Engine Need help with 5.0 ho speed density build

Tugamypuda

Member
Jul 30, 2018
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Fort worth tx
hey guys so I've got an 87 foxbody with the 5.0 ho engine. Blew a head gasket. Thought I'd pull engine out to fix engine mounts maybe freshen up engine and see what was actually in the engine. Bought a year ago and just been my daily driver. So I tore it down and found cam is trashed and 1 of the skirts was scored up. Was gonna do a stock rebuild but figured if I can get a lil more hp out of it with a budget build between 1k to 2k than why not. Thought about doing the mass air conversion (not really needing it right now) but from what I've read seems overwhelming and maybe out of my price range on top of everything else.. Maybe I can just do a bigger cam like the e303 with no issues. Been sitting on some patriot heads for awhile with 65 cc. Looks like it has new push rods and some blue f72 roller rockers. Don't know if that means anything. Everything else is stock. I can do the work but don't know all the specs so if someone is willing to help me pick out parts for this build would be very appreciated. Thanks.
 
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jrichker

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hey guys so I've got an 87 foxbody with the 5.0 ho engine. Blew a head gasket. Thought I'd pull engine out to fix engine mounts maybe freshen up engine and see what was actually in the engine. Bought a year ago and just been my daily driver. So I tore it down and found cam is trashed and 1 of the skirts was scored up. Was gonna do a stock rebuild but figured if I can get a lil more hp out of it with a budget build between 1k to 2k than why not. Thought about doing the mass air conversion (not really needing it right now) but from what I've read seems overwhelming and maybe out of my price range on top of everything else.. Maybe I can just do a bigger cam like the e303 with no issues. Been sitting on some patriot heads for awhile with 65 cc. Looks like it has new push rods and some blue f72 roller rockers. Don't know if that means anything. Everything else is stock. I can do the work but don't know all the specs so if someone is willing to help me pick out parts for this build would be very appreciated. Thanks.
Speed Density won't work with what you are doing.... here's why....

Computer system differences in 86-95 Mustangs.

Revised 15-Jan-2018 to add requirements for larger fuel system components to support large changes in airflow through the engine.

All 5.0 foxbody engines from 86-95 are OBDi
OBD1 comes in Speed Density and Mass Air Flow versions. It differs from OBDII in that diagnostic data cannot be streamed through the diagnostic port in a real time mode. The diagnostic data is stored in volatile memory and dumped on command by an external jumper or code reader connected to the computer’s diagnostic port. Watching the Check Engine Light, an external test light or voltmeter are all that is need to dump the codes on an OBDI system. An OBDI code reader can be used, but it isn’t an absolute necessity.

ODBII is capable of streaming data through the diagnostic port in real time mode. It requires a code reader that handles the OBDII data format. No code reader, no way of knowing what the codes are. The plus is you can watch changes in sensor data as they happen, and use the information to plan changes in the computer's program. OBDI requires a laptop & some specialized hardware to do the same thing.

Both OBDI & OBDII have adaptive learning to accommodate changes in sensor output, so as the sensors and airflow values change, the computer adjusts for them. Mass Air systems have a greater range of adaptive learning than Speed Density.

Speed Density uses Manifold vacuum (MAP), Throttle position (TPS) and RPM, & Air Temperature (ACT) to guess how much air the engine is pulling in. Then it uses all of them plus the O2 and ECT sensors to calculate the air/fuel mixture. It is dependent on steady manifold vacuum and minimal changes in airflow from the stock engine configuration to maintain the proper air/fuel ratio. Change the airflow or vacuum too much and the computer can't compensate for the changes, and does not run well. Forget about putting a supercharger, turbocharger or monster stroker crank in a Speed Density engine, because the stock computer tune won’t handle it. Every time you seriously change the airflow through the engine, you need a new custom burned chip to make the engine run at peak performance. Most aftermarket cams will not work well with Speed Density, and that includes the Ford letter cams.

Mass Air uses a Mass Air Flow meter (MAF) to actually measure how much air is being pulled into the engine. The computer uses this information and inputs from the O2, TPS, ACT, ECT, RPM and Barometric Pressure (Baro) sensors to calculate the proper air/fuel ratio. It is very tolerant of changes in airflow and vacuum and tolerates wild cams, high flowing heads, and changes in displacement with minimal difficulties. Just remember that large changes in airflow require more fuel than the stock fuel system can deliver. At that point, you will need larger injectors and a larger fuel pump to make the engine run like it is supposed to. Larger injectors can be used with either an aftermarket calibrated MAF or a custom dyno tune. This makes it possible to use the stock computer with engine displacements from 302-408 cu in, and make many modifications without a custom dyno tune chip. Put a new intake manifold on your 331 stroker and the computer figures out how much more fuel to deliver without having to have a new chip burned to accommodate the extra airflow.
 
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Tugamypuda

Member
Jul 30, 2018
36
1
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34
Fort worth tx
I know the differences between the 2 but have read that some ppl have found a way around it. This isn't my final build it breaking down forces me to do a rebuild. I don't have much time for this or I would take the time to do it correctly. I was just hoping that maybe I can get a lil extra hp out of it since I'm doing the rebuild anyways. Some ppl say as long as u don't go over 220 lift your good or maybe putting some ev6 19lb injectors in. Just looking at options. What all do I exactly need for mass air conversion? How much does it really cost to do mass air conversion. I've seen ppl selling partial kits on ebay for like 600 bucks.dont need anything crazy this is my daily driver. I drive maybe 100 miles a week.
 

Monkeybutt2000

Advanced Member
Aug 11, 2019
429
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Lafayette,IN
It's the cam duration that messes with the SD. I ran a 95 Cobra engine SD in an 87 LX. Ran great with 24# injectors and 1.7 rockers. Just played with fuel pressure and idle screw.
 

Tugamypuda

Member
Jul 30, 2018
36
1
8
34
Fort worth tx
Thank you. Alot of ppl telling its not possible but I've read ppl who have. I have patriot heads to put on. Don't remember specs. What all do i have to change to put a bigger cam in? I found a list with compatible cams just don't know which one to use yet.
 

General karthief

wonder how much it would cost to ship you a pair
Mod Dude
Aug 25, 2016
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Ok, here's my thoughts, not that they hold any weight but observations over the few years hang'n here.
Speed density does not always play well with modifications, the factory used it on a variety of 5.0 equipped cars and trucks but in 88 they switched to mass air for California emissions on the HO 5.0 (maybe others but we are talking about mustangs) in 89 it went across the board in 5.0 HO mustangs, why? Technology got better. It was more, lets say 'adaptable ' to changes.
Of course technology has moved on from eec-4, but the point is when it is possible to easily upgrade, like the mass air conversation I feel it should be done.
Now some have claimed success with modifications on SD cars and there are other engine control systems out there that can butter your toast better just by plunking the Benjamins on the table. Research and planning will lead to a happy motoring experience.
 

Mustang5L5

i'm familiar with penetration
Mod Dude
Feb 18, 2001
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If you pay attention to the cam specs, you can certainly stay with SD. However, having done the SD-to-MA conversion myself, I wouldn't view the conversion as a big enough hurdle to limit the mods you do. It was a very easy swap to perform.

The biggest cost is going to be the ECU. You'll need the A9L if 5-spd, or A9P if AOD. After that, it's the price of a meter, the intake tubes and the harness is $40.
(about 1/4 the way down).
 

Monkeybutt2000

Advanced Member
Aug 11, 2019
429
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Lafayette,IN
I applaud you for trying to get the most out of the SD system. I did it just to see how far I could go,mind you this was 20yrs ago. If it were me,I'd swap to mass air. That way you're not limited to cam selection. Or just run a stock cam, I went 12.80s on one.
 

Dan02gt

10 Year Member
Mar 2, 2003
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Greenville, NC
While I would heavily recommend going mass air there are a few cams out there that are speed density compatible. You’re looking for a cam close to the 115* LCA that the stock cam has. The comp XE264HR-14 has a 114 LCA and might work for you. A E303 is on a 110* and would run terrible.
 

Willybill32

Active Member
Jul 16, 2019
193
86
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Lexington, KY
As I just posted on another thread, I converted my ‘86 to mass air maybe 25 years ago, and it wasn’t difficult, just tedious. I used a Ford kit complete with the computer and bought a tool to unseat the pins in the connector so I could move the pins as required. Car ran great with mass air.

I’ve recently done an upgrade on the stock 5.0, with TFS Twisted Wedge aluminum heads, E303 cam, 24lb injectors, etc. and the mass air accommodated those changes. I will tell you that it’s a blast to drive above 1,500 RPM, but difficult below that speed.