Have stock heads cleaned/rebuilt or buy GT40?

94GTMustang5.0

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May 29, 2009
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Okay, heres the deal. I'm still deciding on how I want to do this.

I recently tore down the motor of my 89 LX to get to the headgaskets (which i thought were blown, turns out the previous owner decided to put the motor back together without the dowel pins, and the head gaskets didnt set right and were leaking combustion gasses into the cooling system.) And I have been calling machine shops around here, the most noteworthy one being Clearwater Cylinder heads.

Most shops want $200-250 to clean the E7s, check for cracks and rebuild them. They all have told me that because these heads are iron, they need to fully disassemble and rebuild them to check and clean them properly.

Should I throw down the money on these heads, or should I go to ebay and spend the extra money on the GT40 heads? its $600 for a set of GT40s, and they are already cleaned and checked and ready to bolt on.

Do you guys think the GT40's are worth it? How much power could i gain?
Do they require any kind of special modification to bolt up to my motor?
 
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Mustang5L5

Put lubricant all over the balls
Mod Dude
Feb 18, 2001
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Gt40s can be had for 200-250 these days. So $400 to check and clean the gt40s vs 200 for the e7s?

Most guys here just upgrade the springs (especially if 40ps) and just slap them on
 

stykthyn

I want to measure mine. It doesn't look that tall.
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Jul 6, 2006
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I pulled a set of gt40 heads along with the intake for 200. Another 250 to have them cleaned gone over and upgraded springs installed. Sold the old heads and intake for 100. So for 350 roughly I had a new top end. I would definitely look for a set of gt40 heads over cleaning the stockers. Be sure to upgrade your intake if you can to get the most bang from the new heads.
 

94GTMustang5.0

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May 29, 2009
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Where could I get GT40's for 200 bucks? I know the yards here have a ton of explorers, but most of them have been ripped up and are almost completely gutted.

I would like the performance boost of the GT40s, but do they require special gaskets or bolts? any modification?
 

Mustang5L5

Put lubricant all over the balls
Mod Dude
Feb 18, 2001
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Direct bolt on swap with e7s

Check the classifieds and junkyards. With the amount of explorers flooding the yards these days, they are plentiful

I got my gt-40p heads for $200

Gt40 heads are direct bolt on.....nothing special needed but I would swap the springs out
 

robo

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Jan 2, 2004
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also, consider this, any 200 dollar junk yard sourced heads should be considered "cores" and should be completely gone through before you waste time and money installing them only to find out they are not flat, need a valve job, have bad seals, the guides are worn etc....
 

stykthyn

I want to measure mine. It doesn't look that tall.
10 Year Member
Jul 6, 2006
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Considering a shop will have to put new springs on its not a bad idea to have them give the heads a check while they are in there. New retainers, seals, and freeze plugs are all standard items to be replaced.
 

f8tlfiveo

My wife likes my spool and blow-off valve.
Aug 8, 2007
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Gt40p heads from Odessa cylinder head.. Got them on eBay shipped to my door for 371$.. Rebuilt with new valves..they didnt have a core charge on e bay either..
 

94GTMustang5.0

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May 29, 2009
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I have BBK equal length shorties, and they are pretty bulky and it appears it would be a pain with the "P" heads.

I remember someone saying they cut or modified a spark plug socket and used a wrench on it to install plugs without changing headers, does anyone know who that was or do they have any info on that?
 

94GTMustang5.0

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May 29, 2009
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also, what kind of increase in power will i see with GT40 heads vs the GT40P? im just putting my stock intakes back on i dont have the money for the GT40 intakes
 

stykthyn

I want to measure mine. It doesn't look that tall.
10 Year Member
Jul 6, 2006
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Both heads are within a few hp of each other. I prefer gt40s as you don't need special headers.
 

ID89GT

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May 26, 2008
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There is a guy selling GT40 heads locally here for 350 bucks. I would check locally online on craigslist or something, they are pretty easy to find.
 

rd

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I have the GT40's and they are a worthwhile upgrade over stock. Did the same math, cost to clean and redo the valves vs the upgrade, so I got GT40's from a guy who never installed them. Other set was from a Lightning and I did upgrade to some Comp Springs.