Have 25 T running, but is running ruff and way to rich. after turning off gas and just before carb runs out of gas it smooths out and runs fine for a few seconds. If I try to run the engine faster it gets worse. I can have carb adjustment completely turned off and does not make any difference. Have lowered the float several times and that doesn't seem to help. It has new needle and seat and seems to be seating fine. What am I missing or how do I correct the rich fuel mixture. It is running unleaded gas with no alcohol.
It is a Holley NH Carburetor with center drain
Has it been rebuilt? Does the main idle adjustment have a groove in it?
Needle and seat are new. Spray nozzle and seat are new. All gaskets have been replaced. Shafts seem to be in good shape.
It can only be a couple of things.
1. Choke not staying open. (Broken spring)
2. Spray nozzle leaking at the gasket.
3. Main jet air vent plugged
Same thing happened to me. Turns out that I had the set nut too tight. After I loosened that up a bit I got 5 more turns in on the needle before it bottomed out. Mystery solved! Good luck! Daryl
1. Choke is open. New spring.
2. Spray nozzle leaking at gasket. New gasket was installed
3. Main jet air vent plugged. Can someone enlighten me on that one. How to check to see if is plugged, and if plugged how do you remedy it.
4. Does float level effect the richness of it running? "T" book states 1/4 inch from cast to top of float. I have changed the float level so it should stop gas flow sooner but no change in richness.
Did you unscrew the needle valve before installing the spray nozzle? The spray nozzle could have bottomed out on the rod before sealing the gasket (washer).
Check for cracks in the lower body.
Is the plug installed in the lower idle circuit drilling? It may not be sealing. This drilling bypasses the spray nozzle and is a direct port to the fuel bowl.
Too high of a float setting (or leaking float valve) and gas will run out of the carb inlet (if the needle valve is open) and bowl vent. Too low of a setting and you'll run out of gas at high speed.
(quick question) When running out of gas at high speed, Does the engine run fine then die like it ran out of gas and then pick up again (repeating this process over and over) making the car surge and ride like a stubborn animal?
Yes Kep, it could. There's no fuel for the engine to burn until the bowl refills.
I also had a carb that was way too rich and it was like what Daryl said. The spray needle locking adjustment was way too tight and provided a "false bottoming" of the spray needle when turned down. A quick comparison with other NH's on other motors showed that there was a lot more thread above the locknut and the top of the spray needle was way high compared to other carbs. I swapped out the lock nut for one from another carb and it let the spray need go way down into the carb and then 1.5 turns back for starters and the whole thing ran like a top. Measure the distance from the top of the locknut up to the bottom of the 2 holed cross piece at the top end of the spray needle and post us that dimension. A little comparison might reveal if you are having this same issue or not.