrel bent head pipes.

Pump gas 505, bowl blended rpm heads, 6bbl, stock carbs with jet plates, comp xs290s cam, 2-2 1/8" headers...... 650tq/600hp.

[BSB67]

I think part of the attraction for the pro-manifold guys is the fact that its a little more insulting when your freshly defeated opponent looks under the hood and sees them.

It's like a master/card moment:

- TTi ceramic coated headers, $900

- mandrel bent 3" exhaust system attached to your TTi headers, $600

- the expression on the persons face you just beat when they look under your hood and see you don't have those things?  Priceless.

Absolutely.  Second to me, you know more about my car than anyone else.  But there is the characteristics of the car and cost too, to a lesser degree that were part of the consideration.  If you look at the motor in a vacuum, I put on CNC ported heads, and a roller cam - items not needed with this motor if I went with headers and a different FT cam.  Probably an additional $2,500, maybe $3,000.  But i did not buy the headers, the corresponding exhaust system and used my stock converter ($800?).  The car is extremely docile.  My wife drives it with ease.  It runs through the neighborhood in 3rd gear at 1100 rpm nicely. It does not have part throttle kick down, and stays in third gear when I role through a stop and accelerates nicely without getting fussy.  I've had looser converters in the past and not my cup of tea any more.  Not a fan of working around headers either. I wanted to go 11.99, as you know, and it did that the first time at the track in mid summer.  From my perspective it did not cost me much more, and I got exactly what I wanted.

[PRH]

It would make a nice candidate for an enjoyable "Drag Week"....... As well as get some people scratchin their heads.

Less porting, no roller....... Maybe some 3.55's to make up for those losses....... Would probably still run an 11.

I often use your car as an example when I'm putting forth my argument that "cubes are your friend".

[BSB67]

It would make a nice candidate for an enjoyable "Drag Week"....... As well as get some people scratchin their heads.

Less porting, no roller....... Maybe some 3.55's to make up for those losses....... Would probably still run an 11.

I often use your car as an example when I'm putting forth my argument that "cubes are your friend".

Yeah.  For bigger power with milder manners, bigger IS better.

For the cam that I have now, I don't think I'd really give up much with the right solid FT.  The only reason I went roller to begin with was my personal fear of losing a lobe. 

Did you have a question to me about what I would recommend to get a stock stroke 440 with manifolds on pump gas into the 11's?  I thought I read that, stepped away for dinner, and now it's gone.  I was working up my response.  You know that I have a boat load of thoughts on that, and it would be a fun discussion, but we are highjacking the OP thread.  You know I started down that path with doing a std stroke iron headed motor with those 915s with the std valve sizes.  I was planning on making enough power to theoretically make 11s, based on mph, but my car would never see it.  I got pretty seriously side tracked with life, but will get back to it.

[PRH]

Did you have a question to me about what I would recommend to get a stock stroke 440 with manifolds on pump gas into the 11's?

I did, but was going to use it for a cost comparison between that and a header type build....... Then figured there's so many ways to go about it, that it was probably a wast of time.

 

[c00nhunterjoe]

I dont think this is sidetracked at all. The origonal question pertained to manifolds and hp loss/potential. All of the discussion on this thread has shown many variables as to how much power in different applications and shown that you can make a certain power with them, at a much larger price given certain goals. Every answer from all of us has added more information for the OP to digest and will help make a much more educated decision before he starts spending money, potentially on the wrong parts if not careful.

[BIGBLCK11]

   Very interesting.  Please carry on.   

[PRH]

I'd have to dig through some old dyno sheets for the exact numbers, but this is the gist of something that we found when I first tested a FAST build......

This was a 6bbl 499 with high quality internals, 13.5-cr, .640 roller.

The motor was originally built with stage 4 heads. Fully ported, 2.14/1.81 valves.
They use slightly offset intake rockers so the pinch area can be opened up more than a std head.

They had been running this motor for a few months when they decided to change the heads to legal castings(906's).

The 906's had smaller runners than the stage 4's, and the peak flow numbers were very close between the two, with the stage 4's having slightly less low lift flow, but better high lift numbers.

They were hoping the 906's wouldn't lose too much power.
The motor was run with the stage 4's, and the heads were swapped on the dyno.

It made about 25-30hp more with the 906's.

Both sets of heads are way undersized for a high compression 499 with a roller cam.
I'm of the belief that if this build were based on a more "traditional" approach to making power(headers, normal cam), that the added port volume and added area at the pinch could have been parlayed into a power improvement over the 906's.
However, with the plugged up exhaust, the added velocity created by having smaller ports helped overcome the reversion you get from not having effective scavenging with the ex manifolds, and ended up making more power.

It was another clear illustration to me that when it comes to making power with restrictive exhaust, you might have to forget a lot of what works for "normal" applications.

I will add this however.......Russ's heads are quite a bit bigger(and flow a lot better) than either set of the heads that were used on that 499, and his motor made more power with less compression...... So in that sense, it's contradictory to what we found with that head swap.

[firefighter3931]

Did a search and found this interesting article on a FAST Hemi Challenger using factory manifolds switching from an H-pipe to an X-pipe with good results.  

http://www.hotrod.com/articles/mopp-0301-dodge-challenger-x-pipe-exhaust/


This one (Hot Rod article) is a Hemi that swapped a 2.5in "H" for a 2.5in "X" so it's an apples to apples comparison. It would be interesting to see how a Wedge with a set of HP manifolds using a 3in X-pipe would respond on say a 493 with ported aluminum Stealths/Sidewinder/RPM/Trickflow heads.  



Ron

[Mike DC]

 
I'm surprised those F.A.S.T. classes allow changing something like H-to-X pipe.  Aren't they too anal about factory appearances for that?  



I've always thought it would be more interesting to see an "almost-F.A.S.T." class.  

Allow day-2 modifications like headers & slicks (but they have to keep stock wheelwells).  People could run aftermarket intakes & heads as long as they are rough-cast & painted to look stock, etc.   Generally allow anything that would have gone under the local street racer's nose 50 years ago.   

The existing F.A.S.T. concept is cool but I think they went a step too far by demanding OEM tires & exhaust manifolds.  It's like when you see all the restored Hemi cars with dog-dish wheel/tires - that's not how those cars really looked on the street back in the day.

[c00nhunterjoe]

 
I'm surprised those F.A.S.T. classes allow changing something like H-to-X pipe.  Aren't they too anal about factory appearances for that?  



I've always thought it would be more interesting to see an "almost-F.A.S.T." class.  

Allow day-2 modifications like headers & slicks (but they have to keep stock wheelwells).  People could run aftermarket intakes & heads as long as they are rough-cast & painted to look stock, etc.   Generally allow anything that would have gone under the local street racer's nose 50 years ago.   

The existing F.A.S.T. concept is cool but I think they went a step too far by demanding OEM tires & exhaust manifolds.  It's like when you see all the restored Hemi cars with dog-dish wheel/tires - that's not how those cars really looked on the street back in the day.

You mean like nhra stock?

[Mike DC]

     
Kind of.  I was picturing a little bit more dedicated day-2 look about it though.   

[c00nhunterjoe]

     
Kind of.  I was picturing a little bit more dedicated day-2 look about it though.   

Im not foloowing the class you are referencing? Help me out. Lol
You dont get much more stock looking then nhra stock. No cut wheel wells, all stock suspension components, no electronics, foot brake only, stock heads, stock intakes, stock carbs.

[Mike DC]

NHRA stock has wild paintjobs, sponsors' logos all over the cars, wheelie bars, sometimes the wheel rims are newer, super-skinny front tires, etc.  I'm picturing a class that genuinely looks like muscle-era street racers.   

[c00nhunterjoe]

I could post dozens and dozens of vintage street racing photos of cars on slicks with skinnys up front. Many have stickers on the windows as well. Maybe not fully covered bodies, but lots of stickers. F.a.s.t class is suppose to look like cars off the showroom floor and they draw crowds because of that given the et they run.

[Mike DC]

  
Lots of cars still make passes down dragstrips today without the modernizing looks, too.  


I just think it would be cool to see a class with stock paintjobs/colors (a few speed-shop stickers are ok), stock interiors, the front/rear tire mismatch isn't enormous, etc, etc.      

It seems like every time I hear a few guys talking about about F.A.S.T. then somebody says "Man, think of how fast so-an-so's car would be going with headers & slicks on it . . . "  

[c00nhunterjoe]

You are still describing nhra's stock class. Not all of them are stickered up. Beyond that, there are tons of nostaligia circuits that are basicly the same thing but for muscle cars only.

[Mike DC]

You are still describing nhra's stock class. Not all of them are stickered up

Meh, well.  Maybe I am.  It just never looks like day-2 racers when I happen to see it.

[c00nhunterjoe]

You are still describing nhra's stock class. Not all of them are stickered up

Meh, well.  Maybe I am.  It just never looks like day-2 racers when I happen to see it.

I would love to continue this topic but we are way off base from the origonal question. Lets start a new topic on nostalgia racing and this could get very ineteresting. Im in.