GT40P heads, replace the springs?

mr.n · Nov 5, 2008

Are you guys replacing the springs on your junkyard upgraded gt40p heads?
I'm looking at running a set as is, with new seats.
Not sure if the trail riding RPM's would need new springs.

Other than new plugs, headers and gaskets... any other basic mods needed?

green77bronco · Nov 5, 2008

I've read from previous post that the P's aren't a good choice for EB because of Header placement. I'm sure someone on this list will chime in and give more details.

DirtDonk · Nov 5, 2008

Don't know about the springs mr.n. I've got a set with stock springs and was thinking I'd need to change them out, depending on which cam I go with. If you stick with any kind of stock cam, you're probably fine with the stock Explorer springs for normal rpm ranges.
Other than the age and condition of the springs, the choice of cam is probably the main factor.

Paul

Hal9000 · Nov 6, 2008

Basic rule of thumb; ALWAYS replace springs if you're changing cams. Over time springs will take a set to a specific amount of lift and they will fatigue preferentially. If you change the amount of lift or duration, you can run into problems with springs spontaneously breaking. The worst example I saw was a 4 cyl engine that broke 5 of 8 springs within 20 miles of having a new cam installed.

broncnaz · Nov 6, 2008

I dont think the springs have to be replaced but they should be checked to ensure they are compatible with your cam the P heads will have springs designed to work with roller cams and may have higher seat pressures than a standard flat tappet cam needs so they may cause problems. P heads are not the greatest for bronco use but I guess if you have them then they are slightly better to use than stock heads. It would probably be a very good idea to put on new springs matched to your cam irregaurdless.

mr.n · Nov 6, 2008

That's the kicker... The Stock Mustang 5.0 cam has more lift than the stock explorer.

I've read about Mustang guys that float the valves at 5,000 rpms.
Mine doesn't see that high often, but every now an again.

I'm leaning towards trying them as it, can always replace them while the are on the motor.

Any thought to porting an explore lower intake?

broncnaz · Nov 6, 2008

Since your using a roller cam than they shouldnt be a problem although 5000 rpm is kinda low. I'd still change the springs. As you've kinda pointed out your planning on lower RPM's so I dont really think porting the lower will help any but I would port match the lower with the heads and the upper.

mr.n · Nov 7, 2008

broncnaz said:
Since your using a roller cam than they shouldnt be a problem although 5000 rpm is kinda low. I'd still change the springs. As you've kinda pointed out your planning on lower RPM's so I dont really think porting the lower will help any but I would port match the lower with the heads and the upper.

Plan on gasket matching, easy enough to do.

What about a 1" space between the upper and lower?
- rumors are more toque, but I can't image much. I've the space

broncnaz · Nov 10, 2008

Worth a shot might there fairly cheap not be noticeable but it will isolate and keep the upper cooler.

GT40P heads, replace the springs?

mr.n

Sr. Member

green77bronco

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DirtDonk

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Hal9000

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broncnaz

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mr.n

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broncnaz

Bronco Guru

mr.n

Sr. Member

broncnaz

Bronco Guru

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