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For the past couple years, I've noticed a lower end knock on my '55 Firedome upon cold start. The knock eventually goes away after oil pressure builds, however, over the two years the knock has naturally gotten worse (lasts longer), not better. There is no knock once oil pressure builds or when driving.
The local shop that does much of my service noticed the knock and to their ear it sounds like rod knock. Since I do little of my own repair and have little experience servicing the lower end of an engine, your experience and advice is welcomed. Planning ahead I recently purchased an NORS Federal Mogul standard size bearing set on eBay. My shop says that so long as the oil pan can be dropped without raising the engine - which it can - they can R&R the main bearings with the engine in the car. Is that correct? What else should be done while they have the oil pan removed? Will new bearings likely eliminate the knock?? Any other thoughts, advice or recommendations???
Mark
Mark, I can not say anything about the bearings; but when you have the pan off - you really want to make sure the oil pump strainer is clean. I have seen some real bad stuff in these. It was not in my Desoto, but another car I own. I want to remove the pan on the Desoto to make sure I have no problems there - just a matter of time. If you have never had the pan off, this strainer could be the problem or at least a part of it.
Should wait to see if your crank is std. before buying the bearings. also, since you have to remove so much of the front engine to drop the pan, take the heads off and make sure the valves are good. valves and bearings together are a must. and, what the hell, youve gone that far, take out the pistons and replace the rings. The three together will make that engine purr. ps. I have that cold start problem in my 55 and I'm convinced the gas either boils away in a week or I need a check valve in the line to keep it from draining backwards..it takes too long to get the gas to the carb. after it sits a week or longer. dave
Paul...thanks for your feedback. I've had the oil pan down recently and the sludge removed; wasn't that much. The oil pump pickup screen was cleaned then.
Dave...thanks to you as well. The engine has 50,000 miles; I bought the car in the early '80's with 32,000 miles so I'm reasonably confident that the crank has not been ground and the standard bearings should be OK. Ideally, I'd have the engine pulled and everything else done, however, aside from the knock the engine runs fine and uses little oil in normal use.
Your comments about cold starting are consistent with what I have heard and experienced. It seems the fuel drains out of the carb such that you have to pump it several times before it will fire, thus eliminating any choke settings.
Thanks again for your feedback and advice!
Mark
I've done this. You have to pop the tie rod apart and drop the pan. Pull one bearing at a time and use plasti-guage and check to check your bearings. Even though the engine has never been apart, you can't be certain that the bearings are std. So you'll have to mic the crank journals to see what size you need. If you have an audible knock, you might be able to determine which bearing is loose just by feel. When you pull the bearing caps, it will probably be evident which bearing is worn. Yes, this can all be done with the engine in the car and does not require much other disassembly. I recommend you put the car on a lift for this job.
I repeat for emphasis, do one bearing at a time. Do not mix and match bearing caps, they must go on the same place and the same way that they came off. You must use a torque wrench when putting the caps back on. Make darn sure the bearings fit the caps and are installed correctly.
Good Luck!
Steve
If you take the bearing cap off, take the bearing out of the cap and look at the back side, most bearings are marked there. If it says std. the crank has not been ground, if it says .010 or.020 the crank has been ground.
Paul
This is what I'd do in this situation. Since it makes noise for a while when cold have your shop pull one plug wire off at a time. When the noise goes away or is quieter that's the bad rod, wrist pin, or piston.
Tim Mabry
The Lost Cause Garage
47 Suburban
57 Sportsman 4dr HT
Guys...thanks for all the expert advice. Since the pan is going to be dropped one way or the other, I'm planning to have both the rod and main bearings replaced. The show owner did say that they will try to determine from where the knock is coming before changing bearings. I've got an NORS rebuilt oil pump; once we are certain it's working properly we'll install that as well.
I'll be printing your replies for their education, although they work on quite a few older vehicles. Never hurts to be reminded of proper procedure.
Mark
