Carb'd 460 at altitude
#16
01-28-2016, 01:41 PM
#17
09-03-2018, 08:16 AM
Trouble with my 460 at low altitude
ok so I bought my truck from Apple Valley California, She runs but she runs rough like she is missing, I tried to tune her to factory but the carb back fires. I have tried to tune the idle air mixture but it does nothing. I live in Vicksburg, MS. My current altitude is 750 above sea level the truck specs is 1977 F150 (J) 460ci/ c6 auto calif compliant still has the motor craft 4bbl factory stock with emissions. What should I do? I already have new plugs, wires, battery cables, battery, cap and rotor, new vacuum lines radiator, radiator hoses, the trans was recently rebuilt and the rear end has been clean and serviced. Am I missing anything to get her to run smooth. Thank you
#18
09-03-2018, 10:18 AM
I would check first to make sure everything is setup according to Hoyle. Stupid stuff to be sure, though very common mistakes that a PO might have done - like plug wires swapped around, firing order wrong.
Next, using a piston stop, verify that the true TDC for the #1 piston coincides with the mark indicated on the damper. This is a very common defect as the outer inertia weight on these older trucks slips off its clock or index, making the timing marks innacurate.
A mechanic's vacuum gauge connected to manifold will show the health and tune quickly. A stock motor in good shape should pull 19" to 20" of vacuum at sea level with a perfectly steady needle.
Next, using a piston stop, verify that the true TDC for the #1 piston coincides with the mark indicated on the damper. This is a very common defect as the outer inertia weight on these older trucks slips off its clock or index, making the timing marks innacurate.
A mechanic's vacuum gauge connected to manifold will show the health and tune quickly. A stock motor in good shape should pull 19" to 20" of vacuum at sea level with a perfectly steady needle.
#19
10-12-2018, 05:26 PM
im lost
i have a 1986 460 with a factory holley 4 barrell carb......put it in my 71 f100...ran like a dream .so i thought i would do an up grade and but an aluminum in take so i did . i go a weidman stealth....... put all together runs ok but no power at all have had intake off twice ..thought maybe gaskets were leaking ...no vaccum leaks....runs fine when not in gear but put in gear and give it gas and nothing i was laying rubber threw all three gears before .... is the carb not happy with this intake? fyi ..carb has been rebuilt has a new hei distrbutor.....any help would be great in lost
#20
10-13-2018, 08:38 PM
i have a 1986 460 with a factory holley 4 barrell carb......put it in my 71 f100...ran like a dream .so i thought i would do an up grade and but an aluminum in take so i did . i go a weidman stealth....... put all together runs ok but no power at all have had intake off twice ..thought maybe gaskets were leaking ...no vaccum leaks....runs fine when not in gear but put in gear and give it gas and nothing i was laying rubber threw all three gears before .... is the carb not happy with this intake? fyi ..carb has been rebuilt has a new hei distrbutor.....any help would be great in lost
You should start your own new thread on this question. Have you checked your new distributor to make sure it's timed correctly or doesn't have some other issue that would cause a loss of power?
#21
09-10-2020, 10:08 AM
Location?
I brought a 460/C6 up from sea level to 7200ft and it required about 3 jet sizes down. I use an O2 sensor hooked up to a readout to tune it. You should be able to set it just slightly rich at 10K ft and run fine at 5K ft.
This is the updated version of the kit I use:
Home » Shop » Wideband O2 » O2 Controller » NTK AFRM GEN2 - Air Fuel Ratio Monitor Kit - Wideband O2 - PN 90067 - w/ NTK Sensor
You could tune it to about 12.5:1 at your altitude and be good at 5K ft.
This is the updated version of the kit I use:
Home » Shop » Wideband O2 » O2 Controller » NTK AFRM GEN2 - Air Fuel Ratio Monitor Kit - Wideband O2 - PN 90067 - w/ NTK Sensor
You could tune it to about 12.5:1 at your altitude and be good at 5K ft.
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