split port vs stock s/c heads

boogeyman

Registered User
for the sake of argument what power diffrence would u see doing a direct swap from stock mild ported s/c heads to ported split port heads everything else being the same boost levels both tuned for optimal power same fuel so on and so forth

been pondering doing a split port swap since i have a set sitting around from a 99+ wrecked car
would u say it would be worth 40hp 50? maybe
 
i know the intake will not work thats a pretty obvios issue i believe that morana has an intake that will work for the swap
 
I talked to morana one time and he mentioned about switching to those heads. He said stock they flow about as good as a fully ported set of sc heads. Cant remember any specific numbers, but according to him it would be a good upgrade if you can adapt an intake to work with it, which he talked like he would be willing to do.

chris
 
im just thinking why u would spend 1k+porting a set of stock s/c heads when u can port a set of split ports get a intake and make very good power sure u may be into it for more money but u wouold be eliminating the poor flowing stock heads from the equasion then when u go big with a blower or other mods u would get the full potentian from them because u are not corking the air flow path with the stock heads
 
im just thinking why u would spend 1k+porting a set of stock s/c heads when u can port a set of split ports get a intake and make very good power sure u may be into it for more money but u wouold be eliminating the poor flowing stock heads from the equasion then when u go big with a blower or other mods u would get the full potentian from them because u are not corking the air flow path with the stock heads



Mainly because there hasn't been an intake manifold that will work with an SC blower configuration. From what I can see on Morana's website, there still isn't. The manifolds offered by Morana are for normally aspirated, centrifical superchargers, turbocharger or a bottom discharge M112 without an intercooler.

http://www.moranav6racing.com/category.html?CategoryID=2

David
 
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i would think that a split port intake for a factory type intake would be more usefull than the m112 bottom discharge intake since the split port heads are quite plentifull in junkyards
do you think that since morana seems to be able to create the intakes that we need as a cast part that if enuff people showed intrest that he may create something for us ?
 
i would think that a split port intake for a factory type intake would be more usefull than the m112 bottom discharge intake since the split port heads are quite plentifull in junkyards
do you think that since morana seems to be able to create the intakes that we need as a cast part that if enuff people showed intrest that he may create something for us ?

I seriously doubt it, because there aren't a lot of people interested enough in split port heads to make the swap, especially now that single ports have been shown capable of over 800 rwhp. I also don't believe some of the huge flow number claims that were being thrown around for the split ports vs single ports.

David
 
problem with the split ports is that the exhaust sucks, they actually flow less than the stock supercoupe heads, would require a bunch of love to make them happy, but do-able

figure this way, a stock supercoupe makes 140hp n/a
a stock split port makes 200hp n/a

they make almost the same power without a blower as the supercoupe does with a blower

i would expect 345rwhp or roughly a 145 rwhp gain from a properly setup split port head swap from a stock supercoupe head all else being identical
 
i would expect 345rwhp or roughly a 145 rwhp gain from a properly setup split port head swap from a stock supercoupe head all else being identical

If that were true, using a normally aspirated intake manifold with split ports vs. a normally aspirated manifold on single ports should show the same gains with a turbo or centrifical blower.

David
 
ok so lets eliminate the stock blower from the issue say for example u have all out ported single port s/c heads and all out ported split ports running a turbo or centrifugal blower both running a similar fully ported intake do you think that the spilt ports will out run the stock heads by a large amount ?vor would the diffrence not be worth the effort ?
 
yep thats true thats where i got my horsepower figure from

I think your expected HP gain figure is insanely high. Swapping from single port heads and intake to split port heads and intake, results in an average increase of 35 HP after retuning.

On a full blown max effort set of ported single heads vs ported split heads with a turbo or centrifical blower, the split port will make about 30 rwhp more than the single port.

David
 
I think there is allot more to the N/A vs SC number debate on these heads. One is the intake to exhaust port volume ratio and proper camshaft selection for the head chosen.

Regardless....I font know what Morana has been up to but I cant believe some of the stuff hes selling nowadays
 
problem with the split ports is that the exhaust sucks, they actually flow less than the stock supercoupe heads, would require a bunch of love to make them happy, but do-able

figure this way, a stock supercoupe makes 140hp n/a
a stock split port makes 200hp n/a

they make almost the same power without a blower as the supercoupe does with a blower

i would expect 345rwhp or roughly a 145 rwhp gain from a properly setup split port head swap from a stock supercoupe head all else being identical

There are a couple things you should probably figure into this equation.
First, a 99+ 3.8 has a 9.3 to 1 compression ratio vs the supercoupes 8.2 to 1

2nd, the exhaust on a stock sc is down right terrible, and i would imagine the mustangs exhaust flows much better than ours stock for stock.

As Dave already said, single ports have made 800+ rwhp, while a v6 mustang running a similarish setup with split ports made about 660 rwhp.

The real problem, as has been said before, is the intake manifold. If there were a better flowing intake available, even the m90 would likely be able to make much more horsepower.
 
As Dave already said, single ports have made 800+ rwhp, while a v6 mustang running a similarish setup with split ports made about 660 rwhp.

There were numerous differinces in these two combos, and for that reason can't really be directly compared. For example the single port motor that pulled over 800 rwhp had a manual transmission, much more agressive solid roller cam, more ignition timing and more boost, than the split port automatic trans with a middle of the road hydraulic roller cam.

On the 800 plus rwhp motor, swapping over to the best flowing split ports and best flowing split port manifold would result in the same 30 rwhp increase. Whatever extra power you can get from the motor normally aspirated by switching to split ports is going to be the same amount extra you will end up with after the power adder. In this examole if it made 800 rwhp with singles, you could expect right around 830 rwhp with split ports.

David
 
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not sure what car you guys are talking about that made 660. but the one i think of is Garys old car. and at the time it was a 5 spd. and was on like 16 or 17psi very very mild tune. had a solid roller(kinda mild)

also there has been a auto split port that made 668rwhp name is lou it has a twin turbo set-up. think this car has a hyd roller for sure. its his street car.

like david said compare similar set-ups.

and 30hp gain na will be more gain underboost. lets just use say 200hp plus lets say 15psi should get you 400hp. now take 230hp add 15psi and you get about 460hp. those gains are not set in stone. but you get the idea.
 
No split port is going to outflow Casey's single ports. Ain't happenin. But Casey's heads have a lot of work done to them. Stock for stock the split ports are nice. The exhaust doesn't flow a lot but it is very efficient, particularly at low lift which is important for blow down. The biggest problem with split ports is the goofy split port and the thin wall castings. There just isn't much room for porting the intake side. For this reason it is quite possible to get a single port to flow every bit as good as the best single ports. Both will take work to get there though.

Stock for stock the SP heads will add as much as 50rwhp to an SC engine if you can make it work out, but the amount of work/expense to adapt the blower puts you right back where a set of fully ported SC heads would put you. So it's kind of a wash.

Also, when talking about power and boost levels, you have to keep in mind that air mass and cylinder pressure are different than boost alone. A really efficient set of heads allows you to run the same cylinder pressure at less boost. For example, a badass set of heads might reach dangerous (for pump gas) cylinder pressure at 15psi. With a crappy set of heads you might need 19psi to get the same result. The 15psi combo might make 20rwhp more than the 19psi combo, both will be at the limit of pump gas.

I'm not trying to say crappy heads are as good as good ones, just that understanding a little bit about what is going on in the motor is key to getting the most out of it.
 
I suspect intake and exhaust port velocity has a good bit to do with why the split port engine makes more power in N/A form.. Not just the flow numbers.

Isn't the split port combustion chamber similar to the trick flow twisted wedge heads? I thought I read that somewhere.

The smallish exhaust ports (high velocity) has turbo written all over it :D

Jeramie
 
from what i have been reading the intake seems to be the huge bottleneck on these engines stock m90 setup or otherwise why has no one figured out a way and brought it to market to cast a better intake for the m90 setup if there are large gains to be made from the heads but the intake is still a major issue why has no one addressed it it seems morana sells all kinds of odd setups for the 3.8 is the s/c so much more difficult to make something better flowing for that the rest of these intakes he makes or is the only real option to extrude hone the factory intake ???
 
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