| Slant Six Forum https://slantsix.org/forum/ |
|
| main jet for best mpg?? https://slantsix.org/forum/viewtopic.php?t=39290 |
Page 1 of 1 |
| Author: | hydrive1953 [ Sun Mar 07, 2010 2:39 am ] |
| Post subject: | main jet for best mpg?? |
I have a 1975 Dodge Dart with a slant six, 1945 carb, auto trans, 7 1/4 rear end. What I would like to know, what is the best main jet for all around use and best for mpg all weather driving. I need to go through my carb, and while I have a go at it I want to change out the jet. I am running rich now that the weather is getting above freezing. I am still getting 16-17 mpg. I smell gas bad on the worm-up only. My plugs are getting sooty. I think that I have the choke set right. |
|
| Author: | SlantSixDan [ Sun Mar 07, 2010 7:14 am ] |
| Post subject: | |
If the exhaust smells like raw gas during warmup and the plugs are sooty, that suggests the choke is not set correctly. What is the history/condition of the carburetor on this car? |
|
| Author: | Aggressive Ted [ Sun Mar 07, 2010 9:35 am ] |
| Post subject: | |
Along with Dan's question.....here are a few things I have experienced on a stock SL6. The floats sometimes stick/rub on the inside of the fuel bowls causing the fuel inlet not to close which cause excess fuel enrichment irregardless of the main jet size. Make sure they are free floating and not rubbing...... My floats had become fuel soaked and swelled. A new float kit solved the problem. Mine had run very rich like yours. The stock jet size for a 1945 in 1974 was a 612, which is a close tolerance #61. At best I could get on trips was 22 mpg with the stock jet. Most of the time the average was around 18 mpg. Earlier carbs came with a #58 jet which I tried and was able to reach 24 mpg on a trip but not consistently around town . It seemed way to lean for daily driving. I was always into the power valve to get it going. After trying (3) 1945's, which one was a new one because I heard they can deliver better mileage upwards of 28 to 30 mpg, but never realized it. I was offered a 1920 Holly Economaster and have been extremely impressed with it in terms of tuning range, economy and performance. I can run a #66 jet for drag racing which makes it feel more like a 318 under the hood (mpg drops to 20) or a #56 jet for max mileage (25+ mpg). You can change a jet in about 3 minutes...by removing only 4 screws. Since the Economaster change, I have tried several stock 1920 designs and have gotten an average 20 mpg on up depending on condition and tuning. |
|
| Author: | /6 Matt [ Mon Mar 08, 2010 3:58 am ] |
| Post subject: | |
Sorry to steal the thread, but where do you get different jets? Are they universal or does it have to be specificall for my carburettor (holley 1920)? |
|
| Author: | Aggressive Ted [ Mon Mar 08, 2010 7:25 am ] |
| Post subject: | |
Most good auto parts stores.....just stock Holley jets that would go any of their carbs....nothing unique for a 1945 or a 1920 Holley. |
|
| Author: | SlantSixDan [ Mon Mar 08, 2010 10:17 am ] |
| Post subject: | |
Actually, there are at least two different physical sizes of Holley jet; it's not "one size fits all Holley models". The 2280 2bbl, for example, uses the smaller size. |
|
| Author: | 75duster [ Mon Mar 08, 2010 10:19 pm ] |
| Post subject: | |
in terms of jets, do ones out of other carters work in bbds as well? |
|
| Author: | RustyRamcharger [ Sun Mar 14, 2010 5:55 am ] |
| Post subject: | |
If the carb has a nitrophyl (gray/black plastic) float, replace it. They absorb fuel over time and lose bouyancy. The fuel level in the bowl will be high with little control of the fuel level if this happens, and the engine will run rich and frequently flood. Holley carbs will likely have brass floats, so fuel absorption over time is not an issue unless it develops a hole. Holes in brass floats can be repaired with solder after the float is emptied. Ken 
|
|
| Author: | SlantSixDan [ Sun Mar 14, 2010 9:25 am ] |
| Post subject: | |
No, actually, all the Holley 1bbl carbs used as original equipment on slant-6s (1920, 1945), and the 2280 2bbl as well, use Nitrophyll (foam) floats -- not brass. There is a brass float available for the 1945, but not for the 1920. |
|
| Page 1 of 1 | All times are UTC-08:00 |
| Powered by phpBB® Forum Software © phpBB Limited https://www.phpbb.com/ |
|