[Z Code 400]

Yesterday, I had my Formula dyno'd in preparation for the upcoming '092' cylinder head and .466"/.466" - 220°/226° @ .050" - 111.5° LSA camshaft swap. The previous baseline was 146.8 RWHP @ 4200 rpm and 204.1 lbs/ft RWTQ @ 2700 rpm. This was in totally stock condition with log manifolds and single exhaust. The car also passed it's last smog check in this state of tune.

Pretty sad performance!!!!

Since that test, I have recurved the HEI, installed the MSD Low Resistance Bushing, and installed AC plugs gapped at .080" with new AC Delco plug wires. I also built a Q-Jet from a 17058553 main body and a 7045568 air horn. I installed new bushings in the throttle body and secondary air valve shaft (upper) as both were badly worn.

Ignition timing is 20° BTDC @ idle with 36° BTDC total timing @ 3000 rpm and 8° of ported vacuum advance. Test was conducted on 87 octane fuel with no additives whatsoever.

I used .075" jets with a set of Cliff's new .045" metering rods, a 'Blue' power piston spring (from Cliff) and .070" upper and lower air bleeds. The idle tubes were enlarged to ..037" and the idle down channel restrictions are .047" in diameter. I used a 'G' hangar and .051" secondary metering rods.

I also installed a set of Heddman #28150 4-Tube Headers, 2.50" mandrel bent headpipes, an 'H' pipe and a #42585 Flowmaster Transverse Muffler with dual 2.50" mandrel bent tailpipes, exiting in the stock location.

The test was conducted at 88°F ambient temperature and 36% relative humidity. The ambient barometric pressure was 29.90in/Hg and the elevation at the test site was 100' ASL. The operator estimated a 22% loss factor. Coolant temperatures were in the 160° to 180° during testing.

The new figures were 247.6 RWTQ @ 3300 rpm and 201.3 RWHP @ 4200 rpm. I was unable to get an A/F ratio reading during this test as there was a problem with the sensor.

The tests will be conducted again once the '092' heads and new camshaft have been installed. I will post the results to this thread and track the performance gains.

I hope this information is helpful...Robert

P.S. The .080" plugs were used as they generated the lowest (cleanest) overall tailpipe emissions.