The cam is made more for torque than the HO cam.  The springs are fairly weak and they have the "rotator" setup on the exhaust which makes valve spring and retainer setup a little awkward.  Alex Parts has a valve spring kit that uses the stock oddball exhaust valves but there is also an option with the kit if you install standard height exhaust valves.  Most say that the stock Explorer springs are good to about 4500 RPM when mated to the less aggressive Explorer cam.  https://www.alexsparts.com/sb-ford-gt40p-drop-in-valve-springs-kit-hyd-roller-580-lift/  I would recommend installing new springs if you go to an HO cam or hotter to avoid any float.

I found a 2000 5.0 at the pick and pull for $100 but had to pull it myself - using it to mock up my drivetrain.  Only 125k miles but same deal - virtually no wear.  Apparently a few of the cylinders tend to go "oval" with age but for what you are doing, I probably wouldn't do anything more than a hone.  Might be best to have a shop that has the block plates do it to get the best possible pattern.

GPatrick wrote:

The cam is made more for torque than the HO cam.  The springs are fairly weak and they have the "rotator" setup on the exhaust which makes valve spring and retainer setup a little awkward.  Alex Parts has a valve spring kit that uses the stock oddball exhaust valves but there is also an option with the kit if you install standard height exhaust valves.  Most say that the stock Explorer springs are good to about 4500 RPM when mated to the less aggressive Explorer cam.  https://www.alexsparts.com/sb-ford-gt40p-drop-in-valve-springs-kit-hyd-roller-580-lift/  I would recommend installing new springs if you go to an HO cam or hotter to avoid any float.

I found a 2000 5.0 at the pick and pull for $100 but had to pull it myself - using it to mock up my drivetrain.  Only 125k miles but same deal - virtually no wear.  Apparently a few of the cylinders tend to go "oval" with age but for what you are doing, I probably wouldn't do anything more than a hone.  Might be best to have a shop that has the block plates do it to get the best possible pattern.

I used Alex's springs when I rebuilt my 90 5.0 with GT40 heads.....they have great customer service either on the phone or email.  Highly recommend them...

I have a 5.8 351w F150 1995 camshaft you can have if you want to pay for the shipping.  

Steve, the 5.0 I rebuilt had the E303 cam in it and I reused it.  I contacted Alex's parts, gave him the cam card info and he sent me the recommended springs for the GT40 heads......it all works well.
If you have to spring for a new E303, look at Late Model Restoration....$199 there.....plus you'll be spending your money with a Texas company!

Steve, I put a 97 GT40P in my 66 a couple years back. I did a write up of what's needed to swap one into a early Mustang. To quick answer on a few things. The Explorer cam has about 10* less intake duration then the 5.0 cam, exhaust is the same. I'm running a 91 5.0 cam. It's a great combination with the GT40P. Even tough it gives up a little low end to the Explorer cam, it still makes a ton of low end power. I don't think you'll have any issues with the 5.0 cam in the truck. I second Alex's springs, I installed his .540" springs. originally I was going to install a free E303 cam but somewhere it got wet and rusted. Not all 5.0 cams are the same. The best ones are the 85 to 89, after that they fiddled with the intake ramps, more gentle.  Even with the later 5.0 cam it still screams! If you're running a mechanical distributor, you do not need more then 30* total mechanical advance. These heads are very combustion efficient and anything more is wasted on pumping losses. I run the cheapest 87 money can buy and no matter how hard I've lugged it, it won't rattle. I was running a set of Crane Cobra 1.72 rockers for a while but went back to stock stamped rockers. The aluminum rockers are very noisy, I didn't notice any adverse effect going back to the stock 1.6 stamped, seems to run better.

Exhaust manifolds. Even with the altered pug angle you shouldn't have too many issues. Even the stock early rear exit Mustang A&C code manifolds can be made to easily work with the P heads. The K manifolds will fit perfectly but I wouldn't waste my money on them. Mustang360 did a test between the A&C, K code and try y headers on the same car on the same dyno. They found ZERO difference in power! Only the try y made more power.

So here's my build. I think you'll find a lot of useful info. I love these motors! Any questions, feel free to ask.     https://forums.vintage-mustang.com/vintage-mustang-forum/1012953-got-my-gt40p-up-running-my-66-a.html





 

Last edited by Huskinhano (9/25/2018 4:11 PM)

MS wrote:

Thanks huskinhano.
Why are the new springs required with a stock GT cam? Remember, this is a truck that won’t get revved high with an AOD.

I put the springs in because I was going to install a free E303 cam, well it cost me $14.70 for shipping. Somewhere along the line the cam got wet and a couple of the lobes had enough pitting the cam wasn't viable. But with 300K miles on a slighlty more agressive cam, I think it's a no brainer. Alex's parts are very reasonable. He's great to work with, he suggested new seals and spring shims. I got all my springs right at 1.78"
 

Huskinhano wrote:

Steve, I put a 97 GT40P in my 66 a couple years back. I did a write up of what's needed to swap one into a early Mustang. To quick answer on a few things. The Explorer cam has about 10* less intake duration then the 5.0 cam, exhaust is the same. I'm running a 91 5.0 cam. It's a great combination with the GT40P. Even tough it gives up a little low end to the Explorer cam, it still makes a ton of low end power. I don't think you'll have any issues with the 5.0 cam in the truck. I second Alex's springs, I installed his .540" springs. originally I was going to install a free E303 cam but somewhere it got wet and rusted. Not all 5.0 cams are the same. The best ones are the 85 to 89, after that they fiddled with the intake ramps, more gentle.  Even with the later 5.0 cam it still screams! If you're running a mechanical distributor, you do not need more then 30* total mechanical advance. These heads are very combustion efficient and anything more is wasted on pumping losses. I run the cheapest 87 money can buy and no matter how hard I've lugged it, it won't rattle. I was running a set of Crane Cobra 1.72 rockers for a while but went back to stock stamped rockers. The aluminum rockers are very noisy, I didn't notice any adverse effect going back to the stock 1.6 stamped, seems to run better.

Exhaust manifolds. Even with the altered pug angle you shouldn't have too many issues. Even the stock early rear exit Mustang A&C code manifolds can be made to easily work with the P heads. The K manifolds will fit perfectly but I wouldn't waste my money on them. Mustang360 did a test between the A&C, K code and try y headers on the same car on the same dyno. They found ZERO difference in power! Only the try y made more power.

So here's my build. I think you'll find a lot of useful info. I love these motors! Any questions, feel free to ask.     https://forums.vintage-mustang.com/vintage-mustang-forum/1012953-got-my-gt40p-up-running-my-66-a.html





 

   Very nice!
 

Check www.corral.com  that’s a popular late model Mustang forum with a Windsor section as well as a Windsor parts section. That’s whereI got mine from. Lots of good used parts there.

Thanks!

Let me know where to send a check.
I’ll take it!