Raggedyman

Update: The engine is back together and I have approximately 30 minutes of idle time in the garage and about 25 miles on it so far. It still runs very strong and I have no doubt it'll blow my '01 4.0l away easily. I have installed the thermostat and checked, and rechecked, the coolant level and so far so good. I replaced the cherokee water pump with a stock '94 wrangler water pump and used a belt pulley from an '00 grand cherokee to run the belt correctly since the wrangler pump sticks further out and the stock wrangler pulley doesn't go far enough back towards the engine to safely run the belt. I didn't have a wrangler mechanical fan but I do have the cherokee mechanical fan, and it bolts up just fine. It pulls plenty of air and fits inside the shroud easily since it's a couple of inches smaller in diameter. I feel much more comfortable using the mechanical fan in it's normal position instead of offset like the cherokee does. The temperatures on the passenger side of the block run about 5-8 degrees cooler around #1 than they do towards the middle 3-4-5. #6 also seems to run a few degrees cooler than the middle. I'm also a few degrees cooler on the head right at the plug on #1. The exhaust header runs also seems to run much cooler on #1....approximately 10-40 degrees cooler in various spots. I also replaced my sketchy oil pressure gauge and now it's steady around 65 while running and 45 while idling when it gets warmed up. I'm running the 195 degree tstat but when my temp climbs up to nearly 210, it drops back to 195 very quickly and pretty much stays there. More to come as the miles start adding on....

I'm hoping to use a noid tester to check the firing of the injectors at the connectors. The wiring harness was also taken from a cherokee and various pieces were added/removed to make it work with my YJ. That said, I really didn't touch the injector section so I didn't take a close look at the connectors other than making sure the grounds were good. I also plan on using a stethoscope to listen to the injectors as they fire...maybe I can catch something. The header is a stock wrangler header with a stock O2 sensor in the normal position. I drilled and added another bung about 4 inches further down the pipe and I'm running an older AEM wideband. In truth it's about 8 years old but the readings seem to follow along pretty good with WOT and release so I'm only assuming it's reading fine. I did check the temps with my handheld heat gun but they climb higher than 500 degrees at the first bend and my heat gun won't go any higher. I did not, however, check the other side of the block. I'll be sure to check that this time. My plugs never showed any signs of detonation or lean.....they were all a nice tan/brown coloring. I was thinking of testing the oiling by submerging the pickup in a bath and priming the system again with the oil pan off. I know it'll make a mess but I should be able to rig up a catch basin. Think that would show me anything on the bottom side?

Thanks for all the info, I'll definitely check into the fuel side as I put it all back together. The injectors were bought off ebay, but from a supposedly good site that cleans and tests each set. I was thinking on swapping the injector but if it is bad then I'm just going to be repairing another piston....but at least it'll tell me what's wrong. I was also going to rig up a noid tester using some led's to check the signals coming from the ecu. I did pressurize the fuel rail and check the injectors and the spray patterns look good with no leaks. Number 1 injector is at the feed/return side of the fuel rail and I was initially running the fuel pressure at 30psi. If I remove the vacuum hose to the fuel regulator I can get the pressure up to 40psi. Perhaps that's part of my problem from the start. Maybe I'm running too low of fuel pressure. Current build theory, from what all I've read, needs a higher fuel pressure for the 24lb injectors. It just doesn't make sense that I'm only having this issue on one cylinder. My heat gun maxes out at 500 degrees so I'll try to find a different one that reads higher. The ecu is just a junkyard ecu, so I could have issues stemming from that even though I get no codes. I have a second ecu but I think it was from a grand cherokee with the 4.0. I'll check the pinouts and see what I can find out.

The lack of lubrication was my initial diagnosis as well. With the oil rings scraping oil from the cylinder walls to lubricate the wrist pin I immediately started there. The inside of the piston shows a dark spot indicative of oil burning, but I blamed that on the heat from the scoring since it was only on that side of the piston. The second set of rod bearings did not have the oil hole but the general consensus was that it was not needed and some bearing manufacturers have stopped doing it. I have added that oil hole on this set of bearings. I am running the stock 4.0 oil filter adapter and filter, but I swapped in a melling high volume oil pump. Due to the size of the pump, I had to clearance the oil pan. I used a 3/8" drill bit coated with grease when I was fitting the pan to get a good amount of clearance around the pickup screen. I had also read of others having issues with the fitment of the pump to the block so I made sure that wasn't happening. I'm using the stock yj gauge and my idle pressure is 40-42psi and running is 58-60psi. However, the gauge can get sketchy as times so I'll try getting a mechanical gauge to double check. My rod bearings don't show any bad wear on any of the sets I pulled, and each time my clearance was between .002-.0025" using plastigauge strips. I don't see any indication of heat around the cam bearings and I did double check their alignment in the block. However, I did not pull the main bearing to check it on any of the teardowns. I'll try that as well just to make sure.

Hmmm, how early? My build uses a 1994 cherokee block and head. As far as I know the machine shop did use a torque plate, although I didn't specifically ask. Thanks for all the good info, I'll definitely keep it all in mind.

Yes, the rods, crank, head and block were all checked at the machine shop before the initial build began. The crank was turned down .010/.010.

Thanks for taking the time to respond, I really appreciate it! I was running the cherokee water pump, which is reverse rotation, and using the same serpentine belt configuration normal for the engine. I also had the fan in place offset from the center of the engine and running a separate electric fan using the fan control relay and wiring. I checked the actuation of the fan controls and checked to be certain that it was a puller fan and not pushing....it's mounted on the engine side of the radiator. It's the standard cherokee 4.0 engine/head and I'm using a fel pro 26211pt head gasket. I compared it to the original gasket back when I first assembled the engine and the passages were the same. On this rebuild, however, I've switched back to the wrangler water pump which is also reverse rotation. I found a pulley from a grand cherokee that extends further towards the block and accommodates the longer shaft of the wrangler pump. I've double checked the piston/wall clearance and piston diameter and they are within spec. All pistons are correct in the bore and the oil hole is in the new rod bearing and aligned with the hole in the rod. I installed new rings on this go around and checked the gaps for each and they are within spec. I pulled the thermostat for the initial running and I'll put it back in as soon as I can, I just wanna make sure I don't develop an air pocket at that point. I checked the angle of the engine and I'm sitting at 4 degrees high to the front, all things considered. I was thinking of getting the rear of the engine higher than the front and pulling the coolant sensor in the back of the head to bleed off any air bubbles. The engine is currently in a 1990 yj and I'm running all the stock gauges. I rewired the engine harness and connector plug to match up to the yj bulkhead connector, and swapped in the yj oil pressure switch to run with the gauge. I also rewired the emission malfunction indicator light to be my check engine light. All things considered, when she runs she runs great. All the gauges function normally, although my oil gauge is a little sketchy at times and requires a tap on the face. I'll use my heat gun to check the block during the initial running to see if I can find any issues.

Hello all! Hoping you folks can help me figure out my problem with a 4.6 stroker that I've built. After the first assembly there were no issues with the break-in process which followed the cam manufacturers directions using comp cams break-in oil and lube. I did the normal easy break-in driving for about 50-75 miles around town and then drove it to work, 50 miles one way. When I started it up after work it was knocking. The knock doesn't go away with time or heat, it gets quieter during running but slowing to idle it's there every time. I got it home and immediately tore it back down to find the #1 piston slapping and scoring the one side of the cylinder wall. I pulled the piston and found it somewhat tight at the wrist pin. I ordered a new piston due to the damage and honed the cylinder wall to clean up the scoring. The second assembly was fine and I did an abbreviated break-in again and all seemed well. I drove around for about 100 miles around town for a few days with no issues. Starting it back up the next morning though it was knocking again immediately. Tearing it down once again I found the exact same thing with #1, slightly tight wrist pin and all. None of the other pistons show any issues. I've replaced the piston once more, installed new rings and new rod bearings but I haven't reassembled the rest of the engine. The first rod bearing set had the oil hole but the second set did not. This last set didn't either, but I cut a groove using a dremel and cleaned it up just to get the extra oil. I went to a different machine shop following some recommendations that the shop installing the piston was causing possible issues. The new shop pin fit the new piston. The new shop is an old school engine machine shop and he offered me two possible causes.....air bubble trapped around the cylinder causing elevated temperatures, and too much fuel causing elevated temperatures and possible fuel wash into the cylinder. I went home and pressure tested the fuel rail. The injectors are holding and the spray pattern is good. I also run a wideband O2 sensor and I'm running between 14.5 and 15.1 on the gauge. He recommended pulling the thermostat on the initial running to clear out any possible air trapped around the cylinder, before reinstalling it. What am I missing....? Specs: 1990 4.2 crank turned down .010/.010 with all new bearings, thrust is at .002, plastigauged all bearings at .002 - .0025 1994 Cherokee 4.0 block, 4.0 rods, block bored .030 over and magnafluxed/tanked Quench is .062 using .040 head gasket New Icon ICC 944 pistons .030 over, verified at 3.902, new rings, down .022 in the bore Comp cams 68-231-4 cam and lifters Bosch 24lb fuel injectors, cleaned, checked and verified to be working normally Cylinder bores are 3.9045 and pistons are 3.902, .0025 clearance per manufacturer 190 degree thermostat Thanks in advance for any help everyone!