5.0 HO Conversion Questions

Topic: 5.0 HO Conversion Questions (Read 6187 times) previous topic - next topic

5.0 HO Conversion Questions

January 06, 2008, 09:15:11 PM

Is there a thread covering the HO conversion start to finish?

Plan to use E7 heads (I shop @ Pick-n-Pull), Is there a "best" donor vehicle? I have heard that GT40 heads were used on Merc Mountaineers. If its true, what years? After looking at the flow chart thread the GT's would seem to be a better choice.

Short block is bored 40 over with flat top pistons... I have heard that valve clearance can be an issue. I want as much cam as possible. Any recommendations?

Any pitfalls to look out for while doing this conversion?

I know just enough about all this to be dangerous so I would really appreciate some divine guidance here.

5.0 HO Conversion Questions

Reply #1 – January 06, 2008, 11:18:58 PM

e7 heads will be your best bet because the gt-40's can need special headers. Also you wouldn't want to go much above stock mustang spec cams or you could get clearance problems. also I think most heads need the dished pistons as apposed to the tbird/cougar flat tops. Check out http://www.coolcats.net under the tech section.

5.0 HO Conversion Questions

Reply #2 – January 06, 2008, 11:25:05 PM

The GT40's use standard 5.0 headers.The GT40-P heads need the special headers.The E-7 heads can be easily found on any fuel injected 5.0 pickups (Ford,of course).Probably cheaper to get them from a truck than a Stang,even though they are the same thing.People seem to think that the Stang parts are worth more.I'd be really careful with the GT40 heads and flattop pistons.If you use them,do a PTV clearance check to make sure everything is O.K.

5.0 HO Conversion Questions

Reply #3 – January 06, 2008, 11:48:55 PM

Or I have a couple sets of E7's laying around.

FYI, there does exhist an early and late 1997 version of the GT40P heads and they changed them again in 1998. I have used the 1998 version in the past which were off of an Explorer. Mine had the thermactor bosses trimmed out of the exhaust port, not because they were very large but because I felt that they would cause a little bit of turbulence but not necessary to build power.

If you are installing a HO engine into a speed density car, you will of course need a different computer, repin the wire harness to work with the mass air system, don't forget to unplug the map sensor on the firewall because the mass air computer no longer uses it. Because you no longer use the thermactors in the heads your EGR is mostly useless and could be eliminated. This requires a diode trio assembly which I can forward to you. I got mine from a friend of mine on another forum. It turns the check engine light off on your dash and it worked great. The biggest difference between the speed density and the HO engines are the firing order and injector pulse order. They have to be changed because of the camshaft timing events being different. The nice part about it is that the cranks are the same part number and therefore would not need to be changed if you are planning on using the old speed density block.

Beware if you are using the speed density block! When I installed my "P" heads on that block I tested the pitson to valve clearances and my E303 camshaft with .498 gross lift with 1.6 rocker arms made contact, I have pictures of the clay i used. The reason for the contact results from the pistons that were used in my particular engine. The were flat tops without valve reliefs. I found it less time consuming to purchase a HO short block which can be seen in my picture post on this board. Header wise, the flowtech equal length shorties do not work well because they are tight on the number 4 cylinder and I burnt off a couple plug boots until I went with the MAC unequal lenght shorties. I used the 4048 Accel plug wires in a pinch because I had a set and they had 90 degree boots on the head end. That helped a lot. You will have to dimple the headers on the driver's side slightly to clear the steering shaft. I found that the stock valve springs used on the "P" heads needed to be upgraded because of the potential for valve float and binding, I used the Ford Motorsports springs that end in A50. They worked very well.

5.0 HO Conversion Questions

Reply #4 – January 07, 2008, 01:26:29 AM

Here is what you need for a BASIC HO conversion. First off a mass air conversion is NOT required. It's easier and cheaper to do it speed density to start out using all stock Mustang stuff. Here's what you'll need...

HO Throttle Body, EGR Spacer, Intake
Stock HO Cam
E7 Heads
19# injectors
HO Headers, H Pipe and Custom cat back system
HO speed density EEC-IV
One of these Speed Density EEC-IV processors:

DA1 5.0 87 Mustang SD-SFI / Manual
DB1 5.0 87 Mustang SD-SFI / Manual
DC 5.0 Mustang SD-SFI / Auto
DE 5.0 Mustang SD-SFI / Auto
GJ1 5.0 Mustang
VH2 5.0 86 Mustang SD-SFI
VJ1 5.0 Mustang
VM1 5.0 86 Mustang SD-SFI / Manual
VP1 5.0 86 Mustang SD-SFI / Manual
VR1 5.0 86 Mustang SD-SFI / Manual
D9S 5.0 88 Mark VII SD-SFI
DX3 5.0 87 Mark VII
DY3 5.0 88 Mark VII

You'll need to change your IGNITION firing order to the HO (351W) firing order because of the cam swap. NO OTHER WIRING CHANGES ARE REQUIRED!

For more info I'd definitely visit Eric's Coolcats site.

5.0 HO Conversion Questions

Reply #5 – January 07, 2008, 06:48:15 AM

Any mod could be put on by it self the only rule is CAM and ECM must be change together then put the SP wires in there correct places.

5.0 HO Conversion Questions

Reply #6 – January 07, 2008, 07:47:20 AM

Required reading: http://www.coolcats.net/tech/advanced/ho_conversion.html

5.0 HO Conversion Questions

Reply #7 – January 07, 2008, 10:31:48 AM

Quote from: Its1FastCat;196186

If you are installing a HO engine into a speed density car, you will of course need a different computer, repin the wire harness to work with the mass air system, don't forget to unplug the map sensor on the firewall because the mass air computer no longer uses it. Because you no longer use the thermactors in the heads your EGR is mostly useless and could be eliminated. This requires a diode trio assembly which I can forward to you.

No wiring changes necessary if he runs speed densety...

MAP becomes a BARO sensor with no vacuum, but remains electrically connected...

Also the thermactor solenoids can be left in place and you'll never get a CEL(least I don't)...

5.0 HO Conversion Questions

Reply #8 – January 07, 2008, 07:25:03 PM

I'd leave the EGR stuff in place (I did on my 88). The EGR system shuts off at WOT anyways and helps fuel economy so why not keep it. The 88 doesn't have any Thermactor stuff though. I did leave the solenoids in place though so the CE light wouldn't drive me nuts;) .

5.0 HO Conversion Questions

Reply #9 – January 07, 2008, 07:42:11 PM

The thermactor and EGR are unrelated..

5.0 HO Conversion Questions

Reply #10 – January 07, 2008, 07:44:50 PM

Quote from: CougarSE;196335

The thermactor and EGR are unrelated..

I know I'm just saying leave the EGR stuff on the car because it helps fuel economy and get ride of the thermactor stuff if you don't have to pass emissions.

Project H.o.

Reply #11 – January 07, 2008, 11:09:55 PM

Thanks for all the info:D

Went to Pick-n-Pull today and started drooling immediately. First car in the first Ford row was an 88 Linc H.O. Pulled the computer first and the code checked out (VL2). Now I'm foaming at the mouth and happily start to pull parts. I got everything I needed by 3 PM and headed home. Nothing better than coming home and checking out your plunder right? Thats when I checked the castings on the heads and I now have a nice set of E6 heads! The computer was as originally installed and the plenum had an H.O. Badge... I thought the two were not compatable. Could these be acceptable? If not I will take them back and get some E7's. Not to mention the plenum, MAF, MAP & TPS. The injectors are Tan so I guess they are O.K.

Headers: The Linc had what looked to be factory tubes. The H pipe is gone but the headers are there. Will they fit in my 87 or should I get a set of stock mustang headers?

Computers: I got the VL-2 out of the Linc and also found a DY3 in the trunk. Can these be tested or is the test when you fire it up?

5.0 HO Conversion Questions

Reply #12 – January 07, 2008, 11:31:56 PM

'86 Stangs & '86/ '87 LSC Lincolns used E6 heads, same as on the SO 5.0... Those use the long reach 3/4" spark plugs, easy to spot 'em by pulling a plug... BTW those engines are rated at 200hp, mainly because of the heads...

5.0 HO Conversion Questions

Reply #13 – January 08, 2008, 05:53:46 PM

Go back and get some E7's... E6's, which you already have on your car, suck.

5.0 HO Conversion Questions

Reply #14 – January 08, 2008, 06:04:19 PM

The injectors should be orange for the HO 19lb.
Tan are the SO 14lb that your car already has.

The plenum should have an H.O. cast in it under where that plate sits. That will verify if it's correct. You could always measure the bore but it's easier to look for the cast.

Those headers will fit just fine. I've been running with them for nearly 4 years now.
Just don't forget that you'll need an h-pipe because of the location of the O2 sensors.