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Developed a tick/knock on a fresh 355. Feeling pretty defeated. I’ve been driving it a bit hard while tuning PE and then there it was that familiar sound. I’m all but certain rod knock. It’s most audible in the 2-3k rpm. Oddly if I take it up to 5k then let it coast down in 1st gear, I don’t hear it but it may be just drowned out. In the garage, if I poke my head down low by the wheel well and rev via the cruise servo it’s bottom end. I don’t have the time for this again, not to mention the money that went into it. It pulled me away from the family for too long last time so I think this may be curtains for me. I’ll cut the filter open to see but I’m expecting glitter.
not sure what a C4 is really worth with a bum engine, prob lot much. Rest of it is in good shape with rebuilt suspension and plenty of other goodies but I don’t know how far that goes.
Sorry, that is a bummer, if your finances could allow it just jerk it out and send it to a shop to fix the issue or let them do a cheap 383 rotating assembly up grade. This way you should have a reliable car again and take minimal time away from your family...
I also pray its something simple and not the rod bearings... Good Luck be Blessed...
I’m still tossing around getting rid of the car or just letting it sit for a day when my so and I can make it a project, however he isnt even 2 yet, so realistically that day is more than a decade away and I know letting it just sit that long will deteriorate the rest of the car.
I just don’t have the time especially to put into it. Let alone money, it’s hard to keep sinking cash into a 30 year old car that is will never be worth even a fraction as much as what you put in it.
the most I’m going to do in the next few weeks is confirm it’s a rod. I’ll pull the pan and wiggle each and pull the caps if needed. I’d love for it to be something less, a timing change, a lifter. I’m nearly certain though.
Took a few minutes and drained the oil this afternoon. I drained it into a clean drain pan. Oddly, oil is clean. No sparklies whatsoever that I could find. I even dragged a large coffee filter through it to see if it could collect any, nope. I drained the container into another container to see if anything settled on the bottom and still, nothing. I cut the oil filter open and found some, minimal, metal flake but honestly don’t know if that was from my cutting or from the engine. I didn’t think to check if any of it is magnetic, if so then I think from the filter can and not bearing material. I used an exhaust pipe cutter which is like a giant pipe cutter that goes round and round, so relatively clean cut but the tool is old and the cutting wheels chipped so not the best.
Either way, there is a noise that should not be and I’m 95% certain it is bottom end and not valvetrain related. I’ll pull the pan this weekend and expect to find my bearing bits there or wiggle each rod cap and find where it’s loose. I’ll pull each cap too.
all this said, after some deliberation and discussion with wife… arrived that the decision that I probably knew from the onset, keeping it. Will fix. Telling myself (and the wife) that I’m done with driving it hard - cruiser only here on out. We shall see, I’ve been addicted to horsepower since I was a kid so it’ll be particularly hard not to have anything in the stable that I can let loose on.
Yah, I hear you. I’m not an animal with it and never with another car in sight. I’m an on-ramp accelerator fun and even then rarely break 70. I think the tuning for WOT was the most aggressive I’ve been with it and certainly the highest I’ve ever revved it as I was trying to get data for the full range. The cam seemed to want to wind to 6300 at most and my highest datalog was under 6400. I still think it should have survived that and while I expect to find a spun rod bearing, it bothers me that I’m unlikely to know exactly why. It had quality parts, balanced, and I was meticulously on assembly and cleanliness. It made power beyond my expectations as I got the AFRs right.
If it's a rod bearing you can change one out in an afternoon with the engine in. Maybe that one had to little clearance. I did mention to be careful with the tuning. It's a lot to learn and risk. Sorry to hear!
I think you did! I learned the lesson the hard way instead!
I’ve already had in the back of mind - if the bearing didn’t spin and damage the crank and big end of the rod - can I get away with new bearing shells… Probably wishful thinking! I did plastigauge before final assembly and had a consistent 2 thousands across all 8. I do have the bypass in the filter adapter plugged so 100% of oil is filtered. That gives me some confidence that it didn’t send trash all through the engine. I should have time to get the pan off on Saturday to find out what the damage is.
I had one do that and it was okay with a new bearing with slightly more clearance. Also had the bypass plugged. The engine went on racing for some years.
Pulled the pan. Found a small amount of bearing material in the bottom. Proceeded to pull each rod cap starting at the front journal and working my way back. So happened that #7 was the last that I pulled and there was the culprit. Bittersweet as I like finding no dad age, but at the same time if I didn’t find a spoiled rod bearing then that just means something else was broke. The great news is that it did NOT spin the bearing. It was the only one that the bearing shell remained on the crank journal when I removed the cap. Was a deep breath plucking it off the crank. Crank looks OK! The bearing is worn into the copper and some of that copper seems deposited on the crank journal but I cannot feel any of it with a fingernail. I think it’ll clean up. I think the plug in the oil filter bypass saved the rest of the engine.
I’m feeling OK about throwing a new set of rod bearings in all 8 rods and sparing myself the ordeal of pulling the engine but looking for your input here. Bottom line is, I don’t know why it spun other than to say rpm/power. Which was close to 6400 and seat of pants would say north of 400hp.
When I assembled the engine, all 8 rods had 2 thou clearance (plastigauge by me after the machine work was done). Would you put the same clearance bearing in?
pics..
Total of bearing material found. #7 cap and shell #7 journal. I would say this looks worse in the pic than in person. It’s a bit dirty for sure and has some copper deposited on it. I cannot feel any imperfections with a fingernail.
Adding a pic of a non problematic bearing/cap. This was from #2. A little more wear than I expected but also not able to feel this with a nail and the journals looked perfect for all but #7, which again feels smooth but has copper on it. Suggestions to clean without scratching?
04-08-2024, 06:00 PM
Turning in the towel..
