Welcome Visitor! Please take a few seconds and 
So I just spent a lot of time and money rebuilding my Rangers 4.0 ohv after it developed a knock type sound at 340k miles (180k of which were mine). It appears only on tip-in and light acceleration to the naked ear. Except on cold startup when it can sometimes be heard briefly at idle after the first minute and then for a couple minutes. Sounds heavier than a lifter tick and lighter than a full on rod knock. I never could fully confirm the noise source but the heads, pistons, and valves did have alot of carbon build up and several cylinders had worn down valve seats. But decarbonizaton treatments never helped nor did heavier weight oil, rislone, mmo or any other snake oil I may have tried. Original rockers, and pushrods were all worn, lifters were original but had no obvious collapse and no damage to rollers or needle bearings. I did compression and leakdown testing and found cylinder 6 was the worst (which was where the worn exhaust valve seat was. But overall compression was decent (average 175).
I am a Ford ASSET graduate and 5 year dealer technician (2006-2011), 13 years handyman/mobile mechanic). This is my first complete engine rebuild besides school but I was very thorough about the process and followed all procedures for bearing and ring clearances. I took the disassembled engine to a reputable machine shop, they went over it and said it needed heads but the block, pistons, and rods were ok and just needed the bores honed and the crank polished. They did not provide any recorded measurements but assured me everything was measured to spec. They also said they could reuse the valves and springs in the new bare heads, and had tested the springs to ensure correct spring rate. They reground the seats and valves to ensure proper fit but did not lap them, but said they vacuum tested them.
I replaced all pushrods(Melling), lifters (melling), rocker arms(melling), full timing kit, oil pump, all sensors (SMP), injectors (SMP), pulleys including balancer, power steering pump, water pump, filters, hoses.
I have now put 1000 miles on the engine and the noise is exactly the same as what it was before I took it apart. Except now there is also a lifter rattle type noise on startup after sitting overnight. I purchased a Steelman chassis ear from Amazon and drove it for 500 miles moving microphones around trying to pinpoint the noise. The microphone levels are not all equal so some mics are louder than others but it appears to be coming somewhere from the drivers side of the engine but top vs bottom cannot be determined, and neither can the specific cylinder. I removed the drivers valve cover, checked for play in the valvetrain, found none initially. I pulled rocker arm assembly and checked pushrods by rolling on flat surface, none appeared bent. I reassembled and ran the engine, still had the noise. Then I left it sit overnight, pulled the valve cover again and found some slight lifter leakdown on 2 lifters, cyl 5 intake and cyl 6 exhaust.
I’m not sure if this is the source of my driving noise but it seems like the only evidence I can find without further tear down. The only other thing I can suspect is piston slap which seems likely given that the pistons are original although not worn on the skirts at all (can still see original machining marks all the way down), and the cylinders all had crosshatch still visible and no serious scoring or wear from piston skirt slap. But if the machinist didn’t measure cylinder to piston wall clearance adequately, they may have missed something.
My question is has anybody had this experience, or have any suggestions for things I may be missing. Thanks!
I am a Ford ASSET graduate and 5 year dealer technician (2006-2011), 13 years handyman/mobile mechanic). This is my first complete engine rebuild besides school but I was very thorough about the process and followed all procedures for bearing and ring clearances. I took the disassembled engine to a reputable machine shop, they went over it and said it needed heads but the block, pistons, and rods were ok and just needed the bores honed and the crank polished. They did not provide any recorded measurements but assured me everything was measured to spec. They also said they could reuse the valves and springs in the new bare heads, and had tested the springs to ensure correct spring rate. They reground the seats and valves to ensure proper fit but did not lap them, but said they vacuum tested them.
I replaced all pushrods(Melling), lifters (melling), rocker arms(melling), full timing kit, oil pump, all sensors (SMP), injectors (SMP), pulleys including balancer, power steering pump, water pump, filters, hoses.
I have now put 1000 miles on the engine and the noise is exactly the same as what it was before I took it apart. Except now there is also a lifter rattle type noise on startup after sitting overnight. I purchased a Steelman chassis ear from Amazon and drove it for 500 miles moving microphones around trying to pinpoint the noise. The microphone levels are not all equal so some mics are louder than others but it appears to be coming somewhere from the drivers side of the engine but top vs bottom cannot be determined, and neither can the specific cylinder. I removed the drivers valve cover, checked for play in the valvetrain, found none initially. I pulled rocker arm assembly and checked pushrods by rolling on flat surface, none appeared bent. I reassembled and ran the engine, still had the noise. Then I left it sit overnight, pulled the valve cover again and found some slight lifter leakdown on 2 lifters, cyl 5 intake and cyl 6 exhaust.
I’m not sure if this is the source of my driving noise but it seems like the only evidence I can find without further tear down. The only other thing I can suspect is piston slap which seems likely given that the pistons are original although not worn on the skirts at all (can still see original machining marks all the way down), and the cylinders all had crosshatch still visible and no serious scoring or wear from piston skirt slap. But if the machinist didn’t measure cylinder to piston wall clearance adequately, they may have missed something.
My question is has anybody had this experience, or have any suggestions for things I may be missing. Thanks!
Last edited:
