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'69 Chevy C10, 400sb, basically stock with a torque cam and a Performer RPM intake with a stock Q-Jet and exhaust manifolds running through a TH350 with a towing shift kit. Just under 24k on a complete rebuild 8-9 years ago, the TH350 was completely rebuilt about 2 years ago.
I haven't driven the truck much in the past few years because I haven't really needed it and it is such a gas hog. Last summer I pulled the engine and cleaned it up and resealed the oil pan and installed new front and rear main seals since it had begun to leak more than I liked.
Recently I noticed that the engine oil cooler had a line with a small hole in it so I decided to pull the line and have it replaced. In the end, I never really liked the cooler and even though it allowed the engine to carry an additional quart of oil, I never felt it did much good, allowed for additional oil leak spots and was probably partly responsible for my somewhat low oil pressure at idle (about 19-21 at warm idle, goes up to 50+ at anything off idle). While trying to get the offending line off, I decided it was easier to pull the oil cooler altogether. If I find it runs hotter than it did before, I can always reinstall the cooler. I do have an additional cooler for the trans in addition to the cooler in the radiator. Cooling upgrades include a 4-core radiator and a high volume aluminum water pump. With the addition of the new water pump at last year's clean up, it stays at 180-200 pretty much all the time whether cruising or towing and regardless of the outdoor temps.
Well, I drove it tonight for the first time since the oil cooler removal and what do you know, the warm idle oil pressure is 45. I don't think an idle pressure of 20 is exactly bad, but it is comforting to know it's back into a much more comfortable range. I can probably switch back to 10w-30 on the next oil change.
Anyway, finally to my real question. Recently, and before AND after the oil cooler removal, I noticed an odd sound coming from the engine at idle. It sounds like a very subtle rattle, kind of like a muffled version of a diesel at idle. It's not any of the accessories, the alternator is making a solid whirring sound and the AC compressor is silent since the AC isn't running. The rattle does speed up with engine speed but basically is so soft it gets drowned out by exhaust and fan noise as the engine speeds up but as best I can tell, it goes away entirely at about 1500-2000. Here's the kicker: the sound remains exactly the same whether the engine is idling in gear or in neutral/park.
If it was a rod or a main going bad, or perhaps the oil pump or distributor going bad, I'd think the sound would get louder with engine speed and/or with a load on the engine. And now with the increased idle oil pressure, the sound is exactly the same as it was before so maybe I'm not hearing a rod rattle? Maybe I just have the timing set too high? It does NOT rattle or ping under a heavy load now, it has in the past and I know what that sounds like and that's not the sound I'm hearing now. Also, when I cleaned up the engine last year, I checked the mains and rod bearings and everything look okay, clearances were still great. I didn't hear this noise before last year's clean up, maybe the new water pump is making this noise? I'm having a hard time localizing the sound, but it is definitely in the engine compartment. It's not an exhaust leak tick nor is it ticking lifters, I know those sounds and that's not what I'm hearing. It runs like a champ and starts in an instant.
I haven't driven the truck much in the past few years because I haven't really needed it and it is such a gas hog. Last summer I pulled the engine and cleaned it up and resealed the oil pan and installed new front and rear main seals since it had begun to leak more than I liked.
Recently I noticed that the engine oil cooler had a line with a small hole in it so I decided to pull the line and have it replaced. In the end, I never really liked the cooler and even though it allowed the engine to carry an additional quart of oil, I never felt it did much good, allowed for additional oil leak spots and was probably partly responsible for my somewhat low oil pressure at idle (about 19-21 at warm idle, goes up to 50+ at anything off idle). While trying to get the offending line off, I decided it was easier to pull the oil cooler altogether. If I find it runs hotter than it did before, I can always reinstall the cooler. I do have an additional cooler for the trans in addition to the cooler in the radiator. Cooling upgrades include a 4-core radiator and a high volume aluminum water pump. With the addition of the new water pump at last year's clean up, it stays at 180-200 pretty much all the time whether cruising or towing and regardless of the outdoor temps.
Well, I drove it tonight for the first time since the oil cooler removal and what do you know, the warm idle oil pressure is 45. I don't think an idle pressure of 20 is exactly bad, but it is comforting to know it's back into a much more comfortable range. I can probably switch back to 10w-30 on the next oil change.
Anyway, finally to my real question. Recently, and before AND after the oil cooler removal, I noticed an odd sound coming from the engine at idle. It sounds like a very subtle rattle, kind of like a muffled version of a diesel at idle. It's not any of the accessories, the alternator is making a solid whirring sound and the AC compressor is silent since the AC isn't running. The rattle does speed up with engine speed but basically is so soft it gets drowned out by exhaust and fan noise as the engine speeds up but as best I can tell, it goes away entirely at about 1500-2000. Here's the kicker: the sound remains exactly the same whether the engine is idling in gear or in neutral/park.
If it was a rod or a main going bad, or perhaps the oil pump or distributor going bad, I'd think the sound would get louder with engine speed and/or with a load on the engine. And now with the increased idle oil pressure, the sound is exactly the same as it was before so maybe I'm not hearing a rod rattle? Maybe I just have the timing set too high? It does NOT rattle or ping under a heavy load now, it has in the past and I know what that sounds like and that's not the sound I'm hearing now. Also, when I cleaned up the engine last year, I checked the mains and rod bearings and everything look okay, clearances were still great. I didn't hear this noise before last year's clean up, maybe the new water pump is making this noise? I'm having a hard time localizing the sound, but it is definitely in the engine compartment. It's not an exhaust leak tick nor is it ticking lifters, I know those sounds and that's not what I'm hearing. It runs like a champ and starts in an instant.
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