Gt-40 heads
- Thread starter jimbo01
- Start date
benT
Active Member
These are decent stock heads, but might require different headers for clearance due to to the spark plug being relocated from the earlier style heads. I've never tried them personally. I ended up buying assembled World Windsor Jr. heads for my 302 in my '27. There are fairly inexpensive as far as heads go and made decent power.
Screaming Metal
Active Member
Good heads, make good power just have to set them up accordingly. There are a few heads that bolt onto the Ford Small Blocks and you can get a noticeable gain. BUT, usually those are like a mild 4bbl motor, you can bolt them on, and expect a 12 to 15 Horse increase. Sometimes a little less or a little more, just depends on your setup. They breathe well.
Back in the day, you could actually go to the Ford Parts Dealer and order a conversion to bolt on a good set of heads for a 20 to 30 Horse jump. They were just like the Chevy parts dealer, you could order all kinds of good speed stuff thru them. You still can a little....but not much.
If you have a good performance motor, a mild cam, good ignition and headers, if your running stock heads and bolt on the GT 40's, you will feel it. Just like bolting on a good set of W32 heads....
The Numbers you used to get on the dyno back 15 years ago don't apply today. Todays pump gas formulas have changed, their burn characteristics have been altered. This messes with the tuning, and the compression and your ignition. If you have a classic Muscle Car, you'll notice you car running better with more timing. This is because of the burn time differential.
Because of the fuels today, when we run in a motor on the dyno, we include barometric pressure, temp, motor coolant temp, F/A ratio in each headpipe, F/A in the collector, overall bank temp in the collector, valve lash, timing, cylinder pressure....and a lot more info, that way the installer can duplicate the HP numbers closely.
Just don't expect the head swap to perform miracles. If you have a bone stock 1969/70 302 with a cast iron 4bbl, and log exhaust and you bolt on the GT40's....don't expect much. And this is a motor is great shape, ie, just been freshened up.
If you have a decent intake, and have headers (which T Doesn't?), you'll feel it. Add a little cam, rejet the carb and set your ign. timing curv. correctly, it'll open your eyes....
Back in the day, you could actually go to the Ford Parts Dealer and order a conversion to bolt on a good set of heads for a 20 to 30 Horse jump. They were just like the Chevy parts dealer, you could order all kinds of good speed stuff thru them. You still can a little....but not much.
If you have a good performance motor, a mild cam, good ignition and headers, if your running stock heads and bolt on the GT 40's, you will feel it. Just like bolting on a good set of W32 heads....
The Numbers you used to get on the dyno back 15 years ago don't apply today. Todays pump gas formulas have changed, their burn characteristics have been altered. This messes with the tuning, and the compression and your ignition. If you have a classic Muscle Car, you'll notice you car running better with more timing. This is because of the burn time differential.
Because of the fuels today, when we run in a motor on the dyno, we include barometric pressure, temp, motor coolant temp, F/A ratio in each headpipe, F/A in the collector, overall bank temp in the collector, valve lash, timing, cylinder pressure....and a lot more info, that way the installer can duplicate the HP numbers closely.
Just don't expect the head swap to perform miracles. If you have a bone stock 1969/70 302 with a cast iron 4bbl, and log exhaust and you bolt on the GT40's....don't expect much. And this is a motor is great shape, ie, just been freshened up.
If you have a decent intake, and have headers (which T Doesn't?), you'll feel it. Add a little cam, rejet the carb and set your ign. timing curv. correctly, it'll open your eyes....
Screaming Metal
Active Member
Depends, as Ben stated, theres alot of alum. heads out there that give you a decent increase, their prices are becoming affordable for the everyday rodder. If you look around, you can find a complete set for $450-$550. Pay attention to your CR and your timing. Also, don't forget that alum heads will act like a heat sink also. And some motors will make more horses with a set of cast heads....
Screaming Metal
Active Member
I you have a 600 cfm vac secondary carb, a 1500-6000rpm hi-rise dual-plane intake, something like a hi-energy cam, with of course your headers, expect a smile.
Also, let me add, that the length of the individual pipes on cheap T headers are not conducive for max power. The primary tubes are just too long, and with the (2) 90-degree bends. Don't get me wrong, they are alot better than logs....and look alot better. If you get the big tube headers that are equal length, (staggered up in the collector) they are tuned for max power, but they are not cheap.
Small primary pipes make for good low end, big ones male more top end. But, If you have long primarys, and you go big, you can still have great low end, the extra length is causing extra backpressure.
Also, let me add, that the length of the individual pipes on cheap T headers are not conducive for max power. The primary tubes are just too long, and with the (2) 90-degree bends. Don't get me wrong, they are alot better than logs....and look alot better. If you get the big tube headers that are equal length, (staggered up in the collector) they are tuned for max power, but they are not cheap.
Small primary pipes make for good low end, big ones male more top end. But, If you have long primarys, and you go big, you can still have great low end, the extra length is causing extra backpressure.
jimbo01
Member
I was wondering about the header issues as well. I've been reading different Mustang forums and seen where this had been mentioned and the information is all several years old. I wondered if the headers their using are along the line of block huggers vs what were using spaghetti style. I have to believe that our headers offer more clearance unless I'm missing something.
My intentions at this time for the 1967 302 are running duel quads, mild cam & flame thrower ignition & module to replace the point set up that it has at this time. My idea is to let this thing breath and achieve a different sound through the exhaust and only I'm looking for low end. The heads that are on now are just the regular 2V and I'm thinking this is an area for some improvement.
I'm just thinking out loud with this thread and bouncing ideas off you fellas. I'm also not sure if a set of GT-40 heads can be had for the price & direction of what Ben went with.
benT
Active Member
If you do go with the Windsor Jr., definitely price them out at several places. I've found that Northern Auto in Iowa has them for less than Summit. I called up Summit, had them price match and ship for only $8. Northern has them now for about $565/head assembled.
BTW, my setup is similar to what you are planning: .30 302, flat top pistons, Comp Cam, Windsor Jr. heads, offy dual quad intake, and edelbrock 500s
BTW, my setup is similar to what you are planning: .30 302, flat top pistons, Comp Cam, Windsor Jr. heads, offy dual quad intake, and edelbrock 500s
fordsbyjay
Active Member
You get what you pay for. They are cheap and they make minor improvement over original heads. They are on plenty of Explorers and can be had real cheap. Depending on funds I would use them only as a last resort.
Rogers23T
Member
I think the reason the GT-40 heads were brought up was probably due to a cost factor. The "X" heads being aluminum are a great way to go since they are comparable to an AFR 165, & out flow the "P". And let me tell you if you have never ported heads... Its WAY easier to port aluminum then cast iron. Plus they are a lot better looking polished then painted heads. The website I found flow chart on was carbdford dot com, not going to put the hyperlink in because I know the rules on the board. I only site it so you can see the flow on the heads you're interested in.
Screaming Metal
Active Member
You might also want to call RHS (Racing Head Service) in Tn. They usually have a good price on heads and parts....
Yep , I definetly no engine expert , but my understanding from when I worked building Cobra replicas, was that the GT40 heads were one of the better Ford heads, but by no means in the league of Edelbrocks, Dart or AFR etc. Sort of like comparing the aluminum Corvette heads to any of the aftermarket heads. I'd spend a few hundred bucks more and get something considerably better than the GT40 heads, unless you just want the look of aluminum heads on your ride.
jimbo01
Member
I know there were 3 different heads made. GT-40-X are the aluminum, GT-40-P are cast iron and have the relocated plug location & the GT-40 that have the traditional plug location. I figured the aluminum would be the hardest to find followed by the GT-40. If you do a search on the web for any of these heads you'll come across Ford sites with people claiming great results. I believe I read one site were the claim was a 50 HP gain from this simple bolt on. I thought to myself "50 HP of neck snapping power". I knew the numbers had been embellished some, maybe as much as 40 HP. That's when I turned to you guys for your input on these heads. I still believe Ben had the right idea and buy a nice set of aftermarket heads that are ready to go.
Screaming Metal
Active Member
Well Jimbo, your right.That is based on a stock motor. If you have a 40-50 horse jump by simply bolting on heads, theres something wrong big time! hahaha....
That number is arrived by those heads bolted on a stock motor, WITH a good alum. intake, a decent cam, rejetted carb, and headers.
The same thing with blowers. You have to have the carbs and the exhaust to handle it.
I used to look in the books and read, a stock bla bla bla 350 put out 175 horses in such and such a car. The old chilton repair manuals used to tell you all this.... The BIG THICK Bibles, I called them.
Then, in Popular HotRodding, they would show a buildup of a 350 that would get you 500 horses.
All your parts have to match!
If you look at the parts numbers, theres more than just 1 or 2 parts difference between a 175 horse low compression 350 in the stationwagons and the 350 horse 350 that chevy offered in the Vettes, Cameros, Chevelles. Its all those little parts add up to the whole....
That number is arrived by those heads bolted on a stock motor, WITH a good alum. intake, a decent cam, rejetted carb, and headers.
The same thing with blowers. You have to have the carbs and the exhaust to handle it.
I used to look in the books and read, a stock bla bla bla 350 put out 175 horses in such and such a car. The old chilton repair manuals used to tell you all this.... The BIG THICK Bibles, I called them.
Then, in Popular HotRodding, they would show a buildup of a 350 that would get you 500 horses.
All your parts have to match!
If you look at the parts numbers, theres more than just 1 or 2 parts difference between a 175 horse low compression 350 in the stationwagons and the 350 horse 350 that chevy offered in the Vettes, Cameros, Chevelles. Its all those little parts add up to the whole....
fordsbyjay
Active Member
The GT40 heads came out on the 93 Mustang Cobra. They were rated at 235 hspr vs the standard 5.0l @ 220 hspr. This was also with the better GT40 intake manifold, larger throttle body and bigger injectors so I don't see them bringing very much gain over a stock 5.0l head. The P head came out in the Explorer around 97/98 and was supposed to flow slightly better than the gt40 head and bump compression a touch yielding 215 hspr. The 94-95 Mustang Cobra was rated at 240 hspr with GT 40 heads. I'm sure once you put on a decent intake, cam and headers it would help get you up closer to 300.
Like everything it depends on your budget and goals just don't go in expecting a lot or you will be disappointed.
Like everything it depends on your budget and goals just don't go in expecting a lot or you will be disappointed.
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