MomoJeep
Basic User
- City
- Seattle
- State
- WA
Hey guys,
I'm wondering if I push my engine too hard and/or are under-powered? Or if I'm just having some bad luck. I really don't want to be messing around with engine problems. I want something that works reliably. Here's what I'm running and here's what's happened:
Original 258 rebuilt block (bored over). Mild RV cam. 4.0L head conversion with Mopar MPI. This head conversion includes some blocked off water jacket passages in the head that don't exist on the block.
3.31 gears, AX-15 5sp w/overdrive, D300. 32" tires. Hard top and rook rack and typically carrying gear/people. Some long roadtrips, some desert heat (Utah), and then sitting for a a year or two in the wet PWN climate (before the most recent failure).
First failure: A long time ago, shortly after the rebuild, some kind of valve issue. The rebuilder used Stainless Steel valves. Something bent I think. So I brought it back and he put in regular
valves.
Second failure: The valves started tapping hard after a long Western US roadtrip with three people and lots of gear (roof rack included). Jeep is loaded down heavy. Mountain passes and hot deserts in summer. Turns out the valve seats were hammered down into the head and the head itself was damaged and not salvageable.
Third (current) failure: After the previous failure, I found a place in Florida selling used heads reconditioned for the exact conversion. The water jackets came already plugged. I had a professional shop do the work. There was some issue in the previous head of measuring and getting custom pushrod lengths, which I did DIY. This time around, the shop made them all the same standard length and believe compensated by machining the posts / mount surfaces. So I have ran this version now for a few years. It was running strong right after this new head was put on. Then it sat out in the wet PNW climate for a year or two with me just firing up the engine for 20 minutes every now and then. Then I started drving it again. Did a long roadtrip from WA state to UTAH last spring/summer. No problem. Did another one this fall and saw the gas mileage dropping and engine idling rough. Check fuel, spark, compression and air, all good. Replaced old (dead) Oxygen sensor, but still running rough. Took to the shop, they are saying I have a bad exhaust valve on Cyl #2. It's dropped down in the valve seat and is sticking. Sound like we can pull the head and re-do the seats, and re-use it. BUT...
Why is this happening? Should I not be driving (up tp) 70+mph on long roadtrips with my jeep loaded down with this engine? Have I overloaded it? It's incredibly torquey so I didn't think I was underpowered.
Or is this just bad luck?
I'm wondering if I push my engine too hard and/or are under-powered? Or if I'm just having some bad luck. I really don't want to be messing around with engine problems. I want something that works reliably. Here's what I'm running and here's what's happened:
Original 258 rebuilt block (bored over). Mild RV cam. 4.0L head conversion with Mopar MPI. This head conversion includes some blocked off water jacket passages in the head that don't exist on the block.
3.31 gears, AX-15 5sp w/overdrive, D300. 32" tires. Hard top and rook rack and typically carrying gear/people. Some long roadtrips, some desert heat (Utah), and then sitting for a a year or two in the wet PWN climate (before the most recent failure).
First failure: A long time ago, shortly after the rebuild, some kind of valve issue. The rebuilder used Stainless Steel valves. Something bent I think. So I brought it back and he put in regular
valves.
Second failure: The valves started tapping hard after a long Western US roadtrip with three people and lots of gear (roof rack included). Jeep is loaded down heavy. Mountain passes and hot deserts in summer. Turns out the valve seats were hammered down into the head and the head itself was damaged and not salvageable.
Third (current) failure: After the previous failure, I found a place in Florida selling used heads reconditioned for the exact conversion. The water jackets came already plugged. I had a professional shop do the work. There was some issue in the previous head of measuring and getting custom pushrod lengths, which I did DIY. This time around, the shop made them all the same standard length and believe compensated by machining the posts / mount surfaces. So I have ran this version now for a few years. It was running strong right after this new head was put on. Then it sat out in the wet PNW climate for a year or two with me just firing up the engine for 20 minutes every now and then. Then I started drving it again. Did a long roadtrip from WA state to UTAH last spring/summer. No problem. Did another one this fall and saw the gas mileage dropping and engine idling rough. Check fuel, spark, compression and air, all good. Replaced old (dead) Oxygen sensor, but still running rough. Took to the shop, they are saying I have a bad exhaust valve on Cyl #2. It's dropped down in the valve seat and is sticking. Sound like we can pull the head and re-do the seats, and re-use it. BUT...
Why is this happening? Should I not be driving (up tp) 70+mph on long roadtrips with my jeep loaded down with this engine? Have I overloaded it? It's incredibly torquey so I didn't think I was underpowered.
Or is this just bad luck?
