Engine Max valve lift on " P " heads

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Oct 4, 2020
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Has anyone here had any experience with max valve lift on gt40P heads? Took these heads over to the machine shop and they will measure for me but I was wondering if anyone could learn me with there experiences with P heads.....
 
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Waste of $ time and effort for 30 HP, i.e. buy some aftermarket alum heads and get 100 HP.
Everybody isn't looking for 100hp more... Not interested in Blowing or turboing it either.. Interested in having a nice driving convertible to drive to the Keys, St. Pete, or maybe up to the Pensacola Naval Air Museum....

I am asking how large a lift cam I can safely install in my "Grocery getter" without having to cut the the valve guides to make sure the cams I am looking at will be OK without putting alot of money into this car where I don't need to put it...
I have "read" up to 600 lift with the 1.6 to 1 rocker arms? Can anyone confirm this?? Thanks
 
I'm pretty sure the heads won't necessarily be the limiting factor as far as your cam selection goes, it'll be the valve springs and piston to valve clearance. I don't know the numbers off the top of my head, but stock Explorer GT40 heads valve springs are only good to something like .400 lift at the valve. The good news is there are a few different sources that sell a kit for these heads to be able to get you into the .550 range or so. Trick Flow sells a kit, and there's a site called alexparts.com that sells different kits as well:


So if you are looking at a specific cam, select the correct springs and you should be good - just don't forget to check PtV clearance when you're putting everything back together! :)

On a side note, if you're interested in building a pretty good combo on your own, I suggest watching this video. I think he does an excellent job explaining the cam and head flow relationship.


View: https://youtu.be/JPAeepqrY-0
 
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I plan on purchasing some bee hive "drop" in springs good up to 600 lift.. My machinist seemed to be concerned about the valve guide clearance with a cam much over stock lift? He has had to machine down the valve guides on some engines ( not specifically GT40 P heads)
karthief, there is a plan here, just looking for some others experiences here with gt40 heads....
Heads are being mag'd and checked now...
 
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I never got to run the Explorer heads I had, but I don't think there's any issues with lifts in the mid .500s as that's about where I was looking to go with them. It wouldn't hurt to have them checked to make sure, but I don't think they'll have to machine the guides if that's the route you're looking to take.
 
Over .500 isn't going to gain you much. I was trying to find a flow bench video on the GT40P's but can't seem to locate it. I found one for TFS170's and going from .500 to .600 showed no gain. I can't imagine 40P's would do better.

There's a number of spring kits for .550 lift on those heads, so I believe that would be the max i would target.
 
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Over .500 isn't going to gain you much. I was trying to find a flow bench video on the GT40P's but can't seem to locate it. I found one for TFS170's and going from .500 to .600 showed no gain. I can't imagine 40P's would do better.

There's a number of spring kits for .550 lift on those heads, so I believe that would be the max i would target. I cannot find any springs for over .550.
I agree with you about the flow numbers ( my research) ..
the bee hive spring kits I am looking at are under 525 or 600...
 
I never got to run the Explorer heads I had, but I don't think there's any issues with lifts in the mid .500s as that's about where I was looking to go with them. It wouldn't hurt to have them checked to make sure, but I don't think they'll have to machine the guides if that's the route you're looking to take.
The machine shop is going to check the clearance after I buy the parts.. I didn't want to end up with a cam that did not work hence the reason for my question
 
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Actually i must amend my post. AlexParts does have .600 lift springs. It's been a while since i've had my GT40P heads so i forgot the research I did on them.


I *think* you should be good up to .600 but don't quote me on that. Let us know what the machine shop says
 
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I'm pretty sure the heads won't necessarily be the limiting factor as far as your cam selection goes, it'll be the valve springs and piston to valve clearance. I don't know the numbers off the top of my head, but stock Explorer GT40 heads valve springs are only good to something like .400 lift at the valve. The good news is there are a few different sources that sell a kit for these heads to be able to get you into the .550 range or so. Trick Flow sells a kit, and there's a site called alexparts.com that sells different kits as well:


So if you are looking at a specific cam, select the correct springs and you should be good - just don't forget to check PtV clearance when you're putting everything back together! :)

On a side note, if you're interested in building a pretty good combo on your own, I suggest watching this video. I think he does an excellent job explaining the cam and head flow relationship.


View: https://youtu.be/JPAeepqrY-0

Anybody who is thinking of a cam needs to watch this video.. Best 42 minutes explaining how to at least get you in the right direction for what info you need in making a cam selection......
Glad I did not buy the cam I was going to buy after watching this and advice from lilcbra and mustang5L5... Thanks
 
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I'm pretty sure the heads won't necessarily be the limiting factor as far as your cam selection goes, it'll be the valve springs and piston to valve clearance. I don't know the numbers off the top of my head, but stock Explorer GT40 heads valve springs are only good to something like .400 lift at the valve. The good news is there are a few different sources that sell a kit for these heads to be able to get you into the .550 range or so. Trick Flow sells a kit, and there's a site called alexparts.com that sells different kits as well:


So if you are looking at a specific cam, select the correct springs and you should be good - just don't forget to check PtV clearance when you're putting everything back together! :)

On a side note, if you're interested in building a pretty good combo on your own, I suggest watching this video. I think he does an excellent job explaining the cam and head flow relationship.


View: https://youtu.be/JPAeepqrY-0

I like your style. You may need a few motors to play with. The factory cams have pressed on lobes. Clay the motor. Do it yourself. Not a ton of billet cams out there to choose from anyway. Used to have a guy regrinding camshaft lobe profiles in the Salt Lake City market who was pretty good at it. They had some success
 
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Has anyone here had any experience with max valve lift on gt40P heads? Took these heads over to the machine shop and they will measure for me but I was wondering if anyone could learn me with there experiences with P heads.....
I'm getting ready to install some GT-40Ps on a fresh shortblock and will give you my .02 worth. I did some accepted home porting mods to my heads and used Alex's beehive spring kit: https://www.alexsparts.com/new-sb-f...t-max-output-525-lift-vsk7eb49-mc-hyd-roller/
My cam lift is ~.500, which is why I used the .525 max lift set. This kit uses special retainers/locks for the intake and exhaust. You won't need to cut your valve guides for this kit. Even with the port work, these heads aren't going to benefit much above .500 lift. I got an explorer longblock in excellent condition for $350, so why not use the GT-40Ps? I'm replacing the hypereutectic pistons with factory forged units in case I want nitrous later. This along with my other mods should get me ~300 flywheel horsepower. Plenty for what I need.
 
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