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Hello everyone,
I just brought home a complete engine from a 2000 Ford Exploder! The junkyard was having a sale so it was really cheap.

My original intention was to put the heads on my 1970 Mustang's original 302 (along with a cam swap), but now I'm wondering if I should cam the Explorer engine and use it instead. I am new at all of this and have a few questions:

Which combination would result in higher compression: GT40P heads on my flat tappet 302, or on the Explorer roller cam block?

How do I go about figuring out what length pushrods I need (assuming I stick to the stock Explorer rockers)? If I use the complete explorer engine I can obviously just reuse them unless I deck the heads, in which case I would need to get ones that are shorter by however much I had shaved off the heads (correct?)
What about the gt40p heads on my original block? How do I know what to use then?

How much of a benefit does the roller camshaft design have?


The sentimental idiot in me wants to keep my car's original block, but being rational about it, I don't want to leave significant hp or fuel economy on the table.

Thanks in advance!
 

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By all means just throw that whole GT40P in! I'm running one in my 66. The stock cam isn't to bad but the Mustang 5.0 cam works very, very well in this motor. It's a far more effective cam in the GT40P then the old Mustang 5.0 simply do to the superior GT40P heads. Smooth idle, very broad power band that pulls to 6K very quickly. Replace the stock valve springs with a upgraded set. I was going to put a free E303 cam that someone gave me. Unfortunately it got wet at some point which is why I put a stock Mustang cam. I'm glad it worked out this way. The stock Mustang cam is staying. What is nice about the P head, it's very combustion efficient and needs only 30* total mechanical timing

Anyway, here's my swap. https://forums.vintage-mustang.com/vintage-mustang-forum/1012953-got-my-gt40p-up-running-my-66-a.html
 

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Pop that whole sucker in, with your original 302's front cover, an applicable fuel pump eccentric, plug the dipstick hole in the block with a 3/8 metal cap and, if you have a manual transmission you'll need a clutch pivot ball adapter as there's no boss on the Exploder block.

To address your questions, the GT-40P heads have between 60-63cc chambers (most are in the 60.6cc range). The '70 302 heads had a 63cc chamber so you'll gain a bit of compression using the heads on your '70 block, but not as much as using the entire 5.0 due to piston differences.

The GT-40P heads would probably be okay on your '70 block, as-is, since the valve springs are THAT much stiffer than stock flat tappet springs. As far as pushrods the only way to be safe is with an adjustable checking pushrod... they're not that expensive and you can also make one up with a couple scrap pushrods and some threaded stock.

What advantages does the roller cam have over the flat tappet? Better ramp profiles, lots easier break-in routine, easy cam changes without replacing lifters, etc. FWIW, the stock Explorer cam, F4TE-6250-BA is a VERY good low-end torque and throttle response piece. It's pretty much all done above 4,500 rpm for power production though. If you don't do a lot of high rpm use (and who WOULD if you don't have to?) then you'll find it great for street use and fuel mileage. A good alternative is the M-6250-B303 "B" cam or even the stock Mustang 5.0"HO" cam for a little bit more rpm.
 

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i agree with the others, just use the entire explorer motor in your stang.
 

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"All in"
 
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