Head/ Valve Problems?
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Head/ Valve Problems?
I have a 1985 F-150 with the 5.8L Windsor HO, the truck runs spectacular when it is warmed up... But not quite what I would expect. When the truck is at a dead stop and you punch it, it stutters or backfires... Even after tuning the carburetor... The engine seemingly looses coolant every oil change but there is no evidence of where it could be leaking. My question, does it sound more like a cracked head, bad valves, or head gasket? Another question would be, doing a rebuild, minus crank and new heads, would that possibly fix my problem?
Lead Driver
Joined: Jul 2009
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From: Sheffield, AL
Welcome, Cowboybrad351!
Many questions. Is this truck new to you? Does the exhaust seem to emit steam even after warming up? Use the "search" feature and read about compression testing as well as leak-down testing. There are kits where a coolant sample can be tested for exhaust gasses. Do some diagnostic work before tearing into the engine for major repair.
You mentioned tuning the carburetor, but have you checked the sparkplugs, distributor cap and rotor or sparkplug wires? What about the ignition timing? That has a lot to do with how the engine performs.
Many questions. Is this truck new to you? Does the exhaust seem to emit steam even after warming up? Use the "search" feature and read about compression testing as well as leak-down testing. There are kits where a coolant sample can be tested for exhaust gasses. Do some diagnostic work before tearing into the engine for major repair.
You mentioned tuning the carburetor, but have you checked the sparkplugs, distributor cap and rotor or sparkplug wires? What about the ignition timing? That has a lot to do with how the engine performs.
Lead Driver
Joined: Nov 2013
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I certainly wouldn't condemn an engine's internals without first replacing the spark plugs, plug wires, distributor cap, and rotor. A fault with any of those components could cause the problems you've described.
If no help, next is a compression test.
After that, you may want to consider a dynamic compression test. It's kind of odd and time-consuming, but will isolate problems (such as a broken valve spring) that won't show up in a regular compression test:
http://www.misterfixit.com/
As far as the coolant usage, you may find this recent thread of interest:
https://www.ford-trucks.com/forums/1...u-guys-do.html
FWIW, my 351W goes through a fair amount of coolant but I've never been able to track it down. I just keep the coolant topped off. $20 of coolant per year beats $2000 for a rebuild.
If no help, next is a compression test.
After that, you may want to consider a dynamic compression test. It's kind of odd and time-consuming, but will isolate problems (such as a broken valve spring) that won't show up in a regular compression test:
http://www.misterfixit.com/
As far as the coolant usage, you may find this recent thread of interest:
https://www.ford-trucks.com/forums/1...u-guys-do.html
FWIW, my 351W goes through a fair amount of coolant but I've never been able to track it down. I just keep the coolant topped off. $20 of coolant per year beats $2000 for a rebuild.
Lead Driver
Joined: Nov 2013
Posts: 7,178
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I was reminded of the choke after reading the resolution in this thread:
https://www.ford-trucks.com/forums/1...condition.html
One more thought on your concerns of the stumble being connected to a possible coolant loss. If you had an internal coolant leak, it would have to be really severe to cause poor performance. Any such problem that bad would be super obvious in a compression test or a pressure test of the cooling system. Definitely run some routine diagnostic tests before assuming the engine is toast.
Also, what about the accelerator pump operation? With the engine off and choke plate fully open, quickly cycle the throttle. You should see gas squirt down the carb throat.
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strider3700
1987 - 1996 F150 & Larger F-Series Trucks
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Feb 8, 2014 06:58 AM
