GT40s vs GT40Ps - The Numbers

I thought the old 5-oh/302 guys would be interested in this info.

----
The GT40's have 1.85"/1.54" valves, GT40P's have 1.85"/1.46" valves,
and the stock E7TE's have 1.78"/1.46" valves.

Based on that information, I would expect the GT40 Iron head to
significantly outflow the P's, but that would prove an incorrect
assumption. The P's not only outflow the original GT40 heads, but they
do it everywhere. There is no advantage for the GT40 iron's until above
..500 lift. Since the GT-40P heads aren't designed for optimum flow
above .500, and the overall flow of either head doesn't support the
kind of flow you'd expect to get from a wild cam combo, the high lift
flow isn't as important as it would be with a more aggressive
combination. The P heads also come with 59cc combustion chambers, which
will increase your stock 5.0HO engine compression to about 9.5:1 while
the GT40's 65.5cc chamber hurts your compression dropping it to about
8.8:1. Compression ratios are not the most important thing in engine
performance, but so long as you're staying under 10:1 you should be
able to pick up some free horsepower here.

Back when the P heads first hit the scene you could pick up a set for
only about $400. Now they are becoming scarce, and you should expect to
pay in the neighborhood of $500/set. A set of brand new, stock
GT40P's will flow 190cfm from .400 to over .500 lift intake, peaking
at about 195cfm. That's a serious improvement over stock, and well
matched to mild head/cam/intake combinations. E7TE's flow up to about
155cfm intake side peak, at .500 lift. A home ported set will get you
about 165-170cfm, while a pro ported set is in the neighborhood of
190-200cfm. To get more than that, you're going to have to pay big
bucks for the porter to replace the valves to a larger size, and really
put some work in.

When it comes down to making choices for your heads, it's important
to decide where you're going, and what you need. The GT-40 Iron heads
do sport some enhancements beyond the P's. For a forced induction
combination, the Iron's do have a lower compression ratio, and in the
case of more aggressive camshafts the Irons usually came with GT-40
valvetrain, good for about .520 lift while the stock P head springs
only go to .500. If you were to use an XE series camshaft with a great
deal of lift, the GT-40 Iron head would probably work better than the P
head for pure, peak flow due to the more linear flow characteristics
the Irons have continuing past .500. The added advantage is the GT-40
heads work with common headers, and the P heads require specific, and
more expensive GT-40P headers in almost all cases. The GT-40P head;
however, has it's advantages too. A more efficient combustion chamber
design delivers a better burn, a little more compression for more power
in a N/A configuration, more peak flow at the valve lifts most
combinations involving these heads will experience, and a superior area
under the curve. By under the curve, I mean the flow rate viewed as a
graph. If you take the horizontal X axis, and label it "Lift", and the
vertical Y axis, and label it "Flow" plotting the flow curve out
between the heads would be interesting to look at. It all adds up to a
definite advantage for the P head in most applications.

*GT-40 Irons only feature flow rates up to .500 lift, although flow at
..600 lift may be slightly higher. Estimated maximum lift for GT-40
valvetrain.

The data used comes from Fletch's Carbed 5.0 Website, but based on
other sources, is consistent with what other flow testing has provided.
The Flow data is apparently not from the same bench, but is represented
at the industry standard of @.28".

Now the question is obviously, why? The GT-40 Irons were Ford's high
performance entry into the small block marketplace, and they feature a
bigger exhaust valve than the P heads. The P heads were a last minute
change to keep the 5.0 Explorer's passing emissions into the near
future because the 4.6L SOHC engine wasn't yet available in the
Explorer. Ford didn't want to make the P head. To speculate why it
was made the way it was, Ford didn't want to lose a leading market
share in the most profitable line of vehicles in production. The market
was crying out for a V-8 offering in the mid sized SUV market, and Ford
only had one engine that was available to squeeze under the hood. The
35 year old 90* based 5.0L V-8. The 5.0 was being phased out because
Ford didn't want to invest the money to keep it up to par with
emissions. That would, and eventually did, require a head redesign. The
result was the GT-40P series head. Ford was forced to pump technology
into the 5.0's head to increase the burn efficiency so the Explorer
would pass more stringent emissions standards. They did a good enough
job so that they could get rid of the large exhaust thermactor bumps
that plagued the GT-40 Iron and E7TE heads. This freed up a lot of
space in the exhaust port, and all the technology going into the head
design helped out the burning properties of the air/fuel mixture. The
market also wanted more power, and truck enthusiasts wanted more power
at lower rpms. To keep the engine smooth and powerful down low, the
head had to flow well with a relatively mild camshaft, but Ford
didn't want to sacrifice the ability to keep running strong as the
rpms increased, which had resulted in trailer hauling wins vs
competitors. The higher rpms Ford vehicles were able to sustain kept
the truck in the lower gear longer, which in turn enabled more average
horsepower to be produced.

Regardless of whether the speculation on my part is accurate, the facts
are. The GT-40P makes more power at the strip. Class leaders in what
was previously known as Trophy Stock (now Street Warrior) are running
faster than ever, thanks in large part to the GT-40Ps advantages.
It's more efficient burning yields more power, and it's better out
of the box flow makes for a better head.
----

Here's the site if you wan to take a look.

http://www.themustang-net.com/tech_articles/gt40p.shtml

Patrick
'93 Cobra

You thought wrong! No more facts. We're sick of facts. Cut it out.
We're on to you and your whole agenda. Stop reading, stop typing, and
stop trying to tell us things we don't already know.

180 Out

In article .com>,
> wrote:

> You thought wrong! No more facts. We're sick of facts. Cut it out.
> We're on to you and your whole agenda. Stop reading, stop typing, and
> stop trying to tell us things we don't already know.
>
> 180 Out
>

Abso-friggin-lutely right, and let's not mention that Hot Rod ran
the P head against the 305 Vortec on 351 and 350-inch motors,
respectively, and the P choked big time. It's optimized for 302 inches
and that's all she wrote. The Vortec, predictably, worked twitchinly on
the 350.

But we not only knew this already, none of even care.

--
CobraJet
Thunder Snake #1

CobraJet wrote:

> > You thought wrong! No more facts. We're sick of facts. Cut it
out.
> > We're on to you and your whole agenda. Stop reading, stop typing,
> > and stop trying to tell us things we don't already know.

> Abso-friggin-lutely right, and let's not mention that Hot Rod ran
> the P head against the 305 Vortec on 351 and 350-inch motors,
> respectively, and the P choked big time. It's optimized for 302
inches
> and that's all she wrote. The Vortec, predictably, worked twitchinly
on
> the 350.

> But we not only knew this already, none of even care.

You both are SO stupid! My car runs 12's, and does it with heads that
are comparable to the Ps. Plus, the styling of the Ps are light years
better than the Vortec heads. The Ps had big chrome valves and had
really cool angles. They didn't care, and didn't worry about, all this
aerodynamic flow and efficiency crap. Everything on them were just
really big, and it worked! Bigger is better, baby! Where as the
Vortec heads are slicked up, generic, disposable, POS like all the rest
of the fancy shmancy new heads. With their smooth pansy-ass contours,
and cookie-cutter designs, the Vortecs will never measure up to
classics like the Ps. Not that either of you will ever understand what
I talking about because neither of you are true auto hobbyists. You're
both wannabes who'll *never* get it! Now go away... go bench race in
some other NG.

Patrick
'93 Cobra

wrote:
> CobraJet wrote:
>
>
>>>You thought wrong! No more facts. We're sick of facts. Cut it
>>
> out.
>
>>>We're on to you and your whole agenda. Stop reading, stop typing,
>>>and stop trying to tell us things we don't already know.
>>
>
>> Abso-friggin-lutely right, and let's not mention that Hot Rod ran
>>the P head against the 305 Vortec on 351 and 350-inch motors,
>>respectively, and the P choked big time. It's optimized for 302
>
> inches
>
>>and that's all she wrote. The Vortec, predictably, worked twitchinly
>
> on
>
>>the 350.
>
>
>> But we not only knew this already, none of even care.
>
>
> You both are SO stupid! My car runs 12's,

The wind has buffeted you such that your stream of pee has hit you in
the face. I see you have now attempted to pull a 180, but have sadly
failed.

and does it with heads that
> are comparable to the Ps. Plus, the styling of the Ps are light years
> better than the Vortec heads.

A light year is a quantitative measure, not a qualitative one. It's
about 5.87 trillion miles, give or take. I wouldn't want to try to be
too precise and **** IT UP, because everything is relative, you know...

The Ps had big chrome valves and had
> really cool angles. They didn't care, and didn't worry about, all this
> aerodynamic flow and efficiency crap.

Inanimate objects have a difficult time caring about anything. Quit
being anthropomorphic; you're taking things far too seriously here.

Everything on them were just
> really big, and it worked! Bigger is better, baby!

This is the one place where you state actually fact.

Where as the
> Vortec heads are slicked up, generic, disposable, POS like all the rest
> of the fancy shmancy new heads. With their smooth pansy-ass contours,

Intake ports should never be completely smooth; a bit of roughness
increases combustion efficiency due to improved atomization.

> and cookie-cutter designs,

It's called mass manufacturing.

the Vortecs will never measure up to
> classics like the Ps.

"Classic" is generally defined as older than 20 years.

Not that either of you will ever understand what
> I talking about because neither of you are true auto hobbyists. You're
> both wannabes who'll *never* get it! Now go away... go bench race in
> some other NG.

If you are talking to yourself in some way, then you get a score of 100%
on this one. If not, you still score 50% by default, so it wasn't a
complete failure, from that perspective.

--
Wound Up
Snake #65

In article >, Wound Up
> wrote:

>
> The wind has buffeted you such that your stream of pee has hit you in
> the face. I see you have now attempted to pull a 180, but have sadly
> failed.

Uh, I think you missed the point, bitter though it was.

--
CobraJet
Thunder Snake #1

If his posts really bothered you so much you'd just add him to your
killfile. Personally, I think you're just a whiney little ******* who likes
to bitch about things. STFU. oh, and welcome to my killfile.

-Mike

--
A happy kid behind the wheel of a 98 Mustang GT
Cold air intake
FRPP 3.73 gears
Steeda Tri-Ax Shifter
Flowmaster 40 Series mufflers (self-installed woohoo)
Hi-speed fan switch
255/60R-15 rear tires
Subframe connectors
Aluminum adjustable clutch quadrant


> wrote in message
oups.com...
> You thought wrong! No more facts. We're sick of facts. Cut it out.
> We're on to you and your whole agenda. Stop reading, stop typing, and
> stop trying to tell us things we don't already know.
>
> 180 Out
>

In article >,
> wrote:

> If his posts really bothered you so much you'd just add him to your
> killfile. Personally, I think you're just a whiney little ******* who likes
> to bitch about things. STFU. oh, and welcome to my killfile.

Uh, Mikey, don't interrupt the grownups making fun of each other.
It's impolite.

>
> -Mike
>
> --
> A happy kid behind the wheel of a 98 Mustang GT
> Cold air intake
> FRPP 3.73 gears
> Steeda Tri-Ax Shifter
> Flowmaster 40 Series mufflers (self-installed woohoo)
> Hi-speed fan switch
> 255/60R-15 rear tires
> Subframe connectors
> Aluminum adjustable clutch quadrant
>
>
> > wrote in message
> oups.com...
> > You thought wrong! No more facts. We're sick of facts. Cut it out.
> > We're on to you and your whole agenda. Stop reading, stop typing, and
> > stop trying to tell us things we don't already know.
> >
> > 180 Out
> >
>
>

--
CobraJet
Thunder Snake #1

CJ, while I realize that it gets you off to put others down.. sometimes it
just gets ****in old. Why don'tcha find a new hobby to try once in a while?
You still have some "growing up" to do.. Mr. grown up.

-Mike

--
A happy kid behind the wheel of a 98 Mustang GT
Cold air intake
FRPP 3.73 gears
Steeda Tri-Ax Shifter
Flowmaster 40 Series mufflers (self-installed woohoo)
Hi-speed fan switch
255/60R-15 rear tires
Subframe connectors
Aluminum adjustable clutch quadrant


"CobraJet" > wrote in message
...
> In article >,
> > wrote:
>
> > If his posts really bothered you so much you'd just add him to your
> > killfile. Personally, I think you're just a whiney little ******* who
likes
> > to bitch about things. STFU. oh, and welcome to my killfile.
>
> Uh, Mikey, don't interrupt the grownups making fun of each other.
> It's impolite.
>
> >
> > -Mike
> >
> > --
> > A happy kid behind the wheel of a 98 Mustang GT
> > Cold air intake
> > FRPP 3.73 gears
> > Steeda Tri-Ax Shifter
> > Flowmaster 40 Series mufflers (self-installed woohoo)
> > Hi-speed fan switch
> > 255/60R-15 rear tires
> > Subframe connectors
> > Aluminum adjustable clutch quadrant
> >
> >
> > > wrote in message
> > oups.com...
> > > You thought wrong! No more facts. We're sick of facts. Cut it out.
> > > We're on to you and your whole agenda. Stop reading, stop typing, and
> > > stop trying to tell us things we don't already know.
> > >
> > > 180 Out
> > >
> >
> >
>
> --
> CobraJet
> Thunder Snake #1

In article > ,
> wrote:

> CJ, while I realize that it gets you off to put others down.. sometimes it
> just gets ****in old. Why don'tcha find a new hobby to try once in a while?
> You still have some "growing up" to do.. Mr. grown up.

You don't really want to go down this path, do you?

>
> -Mike
>
> --
> A happy kid behind the wheel of a 98 Mustang GT
> Cold air intake
> FRPP 3.73 gears
> Steeda Tri-Ax Shifter
> Flowmaster 40 Series mufflers (self-installed woohoo)
> Hi-speed fan switch
> 255/60R-15 rear tires
> Subframe connectors
> Aluminum adjustable clutch quadrant
>
>
> "CobraJet" > wrote in message
> ...
> > In article >,
> > > wrote:
> >
> > > If his posts really bothered you so much you'd just add him to your
> > > killfile. Personally, I think you're just a whiney little ******* who
> likes
> > > to bitch about things. STFU. oh, and welcome to my killfile.
> >
> > Uh, Mikey, don't interrupt the grownups making fun of each other.
> > It's impolite.
> >
> > >
> > > -Mike
> > >
> > > --
> > > A happy kid behind the wheel of a 98 Mustang GT
> > > Cold air intake
> > > FRPP 3.73 gears
> > > Steeda Tri-Ax Shifter
> > > Flowmaster 40 Series mufflers (self-installed woohoo)
> > > Hi-speed fan switch
> > > 255/60R-15 rear tires
> > > Subframe connectors
> > > Aluminum adjustable clutch quadrant
> > >
> > >
> > > > wrote in message
> > > oups.com...
> > > > You thought wrong! No more facts. We're sick of facts. Cut it out.
> > > > We're on to you and your whole agenda. Stop reading, stop typing, and
> > > > stop trying to tell us things we don't already know.
> > > >
> > > > 180 Out
> > > >
> > >
> > >
> >
> > --
> > CobraJet
> > Thunder Snake #1
>
>

--
CobraJet
Thunder Snake #1