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My dad had a bra
SN Certified Technician
Sep 5, 2001
Fort Knox, KY
Actually, mine was the only answer to the question he asked, given that he specified no boost or spray. He probably figures there are more ways and better insight. Still, he's been referred to the dyno thread, which is another place to get a good feel for good combos and bad ones. There are some other ways to get to 300 rwhp n/a, but I feel my advice is the most straight forward, bolt-on solution.
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May 4, 2019
Actually, mine was the only answer to the question he asked, given that he specified no boost or spray. He probably figures there are more ways and better insight. Still, he's been referred to the dyno thread, which is another place to get a good feel for good combos and bad ones. There are some other ways to get to 300 rwhp n/a, but I feel my advice is the most straight forward, bolt-on solution.
I appreciate jt. I couldn’t find the dyno thread like I said I’m kind of new to this could you possibly link it for me ? If so thanks in advance


Eaten, greased and played with my balls
You'd be best off with 380 flywheel hp on the engine dyno with the exhaust system attached.

300 rwhp needs about 380 hp net to make the target with a T5 manual gearbox.

I'm into GT40's and Panteras, and 351C 4V's. The history on these is clear.

Factory 300 rwhp ratings with just the 289 actually happend in 1967.

If you all (in my words) are arguing about anything else, you need councelling, IMHO.

The 351C 4V's were doing 300 rwhp in late 1970, when the 310 and 300 degree cam was added to the Australian export engines.

The 1972 290 degree hydraulic cammed Panteras were making almost 300 rwhp.

The time between the early 70's and emissions era of the OBDII era had Saleen looking at how much power you could make with the air flow restricted stock Cobra style intake. With a 5.8 engine, alloy Edelbrock heads, and a clean bill of Federal Motor Vehicle emissions, it was 371 hp net at 5100 rpm.

The S-351s started with '94 Lightning 5.8 short-blocks, to which Saleen added Edelbrock aluminum heads, 30-pound injectors, a roller camshaft and lifters, a 77mm mass-air sensor and 65mm throttle body. The final tally was 371-rated horsepower at 5,100 rpm and 422 lb-ft of torque at 3,500

And that sure looks like the stock GT40 style intake.


That engine almost heals over past 5000 rpm, and the 1.294" taller deck and lower EFI intake does its best to enusre the upper intake isn't a pinch point to power.

It took about 33 years for the 5 liter Windsor with iron GT40P heads to make more power than the 1969 Boss 302 engines. They never did it factory, but they sure can with the right cam and upper and lower intake, MAF, injectors and a little fettling.

Going back to 5 liter OHV engines.

300 rwhp is easy with just GT40P heads. de Tomaso almost did it with the first European Emissions 305 hp Pantera Si in 1991, but it got downgraded to 248 hp the next year..

The early small block Ford GT40 289's certainly did the 300 rwhp thing.

So did the 351 Saleen with alloy heads. So did the stock iron Explorer headed T3 Falcon and Falcon Pursuit 250.

Doing 300 rwhp is as easy as finding the right intake, cam, MAF and injectors.

If you want 300 rwhp, you follow the 5.6 liter T3 Tickford build list, and don't add the stroker crank. Longer rods and short deck pistons is what I'd use.

You can keep the Explorer GT40P heads, but you need the Upper and lower intake, MAF and injectors. This is because the air flow of even the Showa GT40 upper intake is lousy.

An upper and lower intake like this




MAF was the 4.6 liter Quad Cams 82 mm item

Mild porting, the right valve springs, rockers and making sure the EECV system isn't running lean will help.

That 335 flywheel hp and 369 lb-ft was with a 5.6 liter engine reving to 5250 rpm for power, but able to take 6000 rpm.

It was just the tip of the ice berg for that engine, and Ford Australia downgraded to non alloy heads after a run of 500 alloy headed 5.0 liter engines.

For any EFi pushrod 302, you just need more cam, and an EECV flash, or a later EECIV re-calibration to do it.

In terms of what even a 295 hp 2002 5 liter Windsor OHV V8 is, (a 40 year old rework of a 289), the engine gave an exceptional account of itself against the same years 5.7 liter LS1's. The T3 335 hp 5.6 stroker was in another catagory. Meaner, harder edged, not as smooth, but still able to take years of 4000 pound luxo barge punishment with reworked stock 'Exploder' heads and blocks. It was all because Ford Australia had the last remains of Aussie Jac Nassers aborted work in allowing the Premier Automotive work on putting Aston Martin hand building engine bay process into stock cast iron thin wall blocks.

Ford Australia re built the US import 351C engines from 1970 to 1972 with QC engines, then stopped when Total Performance had a melt down.

For 1999 to 2002, the 1970-1972 QC process got re-started with Tickfords ex Aston Martin engineer Dave Flint, and then continued with the Quad Cam 5.4 in 2002 and then the later Quad Cam 5.0 engines untill 2016.

The 5.0 Explorer blocks were the low point in quality compared to the early blocks, but a little spit and polish, and you had an extra 120 hp with stock Ford Motor company parts.

The Aussie use of special EFI upper and lower intake air managment, the use of non forged pistons with long rods, cast cranks, and plateu hone bores to be kinder to the block at 6000 pm, all of it has filtered into current US practice.

Main bearing block girdles,
upper block ties, and the simplicity of using the junk yard Aussie EECV, or EMS computer systems when there isn't IM testing,

well, that opens the door to streetable 400 hp at 6500rpm 5.0 liter combinations which won't split blocks at 7000 rpm.

That's why I like 5.0 engine build ups like this.

Don't be scared of EECIV or EECV.

Its got some issues, but you can swap the whole system over if you have the pinouts, and its really nice if you have it working with 380 hp and not tripping a check engine light. Some Four eyes have MIL lights... the transfer of a broken scrapped SUV engine into an old Fox platform makes it a HSV...Humanitiran Service Vehicle.
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Eaten, greased and played with my balls
Then you've gotta dyno tune it. EFI or MFI, or Carbed Indepedent Runner V8's are the most likely engines to suffer at the hands of air flow leaks near the MAF or due to exhaust backpressure.r

The David Flint/ David Orchard pairing of finding the missng 37 flywheel hp started in 1977 when the Motor Press Aston Martin V8 Vantage conversion failed to be any quicker than the pre emissions Quad Weber Aston Martin V8 of 1973.

Aston Martins engineers then went on a hide and go seak, and found the exhaust pipe baffles in the mufflers were not the same spec as the test engine.

In 1992, they were playing the same game again at Ford Australia

It is nothing to lose 30 hp from the factory SAE J1349® Net Certified Power rating if you move from stock. The article I posted is proof, and it explained how both a 1992 Ford with a Ford Mustang Cobra engine making 274 hp flywheel could suddenly make only 245 hp flywheel. That's why Ford downgraded the ratings on the Mustang in 1993, as actual required dressings, Cold and Fresh Air systems, exhaust systems, or cold light off runs before the O2 sensor kicks in can be higher. Even a fan clutch could wind off 4 hp.

Most losses are accidental, due to leaks around the MAF sensor. Ford Australia from that 1992/1993 issue quoted David Flint, Tickfords engineer who also worked on the 1978 Aston Martin V8 Vantage project, and that car lost 37 hp just from excess backpressure in a factory exhaust system. He'd Been There, Done That, and the press fall out was a cinch to manage, because you've got to quantify the effect.

I'll bet people wondered why a certain 1970 455 Firebird HO was rated 35 hp differently to a 455 GTO Judge even though it was the same engine. Lead tabs in the secondary bores of the carb. In 1970, it was insurance. [The difference between the GTO and Firebird engines was that the secondary carburetor's throttle linkage had a restrictor which prevented the rear barrels from opening completely, adjusting the linkage could allow full carburetor operation resulting in identical engine performance]

You broke the lead tabs, and you were back with 370 hp in a 3350 pound car to beat the greater than 0.1 hp per pound insurance kick in. :o

In 1992, the rating was really that simple. Just production variances on an EFi engine. The DIN Net rating of a 1993 Cobra engine was 266-274 hp, with 8 hp varinace normal, and another 5 hp off for SAE net. Ford internal J1349 net was 235 for the US Cobra.

Crap happens. An modern EFi engine is a lot more complicated that people realise.

Especailly on the 5.0 and 5.8 EFi engines

Proof of how easy it is to loose 30 hp.......

And that's kinda where EFi is, and always has been, historically.

Not my words.

26 year old History.

All I know is that its nothing to drop 30 hp by just overtightening a 50 cent resonator clasp.

266 to 274 hp and 15.3 second quarter miles, to less performance than the stock 225 hp 5.0. Clearly, a 1 second 1/4 mile ET loss is more than just 20 hp.

According to the inferred info from David Flint, the loss was up to 24 hp (10%) due to lean WOT air fuel.

I can do it in a few turns of a flat head screw.

Page 14 Jan 1993.




Some specfic parts were different, but the engine block was the same, the heads, cam and intake were the same, just reversed like it was on the Bank fire 5 and 5.8 liter trucks and the Panther 5.0 Crown Vic's and Gran Marq's

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My dad had a bra
SN Certified Technician
Sep 5, 2001
Fort Knox, KY
That's a lot of stuff. I appreciate it, because that's knowledge I didn't have, and I'll go over it in more detail, later. I'll just say this about GT40Ps: They flow ~190 CFM. A basic AFR165 flows 260. The cheaper twisted wedge is pretty close to that. At the rule of thumb limits of 2hp/cfm, you're barely at 300 rwhp. Guys in the old factory stock used to take extensively ported GT40 & GT40P heads to over 300 rwhp with "stock" cams. So, it's certainly possible. Then again, they had more money in those heads than an aluminum head would've cost.


Eaten, greased and played with my balls
Its the whole combination flow rate, not the pinch point cfm.

Even Ford hand modified the intake runners on all its Synergy 5000 engines. They weren't 190 cfm after the modifications.


Initially, for 1993 and the return of the GT Falcon, the Australian GT's and XR8 Sprints got a Showa GT40 Tubular intake that was not made in USA, and it had a half inch spacer. Much latter on cars got factory Y303 GT40 alloy heads from Fall 1999 to Spring 2001, but it was withdrawn after the 500 or so heads emptied from the imported stockpiles, and except for the 65 pound weigh saving, there was no HP gain with them as CFM and spark ramps stayed the same.

The first Windsor "Fuelie" in Australia to make 295 hp did so with iron GT40P's, and so did the 335 hp 5.6.

The croosover point for a mildly modified upper and lower in the stock configuration was about 305 hp, and that was right where the first prototype 1991 EA Falcon GT 351 landed after Jack Roush did the emissions work.

xctasy;1821913 said:
.....Jack Roush from 1988 to 1994, had been playing with the 5.8 spec, starting with the 375 hp twin turbo 351w for the 25 Aniversary Mustang,


then sending a engine overseas in Australia. It was a 1990 EA Ford Falcon 351 GT development 'hack'




which was suposed to be written off. Instead, it is proof of just what Jack was up to for the Ford motorcompany world wide.


Windsor 5.8L 351 CID V8
305 hp, 350 lb-ft
0-62 mph - 7.3 seconds
Standing 1/4 mile - 15.4 seconds after factory emiisions and durability test 50 000 miles. The engine was way down on power, and was on LTD rims with 205 65 15 tires in a 3500 pound car. ...
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SN Certified Technician
Aug 27, 2012
In the garage
That didn’t answer my question :spam: head

yes it did. You don't have the comprehension to understand. You picked a bag of mismatched parts that ain't gonna get you there skippy.. You've been told that by people who know more about these cars than 99% of the people out there.

You do know a 306 makes little or no more power than a 302- even with those arp bolts and forged pistons..lol
$2500 to spend?

Here's my advice for a $2500 build making +300rwhp
Explorer JY motor $300
Ed curtis custom cam $300
Ported lower Explorer intake by Tom Moss $300
Set of AFR 165 or TW 190 heads $1200
Crane or FMS rockers $250
pushrods, lifters $200
Gaskets, water pump., seals, timing chain, blah blah $200

what happens at 300rwhp vs 270? Unicorns and virgins fly out of the exhaust?
if you can live with 260-270rwhp and save a boat load of $$

Explorer motor
anderson N41 or TFS 1 cam
Alex's springs
Ported Explorer lower

but hey you knew all this


mechanicus terribilis
10 Year Member
Dec 14, 2010
SW Houston
I think there is something big that we missed here, and is part of his $2500 budget - His short block is trashed.

DO. NOT. REBUILD. THE. OLD. ONE. That is money down the drain that you don't need to spend.

Lemme repeat that.


Instead, do like Mike said, go find a 5.0 explorer in the JY that's less crusty than the others and pluck that motor.
Swap gaskets, and slap it in. They run forever and chances are you won't have any issues with it.

From there:
1) buy a set of heads - if theyre used, be very careful. Make sure they're fresh from the machine shop or you know/trust the seller.
2) Buy a good intake. Holley, Edelbrock, whatever. GT40 won't get you there in stock form, needs to be ported.
3) Call FTI or whoever and order a cam based on the heads you bought and the rest of your car info
4) put it all together and go get it tuned.

You can do that for your budget, if it doesn't go slightly over.
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Eaten, greased and played with my balls

Its not heads, its the whole flow combination.

The intake system is only as strong as its weakest link. By upgrading your throttle body you can help support other mods your fox has and increase throttle response

In order to get a 351 to make 371 flywheel hp, Saleen grabbed an EO and OBDII certified intake manifold, and cut and flitched it for air flow.

Look at the orange cuts

Then added those Edelbrock alloy heads to be sure, to be sure.


To get 300 rwhp, they needed 371 emissiones horses at the flywheel. So do you.

You can do that with GT40P heads....they called them GT40 heads because they are 380 to 390 hp capable heads just like the LeMans heads used in the old Quad Weber GT40 race cars.


227 rwhp is 170 kilowatts. With a four stage auto, you need 340 flywheel hp to make a certain 227 rear wheel hp.

If its a T5 or Tremec, you only need 380 flywhell hp to ensure for certain you hit the big 300, and you'll do that with the best modified iron GT40P heads with a cam and good valve springs.

What you'll then have is an engine that will be strangled from 5000 to 6250 rpm, too lean, and you won't be able to calibrate the engine management system.

The intake, upper intake and exhaust have to match the heads, and the car has to be dynoed to ensure you match it. I wouldn't spend a dime on alloy heads.

Before the Explorer engine, non Cobras, the HO 5.0, had bad heads. After the GT40P, Ford fixed that. Down here, Falcon EB, ED, EF and EL V8s got E7 headed or early GT40 heads, and they just didn't respond unless you added alloy heads. The GT 40P's, (the Aussie AU Falcon V8), they lapped up every 77 to 82 to 90 mm MAF or Throttle body, and you had to use a proper high flow upper and lower intake with a much better single exhaust.

Everyone moves to alloy heads too soon.

RobHerrod said:
"The biggest problem is people coming in with EB, ED, EF and EL V8s and they've got crappy cylinder heads and crappy intake manifolds. You tell people they've got to spend seven or eight grand replacing all that junk and they ask why. Some people reckon I'm ripping them off when I say that, but I'm not - it's just that other people talk rubbish. We sell our own throttle bodies for the Windsor purely because the stock ones are so restrictive."

"Really, I'd recommend drawing the line with just an exhaust and maybe some sort of programmable computer to lean it out. There's too much that needs changing to make those early injected Windsors competitive - I don't think they're very cost effective to get lots of power out of. The EL Series 2 V8 wasn't as bad - it had ceramic-coated extractors, an Explorer type intake manifold, a 60mm throttle body and standard heads. They didn't get the GT40B heads though."

"On EB to EF V8s I find their airflow meter is prone to failure - they drive fine, with plenty of punch and economy but they're running about 15:1 air-fuel at wide open throttle. As lean as buggery. A new airflow meter from Ford is now $1200-1300 and you've also got to make sure it has the right calibration to suit the EEC."

"When someone comes in with an AU V8 it's great - they've already got decent cylinder heads, a good intake manifold a 65 or 70mm throttle body. The AU-onward V8 is a good thing to work with. We make 170 kilowatts at the wheels with a cam, exhaust and computer upgrade and - for about five or six grand - our customers think its grouse."
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Eaten, greased and played with my balls
As final5-0 has said,

That "those older Ford Aluminum heads had no better flow than their iron brothers". A lot like the added spin saying the Bunch of Bananas GT40 upper EFI intake from the early GT40's is able to flow up to 425 hp.


Its just advertorial spin.

By way of example, Ford Australia opted out of continued supply of US made X303 heads and Showa GT40 upper intakes because CNC ported Yella Terra GT40P iron heads tied the block together, and flowed another 40 hp. They said no to the weight saving. 65 pounds off a car is is like adding a free 6.5 hp or more.

Now you got them, you'll have to do the cam, and find a crank girdle and upper block stays.

Ford Australia added the 335 hp 5.6 stroker 342 to the Explorer 5.0 engine block in the last year of OHV V8 production.


It got a crank girdle to hold it all together, as well as a proper intake manifold.

I've seen a lot of cracked 5.0's, so I too would go for these two additional things every time. The stock dog bone valley chest drilling is also a known stress propogation as well, so link bar roller rockers as per NASCAR would be a choice i'd make too.

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My dad had a bra
SN Certified Technician
Sep 5, 2001
Fort Knox, KY
Come on, man. That's not what a guy who just spent money on x-heads wants to read, and it's misleading, anyways. Ford did things differently in Australia, I presume, but you're talking to an American in America with American Ford stuff. 'Murica! :flag:

X303 (64 cc) and X305 (58 cc) heads are far superior to non-ported GT40P heads:




I've seen untouched X heads at 300 rwhp on a stock bottom end 302, though that takes a good combination, and is easier to do with a more premium AFR or TFS offering. Yes, people can run 300 rwhp with P heads or even E7s when ported, but there's no reason to imply they're a better or even equal head. That said, final5-0 must have been referring to the Y303 heads, which, according to common knowledge, are effectively like GT40P castings, but as you can see from the flow charts above and dynos below, that is also not true, though they are not cost effective heads, IMO. I personally haven't seen many Y heads around, though.

GT40P vs. GT40Y aluminum heads on a 302 by a dyno sbf book (Unfortunately did not see a direct P or Y vs. X dyno).

The GT40 intake CAN support 425 hp, though that's at the crank. It is pretty commonly known that the lower end of the GT40/Cobra/Explorer intakes are the restriction. I've never seen anyone dispute that a GT40 upper is slightly better than a stock casting Cobra upper. However, @89stang1 made 364 to the tire (~428 hp at the crank) with an unported Cobra (upper & lower). It was clearly choking the motor at that point, but that's proof positive that they weren't exaggerating about the GT40. Presumably, a ported lower would pick up more, and a GT40 Upper would also pick up more. The best of those intakes would be a ported lower and a ported Cobra/explorer upper pair, though the 10-15 rwhp may not be worth the $$$ or time.

Also, aftermarket block girdles (both crank and lifter valley) are a waste of money on a stock block, as they will break north of 500 rwhp regardless. Maybe Ford Australia did a better job with there girdles. I personally wouldn't spend the money, and I don't know why Ford Australia felt it was necessary for a 335 hp engine. The only thing that keeps these blocks together is avoiding detonation, high RPM, 550+ rwtq, & 500+ rwhp (perhaps 450rwhp with a blower).
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Eaten, greased and played with my balls
Thanx for the info.

Im onside with the evidence.

A little humble pie might be good for me!

Only thing Id add is that block cracking happens well below 350 on many Essex 90 V6s and its not just the 335 hp Tickford 342 that got them in the Ford empire in 2002...the 193 to 210 hp F150 4.2s and Mustang 3.9s got them to keep crank walk in check on those ity bitty aluminum split port headed engines.
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