Another GT40p question

[vxr500]

OK, I know this has been brought up before, but every thread i find on it seems to wander off into a different conversation.

If I buy a set of rebuilt GT40p's for my stock-no emissions-84 5.0 4bbl (I do have an Edlebrock performer intake, and full exhaust with long tubes) will there be a noticeable improvement over my stock heads? Will I need to get new springs? I'm planning on keeping the stock cam as I'm on a budget.

[bwguardian]

Will you see a difference?
Yes, your stock heads have huge combustion chambers and the GT40p heads have much smaller chambers...so you should bump compression up about a point from the stock 8.4:1, just make sure your bottom end is healthy. Also, your stock heads have thermactor humps in the exhaust ports and the GT40p heads have no emissions as they were purdy efficient with the spark plug orientation. Your next restriction will be that intake, but with the stock cam you will be good.

Will you need new springs?
The stock springs are worthless...especially if you are buying a used set with some miles on them. Invest in some decent springs now, just be careful with pressures set as you want to take it easy on the flat tappet cam.

[gmatt]

http://www.fiveohinfo.com/performance/gt40-gt40p.html

[vxr500]

Thanks for the replies. The heads would be rebuilt with new springs, but from what I'm reading, the springs are not good with the factory HO cam. I guess that includes my 84 flat tappet too.

I already have the Edelbrock intake and BBK long tubes, so I should be good there. I'm just looking for a nice 30-35 hp bump. My car runs pretty good, with good oil pressure, but it's an original 84 motor that's never been rebuilt. I did have a new double roller timing chain and oil pump/pickup put in last year. I'm hoping I don't stress the bottom end if I get these heads.

[xctasy]

Things go with things, so you do have to wade through the inforamtion waters a little.


Ford USA had a very difficult climate releasing performance cars into the market, especially between 1987 to 1993 when cars were stillvery light. Ford didn't want another 10 pound per hp insurance industry hike like the 1971 Speed Kills mass hysteria area. Corvettes, F bodies, G bodies and GMC and S10 based trucks were heavy, so GM could play around with turbo or quad cam engines up to an over that 10 pound per hp area. The reason you never found a straight answer was due to the issues relating to dropping in the hot 5.0 and 5.8 GT40 headed engines from the planned 90's cars, which were going to be heavier, into light Mustang Foxes. Ford used all the vagaries of engineering law to cut down the rated output of those GT40 headed engines....


The GT40P head with the right matching to 5.0 HO valve springs in a propely matched GT 5.0 HO is always a 25 to 30 flywheel net hp gain. If you really have a 210 or 225 hp engine, it becomes 235 to may bee 254 hp with a good set of blue printed and matched GT40P heads. The chamber CC's matched, the pistons clearanced to suit, and everything locked in the way a good 5.0 HO should.


Ford via SVO Motorsport, supplied , eventually, about seven deadly aftermarket 303 letter cams (now known as A311, A312, E303, B303, F303, X303 and Z303 as non dealer fitted items, these are effectively Cobra Jet or SuperCobra Jet style roller cam remasters of the best hydraulic "335", Windsor and Boss 302/351 cams form the 70's. These got swapped into 5.0 HO's on a fairly regular basis, and so the GT40 and GT40P heads with these cams make easy 25 to 30 hp gains with the right other stuff. An X 303 with 1.7 rockers makes 577 thou lift, a Z 303 587 thou, so a lot has to be done to make it clear the pistons, and flow well at that lift, but with these cams, the GT40P is still a very good basic head for a scrap yard aquistition.


Just remember, the later 1996 model year to 2000 model year demise, the Explorer ran a split duration roller cam of very low lift, and short durations, F4TE-6250-BA Hydraulic Roller 256 intake, 266 exhaust, 422/448 lift profile just like the just like the lame old 351M/400 engines. It was a pure emissions cam, and you don't see any power increase with it over the 5.0 HO spec engine with E6 or E7 heads , even with its later GT40 spec lower and upper intake the Explorers had.

From 1992 to late 2002, all Aussie 5.0 and 5.6 engines engines always ran the Mustang 5.0 HO spec engine, but after 1995, it was derived from the non HO Explorer "FBT" engine. In the Fox Mustang roller cam engines, there were Piston dowgrades, two official roller cam changes, and 1993 factory derating due to ancillary drive details in SAE net hp tests....these don't reveal the true worth of the three stripe (and four stripe) heads from Explorers, but in production Aussie Falcons, you saw the things Ford USA couldn't report.

First is that the first GT40 three stripe heads made 256 hp net, not the reported 235 of the 1993 Cobra SVT. Dyno tests of stock 1993's on two continenats show 236 rwhp on some dynos, possibly as high as 298 flywheel for a fully blue printed engine. The heads were most of that, but they had to be matched with other things to give what was effectively a 33% boost on a good 225 hp hp net 5.0 HO's.

Ford Australia used the October 1988 E8ZE-6250-CA or F1ZE-6250-AA cam, a very strong 276/266 duration 444 lift cam which became a 472 lift cam with 1.7 rockers.


On your 5.0 HO's, it was the mid year 1984 E5ZE-6250-AA cam of 266/266 444 roller cam,


When the 93 Cobra came out, they used the reduced duration, higher lift F3ZE-6250-CA 1993 Thunderbird 5.0 cam, 270/270 and 479 lift with 1.7's, or 450 with 1.6's as per the 93 T bird.

It stayed with that 270/270 and 479 lift with 1.7's in the 1995 , now named the F4ZE-6250-EA

On 5.8's, they never even got to the other roller cams for the 1995 Cobra 5.8 R SVT, and it used the Windsor version of the Cobra Jet D1ZZ-6250-A and D2ZZ-6250-B cam, effectively the D2JE 6250-BA 351 W marine cam with 270/290 and 481/490 lift


Ford then played around with the US 5.0 engines in Australia, with the factory GT40P heads, but reowrked a little by CNC porting, blue printing, adding 1.7:1 rockers, better cams, headers, and , eventually, 347 stroker cranks to make a 335 hp 5.6 liter engine with a special Modular 5.4 upper intake manifold.



Proof of the part of the boost possiable with the GT40P heads for the last 1998 to 2002 cars is this list:-


5.0 liter ... 235 HP net ... 292 lb-ft ... Falcon Forte and Ghia
5.0 liter ... 268 HP net ... 310 lb-ft ... XR8, up to May 2001
5.0 liter ... 295 HP net ... 321 lb-ft ... XR8, May 2001 and later
5.6 liter ... 335 HP net ... 369 lb-ft ... T series Tickford T3 TE50/TS50 sedans and Pursuit 250 Utility pickup trucks, November 2001 or later

[erratic50]

There are guys with GT40P and 1.7:1 rockers and a free flowing intake, underdrive pulleys, and open exhaust setups running 1/4 mile numbers suggesting just shy of 350 HP. Then add a cam and welcome to the 360 ball park. By comparison About the best you can hope for with unported E7's and any sane cam is still just under 300 regardless of intake and exhaust.

so yes they are a big upgrade. But I would explore aluminum heads instead as the do even more.

[vxr500]

OK-so springs are a must, and maybe 1.7 rockers if they fit under the valve covers.

Another question, can I use the factory "powered by ford" finned valve covers on these heads?

[bwguardian]

OK-so springs are a must, and maybe 1.7 rockers if they fit under the valve covers.

Another question, can I use the factory "powered by ford" finned valve covers on these heads?

The 1.7 rockers will hit the breather baffles on the ends of the "Powered by Ford" valve covers; however, the covers will fit the heads.

[85foxbody]

OK-so springs are a must, and maybe 1.7 rockers if they fit under the valve covers.

Another question, can I use the factory "powered by ford" finned valve covers on these heads?

I had the gt40p heads ,the rocker arms i had on them were the stock rockers from my original heads with the stock valve covers no fitment issues

[Supersonic G.T.350]

Thanks for the replies. The heads would be rebuilt with new springs, but from what I'm reading, the springs are not good with the factory HO cam. I guess that includes my 84 flat tappet too.

I already have the Edelbrock intake and BBK long tubes, so I should be good there. I'm just looking for a nice 30-35 hp bump. My car runs pretty good, with good oil pressure, but it's an original 84 motor that's never been rebuilt. I did have a new double roller timing chain and oil pump/pickup put in last year. I'm hoping I don't stress the bottom end if I get these heads.

Stress the bottom end too much if you get the heads, lol! Dude, your stock 5.0 bottom end isn't as feeble as you think. My old 85 was stock as a stone with 220,000 miles on it before it ever got its first mod. I took it from that too long tubes, spring upgrade, Comp XE276HR, Weiand Xcelerator intake, 650 Speed Demon carb, etc and I twisted it 6500 countless times. It was brutal how bad I treated that little engine and it never pecked, knocked, made a single noise and didn't use much oil in 3000 mile oil changes. You'll be fine bro, enjoy your lil engine.

[xctasy]

Becuse of the 48 years of 302 development, there is nothing to getting a B 303 intensity cammed 5.0 to doing a real 325 hp with carb and intake. Basically what the best Factory 1971 330 hp 351C's did, but with 50 cubes less.



The cam just has to exceed or match the B 303 specs to get the power up. The 351 W marine cam is still an upgrade that matches the B 303 in the Hot Rod 325 hp article.

http://vb.foureyedpride.com/showthre...-Article/page2


But the heads made everything an easy over 300 hp engine. The right carb, cam and intake doesn't miss out one bit to an EFI intake, the EFI holds peak power back, and fatens up torque at the low to mid range. I wouldn't believe the marketing men, despite the brilliance of the GT40 product, its only good for 425 hp if its got nitrous somehwere, it tops out way sooner than 425, and a better 4-bbl carb system exceeds 390 hp with a 650 double pumper on a roller 5.0.

Remember, in one class of endurance racing (International Group A), just a ported stock 4-bbl and that bigger 650 DP ensured a real 390 hp net, before GT40 heads. The European rules weren't policed, the Assie and Kiwi variant s were, so there is acess to better vlaves, better cams, P to Valve cuts and radical internal mods not picked up by the scrutineers.


On EFI, its a Crap fight with the stock EFI topping out at around 325, creating a need to extra MAF calibration to get the engine up to the 371 hp the Saleen GT40's got. Its lots of work on those, but the combinations and methods are well known, and a good EFI engine should be your bench mark.


Your carb/intake manifold will be a loose torque item compared to a good EFI intake, but it will be fat and well filled out with the right work. So little needs to be done.


See http://vb.foureyedpride.com/showthre...hat-EFI-intake

GT40 heads are just wonderfull budget pieces, and the key to making them work is just being sure your cam, compression, and rockers and pushrod lengths all gell together. Ford really di there process engineering well on these iron lump heads, and the block is stout enugh for anything the street can hand out, and for endurance racing as well. Don't forget, it was rare to ever loose an engine due to block splitting in a 400, 600 or 24 hour race. It was timing chains shaking due to the combined 50 acessory drive blancers, and the 34 ounce crank, and sometimes the provisions for extra oil cooler line issues that got these engines a somewhat unpredictable reliablity result. Sometimes great, other times not so, but these were in 100 mph average races where they'd be up to 155 mph or more on straights.

Your little 5.0 HO just needs a little bit of TLC, and it should last a long time.


Quality Was Job No 1....but the engineers and Demmings QA process also worked out just how little they had to do to get them through the 300 hour Wide Open Throttle test....it may have been build down to a price, but the enginering was GOOOD!

[vxr500]

Thanks for all the help guys. I think as soon as money allows, I'm going to pull the trigger on these heads and springs.

Just a few more thoughts. I've read that my BBK long tubes will work with these heads for plug clearance. But I will probably need shorty plugs, 90 degree boot wires, or both. Is this definitely the case? And is there a custom fit set of these wires I can buy that don't require cutting? Are accell u groove the only short plugs available?

[Supersonic G.T.350]

That's pretty much my understanding as well. If you have the 1-3/4" BBK long tubes they're supposed to offer even better clearance.

[Droog]

Things go with things, so you do have to wade through the inforamtion waters a little.


Ford USA had a very difficult climate releasing performance cars into the market, especially between 1987 to 1993 when cars were stillvery light. Ford didn't want another 10 pound per hp insurance industry hike like the 1971 Speed Kills mass hysteria area. Corvettes, F bodies, G bodies and GMC and S10 based trucks were heavy, so GM could play around with turbo or quad cam engines up to an over that 10 pound per hp area. The reason you never found a straight answer was due to the issues relating to dropping in the hot 5.0 and 5.8 GT40 headed engines from the planned 90's cars, which were going to be heavier, into light Mustang Foxes. Ford used all the vagaries of engineering law to cut down the rated output of those GT40 headed engines....

There was some internal politicking involved there, as well. The GT40 stuff was originally supposed to be a step-up option available on any 5.0 Mustang; it was intended as a trump for the upcoming 350 powered F-bodies. The high muckety-mucks dropped the axe on that plan at the last minute, however. Good example of Ford's.... let's say "reluctance" to publish realistic power numbers, though. Funny how the 93 Cobra gets rated at 235 horse when the SAAC Mk1 with basically the same engine carries a 292 horsepower rating.

Ford via SVO Motorsport, supplied , eventually, about seven deadly aftermarket 303 letter cams (now known as A311, A312, E303, B303, F303, X303 and Z303 as non dealer fitted items, these are effectively Cobra Jet or SuperCobra Jet style roller cam remasters of the best hydraulic "335", Windsor and Boss 302/351 cams form the 70's. These got swapped into 5.0 HO's on a fairly regular basis, and so the GT40 and GT40P heads with these cams make easy 25 to 30 hp gains with the right other stuff. An X 303 with 1.7 rockers makes 577 thou lift, a Z 303 587 thou, so a lot has to be done to make it clear the pistons, and flow well at that lift, but with these cams, the GT40P is still a very good basic head for a scrap yard aquistition.

Certainly better cams have come and gone. I've got an old Wolverine 1190 sitting on the shelf just waiting to get stabbed into the next hot rod. But the alphabet cams were a revelation when they came out. They tend to get lost in the "new-part-of-the-week" week shuffle, but most guys don't realize how big a deal some of this stuff was to die-hard Ford guys. My grandfather had a 63 R-code Galaxie with a medium riser top end on the original short block with the old C8AX "Super Stock" cam, and that was pretty much the extent of Ford's help for the loyalists back then. Come about '85 or '86 when the Motorsport book started to fill up with goodies, it was like the heavens had opened and it was raining gumdrops and unicorn ****. I was only a kid, but we'd go to the Ford dealer and I'd paw through the Motorsport stuff like most kids did with the Sears Christmas catalog. Good times.

[bkm]

Thanks for all the help guys. I think as soon as money allows, I'm going to pull the trigger on these heads and springs.

Just a few more thoughts. I've read that my BBK long tubes will work with these heads for plug clearance. But I will probably need shorty plugs, 90 degree boot wires, or both. Is this definitely the case? And is there a custom fit set of these wires I can buy that don't require cutting? Are accell u groove the only short plugs available?

The bbk long tubes work with P heads. I ran 90 degree boots and regular length plugs. I cut down an old spark plug socket with a hex head end and used a wrench to tighten the plugs on the drivers side. Passenger side is cake.

[vxr500]

The bbk long tubes work with P heads. I ran 90 degree boots and regular length plugs. I cut down an old spark plug socket with a hex head end and used a wrench to tighten the plugs on the drivers side. Passenger side is cake.

Awesome, thanks. Which wires did you use?

[bkm]

Taylor cut to fit 8mm.

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