GT40P head conversion

heathen · Oct 14, 2004

I've just converted my 89 GT from the E7TE to the GT40P heads. On the back of the E7TE heads, there are holes for the emissions pipe that connects to the back of each head. The GT40P heads don't have these holes. How do I deal with the pipe since the GT40P heads don't accomodate it? If I just disgard it, how do I deal with the emissions plumbing caused by its absence?
Thanks,
Les

Ray@VSK · Oct 14, 2004

Wow, my Gt-40 Aluminums had em

RYC CUKR · Oct 14, 2004

I removed the crossover pipe and all of the thermactor equipment right down to the h pipe. Then I plugged the port on the h pipe and was done with it. If you do this then you can remove the rest of you smog pump and accessories, unless you live in an area where they do emissions testing.

85_SS_302_Coupe · Oct 14, 2004

Hmm....me and a buddy actually just did this a couple days ago, and his had'em, but his actually came off of an Explorer so that could be a difference. I'd say just cap the holes on each end of the tubes off somehow and just run it like that untill you have to echeck.....I think you might even be able to scrape by on echeck with GT40s unless you're cammed out and have a bunch of other mods with'em. Otherwise, you're headswopping when it comes time for echeck.

heathen · Oct 15, 2004

85_SS_302_Coupe said:
Hmm....me and a buddy actually just did this a couple days ago, and his had'em, but his actually came off of an Explorer so that could be a difference. I'd say just cap the holes on each end of the tubes off somehow and just run it like that untill you have to echeck.....I think you might even be able to scrape by on echeck with GT40s unless you're cammed out and have a bunch of other mods with'em. Otherwise, you're headswopping when it comes time for echeck.

I'm pretty sure these heads were off an Explorer. What I forgot was there may be a difference between California and other state's emissions. I went with an E303 cam, which is supposed to pass emissions. I'm not really worried about removing the smog pump and other stuff, but I am worried about all the vacuum lines, and what might be affected if they're not connected properly.

Michael Yount · Oct 15, 2004

85SS - if his P heads had them, they were drilled/tapped by someone; the P's don't come that way from the factory. You sure your buddy's didn't come off of the 95-early 97 Explorers - those were GT40's (not GT40P's) and they came with the crossover and air injection.

Michael Yount · Oct 15, 2004

Heathen - where are you located?

The air injection system hooks up to both the back of the heads and the catalytic converter. When the engine is cold, the air injection is diverted to the heads - this aids with catalytic light-off. Once the engine warms up a bit, the air injection is routed to the converter. So even with the cross over removed, as long as a car is tested when it's good and warmed up, the lack of crossover piping shouldn't keep one from passing the sniffer. However, a sharp eyed inspector might fail it on the visual alone - the folks that know what they're doing are looking for that air injection piping to be there.

NosPony · Oct 15, 2004

Just plug the holes on the heads with bolts.

85_SS_302_Coupe · Oct 15, 2004

Michael Yount said:
85SS - if his P heads had them, they were drilled/tapped by someone; the P's don't come that way from the factory. You sure your buddy's didn't come off of the 95-early 97 Explorers - those were GT40's (not GT40P's) and they came with the crossover and air injection.

No they're definately factory drilled so i'd say they're not Ps...that's an interesting tip though

Hey since we're on this topic, do you need specific headers for both the Ps and the non-P GT40s? The heads my buddy got had MAC headers with'em....just curious if they were specific for them. I've heard that the Ps have to be specific headers, but not the others?

heathen · Oct 15, 2004

I'm located in Northern California. My heads are definately P's, says so right on them, along with the 4 bars on the ends. P's have different spark plug holes, so they require specific headers, which I purchased from Central Coast Mustang, $209. Even though they're specific to P's, they'll work on any 5.0 head. I really appreciate all the feedback.

Michael Yount · Oct 15, 2004

The headers for the P's will work on any head; the headers for the non-P's will sometimes work on the P heads. The issue is getting spark plug boots that work, and being able to get a spark plug wrench on the plug to get it out with the header on. Be sure you check - a non-P header will bolt right up and look fine - only to discover a year later you can't get your plugs out without removing the header. Some have said they've found shorter plugs that will solve the problem allowing any header to be used with the P head.

85SS - The GT40 head has spark plugs oriented just like the rest of the heads for the engine - only the P is different.

85_SS_302_Coupe · Oct 15, 2004

Michael Yount said:
The headers for the P's will work on any head; the headers for the non-P's will sometimes work on the P heads. The issue is getting spark plug boots that work, and being able to get a spark plug wrench on the plug to get it out with the header on. Be sure you check - a non-P header will bolt right up and look fine - only to discover a year later you can't get your plugs out without removing the header. Some have said they've found shorter plugs that will solve the problem allowing any header to be used with the P head.

85SS - The GT40 head has spark plugs oriented just like the rest of the heads for the engine - only the P is different.

Once again Mike....you are the knowledge man.

Michael Yount · Oct 15, 2004

...until I learn that I was wrong....

jwzg · Oct 15, 2004

If I was home, I'd send you a picture. Since the P heads burn cleaner than previous heads, I had no problem with them not being drilled. Since I'm trying to keep my car stock-looking as possible, I simply removed the diverter valve next to the passenger side header and ran the smog pump directly to the cats. You can use the existing hoses and just use a plastic coupling for heater hoses to join the sections hose from the h-pipe and your smog pump together. Plug the vaccum line and you'll have a simple, clean modification that won't raise eyebrows with inspectors.

Use the FRPP headers as they are quality parts and come with necessary installation hardware. As for plugs and wires, I simply used the Motorcraft, platinum plugs that came in the Explorers for that year head and stock Motorcraft plug wires. You may have to rotate the boot a hair on a couple of the driver side plugs, but as long as you use the plastic routers on the valve-cover bolts, you'll be fine.

heathen · Oct 17, 2004

All very good advice. JWZG's makes lots of sense, still utilizing the smog pump and hooking directly to the cats, leaving the rear emission pipe off with the P heads. Should still pass smog with sniffer and visual. Right now though, I think I'll just leave it all off and get a shorter serpentine belt. vrrrrroooooooommmmm!

Michael Yount · Oct 17, 2004

Heathen - keep in mind, the smog pumps have a tendancy to 'lock up' if they're not used. There's little downside (performance-wise) to having it hooked up; if you short-belt it now and have to hook it back up a year from now to pass emissions, you may find it doesn't work then.

jwzg · Oct 18, 2004

Michael Yount said:
Heathen - keep in mind, the smog pumps have a tendancy to 'lock up' if they're not used. There's little downside (performance-wise) to having it hooked up; if you short-belt it now and have to hook it back up a year from now to pass emissions, you may find it doesn't work then.

Yup, mine locked up just sitting in the garage while off the car. Doesn't take long if they aren't used. It only takes 1/2 hp at engine speed to drive. Hell, I thought about using it as a supercharger

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