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post #1 of 20 (permalink) Old 12-30-2003, 08:31 PM Thread Starter
 
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Is it worth it???

This may not belong in this forum but here it goes,
- Is it worth taking a '94 SC w/ 123,xxx miles on it and begin to mod it out? I got the car at 111,xxx miles and now have the opportunity to begin modding. My real concern is the mileage, can any REAL performance be gained on this kind of mileage?
I love the car, but would selling it and waiting for something better(SC w/ less miles) to come along be a wiser decision? Any thoughts Apppreciated...
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post #2 of 20 (permalink) Old 12-31-2003, 12:57 AM
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I know some of the faster SC's have upwards of 150-180 grand on them. The only problem is when/if the gaskets go will you be able to handle it. If not then I would set aside $1000 for when they do. But the first thing I would do to a car of that mileage is the exhaust.

1990 35th anniversary T-bird SC

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post #3 of 20 (permalink) Old 12-31-2003, 06:56 AM
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My 89 cougar had 160k when I tore it apart ...

96 Mark VIII [email protected] :: 03 radiator/fan - j-modded trans - BBK UD pulley kit - dual gauge pod - 28,000 B&M transcooler (w/ AN fits) - 3.73 locker (with speedo gear) - 180' thermo - 8.5mm wires - colder plugs
soon to install : "fixed" heads and a damn tune. Project snaked8 continues...
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post #4 of 20 (permalink) Old 01-06-2004, 03:38 PM Thread Starter
 
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My friend said that it wouldn't be worth it becasue the engine looses compression over time. Any truth????
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post #5 of 20 (permalink) Old 01-06-2004, 03:42 PM
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if the body is in good shape, then just put a 302 in it and be done with reliability woes.

At 120k be prepared for more maintenance than usual, and the sc needs alot of care to make it run right to start with.

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post #6 of 20 (permalink) Old 01-06-2004, 09:37 PM
 
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THe cross hatching was clear as a bell on my 89 and 90 when the headgasktes were done both at around 120K.
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post #7 of 20 (permalink) Old 01-07-2004, 12:56 AM
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apparently he hasnt been having any problems and actually OWNS one.

1990 35th anniversary T-bird SC

1993 Mercury Cougar 3.8
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post #8 of 20 (permalink) Old 01-07-2004, 02:46 PM Thread Starter
 
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I guess the real issue here is---MONEY. If i can donate thousands to it, it could be a nice (nicer) machine. However, the first thing that needs to be done is to get the car in perfect runnig order. What would you guys suggest I do to it in terms of "maintence" modification. I got the car at 111,xxx miles and it shook really bad. I changed plugs and wires, it went away. Im having a shift kit installed when spring arrives, and also having a tranny cooler installed. Anything else I'm missing? What would you do for this "tune-up"? Any input MUCH appreciated...
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post #9 of 20 (permalink) Old 01-07-2004, 08:59 PM
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Motor Mounts should be very high on the list. If doing a shift kit, you should check out the "J-mod" in the tech article section of the site. With over 100K, if you have the money, might as well do crank and cam sensor, water pump, T-stat, hoses and belts, new bushings in varies places.
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post #10 of 20 (permalink) Old 01-09-2004, 03:14 AM
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On an sc, I consider exhaust to be a great tune up. It really is a preventative thing to do in order to save your head gaskets. That back pressure just kills the HG's. If anything, just delete the third cat and resonator.
-Thomas

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post #11 of 20 (permalink) Old 01-09-2004, 03:24 AM
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Quote:
Originally posted by tony8470
apparently he hasnt been having any problems and actually OWNS one.

OUCH!


Quote:
On an sc, I consider exhaust to be a great tune up. It really is a preventative thing to do in order to save your head gaskets. That back pressure just kills the HG's. If anything, just delete the third cat and resonator.

What does exhaust have to do with head gaskets?

73 ranchero with a 89 5.0 EFI HO/AOD
THE PYL !
91 Tbird lx 5.0 swap
GONE 93 5.0 Stang vert
54 Ford Vicky PAXTON SUPERCHARGED 5.0 HO/AOD
86 F250 Diesel 4x4
GONE 89 Aerostar
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post #12 of 20 (permalink) Old 01-09-2004, 12:33 PM
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Well, In the 3.8's we have a common bond. All of our headgaskets are very likely to go. I already had mine go in the 3.8 N/A. People running pulleys in the 3.8 SC go through headgaskets VERY quickly if they don't get thier exhaust done before hand. I already read a thread on SCCoA of a guy running a 10% pulley and his went about 4 months after he put it on. The 10% overdrive pulley is the larger of the 2 commonly available. The other being a 5%. More overdrive=More boost=more torque and hp. BUT boost can also be measured as the amount of backpressure in the system=more pressure on the headgaskets. More stress on an already weak(ened) part is sure to cause failure. Thats why it's the best idea to get your exhuast done before you do any other modification to the SC.

1990 35th anniversary T-bird SC

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post #13 of 20 (permalink) Old 01-09-2004, 03:20 PM
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Quote:
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That back pressure just kills the HG's.
-Thomas
Miss that part?


P.S.
More boost doesn't always mean more tq or hp.

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post #14 of 20 (permalink) Old 01-09-2004, 03:59 PM
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Sorry but i really dont understand how back pressure from an exaust will cause the head gaskets to blow?????
how much back pressure do you think the exahust can produce? more than the compression of the piston? just wondering?

73 ranchero with a 89 5.0 EFI HO/AOD
THE PYL !
91 Tbird lx 5.0 swap
GONE 93 5.0 Stang vert
54 Ford Vicky PAXTON SUPERCHARGED 5.0 HO/AOD
86 F250 Diesel 4x4
GONE 89 Aerostar
2003 F350 Super duty
1996 Exploder
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post #15 of 20 (permalink) Old 01-09-2004, 04:08 PM
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you have to remember that these are boosted cars. Pushing upwards of 15 psi with those pulleys. I forget where there was an article but someone actually put a probe in various parts of the exhaust and measured the amount of backpressure. It was quite astonishing just how much there actually was. If I can find it I'll post it.

1990 35th anniversary T-bird SC

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post #16 of 20 (permalink) Old 01-10-2004, 01:31 AM
 
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Here is what you were refering to. Although I don't know who wrote it, so I can't really get permission. If anyones got a problem with it I'll take it down.

Having gone the way of overdrive pulleys, cracked heads and blown head gaskets the assertion by Bill Hull that the stock SC exhaust system causes cracked heads and blown head gaskets caught my attention. Tending not to believe everything I hear I decided to do the research required to understand the problem and let physics provide the facts. So, armed with a great deal of motivation (my cracked head episode set me back two grand) I set out to determine if the SC's exhaust system is really as bad as Bill claims.

The test platform was my modified 91 SC which sports ported and chambered heads, high lift cam, overdrive pulley, ported stock exhaust manifolds, large fuel injectors and a few other goodies. I figure the car is a good test platform to determine if a better exhaust system is useful for Super Coupes on their way to making big time horsepower.

I started out by tapping into the stock exhaust system at several points and measured the back pressure at wide-open-throttle (WOT) over a RPM range from 3000 RPM to 5000 RPM. The results are a real eye opener, see the plot below. I had a hard time believing what I saw, 15.5 PSI back pressure at 5000 RPM's!! The pressure readings were so off-the-wall I double checked the readings with another gage, same results.

1.) During the overlap period (the time when the piston is at or near top-dead-center and both the intake and exhaust valves are open) there is more pressure at the exhaust valve then at the intake valve. Which way will air move? Hmmm, exhaust gases are flowing into the intake manifold! Race engines with long tube headers create a vacuum at the exhaust valve during this period to purge the combustion chamber of exhaust gases. Exhaust pressures so high that exhaust gas wants to flow into the intake manifold is obscured.

2.) After the exhaust stroke the combustion chamber is still charged with hot exhaust gases at 15 PSI. Assuming exhaust gas temperatures are 1500 degrees and accounting for the cylinder to combustion chamber volume ratio the intake air temperature is raised by over 1-50 degrees! The tendency of a fuel/air mixture to detonate has been studied for decades, the primary factors are:

A.) Pressure (compression ratio)

B.) Temperature of the mixture

C.) Time (the duration the gas mixture is held at the first two conditions)

D.) Fuel chemistry (octane rating)

There are other factors such as combustion chamber shape, flame pattern, etc. however, temperature is one of the significant factors. In fact, some of the Buick Grand National racers run 160 degree thermostats to reduce engine temperatures 30 degrees in an attempt to reduce detonation while running high boost pressures.

3.) When the piston is moving up on the exhaust stroke it is doing work (pumping air) against high pressure. To move enough air to produce 350 HP (about 600 CFM) at 15 PSI requires around 30 horsepower. I can think of better uses for this energy, like turning wheels.

I'm convinced it was designed that way to make the Super Coupe just a tad bit slower then Ford's dear little pony car.

Considering the above I set out to build the lowest back pressure exhaust system possible. I calculated that two 2 1/2 exhaust pipes would have about 1/2 PSI back pressure, but upon inspection of the SC under carriage I could see it was next to impossible to route two 2 1/2 inch pipe through the channel provided for the exhaust pipe. After pondering the situation I soon realized that one 3 1/2 inch pipe has the same cross sectional area as two 2 1/2 inch pipes and would fit the routing channel nicely. It would also have the same back pressure. Well, several weekends and several hundred dollars later I had built a 3 1/2 inch system from mandrel bends that fit like a glove and even used that original mounting brackets. The design is the same as the original except the pipe sizes were increased. The 2 inch pipes were replace with 2 1/2 inch and the 2 1/2 inch pipe and front muffler were replace with 3 1/2 inch. The system was aluminized and fitted with pressure measurement fittings at the same points as the stock system. The same series of pressure measurements were ran on this system, the graph below tells the story.

The back pressure at the manifold (Before Cat) was reduced from 15.5 PSI to 6.3 PSI, a big improvement. Notice there is only .6 PSI drop between the rear muffler (Before Rear Muff.) and the catalytic converter (After Cat). Things are getting better, but the system still has 6.3 PSI back pressure.
The next two areas to improve are catalytic converters and mufflers. The mufflers I chose were inexpensive or I should say cheap Thrush California Boss Turbo Mufflers with 2 1/2 inch inlet and exit, about $20.00 each. These mufflers didn't improve the back pressure at all, they had the same pressure drop as the original rear mufflers, about 2 1/4 PSI. They were so loud that I could hardly hear the stereo over the roar. I shopped around a bit but couldn't convince myself the mufflers I looked at were both low back pressure and low noise, so I decided to design and build my own. The experimental mufflers I designed are nearly as quiet as the stock system and have a pressure drop of only .6 PSI. So I proved, if only to myself, it is possible to have both low noise and low back pressure at the same time. It would be interesting if someone made a side-by-side comparison of available mufflers to determine which ones really work on blower birds. In any case the back pressure is continuing to drop as can be see in the chart and the power levels are going up a bunch.

My SC with the original exhaust system accelerated from 20 MPH to 55 MPH in 4.17 seconds. With the 3 1/2 inch exhaust system this time was reduced to 3.80 seconds, an improvement you can really feel. I made several 0 to 60 MPH attempts but wheel spin hampered performance, the 245/50 tires don't even come close to holding the power this motor is capable of producing. The best 0 to 60 time was 5.7 seconds, part throttle through most of first gear then nailing it ,after 40 MPH. On the exhaust side I still have high flow cats and headers to install. I am sure both will improve performance since the CAT back pressure is 3.5 PSI (I think this can be reduce to 1/2 PSI) and the exhaust manifold's ability to move air with its small 1 3/4 inch diameter is poor. It is interesting to note that the blower (even with an overdrive pulley) could only build 12 PSI boost after the heads were ported and now with the high flow exhaust the manifold pressure has dropped to 10 PSI. I think it is time for a modified blower cap, perhaps a S blower, larger throttle body, high flow intercooler and a pay raise. All kidding aside, the SC responds very well to an improved exhaust system and makes other modifications possible. Just think how high the back pressure must be if you have a S Blower, larger throttle body, etc. and a stock exhaust system.
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post #17 of 20 (permalink) Old 01-10-2004, 11:21 AM
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YEP YEP thats the one!

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post #18 of 20 (permalink) Old 01-14-2004, 12:23 PM
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I began modding my 90 SC after using it as a daily driver for 7 years, after racking up 174,000 miles! I'm at 182,000 miles now (no longer a daily driver), and still on the original hg's! The first thing I did was open up the exhaust. Then I began with the obvious things, and worked my way up over the last two years. I now have a full compliment of mods (click here if your interested: mods )

The car runs reliably and has far more perfromance than it ever has since I bought it used with 54,000 miles on the od in Dec. '94. Of course, probably a big part of the reason it is still going strong is because I don't beat on it very often...

Nontheless, there is a small oil leak out of the rear main seal, and I was lucky enough to find a newly rebuilt engine/heads with no miles that I can hopefully swap into by spring.

The first thing to do is the exhaust. Second would be to take care of any issues related to reliability/driveability. I replaced the ps pump because I couldn't stand the way the steering felt. Motor mounts to get rid of excess vibration. Front end components and shocks to improve road feel/handling. Brake upgrade. What good is making the car faster if it is irritating to drive?

Use common sense and don't be in too much of a hurry. Add one mod at a time and test drive for a few days/weeks, to see if all is good.

Good luck!
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post #19 of 20 (permalink) Old 01-15-2004, 09:17 AM
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You should have no problem. My 91 SC has 135k with an completely stock engine including original HG. I autox the car 8-10 times a year and road race in 2-3 drivers events per year.

Had the car up to 130mph on the front straight at texas world speedway where I ran 8 20min sessions over two days.

The car shows no hint of any HG issues. When the HG go I plan to do a full rebuild with some upgraded engine internals.

Currently most of my mods are 145mph speedo, short shifter, brakes, wheels, tires, shocks, swaybar and replacement of all suspension rubber.
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post #20 of 20 (permalink) Old 01-25-2004, 10:22 PM
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The 94/95's were on recall and you probably either have newer head gaskets already, if not a newer engine. I found the reman tag on my block when I pulled it to do all of my performance work. It turned out the 95 sc I bought with 63k on the clock had less than 10k on the engine. I'd put the car on a lift and check around the sidewalls for a silver reman tag, you might be one of the lucky ones that got a new engine as opposed to just new headgaskets. As for modding it, if all was maintained correctly, you should have no problems. If memory serves me right, I think xr7dave is still on his original bottom end.

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