Hello everyone! This is my first post on this forum, and I was hoping to tap into this great IH knowledge base. Thank you in advance for any insight you can provide. I have a 68 Travelall with a 1973 IC 392 in it that I have started having problems with. This has been a project for the last 6 years. It has taken significant effort to eliminate the previous owners lack of mechanical and electrical understanding along with their lack of general common sense. The truck had been running well and suddenly it started to run terrible (no know trigger, just seemed to start running rough). It just wouldn’t idle and wouldn’t hold its rpms. You could depress and hold the gas pedal to bring engine up to 2000 rpm where it would hold for a second, then require more gas to keep from dying. As more gas was given a hesitation followed by rpms increasing and dying off again. During this time, we moved so the Travelall got put on hold for about a year. Tried some Seafoam to see if that would help with the valves, etc. with no real change in engine performance. Disheartened and busy, the truck sat for almost another year until I decided to try again. Upon further investigation the engine will start, and it will idle fine while the engine is cold but, as soon as it warms up, it will run terrible, won’t idle, won’t hold RPM’s. Basically, seems like it is running on 5 cylinders. All indications are that this is a tired old motor that could use a rebuild but, that doesn’t necessarily explain why it would suddenly start running like crap. I’ve had vehicle with worse stats that while they were not bulletproof performance demons, they were still drivable. This 392 currently is not. Any incite you could offer would be greatly appreciated. Thank you!
A little data (in no particular order)
1968 Travelall with a 1973 IC 392
4x4 with 8 bolt Dana 44 front and 8 bolt Dana 60 rear (from 74-75 Travelall) (disk brakes front and back)
T98 transmission (I believe) with an NP202 transfer case
Vacuum at idle when it still idled and ran well: 13 in HG to 14 in HG at idle (bouncing needle indicative of sticking valves)
Valve train is welded rocker type: gone through, cleaned, inspected and oiling properly)
Cylinder compression check: IIRC all cylinders were approx. 120 psi and within 10% of each other
All wiring is new (quality wire, weather pack wire and bulkhead connectors, appropriate fuses and relays)
Holley 4150 carb (installed new with approx. 700 miles on it over approx. 4 years) Carb was adjusted by a mechanic who’s daily driver is an IH
Holley Mighty Mite Electric Fuel Pumps 12-427
Flow Rate: 32 gph, Maximum Pressure: 7 psi
Fuel filter before and after pump (both replaced and clear of obstruction)
Fuel psi at carb: approx. 3.5 psi (at cold idle)
Side note – When I got the truck it had an electric fuel pump, as with most of the PO’s work it was a hazard so, I tried to replace the electric pump with a mechanical one, tried 2 different ones. Neither mechanical pump would put out enough fuel to keep the engine running so, I went back to a properly installed electric pump. Ever heard of that in an IH?
Holley distributor (Cardone Remanufactured Distributor, approx. 700 miles on it over approx. 4 years)
Chevron gas with fuel stabilizer added
PerTronix 91481 Ignitor II (approx. 700 miles on it over approx. 4 years)
PerTronix Flame-Thrower Ignition Coils 40111 (Ohm readings - Primary resistance 1.4 ohms, Secondary resistance 9220 ohms (no ballast resistor, full battery voltage (12.5v) to coil) – (approx. 700 miles on it over approx. 4 years)
Plugs: NGK (3332) XR5 V-Power Spark Plugs: .035 gap (approx. 500 miles on it over approx. 4 years)
Plugs have been pulled and cleaned (repeatedly)
Plug wires have all been replaced
All plugs tested with an inline spark tester and are getting spark
All vacuum lines plugged with no apparent leaks.
EGR is blocked off
PCV valve is new and rattles nicely
A little data (in no particular order)
1968 Travelall with a 1973 IC 392
4x4 with 8 bolt Dana 44 front and 8 bolt Dana 60 rear (from 74-75 Travelall) (disk brakes front and back)
T98 transmission (I believe) with an NP202 transfer case
Vacuum at idle when it still idled and ran well: 13 in HG to 14 in HG at idle (bouncing needle indicative of sticking valves)
Valve train is welded rocker type: gone through, cleaned, inspected and oiling properly)
Cylinder compression check: IIRC all cylinders were approx. 120 psi and within 10% of each other
All wiring is new (quality wire, weather pack wire and bulkhead connectors, appropriate fuses and relays)
Holley 4150 carb (installed new with approx. 700 miles on it over approx. 4 years) Carb was adjusted by a mechanic who’s daily driver is an IH
Holley Mighty Mite Electric Fuel Pumps 12-427
Flow Rate: 32 gph, Maximum Pressure: 7 psi
Fuel filter before and after pump (both replaced and clear of obstruction)
Fuel psi at carb: approx. 3.5 psi (at cold idle)
Side note – When I got the truck it had an electric fuel pump, as with most of the PO’s work it was a hazard so, I tried to replace the electric pump with a mechanical one, tried 2 different ones. Neither mechanical pump would put out enough fuel to keep the engine running so, I went back to a properly installed electric pump. Ever heard of that in an IH?
Holley distributor (Cardone Remanufactured Distributor, approx. 700 miles on it over approx. 4 years)
Chevron gas with fuel stabilizer added
PerTronix 91481 Ignitor II (approx. 700 miles on it over approx. 4 years)
PerTronix Flame-Thrower Ignition Coils 40111 (Ohm readings - Primary resistance 1.4 ohms, Secondary resistance 9220 ohms (no ballast resistor, full battery voltage (12.5v) to coil) – (approx. 700 miles on it over approx. 4 years)
Plugs: NGK (3332) XR5 V-Power Spark Plugs: .035 gap (approx. 500 miles on it over approx. 4 years)
Plugs have been pulled and cleaned (repeatedly)
Plug wires have all been replaced
All plugs tested with an inline spark tester and are getting spark
All vacuum lines plugged with no apparent leaks.
EGR is blocked off
PCV valve is new and rattles nicely