Aluminum Heads with Cast Iron Exhaust Manifolds

Interesting how far this thread went...

Thanks for all the input.

But my initial question is rather aluminum heads or iron heads than headers or manifolds.

We can run headers in switzerland but it's easier with stock appearing classic cars than with modified ones. I already have a Gardner exhaust under my car in stock diameter. So no X Pipe as well.
I will be using manifolds for several reasons. Stock look is one of them.

The reason for my original question is budget related. Having heads done over here is really expensive so I might as well go with new or used aluminum heads. But when the knowledgeable people would tell me it's a waste of money when you're using manifolds I'd go with iron heads.

My goal is stock looking engine/car with 450/500hp. After reading a lot on here I think this should be doable. 470 cubes is another option as well. My car will never see a dragstrip as well.

Are ported manifolds prone to cracking?

 

It depends on what the exact specs are, it could go either way.
Are you looking for build recipies?
Anybody really good could outdo a novice with either head in your power range.

 

Thank you, Jim. I'll take that as a compliment then.

I wouldn't really consider anything I've said to be 'strong claims' so much as it is backed up and reinforced by past testing others have done, including OEM engineers. I figure they might know a thing or two about the engines they created from scratch, and so would be a good reference point to extract valuable data.

Arbitrary numbers aside, it's no secret (nor is it anything new) that a restrictive exhaust requires more exhaust emphasis. That's pretty much the gist of what I wanted to say.

I'll be sure to share what I discover here on this website, as always.

 

Keep it to 2.32" on the outlets and you will be fine for the street. They will be fine on alum heads.

 

I have an old idea (theory)...for iron manifolds...
Run 2.25" or 2.5" exhaust pipes off the iron manifold, extending only 6" or 8" into a 3" or 3.5" x pipe. This should produce a "merge collector" scavenging effect, and reduce reversion and pressure waves. In the center, you have the benefit of the X pipe effect. At the back end of the X pipe, you could reduce back to 2.5" with efficient Walker Ultra Flow mufflers.
This sort of relates to the David Vizard pressure wave box idea.

 

That's a good idea.
I'd put it further away from the head, the pipe length for scavenge math's out quite a bit longer than a long tube header and the expansion is for simulating open atmosphere after the scavenge.
Interestingly...those Flotech(?) headers marketed for sbc that are a shorty with one tube placed beyond the collector merge do have the 3" collector pipe's appx. a foot from the engine, where they would supposedly lose torque. I can attest that they do not lose anything down low with high overlap cams.

Hoping this doesn't lead to a whipping.

 

More on manifolds and merge pipes...which I don't mind sharing, since no one takes me seriously anyway and so my idea would be safe from marketing (haha) is a sort of an 'extended' "X" pipe merge, which lengthens the mid-section of the "X where the two pipes meet.

It sorta plays off the idea of a scavenger "Y" pipe that leads into a large single pipe, which is oval and flows as much as the two pipes leading into it, then splits back out into duals.

One could increase or decrease the length of this oval single pipe for tuning purposes on their application.

 

Mr Farmer, The extended x is a valid, workable item, however, diameter choices may play a role. David Vizard had something similar in one of his books. Now check this out...
READ THIS...READ THIS...

TOM RIGHTER wrote in GS X-TRA July / August 2004 on page 12:

"My car is all iron...no headers..."
"Last winter I replaced my 2.5" exhaust with a 3" x-pipe system. I also sawed off the manifold exits and welded a 3" custom flanged collector which made for a true 3" exhaust. I went from running 12.00's to a best of 11.78 @ 115!"

ME....Guys, there are many things we will never try because it doesent fit the theory we have in our heads. But on rare occasions someone will experiment and get great results. The problem is that if the story is retold, and it has no clear theory or logical recipe, the great discovery will still go un-repeated and unrewarded, and the validity of the story may be in doubt as well.
The only theory I can venture to guess with Tom Righter's car, is that the sawed off cast iron manifold had enough blunt end, and increased diameter, to provide an anti reversion dam, and act as a stepped header pipe, ...and something about that really worked. The X may also help draw the flow along as well.
I shared this information because I respect Tom Righter's credibility. And he shares our passion for Buick performance.
...Now, what welding rod will attatch a stainless 3" collector to a cast iron manifold...ummm...

 

That was a good build. The thread was not lost. http://www.v8buick.com/showthread.php?116583-Street-455-build-up-comparisons&highlight=reed+cam
Ray

 

I've read here on the forums (don't remember who said it), about extending a 2 1/2" pipe into a 3" pipe to serve a similar purpose, on the head pipes in-between the manifolds and "X" pipe.

Another form of this method is to place a header reducer (say from 3" to 2 1/2", or whatever dimensions maths out best for you) inside a similar diameter head pipe prior to attaching it to the header collector.

I hear a lot about this Vizard fellow, but never read any of his material until recently when his name was brought up.

One things's for sure: there's more than one way to effectively do something.

Pooling knowledge is something I've always wanted to do here on this website, so that everyone can benefit.


(((I also suspect the best way to go about repeating what that guy did is to weld cast iron to cast iron (skilled welders can do this, including me) using a hybrid mechanical lock/butt welding process for stability and longevity, with a custom cast iron flange type exit, then bolt the 3" head pipe to each one. It would be tedious and involved, to say the least. In this method, one could bolt a 3" downpipe to each manifold, then use the aforementioned 3" to 2 1/2" collector sandwiched between another section of head pipe further back, then lead into the "X" pipe. The physics is sound.)))

 

Thanks for locating this.


EDIT: here's a quote from one of the posters who submitted actual dyno results on untouched manifolds vs ported manifolds vs headers:



"As you can see, the area "under the hat" didnt change as much as you would think. Keep in mind, this is a somewhat "mild" street buildup much like the majority of 455 Buicks across the country. The car has power brakes, and the engine has a TRUE 9.5-1 and stock untouched Stage 1 heads, so the cam was designed with this in mind.

A healthier cam and better flowing cylinder heads will like better flowing exhaust even more.

Right after dynoing this engine, they dyno'ed another 455 with high compression, more cubic inches, very good cylinder head flow and a roller cam. It made 730 hp with the same 1 7/8 headers and 696 hp with the same Gessler manifolds. No stockers were tried but we "feel" like the Gesslers are worth 10 hp over the stockers on a very healthy engine. There is only so much you can do with the "log jam" Buick 455 exhaust manifolds."

In bold: even on a much higher powered Buick 455 with increased CID and using a frickin roller cam, the manifolds did outstanding on a 700 hp engine.

Could this type of build be tweaked even more? Who's to say...

On the mild build with only 14*@.050 exhaust duration emphasis, there was little difference below or above peaks on the manifolds vs headers.

Looking at the cam card further down in the thread, the cam happens to have the exact same duration @.006 (arbitrary) as the OEM cam card I listed earlier (282*), with a total of 28* exhaust duration emphasis @.006.

I've done testing (as well as others here who have also) on single pattern and split pattern cams that were modified to have more lift on the intake lobe (vs exhaust lobe lift) with positive results.

The end result shows a positive outcome for split pattern cams with more emphasis on exhaust duration, but more emphasis with lift on intake.

Food for thought.

 

Vizard is good at bridging the gap between what OEM and designer lever engineers use for often very different reasons and applying it to the hot rodding mainstream's needs in a way that the laymen can understand.
If you think about it, guys like Lingenfelter used his studies and career in emissions and the combustion process and applied it to various forms of the performance world.

 

Remember Grumpy Jenkins??
Check his exhaust ideas...
* Look at his LITTLE PIPE inside a BIG PIPE.......... http://garage.grumpysperformance.com/index.php?threads/x-or-h-pipe.1503/
page down until you see the drawing of the pipes. Then read some of this info.
* ALSO, check out the X pipe slow motion video and think what the "extended x" Gary Farmer referred to could change here.

 

haha ou:

 

I think the little pipe inside the big pipe will possibly benefit the OP's "aluminum heads with cast iron MANIFOLDS" as well as HEADER applications. So hopefully were still going in the right direction.
Certainly Tom Righters idea is on the right path toward efficent use of MANIFOLDS.
X pipe ideas help us ALL.
I'm enjoying this thread.

 

I've seen that x pipe video on Youtube before, but never fully agreed with the physics of how it would actually flow vs the programming for a simulated visualization vs real world flow characteristics.

In other words, it gives a decent representation of how it would flow in actuality, but the programming tends to want the exhaust path to carry down the corresponding exit pipe side while 'ignoring' much of the real-world effect the merge would demonstrate.

Too bad we don't have a glass "X" pipe to show dyed air going past it for a more realistic visual representation, but then even that would need to mimic the exhaust and material temperatures and reflective characteristics for even that to be more realistic. lol

Nor does it show the pulse wave effect on the gasses (all matter can be observed as both particles and waves).

My assertion is that the closer to parallel two pipes are to each other (think header primaries prior to the collector), as well as physically located as close together as possible (a straight line facilitates this nicely (opposing "D" shaped pipes with the straight lines mated together), as opposed to butting up two round pipes--think "Burns'" collector), the harder the draw one will have on the other. Leading this into an oval pipe with similar dimensions as the two parallel pipes would not hinder flow in terms of CFM, but would permit both pipes to work off of each other to aid in a scavenging effect. The oval pipe then exits into a 1-into-2 merge to become a true dual exhaust again. Both of these pipes could in fact be smaller than the entrance pipes, since gasses are cooling at this point as well as each exhaust pulse would have both pipes to exit into, effectively doubling the efficacy of the pipes' flow potential (this has been proven).

So there ya go.


EDIT: one more thing I wanted to add for clarity (hopefully what I typed out isn't too obscure or confusing), is the efficiency of an oval pipe vs a round pipe. Think about the tall, narrow runners on the intake side of the heads/manifold and you'll see that velocity is maintained while flow is increased. The best of both worlds. This makes the 'extended "X" pipe' work even better vs two pipes exiting into one huge round pipe, not to mention the thickness of the oval pipe wouldn't be any thicker than the diameter of the two entrance pipes, so no ground clearance is compromised. Exhaust gas path trajectory is maintained (with less path 'shape change' transition) within the oval pipe better than a round one with two inlet sources sitting side-by-side as closely as physically possible. Win, win, win.

 

We're actually still on track. Manifolds and ways to improve their usage. Maybe not directly, but certainly indirectly. Useful info nonetheless and is still relevant. :TU:

 

One must assume, until proven differently, that most of the gains came from the 3" exhaust outlet.

The majority of gains in porting exhaust manifolds are seen from enlarging the exit, thus lowering the backpressure of the system.

This was further enhanced by a free flowing exhaust system on Tom's car.

Not trying to downplay any pipe theories, just pointing out the known facts in this situation.

JW

 

1 7/8 headers have no business on Rogers Max effort engine. Sure only 34HP with those tiny pipes over the manifolds.. but with the right header, the difference could have been easily twice as much or more. They were not trying to maximize output of that engine with headers.. but just started with the set they had, to note the difference.

Consider the gains below, on a Stage 1 engine like Rogers, but without the limitations of his SA setup.. that's where the power difference is.. they started with 2" headers, and picked up 30HP+ with 2 1/8 headers...

http://www.v8buick.com/showthread.php?46363-2-1-8-Inch-Headers&highlight=headers

Regarding the headers to manifolds test, the coolant temp is 15-20" cooler.. throw that test out completely, it's invalid. I have seen 10* in coolant temp be 10 numbers in torque and HP.

JW