Though I'd post some of the most common questions I'm asked and a couple tricks I've learned over the years.

HO Conversion, You need:
E7 Heads (Found on 87-93 Mustangs, 89-92 Lincoln Mark 7's and 87-96 E/F series w/302 (351w has larger head bolts)
HO ECM, engine computer (Mark 7 to keep cruise on the 88-91 boxes, 86-88 mustang for the 86-87 box)
19Lb injectors 86-up mustang, 89-92 mark 7, 87-96 E/F series trucks (302/351)... They have an orange top.
HO upper intake 87-93 Mustang, 89-92 Mark 7
HO Throttle body
HO cam 86-93 Mustang, 89-92 Mark 7


The 2 modifcations needed:
The linkage arms on the throttle bodies need to be swapped. It's easy and straightforward. Grind, swap reattach with screw, JB weld, or actually weld it. The EGR spacer will need to be enlarged to 63mm. A couple minutes on a lathe fixes it up. The 93-95 Ford lightning and some Aussie Fords use a similar EGR spacer if you can find it.

Common misconceptions:
1. Wiring. There are NO changes to the wiring for the HO conversion.
2. Wiring . There are NO changes to the wiring!

To help you get the most out of the HO conversion:
Dual Exhaust. 2.25" minimum.
Headers: Mustang shorties work with some modification, most people get the H-pipe too and get a cat back exhaust done.
Trans: Mustang/Mark 7 Governor. Raises the shift points to match the engines power band. Transmission cooler is recommended.
shift kit helps too.
Fuel pressure: sometimes you can get away with the stock pump. Check your fuel pressure and make sure it's good at WOT.


Other tips/Tricks
1. Timing is everything! Make sure your timing is correct. If it's off, it'll kill your power and milage. Bump it to 12-14* for a little extra HP, just pay attention to detonation, if it happens, back the timing off.

I will keep this thread open for the time being.
Others can post replies and ask questions regarding the HO conversion.
I will update this from time to time, so re-read it every once in a while.

I'm the nOOb here but from the great information I've gleaned so far from this forum;
You must change to a HO camshaft if you plan to use an HO ECM (and vice-versa) due to different firing orders.

HO throttle bodies should be used in conjunction with 19# injectors.

I'm not looking to build a race car but I believe I would enjoy a little increase in performance. I'm looking at THIS camshaft that is advertised to be compatible with SD/HO computers.

Actually.... NO

HO cam REQUIRES the HO ECM ....HO ECM REQUIRES 19lb injectors.
All 3 parts need to be used in conjuction with each other.
HO throttle body is not a requirement, but sure doesn't hurt to get more air for the extra fuel going in the engine.


I have used that very camshaft before and I was NOT impressed.
several people on the Mustang boards used that cam and weren't impressed either. driveability wise there was no difference, compared to a stock HO cam, advanced 4 degrees and the motor made 5 more HP with the stock HO cam on the chassis dyno.

The cam does indeed work with stock SD systems, however it will NOT work with the factory non-HO, cast pistons and the cam requires heavier valve springs.

Thanks for the (civil) correction, I understand. I didn't know that. I guess Summit has some leftover Crane inventory.It's nice to hear from someone that has actually "been there/done that" than someone that claims "It has to be true, I read it on three other forums!"

Its a compucam, I never knew them to be anything more than a stock-ish replacement cam anyways that is garanteed to be friendly with a stock ecm.

Alex.

What are the differences between the box upper intake and the H.O. upper?
I thought they were identical other than being "flipped".
Thanks!

The HO upper inlet matches the HO throttle body (63mm)
The LOPO upper inlet matches the LOPO throttle body (50-ish mm IIRC)

The intakes are symmetrical. (meaning they can point to the divers side, or the passenger side.)

The EGR spacers are not.
You need to bore your stock spacer to the HO throttle body dimensions. Or find a used lightning EGR

You will also need to remove the throttle control arm on the throttle body itself. It is swagged on. You will need to grind this off, remove the arm, swap it over to the HO throttle body and JB weld/tack weld/drill and tap the arm onto the new shaft.




This was what I did to mine. Drilled and tapped for a 8-32

The HO upper intake has a larger inlet and a larger throat leading the air passages for each cylinder.
HO intake has a 63mm inlet, where the non-HO intake has a 52mm inlet.

the explorer/cobra and GT40 upper intakes have a 67mm inlet, which is why a lightning EGR spacer is needed. the maximum size the stock, CV EGR spacer can be bored is 62-63mm.
even at 63mm the material on the backside of the bored EGR spacer (where it seals to the intake) gets VERY thin.

More useful info, thanks guys!

alright this is a stupid Q but why can we not use the mustang egr spacer or the exploder spacer and sorry again

The EGR is not symmetrical. There is a specific 'Right & Left' If you were to swap the mustang EGR the throttle cable bracket mounting studs would be pointing to the front of the engine, and the EGR would point towards the back.

That is why the other option is to find a lightning EGR spacer, because it too had the intake pointing towards the drivers side. A third option is a Aussie 5.0L EGR spacer... good luck finding one!

As Jeff pointed out, the spacers are symetrical, meaning they will only mount(correctly)in a certian way or location. the Mustang spacer doesn't mount properly when flipped around

The other reason the Mustang EGR spacer does NOT work, the attaching point for the throttle cable(s) bracket is completely wrong for the panther chassis set up.

It's also important to make sure you use the correct EGR for the upper intake you have.
If you have an HO upper intake, have the stock CV EGR spacer bored to the correct size.
If you use an Explorer or GT40 style upper intake, then you MUST use a Gen 1 lightning EGR spacer.
Sealing the EGR spacer to the upper intake is very important and the different spacers will NOT swap between the 2 different manifolds because the different inlet openings.

Reference Pictures:
Bored EGR on Stock HO upper:

Stock LoPo Vs. Stock HO Throttle Bodies:


You must swap your stock vacuum tree from the LoPo upper intake to the HO upper intake.

You can directly swap a Holley Systemax 1 Lower Intake Manifold in place of the stock HO lower intake. You must reuse your stock fuel rail for the HO swap. This intake is no longer in production so if you have the opportunity to buy one, jump on it. I purchased this one of Ebay, NIB, for next to nothing. So keep your eyes peeled! It has significantly larger ports and a 'straightened out' # 1 & 5 runner.

GT-40p Head Identification:

4-Bars: GT-40P heads are cast with 4bars on the end of each head.

Cast 'P': Between the pushrod bores on the underside of the head, there is a 'P' cast into the head.