Fuel starvation or leaning out at highway speed
Posted: Sun Mar 07, 2010 1:54 am
Gents,
I got the car running well. Driving around smaller roads at varying speeds up to 55 mph is a very pleasant experience. Runs at 85 deg C the whole time. However, as soon as I try highway speeds the car suffers lean conditions/fuel starvation.
Symptoms at speeds above 55 mph:
- loss of power - unable to break 65 mph
- will not rev high enough
- heats up to 100 deg C (about a mm from the start of the red marking on the temperature gauge)
Facts:
- new carter fuel pump
- new fuel filter
- new spark plugs NGK bp6
- fresh fuel
- rebuilt strombergs (new needles, diaphragm and the works)
- even 170 psi compression
- starts easily, idles smoothly and runs well up to 55 mph
- valve clearances set within spec
- no undesired knocks or rattles
- new K&N airfilter in the nose of the car
- new Lucas gold coil (grounded body)
- new pertronix dizzy with flame thrower guts (with separate ground wire from body to ground point)
- new plug wires
- ignition advance set by the advance a bit at a time until it knocks, and then back it off 2 degs
- dampers in carbs have oil
- good oil pressure in engine at all revs
I am leaning to one of three potential sources of the problem:
1. needle valve in float chambers set too low - fuel starvation at speed
2. carb jets sitting to high in the body - too lean mixture
3. whatever someone with more experience on this esteemed forum can point me to
How can I tell the difference between 1 and 2 above?
I have reseached the archives but could not find this described.
I got the car running well. Driving around smaller roads at varying speeds up to 55 mph is a very pleasant experience. Runs at 85 deg C the whole time. However, as soon as I try highway speeds the car suffers lean conditions/fuel starvation.
Symptoms at speeds above 55 mph:
- loss of power - unable to break 65 mph
- will not rev high enough
- heats up to 100 deg C (about a mm from the start of the red marking on the temperature gauge)
Facts:
- new carter fuel pump
- new fuel filter
- new spark plugs NGK bp6
- fresh fuel
- rebuilt strombergs (new needles, diaphragm and the works)
- even 170 psi compression
- starts easily, idles smoothly and runs well up to 55 mph
- valve clearances set within spec
- no undesired knocks or rattles
- new K&N airfilter in the nose of the car
- new Lucas gold coil (grounded body)
- new pertronix dizzy with flame thrower guts (with separate ground wire from body to ground point)
- new plug wires
- ignition advance set by the advance a bit at a time until it knocks, and then back it off 2 degs
- dampers in carbs have oil
- good oil pressure in engine at all revs
I am leaning to one of three potential sources of the problem:
1. needle valve in float chambers set too low - fuel starvation at speed
2. carb jets sitting to high in the body - too lean mixture
3. whatever someone with more experience on this esteemed forum can point me to
How can I tell the difference between 1 and 2 above?
I have reseached the archives but could not find this described.