Posted By: Cab_Burge
Fuel supply issues and results - 07/12/11 07:32 PM
I had posted a problem I found with my LM1 on my current Duster engine last week, it would go lean from the hit of the throttle. The motor is a pump gas 518 C.I. 400 block with dished pistons, I had changed the heads, intake and carbs from the last time I had this motor in the car. The motor did not miss, surge, lay down or give me aany indication that it was starving for fuel, it did not run the same MPH as other cars with similar weight and ET 
The wide ban showed it starting the run at 12.8 and going to 15.8 AFR at the end of the 1/4 mile runs at Woodburn several week ago 
I ended up checking the size of the needles and seats in the carb.it is a stock Holley 850 CFM D.P. 4781-7, it had .110 needles and seats so I changed them to a set of .120 (8.25 % increase in size)last week before the race at Madras, the car had ran a best of 6.786 ET and 101.58 MPH with a air density of 3975 FT. one month ago before the change. This past weekend it ran a best of 6.643 ET at 102.97 MPH with the air density at 4501 FT with no other changs than the bigger needles and seats My message is to make sure all of the fuel system parts are big enough and in good enough condition to feed your motor enough fuel so that you can jet the carb. up big enough to slow the car down, which I will do in two weeks at Woodburns Mopar race. If you go stop by and say hello 
The wide ban showed it starting the run at 12.8 and going to 15.8 AFR at the end of the 1/4 mile runs at Woodburn several week ago I ended up checking the size of the needles and seats in the carb.it is a stock Holley 850 CFM D.P. 4781-7, it had .110 needles and seats so I changed them to a set of .120 (8.25 % increase in size)last week before the race at Madras, the car had ran a best of 6.786 ET and 101.58 MPH with a air density of 3975 FT. one month ago before the change. This past weekend it ran a best of 6.643 ET at 102.97 MPH with the air density at 4501 FT with no other changs than the bigger needles and seats My message is to make sure all of the fuel system parts are big enough and in good enough condition to feed your motor enough fuel so that you can jet the carb. up big enough to slow the car down, which I will do in two weeks at Woodburns Mopar race. If you go stop by and say hello