[2.7RACER]

Hello David,

I live and race in Albuquerque, just over 5,000 ft elevation. I installed JE 9.5 pistons 3 years ago hoping to regain some hp lost to high altitude. Retained the CIS and stock cams.
After running this way for the next year I felt it wasn't what I hoped for. Very little gain.

The next year I got rid of the CIS and stock cams. Weber 40 IDA's and Solex cams brought the motor to life.
I already had my exhaust back dated to the more free flowing '74 system with a low back pressure muffler.
I knocked 3/4 secs from my lap times.

The next year I replaced my 8:31 915 Trans with a 7:31 915 trans from a '72.
On the 1.66 mile 14 turn track I picked up 2/3 seconds. I went from 1:39's to 1:36's.

To answer your question, to fully obtain the benefit of higher compression pistons you need to help the motor breath better with more aggressive cams that cannot be run with a CIS system, free up the exhaust and and add 40 mm Webers. This is a great combination, reliable and proven.

The down side is of course it will not pass smog in many states. '74 and earlier models are generally exempt from smog.

The carbs can be set up for performance or mileage by going with larger venturi's for performance or small vent's for better mileage.

My car is a track car. I rarely run it on the street, although it is licensed and legal where I live.