GT40P heads vs Thermactor EGR bidnez

[Str8sixfan]

I'm prepping to install GT40P heads, but I'm kind of at a loss for what steps I need to take to make them work with the rest of my emissions BS on my 1978 Fairmont. As I understand it the EGR were handled externally to the heads on the GT40Ps. I really want the engine bay to look as stock as possible. I don't mind disabling some smog equipment if it makes the combo work better.

Seemed like at one point I saw maybe needing to plug something, or maybe it's tap something into the front of the GT40Ps. Again, I did research long ago, but I can't really figure out where to retrace my steps.

Just trying to put together a plan of action/execution moving forward.

[bwguardian]

The GT40p heads do not have internal thermactor passages because they are that efficient. So the external metal air hoses that go to the back of your stock heads won't have anywhere to go. I think the regular GT40 heads have the internal thermactor passages. Both heads flow about the same but I would still grind out the thermactor hump in the GT40 units...

[gmatt]

Grant, check the bolt holes on the ends of the heads. The ones above the casting plugs. If they are open it'll be obvious and will probably need to be plugged. If they are open, they should already be threaded. Your heads being fresh shouldn't need thread chasing. I think your 302 uses a plate under the carburetor for egr, so you wouldn't need the access on the end of the head(if it has it). I have a set of GT40s on my shelf that don't have this opening, but Ford used a lot of different egr systems, that make it worth checking.

[Str8sixfan]

Gary, I may have to call you. I think I understand what you're saying, but thinking isn't knowing. Would you be open to that?

[gmatt]

Gary, I may have to call you. I think I understand what you're saying, but thinking isn't knowing. Would you be open to that?

sure, I'll message you

[ZephyrEFI]

Thermactor/AIR is the one thing I sh**canned on my engine. If you take it off, no one will notice or care unless you're in a strict emissions testing state.

[Str8sixfan]

Thermactor/AIR is the one thing I sh**canned on my engine. If you take it off, no one will notice or care unless you're in a strict emissions testing state.

My biggest fear was that it would be affecting some other smog piece down stream. However it sounds like this can be eliminated (pun intended) in a vacuum. So perfect, I can retain the majority of the other stuff and it will function as is without the Thermactor hooked up.

[ZephyrEFI]

Yeah, since the P heads don't have ports for it anyway. BUT, you may want to rethink your H-pipe choice since those cats expect to see AIR coming in. At least that's the rumor. I ran mine like that for a while.

[Str8sixfan]

Yeah, since the P heads don't have ports for it anyway. BUT, you may want to rethink your H-pipe choice since those cats expect to see AIR coming in. At least that's the rumor. I ran mine like that for a while.

I'm thinking I can come up with a solution there. I may be deleting for an option too.

[zak]

Starting to look into the above as I hope to swap a 19 K mile GT40P engine into my LTD LX over the winter. Can recall some shops gun barrel drilling GT40P heads to enable Thermactor air - you can drill into the bumps in the exhaust ports and the passage was cast in, if I am recalling correctly.

Why bother? Well I have a brand new 4 converter 86-93 OEM H-pipe waiting to go in. That Thermactor air is used for the forward "light off" cats and if its not there it is possible for them to coke up. Asked a local exhaust guy to modify the H-pipe to eliminate the forward cats and he won't touch it.

Anyone else recall modifying these heads for Thermactor air?

[FoxChassis]

EGR is not Thermactor. Two different systems. Some of the early P heads still had an EGR hole. The later ones did not. None of the P heads had Thermactor ports.

[xctasy]

1. EGR is the under carb addition of inert exhaust gas via the exhaust cross over passage in the OHV V8 or V6 engines. It started quite late, 1973.

2. Thermactor Upstream AIR is Air Injection Reaction via a 31 pound per hour air pump.

Thermactor was a Ford thing from July 1966 289 engines till OBDII in 1996 model year. A few years of the 1996 and early 1997 Explorers had the GT40 three eyebrows which had drillings, but no final access threadings, so not all GT40 heads have the passanger and driver side ports threaded.

The GT40P's are generally not Thermactor capable. Unless you riffle drill them to suit. 22 inch long boring toll required, although a 5 inch drill can make any GT40P compliant to the letter of the law. .

You can add thermactor ports to anything if you want to. Even an alloy plated high ported 3514V Cleveland with the Bob Glidden mod. Its all about if its easy to do.

[xctasy]

grabbergreen84's DRILLING GT40P HEADS FOR THERMACTOR:

Edit 7/21/17: Stupid botophucket!
Here are pics which were luckily still in my computer:








Well, I don't yet know whether or not I ruined a perfectly good pair of $40 junkyard GT40P cylinder heads, but I did drill a Thermactor passage back to the rearmost exhaust port (cyls. 4 & 8 ) on each of them, drilled connecting passages from the roofs of the ports, and drilled and tapped for the bolts which secure the Thermactor crossover tube to the backs of the heads. I'm pretty sure I didn't hit any water or air/fuel, but I guess I'll find out for sure, once I install them. I've got springs from Alex's Parts ordered, and plan to put these heads on my car this summer.
What I'm trying to avoid here, are the error codes 44 and 94, which would occur without this Thermactor mod. They say that those codes won't hurt your performance, but I don't want them there anyway. These passages are for "upstream" air, and the Oxygen sensors will tell the computer if the upstream air isn't there when it should be.

So I brought the heads, lower intake manifold, some fasteners, and an 8 amp corded DeWalt drill out to the garage, and made shavings.



The main Thermactor passage goes through this hole and all the way out the other side, on all Windsor heads which the factory put in Fox bodied vehicles. I don't have access to the kind of tooling which Ford used to do this, so I drilled only to the rearmost exhaust port on each head. (Actually above it.) Doing it this quarter assed way, I'll avoid having to tap a thread for the proper plug at the fronts of the heads.

For what will be the driver's side head you will need a fairly long drill bit, as it's over 4 inches to the center of the #8 exhaust port. The one I initially selected was long enough but stopped cutting, short of the port. I then tried a narrower (and shorter) bit, and was able to get close enough. I ended up drilling the segment from the port passage at an angle, from the upper rear corner of the port, in order to meet the barely-deep-enough main passage. So if you're looking at the side of the head, the passage would be pointing to 2:00, as it goes upward and rearward. The passenger side port passage was easily drilled straight up, at 12:00.
This is why my main passage holes are two different sizes.

On the passenger side head, it's less than three inches to the center of the #4 rear port, so you'll probably already have a drill bit long enough to do the job.




I then drilled through the roof of the exhaust port, and into the passage I'd just drilled. I left the heads standing on end for this, and knew that I'd reached the right place when a bunch of spray lube and WD-40 and metal shavings came out...



I used the same bit for both legs of the passage on the passenger side head, but did not make note of the size. I also eye-balled my angle from the ports into the main passages, and as it seems thus far, was successful.

I then bolted the heads to the lower intake manifold, so I could mock up locations for the holes for the crossover tube's mounting bolts:



The heads and intake will stand up fairly level, with a block of wood under the driver's side front of the "assembly."
I held the tube in place, and marked the hole locations, and drilled them to a depth which I'd eyeballed. I was lucky, and got deep enough on both heads.

I ran a 5/16ths" - 18 - H3 - 4F taper tap into the holes, and ended up wishing I'd had a non-tapered tap as well, but an extra bolt of the proper size made it good enough to thread the proper bolts deep enough to secure the tube tightly to both heads. I'd bought the taper variety, because I also eyeballed the drill bit which I used to drill the bolt holes. I knew it was at least narrow enough...


That looks like a crack between the new bolt hole and the freeze plug, but doesn't appear on the head as I look at it now. It's most likely the product of a crappy cell phone camera, and the filth and crud on the head.

Now I just need to disassemble and clean them, and install new seals and the valve springs, and they will be ready to bolt onto my car. I sure hope it all works right.

[xctasy]

http://vb.foureyedpride.com/showthre...e-EGR-Passages!

Some GT40P Heads Have EGR Passages!

Hey, look! GT40P heads have EGR passages!



I know we'd already established this in terms of my car, but when I was trying to research this, I could find exactly ZERO pictures of P heads from this perspective. So, here's one now!

[xctasy]

Thermactor AIR is not Thermactor EGR. Its often called the wrong thing.

Cross over Exhaust ports are the central part between middle cylinders, and it can feed the inert gas to the EGR valve under a carb.

See this link. Maybee itll show the differences. The Themactor AIR cross overs are the 1978 to 1993 Fox body and downgraded 351 Windsor link tubes.

https://external-syd2-1.xx.fbcdn.net...B6P3gqHPi95YBK

"https://external-syd2-1.xx.fbcdn.net/safe_image.php?d=AQDKJcrE_Z-EyaeX&w=60&h=60&url=http%3A%2F%2Fi.imgur.com%2F9tn qw76.jpg%3F1&crop&_nc_cb=1&_nc_hash=AQB6P3gqHPi95Y BK"

[zak]

Thanks X. Do you think the EGR passage is cast in and just needs machining to open it up?

Now I will have to pull a head and cT scan it . . . was going to leave the heads on the longblock . . .

yes fully and long understood that Thermactor and EGR are different with different purposes, in the end this thread is about what sort of passages are present and/or what sort of machining can be done to backdate GT40P heads to older 5.0L's

[xctasy]

EGR is not Thermactor. Two different systems. Some of the early P heads still had an EGR hole. The later ones did not. None of the P heads had Thermactor ports.

Right there!

I found the pictures to explain the variances. Calling the parts the right stuff will help some.

All heads have enough meat to do the grabbergreen84 modifications, which will stop the left and right upstream Thermactor AIR failure codes.

The EGR and Downstream AIR and all that freaky funk are a way Ford described and prescribed the emissions packages from 1966 to 2002 to cover off Federal Motor Vehicle and overseas Australian/ European Union Tier regulations.

The plug angle and exhaust valve size alone removed the need for Upstream AIR. When modified with drillings fully or in oart, the GT40P heads should pass all aspects of 1990-1993's OBDI.5 with ease.

[wbrockstar]

In the EECIV system,smog pump air is sent to the cylinder heads (upstream air) but only for the first minute or two after the engine is running.After that,smog pump air is then diverted downstream to the lower converters.The only issues the thermactor passages not being there might cause are codes 44 & 94,but if present,those codes wont cause any driveability issues.

The oem 86-93 5.0 4 converter hpipe has two types of converters,but only one of those two need smog pump air to function correctly.The two converter types are: Reduction converters
Oxidation converters

The upper converters are the reduction cats & the lower converters (which are the ones that need fresh air from the smog pump) are the oxidation cats.This is easily apparent by looking at the welded on airtube's location on the hpipe.IOW- the upper cats couldn't benefit from smog pump air since its introduced so far down the hpipe.Without fresh air from the smog pump,the lower cats will clog & fail over time.

The following info is from a thread on another site,but its the best detailed explanation of both the thermactor and egr system's function & purpose.It also has info (rather brief though) about newer cats that require multiple o2 sensors on each bank along with an ecu designed to work with this setup plus newer cats designed to be used with a smog pump in which both the reduction and oxidation catalysts are built into one housing.These would be the cats that are called high flow cats.The following is just a few paragraphs from that thread. For the full writeup (diagrams included) & for anyone who doesn't understand how both of these systems work,any issues either may cause & related trouble shooting info,open the link at the bottom & start reading at post #10 once you open the link.Its a good read.




(Source Jrichker @ Stangnet)

Thermactor air pump (smog pump) supplies air to the heads or catalytic converters.This air helps break down the excess HC (hydrocarbons) and CO (carbon monoxide).The air supplied to the catalytic converters helps create the catalytic reaction that changes the HC & CO into CO2 and water vapor. Catalytic converters on 5.0 Mustangs are designed to use the extra air provided by the smog pump.Without the extra air, the catalytic converters will clog and fail.


Catalytic converters consist of two different types of catalysts:
Reduction and Oxidation.

The Reduction catalyst is the first converter in a 5.0 Mustang and uses platinum and rhodium to help reduce the NOx emissions. When an NO or NO2 molecule contacts the catalyst, the catalyst rips the nitrogen atom out of the molecule and holds on to it, freeing the oxygen in the form of O2. The nitrogen atoms bond with other nitrogen atoms that are also stuck to the catalyst, forming N2.

"The oxidation catalyst is the second converter. It reduces the unburned hydrocarbons and carbon monoxide by burning (oxidizing) them over a platinum and palladium catalyst. This catalyst aids the reaction of the CO and hydrocarbons with the remaining oxygen in the exhaust gas.
What happens when there is no extra air from the smog pump...
Oil consumption and poor tune increase the amount of HC the oxidation catalyst has to deal with. The excess HC that the converters cannot oxidize due to lack of extra air becomes a crusty coating inside the honeycomb structure. This effectively reduces the size of the honeycomb passageways and builds up thicker over time and mileage. Continuous usage under such conditions will cause the converter to clog & fail. The extra air provided by the Thermactor Air System (smog pump) is essential for the oxidation process. It oxidizes the added HC from oil consumption and poor tune and keeps the HC levels within acceptable limits.


https://www.stangnet.com/mustang-for...-to-it.477938/

[mcb82gt]

Will newer converters work well without the Air pump? I need something that will, smog pump long gone.

[emerygt350]

I have had luck finding NOS airpumps on ebay. Particularly when you look for all the versions that are compatible but have a different code. Search the posts. I got my most recent NOS motorcraft pump for something around 35 dollars if I remember correctly.

[xctasy]

I have had luck finding NOS airpumps on ebay. Particularly when you look for all the versions that are compatible but have a different code. Search the posts. I got my most recent NOS motorcraft pump for something around 35 dollars if I remember correctly.

Yep. The aftermarket quality is crap.

As above.

Port in Housing" Cardone 32-291 is the generic type of 1981 to 1987 pump E1TZ-9A486-B Ford Econoline E150 E250 E350 1975-1987, but also fits 5.0 Mustangs till 1992, so it is 31 lb/hr.

Remember, the 5.0 was effectively a truck, Mercury Lincoln home base, so most of its parts are EFi 5.0 from the bigger Lincolns, like the last of the LSC's.

"https://www.amazon.com/Cardone-32-291-Remanufactured-Smog-Pump/dp/B000C41KHG/ref=au_as_r?_encoding=UTF8&Make=Ford%7C54&Model=LT D%20Crown%20Victoria%7C5852&Year=1990%7C1990&ie=UT F8&n=15684181&newVehicle=1&s=automotive&vehicleId= 1&vehicleType=automotive"

Do be careful though. Aftermarket parts break the agreed 50 000 mile EPA durability requirements, and keep your receipt. All emissions gear is life of the vehicle with maintenance intervention.

Smog equipment must be suitable for purpose, and is subject to correct break in, with the right belt tension.

see
http://vb.foureyedpride.com/showthre...urnt-out-again

http://vb.foureyedpride.com/showthre...light=air+pump

[zak]

To summarize, if one is running a stock 86-93 H-pipe or similar year range catted aftermarket H pipe, or 85 and older Y pipe, one can if using GT40P heads eliminate air injection at the heads and head ports, but keep the air injection downstream.

This is because the newer heads have greater combustion efficieny, unlikly to clog up the NOx reduction forward catalyst(s)

Use of the thermactor diverter solenoid is still needed to keep an EEC-IV happy, but both flows can be directed downtream to the downstream cats.

Please let me know if this summary is correct -

[emerygt350]

Yes, that sounds right.

[Badsmurf]

Will newer converters work well without the Air pump? I need something that will, smog pump long gone.

Yes. The job of the thermactor was to induce air into the converters to heat them up faster during cold starts to limit emissions

[emerygt350]

I have new cats on my bbk h pipe and there were options for down stream air and without. I still have a pump so I went with the air.