I lost 10mph off my top end. What the?

[LaGrasta]

I used to be able to tap 100mph. Driving on the freeway to work, I often, just before the exit, open it up. It's sort of an addiction, really.
Anyway, it would just reach 100mph, but for the last week or so, it creeps just above 90mph and that's it. Any suggestions as to why?

 

[fb71]

any change in ambient temp? humidity? different fuel station or grade?

 

[66 Fastback]

I think it is the extra drag caused by the '59 Caddy tail lights and fishtail exhaust tips.
It could be that your plugs are fouled or going away. A slight deterioration of something in the ignition may explain the loss in top end.
Doug

 

[JackFish]

When did you last change the oil? Crappy gas? Plugs?

 

[Mustangaroo]

Check throttle linkage are you still getting full movement of cable to carb? HAve someone floor your pedel while you check to see if the carb is opening fully?

 

[CoupeBoy]

Normally I'd leave this for another of our huckster members but...

How's the diet going?

-ron

 

[Bort62]

Mission Viejo, check for illegals in the trunk ?

Seriously - it's been hotter than hell in So-Cal these last few weeks. 105+ here every day.

 

[LaGrasta]

lot of good thoughts. It has been hot and humid (for here anyway). Oil is fresh however, for the first time, I used Rotella. Plugs are maybe 3 years old/20,000 miles.

I think I'll wait for the temps to change a bit and see what happens, change the oil next time around back to my "old stuff". If I'm still slow, I'll swap out the plugs and see what happens. With these suggestions, my bet is on the plugs.

 

[Anlushac11]

8)

I would check timing and check for vacuum leaks first.

 

[rbohm]

8) one thing i found when i was racing is the heat and humidity really affected the speed a car would hit. hotter, higher=slower.

 

[Mercury Mike]

Those are all good thoughts. Thought I'd let you know though, Anthony, that I got a Duraspark setup now. =) Be jealous! If you wanna get one I'll help you set it up it's eaaaaasy. How's the family/house?

 

[LaGrasta]

Hello Mike. The house is coming along and I've actually started back on the FALCON. I really hope to have it complete by the time Dana Point Falcon Nationals arrive in October. I see an interiour guy this Friday.

As for the DuraSpark, I have Pertronix. After my install, it was a "blow-me-away" difference. I can't imagine swappping to a DuraSpark would make any significant improvement. Would it? Did you swap from points, or a Pertronix set-up?

 

[Mercury Mike]

A pertronix. I had the pertronix in for a few days (it was my grandpa's) and then went to the duraspark, and it was still a pretty big difference. I really dig it. Plus it was a fun install.

 

[hasa68mustang]

Check throttle linkage are you still getting full movement of cable to carb? HAve someone floor your pedel while you check to see if the carb is opening fully?

or if your fast enough floor it and run outside to see if its full throttle before it closes