When to replace a converter?
Posted: Tue Oct 12, 2010 4:29 pm
I have a SBC chevy vega. It is a typical mid 10 car, turbo 400, 4.88 gears, 3060 lbs with me in the car. ( tires 31.25 tall)
The attached image is the datalog session of the last run, 10.80 @ 125. I have had a best of 10.60 @ 132. The current log is with a new t-ram and carbs, and it was pretty fat on this run. Anyhow, The ET seems poor for the mph. It Has an old hand me down 8" coan converter, whose history I don't know.
Is there anything to be learned by the rpm plots?
355 SBC 4340 crank, 4340 h beam rods (6.000)
Probe pistons (12.5 cc dome, should yield 12.5 ish compression.)
Sportsman II heads by Chapman head service
64CC chambers
Intake Exhaust
Lift CFM CFM
0.200 130 101
0.300 177 133
0.400 194 140
0.500 233 141
0.550 260 159
0.600 270 169
0.650 290 179
0.700 290 179
Victor Ram 2 holley 660's,,
Solid Roller)
.630 /.630 lift @ 1.5 , 1.6 Erson rockers used
252/260 duration @.050 lift
cam is straight up, 106 degree lobe centerline.
Crane stud girdles
1-3/4” headers hooker super comps, open exhaust
MSD 6AL, MSD dist. 36deg total timing.
Turbo 400 w/ reverse pattern valve body, trans brake.
4.88 gears,
ladder bar suspension, 90/10 shocks, line loc, M/T 31.25/12.2-15W tires
Et-cetera
The attached image is the datalog session of the last run, 10.80 @ 125. I have had a best of 10.60 @ 132. The current log is with a new t-ram and carbs, and it was pretty fat on this run. Anyhow, The ET seems poor for the mph. It Has an old hand me down 8" coan converter, whose history I don't know.
Is there anything to be learned by the rpm plots?
355 SBC 4340 crank, 4340 h beam rods (6.000)
Probe pistons (12.5 cc dome, should yield 12.5 ish compression.)
Sportsman II heads by Chapman head service
64CC chambers
Intake Exhaust
Lift CFM CFM
0.200 130 101
0.300 177 133
0.400 194 140
0.500 233 141
0.550 260 159
0.600 270 169
0.650 290 179
0.700 290 179
Victor Ram 2 holley 660's,,
Solid Roller)
.630 /.630 lift @ 1.5 , 1.6 Erson rockers used
252/260 duration @.050 lift
cam is straight up, 106 degree lobe centerline.
Crane stud girdles
1-3/4” headers hooker super comps, open exhaust
MSD 6AL, MSD dist. 36deg total timing.
Turbo 400 w/ reverse pattern valve body, trans brake.
4.88 gears,
ladder bar suspension, 90/10 shocks, line loc, M/T 31.25/12.2-15W tires
Et-cetera