Fordnatics List Archive

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Mail From: (email redacted)

I've got a '91 Mark VII with the Ford 5.0L H.O. engine (identical to the
Mustang). I decided to hop it up a bit so I did the following mods. to it:

1. Timing to 14 deg.
2. Remove air intake silencer
3. Installed Super Turbo mufflers
4. Extrude Honed upper and lower intake
5. MAC unequal length headers (1 5/8)
6. 65mm T.B. and EGR spacer
7. K&N filter
8. Adjustable fuel pressure regulator
9. New plugs and 8.8mm wires
10. 4.10 gear

It's important to know that this is a speed density system.

The problem is that the car ran 16.10's fully stock and now runs 15.80's,
far higher than what I expected. Were my goals too lofty or could there be
a problem? Perhaps I need to go to mass air? I figured I'd be knockin' on
the 14's with this combo. I hooked up a volt meter to the O2 sensor and it
reads very low (~.35 volts) in first gear until the rpms get up to around
3500. It looks pretty good above that (.7 volts). Fuel pressure is set to
42 psi. I realize that this is a definite problem that needs to be
corrected. Does anyone see any mistakes in the combo I chose? What gains
would you have expected?

Thanks,
TODD

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Mail From: (email redacted) (Robert King)

>
> I've got a '91 Mark VII with the Ford 5.0L H.O. engine (identical to the
> Mustang). I decided to hop it up a bit so I did the following mods. to it:
>
> 1. Timing to 14 deg.

Not bad. Most folks I know run 13 deg.

> 2. Remove air intake silencer
> 3. Installed Super Turbo mufflers
> 4. Extrude Honed upper and lower intake
> 5. MAC unequal length headers (1 5/8)

This is probably excessive for a mildly modified 5.0.

> 6. 65mm T.B. and EGR spacer
> 7. K&N filter
> 8. Adjustable fuel pressure regulator
> 9. New plugs and 8.8mm wires
> 10. 4.10 gear
>
> It's important to know that this is a speed density system.
>
> The problem is that the car ran 16.10's fully stock and now runs 15.80's,
> far higher than what I expected. Were my goals too lofty or could there be
> a problem? Perhaps I need to go to mass air? I figured I'd be knockin' on
> the 14's with this combo. I hooked up a volt meter to the O2 sensor and it
> reads very low (~.35 volts) in first gear until the rpms get up to around
> 3500. It looks pretty good above that (.7 volts). Fuel pressure is set to
> 42 psi. I realize that this is a definite problem that needs to be
> corrected. Does anyone see any mistakes in the combo I chose? What gains
> would you have expected?

I would have expected gains somewhere in the .5 sec range (close to
what you got,) but I certainly am no expert.

From what I understand, the Mark VII is a bit heavier than the Mustang,
so what may make a Mustang 1 sec faster, may make a Lincoln half a second
faster. I'd recomend trying a few runs with racing slicks and see if that
improves your 60' time.

If you do anything else, convert your computer to mass air, or your
drivability will suffer. Then go for better heads and perhaps a camshaft.

Lastly, replace the entire exhaust with a mandrel-bent 2 1/2" system
with high-flow cats.

- -- Robert King


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This read-only message was archived from a public mail list.
Mail From: (email redacted) (Jeff Cross)


[...Mods to Mark VII Deleted...]

You have probably two different factors contributing to slow times.

Probably your biggest limiting factor right now is mass air.
Mass Air allows the computer to correctly determine the air/fuel
mixture based on the measured amount of air your engine is using.
With speed density it has to base the amount of fuel on a programmed
air usage. Since you have increased you engines ability to breath
with a ported intake, you have increased the amount of air without
increasing the amount of fuel. This would (I think) lead to
pinging, especially with the advanced timing.

The other factor to consider is heads. Having a ported intake
really won't help much if the increased air never makes it into
the engine. The heads may be (and probably are) your next big
restriction. Without increasing the ability of the heads to
breath, all the other stuff you've done may or may not really help
much.

When/if you decide to go with better heads (port stocks, buy new ones,
whatever) you will need to get mass air as well. Right now it is a
little hard to know exactly what the bottle neck is.

-Jeff

This read-only message was archived from a public mail list.
Mail From: (email redacted) (Andre Molyneux)

On Jul 29, 16:51, Jeff Cross wrote:
> Subject: Re: 5.0L advice needed
>
> [...Mods to Mark VII Deleted...]
>
> You have probably two different factors contributing to slow times.
>
> Probably your biggest limiting factor right now is mass air.
> Mass Air allows the computer to correctly determine the air/fuel
> mixture based on the measured amount of air your engine is using.
> With speed density it has to base the amount of fuel on a programmed
> air usage. Since you have increased you engines ability to breath
> with a ported intake, you have increased the amount of air without
> increasing the amount of fuel. This would (I think) lead to
> pinging, especially with the advanced timing.

Speed-density cars are not nearly as problematic as some people
believe. The computer is able to make a pretty reasonable assumption
about the amount of air entering the engine. True, the further you
depart from stock the less accurate the estimate will be, but you
can get additional "oomph" out of a speed-density motor without making
a conversion to MAF. I don't think the original poster has crossed
that line yet.

> The other factor to consider is heads. Having a ported intake
> really won't help much if the increased air never makes it into
> the engine. The heads may be (and probably are) your next big
> restriction. Without increasing the ability of the heads to
> breath, all the other stuff you've done may or may not really help
> much.
>
> When/if you decide to go with better heads (port stocks, buy new ones,
> whatever) you will need to get mass air as well. Right now it is a
> little hard to know exactly what the bottle neck is.
>
> -Jeff
>-- End of excerpt from Jeff Cross

Actually, you'll probably find that as long as you have a reasonable
amount of vacuum at part-throttle that the speed-density system will
find a way to cope. New heads won't absolutely require switching to
MAF.

The biggest limiting factor here is probably weight. Yes, the Mark VII
is based off a Fox chassis, but it's hauling around quite a few excess
pounds in comparison to a Mustang. All that sound insulation and various
other luxury items add weight. Do you know how much the car weighs? If
so, you can use one of the formulas that's been bandied about here
occasionally to get a rough estimate of how much horsepower you're making.
Then you can start to draw conclusions as to whether the mods that were
made produced the power increase you expected or not.



- --
Andre

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This read-only message was archived from a public mail list.
Mail From: (email redacted) (Eric Hedstrom)

> 1. Timing to 14 deg.

Take it down to 13deg, maybe it is pinging (you can't always hear it), and
slowing it down. I don't know if it was 14 before you did anything, or
if you are running some race gas on these runs. 14 isn't always high, just
thought I would mention it.

> 5. MAC unequal length headers (1 5/8)

These are too large for your current setup, but if you get new heads or
a supercharger or something, these will be perfect. 1-1/2" equal length
would be perfect for your car.

> 6. 65mm T.B. and EGR spacer

Since you intake is extrude honed, you prob. did this already, but is the
intake opening actually 65mm? It is 60mm stock... you might want to grind
on it a little.

> 8. Adjustable fuel pressure regulator

42psi may also be too high, I really don't think so, but you might want to
set it back to 39.. maybe 40, 41 max.

> 10. 4.10 gear

Yikes, this alone should have given you the 2 tenths that you gained...

> It's important to know that this is a speed density system.
> The problem is that the car ran 16.10's fully stock and now runs 15.80's,
> far higher than what I expected. Were my goals too lofty or could there
> be a problem? Perhaps I need to go to mass air? I figured I'd be
> knockin' on the 14's with this combo.

Stick with the speed density until you move up to heads, cams, or the like.

> chose? What gains would you have expected?

So far I think you are on the right track with your mods, I noticed you
checked the voltage on your O2 sensors etc, have you made sure that your
throttle body sensor is set to .97-.99 volts? Check between the green and
black wire, see if (KOEO) the voltage is under 1-volt, but not lower than
.97v.

Good luck, I know what it is like having elusive problems, I am having
a major electrical one right now! Tell us how things work out.


(email redacted)






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This read-only message was archived from a public mail list.
Mail From: (email redacted)

Just wanted to say thanks to all who responded to my original post. I
received some good tips and advice.

TODD