Howdy all:
My brother, Dennis, and I have just spent the better part of this past week examining, tearing apart, tuning, and rebuilding Autolite 2100s. As a result, we have more questions and puzzles, and a few, great big Aw-Haas!
We focused on 1.08’s, 1.14s, & 1.21s. We need more 1.23’s & 1.33s to look at before we can make any generalities about them.
The test mule was Dennis’ “Hot6T†Falcon Ranchero. It has a flat-top ‘78 head modified with larger exhaust valves, Ported & polished, 9.7:1 compression, a 264 Clifford cam, dual outlet headers & DSII ignition with a hot coil. All through a T5 and a 7 1/4†3.50:1 rearend. The vehicle weighed in at 2,760lbs. The measuring instrument was a G-Tech accelerometer. This was our first use of the G-Tech meter. It is very sensitive and took some trial and error to get consistency. We were measuring Max HP only. Once we determined reliable comparisons we did not move it or unplug it from power. We tried to find the most level part of back roads and averaged at least five runs, going in three directions to compensate for wind. A total of 33 runs were made with the only malady being a blown header gasket.
Dennis’ Ranchero has a well modified 200, using a modified flat-top log head so that the Autolite 2 barrels were all mounted directly- no adapter. A baseline was taken, followed by a good ignition and timing tune up. Base-lined again with no significant improvement. Ironically, the ignition tune-up made little difference in peak HP. It did start, drive and idle better.
The next test was to determine a baseline with the junkyard 1.08. The 1.08 gave good reliable performance and good mileage (21.8 mpg for 1,270 miles). It was not in bad shape at all. That was followed by mounting a rebuilt 1.21, jetted at #50. It marked an average of a 25% increase over the 1.08 in Max HP according to the G-Tech meter. A statistical comparison of the two carbs is:
Venturi CFM rating Throttle bore Main Jet Shifts
1.08 287 1.55†49 5,000
1.21 351 1.68†50 5,500
It was clear that a modified log head on a modified 200 can benefit from more CFM than we had previously thought. The 1.21 drove well, but has a high idle problem that we will try to solve this PM. It appears that the 1.21 will have a permanent home on the “Hot6T†200- that is until we can find and try a 1.33 Autolite!
We also discovered inconsistencies in Throttle Bore (TB) sizes that are somewhat puzzling. A 1.08 had a larger TB, but with a smaller Venturi!!! We have another garage of carbs to measure, but it appears that 1.08s (‘68 - ‘73) could have a 1.42†or a 1.55†TB, 1.14s (‘64 -’67) have 1.42†TB and 1.21s could have 1.55†or 1.68†Throttle bores.
We had one 1.23 to measure and it had the 1.68†TB.
What next? We’ve ordered a 500 Holley 2300 from Summit for my 250. It will replace a 1.08 also. My 250 has similiar mods as Dennis’. More fun to come. Stay tuned.
This info and more will be in the next edition of the Handbook, which should be out by fall.
Adios, David
My brother, Dennis, and I have just spent the better part of this past week examining, tearing apart, tuning, and rebuilding Autolite 2100s. As a result, we have more questions and puzzles, and a few, great big Aw-Haas!
We focused on 1.08’s, 1.14s, & 1.21s. We need more 1.23’s & 1.33s to look at before we can make any generalities about them.
The test mule was Dennis’ “Hot6T†Falcon Ranchero. It has a flat-top ‘78 head modified with larger exhaust valves, Ported & polished, 9.7:1 compression, a 264 Clifford cam, dual outlet headers & DSII ignition with a hot coil. All through a T5 and a 7 1/4†3.50:1 rearend. The vehicle weighed in at 2,760lbs. The measuring instrument was a G-Tech accelerometer. This was our first use of the G-Tech meter. It is very sensitive and took some trial and error to get consistency. We were measuring Max HP only. Once we determined reliable comparisons we did not move it or unplug it from power. We tried to find the most level part of back roads and averaged at least five runs, going in three directions to compensate for wind. A total of 33 runs were made with the only malady being a blown header gasket.
Dennis’ Ranchero has a well modified 200, using a modified flat-top log head so that the Autolite 2 barrels were all mounted directly- no adapter. A baseline was taken, followed by a good ignition and timing tune up. Base-lined again with no significant improvement. Ironically, the ignition tune-up made little difference in peak HP. It did start, drive and idle better.
The next test was to determine a baseline with the junkyard 1.08. The 1.08 gave good reliable performance and good mileage (21.8 mpg for 1,270 miles). It was not in bad shape at all. That was followed by mounting a rebuilt 1.21, jetted at #50. It marked an average of a 25% increase over the 1.08 in Max HP according to the G-Tech meter. A statistical comparison of the two carbs is:
Venturi CFM rating Throttle bore Main Jet Shifts
1.08 287 1.55†49 5,000
1.21 351 1.68†50 5,500
It was clear that a modified log head on a modified 200 can benefit from more CFM than we had previously thought. The 1.21 drove well, but has a high idle problem that we will try to solve this PM. It appears that the 1.21 will have a permanent home on the “Hot6T†200- that is until we can find and try a 1.33 Autolite!
We also discovered inconsistencies in Throttle Bore (TB) sizes that are somewhat puzzling. A 1.08 had a larger TB, but with a smaller Venturi!!! We have another garage of carbs to measure, but it appears that 1.08s (‘68 - ‘73) could have a 1.42†or a 1.55†TB, 1.14s (‘64 -’67) have 1.42†TB and 1.21s could have 1.55†or 1.68†Throttle bores.
We had one 1.23 to measure and it had the 1.68†TB.
What next? We’ve ordered a 500 Holley 2300 from Summit for my 250. It will replace a 1.08 also. My 250 has similiar mods as Dennis’. More fun to come. Stay tuned.
This info and more will be in the next edition of the Handbook, which should be out by fall.
Adios, David
