joescool2008 said:

As said in other posts that should be in vendor reviews or a PM when mentioning names of vendors in such a matter. Not a junkie for any certain vendor, never bought anything from the guy, just sayin.

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I'm not bashing and mentioning names isn't against the rules here. And I'm not 'revewing' anybody either. It's just an example of why a dyno test wouldn't work. Don't read into it any more than that.

vr41mpg said:

good head + better intake manifold

better head + good intake manifold

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So, it's better cylinder filling VS. 1-2% more even cylinder filling.

I don't know which wins in the overall scheme of things. I'd bet better cylinder filling, but that's just speculation.

I run a stock 1G head with the casting flaws removed on stock sized valves, car has made 1100 at the tires.

I like the 2g head for its structure as it looks like if I was to have a issue with the flexing it would help but I have never lost a HG on this car.

If someone showed me a 2G head would make more power I would gladly switch but every head guy I have spoken to thus far has not felt confident telling me it would make any more power. Of course my setup is not like 99% of the people out there so I am not good for comparisons. Years back I watched, Pruven (IIRC), toast a super ported high dollar race head and switch it between rounds and run the same et and same mph on a bone stock 1g head, hence why I haven't spent a fortune getting one ported. I am all for spending money to make power I just want to make sure I get something for my money. Perhaps there is a point where forcing air into the cylinders shows much less return once you start making a lot of power on our cars.

Now I'm lost, but what's new.Whats cylinder filling?
When the cylinder fills obviously.But what's the science behind it?

LandSpeed-DSM said:

So nice of you to back that up with such a thorough dissertation^

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Sorry dude. But I didn't feel like sitting here and wasting my time explaining something to you that has been covered numerous times.

The magnus cast is better than all of the SMIMs IMO, so its unfair to compare one to another on different heads.

The 2G head with the Magnus Cast > 1G head with the Magnus Cast. Until really high airflow levels come into play. When you start getting into the 85lbs/min+ range, the small ports of the 2G head become somewhat of a restriction, and the larger ports of the 1G head become more of an advantage.

Disclaimer :: I have never tested either. This is all from what I've read about and been told by numerous different people and frankly, it makes a lot of sense to me.

When you mention someones name and then say they use a method and discredit it, im pretty sure thats bashing. Maybe I'm just not good at comprehending english. Could have just mentioned the method and why it is the wrong approach?

Bud92gsx said:

But if you think about it after extensive porting and so forth. The 2g head should be almost identical flow wise to the 1g head.Forget about the velocity of the 2g head at that point.

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Negative. A proper port job on a 2G head does not mean you're smply hogging out the port volume to match the 1G head. The 2G head will always have a smaller port volume unless you trash it with a die grinder because a proper port job focuses on the ceiling rather than the floor.

Bud92gsx said:

Extensive porting of the 1g head should make a very high hp head, with super great flow.

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Marco mentioned that years ago they had to swap out their heavily ported head for a stock port sized head to make a race. The car lost no MPH. Makes you wonder if the available port volume of the 1G head is really needed or not.

@DSMTyson... the magnus v3 cast manifold does not work with the 2g head which is why I brought this up.

Ahhh Proper.Well I don't know anyone who would have their head not ported properly.


But then again most local shops may not know the proper way to port a 4g head.It's sad but it probably happens more than we would like to think.

Now again PROPER comes into play.But then again If your building a high hp car,Why would you risk getting you head ported by a place that doesn't specialize in the 4g head.

99gst_racer said:

Test how exactly? I'm not so sure a dyno is the best measurement tool for the job. It would only add variables.

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This goes back to my post above. It needs to be on an engine dyno with a a2w IC so that part stays stable.. Then the test needs to be exhaustive, with multiple intakes, and multiple cams, and multiple turbo's, even multiple displacements. Then you could say with certainty that x head is better than y head.

The problem is, most people that will do a test will only do a back to back. So you can't say that overall one head is better than the other.

Like Kiggly, he can say that for his setup, the 2g head is superior. But he cannot say it is overall superior, because he has not exhausted all combinations.

Finally, I speculate that the differences are not even enough to matter.

Bud92gsx said:

Now I'm lost, but what's new.Whats cylinder filling?
When the cylinder fills obviously.But what's the science behind it?

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Google it. It's just what it sounds like. Things like camshaft design, head port design, and intake manifold design will affect how well you can fill the cylinders between timing events. With better cylinder filling comes a higher VE. And a higher VE yields a potential for more HP.

And the only reason I mentioned a "proper" port job was because your post seemed to imply that when you port a 2G head, it essentially makes it identical to a stock 1G head, which isn't true.

joescool2008 said:

When you mention someones name and then say they use a method and discredit it, im pretty sure thats bashing. Maybe I'm just not good at comprehending english. Could have just mentioned the method and why it is the wrong approach?

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Maybe so. Because bashing is attacking, which I am not. I'm simply disagreeing with it.

PM me if you want to discuss this more.

bastarddsm said:

This goes back to my post above. It needs to be on an engine dyno with a a2w IC so that part stays stable.. Then the test needs to be exhaustive, with multiple intakes, and multiple cams, and multiple turbo's, even multiple displacements. Then you could say with certainty that x head is better than y head.

The problem is, most people that will do a test will only do a back to back. So you can't say that overall one head is better than the other.

Like Kiggly, he can say that for his setup, the 2g head is superior. But he cannot say it is overall superior, because he has not exhausted all combinations.

Finally, I speculate that the differences are not even enough to matter.

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You're probably right about that last bit. Any measureable difference will probably be reasonably small.

I doubt anyone will ever do such a test though. I think a bench flow test will be good enough to learn from. If a hole flows better on the bench, then it can flow better on an engine, and can make more HP. Whether it does or not depends on the rest of the engine and the tuner.

Nah Paul i actually didnt think about the proper thing.So thanks for mentioning it because lets say the shop down the street doesnt know what the hell their doing.And kills the 2g head velocity,with a crappy port job.

This is where proper and head comes together. A non proper port job can kill any hopes of lets say better than stock performance. Reguardless of which head you choose.



I will also google the cylinder filling. Im always down to. Gain knowlage.

DSMTyson said:

Sorry dude. But I didn't feel like sitting here and wasting my time explaining something to you that has been covered numerous times.

The magnus cast is better than all of the SMIMs IMO, so its unfair to compare one to another on different heads.

The 2G head with the Magnus Cast > 1G head with the Magnus Cast. Until really high airflow levels come into play. When you start getting into the 85lbs/min+ range, the small ports of the 2G head become somewhat of a restriction, and the larger ports of the 1G head become more of an advantage.

Disclaimer :: I have never tested either. This is all from what I've read about and been told by numerous different people and frankly, it makes a lot of sense to me.

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Here's the thing though.. all you are doing is reviewing what you've read and decided to agree with. You do not have hard data either way, few if any do.

Which is what makes me curious, especially when some of the key elements you are trying to use as facts are counter to what is actually seen.

Kiggly is a great example of this.

Not only is he moving well north of 110lbs/min on a 2G head, he is also on a 2.3L that is sucking through those ports.

I think this compliments that head well, in a manner some may find counter intuitive, others may find makes sense.

That 2.3L has much greater piston speeds because it is slinging those pistons around on a 100mm crank, which is why the greater port velocities the 2G is alleged to foster would be a good match from what my understanding of fluid mechanics provides.

Kevin was also one of the first people to buck the trend of arbitrarily calling the max acceptable rev limit on a 2.3 with its "poor" r/s ratio (rod angle) to a mere 8-8.5k

I remember reading a post of his else where (Either ECMLink Forum or NABR) where he stated he wasn't getting out of first till at or around 9.5k where the piston velocity, acceleration and jerk (m/s^3) for the 100mm crank are surpassing F1 figures.

Also, when you are talking about massflow and FI applications.. you made atleast one fatal error in your attempt and logic... things get more complicated than black and white answers of "well above 85lbs/min those ports will become a restriction" because volume and massflow are two different things all together.

If you said "you'd be hardpressed to move more than XX cfm" there might be something to that, but we have the advantage of compressing that charge. Though it is nice to have volume flow on your side. Even then, compressible fluids being what they are, its a supremely complicated issue that will vary head to head and port to port.

Like John said, between all the opinions in the community by those who've been there and done that including Marco and Kevin, all of whom have my utmost respect.. I haven't read, seen or experienced my self anything either way that would sway me towards one head vs the other at this point.

The difference is not likely huge or there would not be so much speculation, even at those power levels.

Seeing as I am aiming to move just shy of 100lbs/min myself with a 71mm turbo, I will be in the market where every little bit adds up.

This is why that inane blanket statement of yours garnered such a response in the first place.

You dont know, and neither do I. Few if any do, and for the most part they sure aren't talking. So try and keep an open mind shall we

haven't read, seen or experienced my self anything either way that would sway me towards one head vs the other at this point.

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perhaps a properly designed intake manifold would steer you towards a particular head hahahah

this is what I was kind of getting at in the first place...

I found the test results for the old SMIM test. It seems that most runners flow within 5% of each other (which is on par with the stock manifold). Magnus claims within 1% on the cast V3 manifold. It would be cool to see it 3rd party tested though. As well as the Hawver, Magnus Race manifold, and any other that wasn't on the original test.

That is some good info and man maybe I should jump to a new intake manifold sooner than later

Also the OP stated about the airflow distribution, good tuning and a good EMS would fix that, no problem. (as proof) Shep didn't have the Magnus cast manifold 5 years ago when he trapped 190+mph. (so obviously the BJ's SMIM, or whichever he was on back then, I don't recall this early in the morning) wasn't holding him back because of airflow distribution.

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I wouldn't say no problem. Having EGT's on each bank of an exhaust manifold to make sure things don't lean out and burn down isn't exactly trivial. Having a manifold with better airflow distribution is always a welcome thing. Having a standalone engine management isn't a trivial thing to tune either. The top guys did tune around issues like that however. For the mere mortals items that are designed from the trial and errors of these guys are a god send.

Without separate cylinder tuning if one cylinder is leaner then the others global fuel has to be added which will make the other cylinders richer which results in loss of power.

My guess based on some fluid dynamics/thermodynamic classes is that the 2g head is most definitely better at the "low hp" numbers. For reasons such as Paul Volk was saying such as cylinder filling/port velocity. The main bottle neck will be the stock valves. As the airflow speeds approach mach speed the volumetric efficiency plummets. That's why the big guys have to run such huge cams. Turning up the boost becomes a diminishing gains endeavor. You can only stuff so much air into an area for a giving second. The farther that valve opens " lift" and the longer that valve stays open "duration" becomes utmost important.

The more we can remove pressure drops along the way will increase efficiency. The bigger volume of the 1g ports in theory should give less of a pressure drop based on fluid dynamics. Only thing is the upper limits of the 2g probably have only been approached by a select few, and even then their are tricks to get more out of a head as many head builders will know.

I would recommend for the sake of simplicity for a 6bolt guy to not worry about getting a 7bolt head and vice versa unless it is for the sole reason to get the magnus cast which is a beautiful piece. However their are other good intake manifolds that will increase V.E. and aren't too bad on airflow distribution either. As long as one isn't trying to tune on a razors edge without the proper gauges and knowledge the other intake manifolds will due just fine. People take the strength of these engines for granted when they run shit tunes and their engine doesn't blow apart.

The moral is that using either head isn't going to matter enough for non record breaking cars. The 2g head can be considered slightly superior, but it isn't going to show up on dyno's or flow blenches because its a moot point with other bottlenecks.

thecman02 said:

The moral is that using either head isn't going to matter enough for non record breaking cars. The 2g head can be considered slightly superior, but it isn't going to show up on dyno's or flow blenches because its a moot point with other bottlenecks.

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You've already mentioned that you don't have any data and you are just taking a guess, how have you come up with a conclusion without any data?

I've used a flow bench before and I can tell you there are a lot of really weird things that happen. I have not flowed either the 1G or 2G heads yet, but I plan to before summer is over. It is not my intention to settle the debate, just to find information for myself. I recently compared two different castings for my van and there was a very clear winner. The difference between those castings was much less than that of the 2g vs the 1g. I've even got a 4g61 head to test!

If the bench racing discussion is continuing, one thing I haven't seen anyone mention are EVO ports, and heads for racing cars. The EVO has small ports like a 2g with a "chapel" shape for the fuel injector. No one that I know of hogs out the EVO to the size of the 1g port. Looking at the cylinder heads for other much higher performance engines, their intake ports are of similar size and shape of the 2G.

My conclusions are just based off of results from high horsepower cars that swapped heads and still had same trap speeds, and the fluid dynamics class I took. Evidence seems to suggest the smaller cross sectional area that a 2g or evo head can flow isn't a restriction and in fact it is a superior design.

I was trying to bring clarity to the OP that he shouldn't lose sleep because he has a 1g or 2g head.

My guesses are that the pressure drop is lower in the 1g head due to the cross sectional area, but the 2g head makes up a little ground due to a better shape/path of the port. I can see how these losses could be off setting or so close that all of the speculation on what is superior doesn't matter.

I'm excited to see some hard numbers with various tests, but for now I only have theories based on trends we've seen from drag cars and fluid flow principles.

The whole point is mute (in regards to the airflow difference between cylinders), with a good EMS (and proper tuning) like I stated earlier. I'm not saying the Magnus manifold is crap, I'm just saying, Put a Magnus v3 on a 1g head (with a stellar tune) and then put a Beyond Redline (or JMFab, or whatever) and also, a stellar tune) and then see who's on top when the smoke clears. Like Paul (99gstracer) mentioned, tuning a setup, then changing something and NOT RETUNING, is what is fudging the results.

Here's some literature that's an easy read with some good points in it.

Drag Racing Cylinder Head Selection: Engine Builder

It might help make some more sense for some people. It definitely explains why you can't assume the 1g is better than the 2g head because of the cross sectional area or just because of CFM's from a flow bench.

The main cross sectional area of both ports are big enough that they aren't a bottle neck. I think in other posts on DSMTuners such as a head debate that Kiggly actually chimed in shows that the bowl was the bottle neck. The thing is, the bowl is the bottle neck in both heads.

I think stock head for stock head with no planned modifications I'd go with the 1g for ultimate power. For lower more sane hp goals the 2g is superior. For heavily modified I'd give the nod to the 2g since its shape starts off better and you can fine tune the size of the port you want. Ideally I'd like to see custom cast heads for our car, but I just don't ever see it happening.

I know this thread is long dead, but want to add only 1g heads has been in deep 7's. All 4 of the cars that has ever run 7's 1/4 miles were done in 1g heads. John shepard, boostin performance, english recing, trevor holland all use 1g heads. Currently No 2g heads nor Evo has ever Crack 7's period.