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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: Boxchevrolet on July 24, 2015, 09:10:23 pm
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hello i swapped a used 1979 305 into my 83 k10 due to a wiped cam lobe on my 350, i have no idea how many miles are on the 305 as was given it from my brother, he bought it for 150 bucks, cold psi at idle with 15-40 is 50 psi, as the engine warms it lowers to maybe 6 psi at 1000 rpms, I'm using a mechanical oil pressure gauge, it docent knock or anything but 6 psi seems really low, I'm thinking its due to high mileage and loose bearing clearances. would it be beneficial to put in a high volume/ standard pressure oil pump to "band-aide" the loose clearances until i rebuild the 350? thanks!
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Sounds like a worn out engine, though possibly a defective oil relief valve as well. You could always put in some Lucas or Motor Honey or something. I'm nursing an old Honda along that way.
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I'm pretty sure its worn out, I've heard you can put a high volume/ standard pressure oil pump in to bring up idle pressure on a worn out motor, the oil looked like sludge when i first drained it, probably because it sat for a year or so. I'm just gonna nurse it till i build my 350
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I'm going to point out here, not to say it's fine, it might be a tired engine anyway. According to GM, a small block should be able to idle with NO mechanical problems at exactly 6 psi oil pressure. Then add 10 psi for every 1000 rpm of rotation. If the engine runs desent, doesn't knock or rattle or tick and doesn't burn oil excessivly, don't worry about. Just use a good quality detergent oil, usually a good quality regular/synthetic blend oil is good for this. Maybe a slightly thicker viscosity if you prefer to have a little more "meat" to your oil, use a quality oil filter and change your oil responsibly.
Do those things and you probably be fine.
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I'm pretty sure its worn out...the oil looked like sludge when i first drained it, probably because it sat for a year or so....
Unless you know the full history of that motor, it's more likely the oil was rarely if ever changed. Using a high detergent multi-vis oil now may loosen all the gunk and circulate it where it doesn't belong. It could also cause the engine to start leaking oil. Stick with straight 30 or 40 weight oil and change it along with a new filter at 1,000 mile intervals two or three times; extend to 3,000 mi service intervals, thereafter. And, don't drive it hard. Once you start changing the oil and filter, the pressure may drop even further as the gunk is purged and drained.
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thankyall, im gonna nurse it till i build my 350, but also the 305 won't idle under 1200 rpms for some reason, the only vacuum hoses are the advance to the distrib, brake booster, and pcv, and timing is set at 8 degrees before top dead center, any ideas on why it may not idle?
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Engine RPM won't drop below 1,200 or the engine dies below 1,200 RPM?
The stepped fast idle cam on the passenger side of the carburetor may be sticky and not allowing the throttle to close completely - wash it down thoroughly with carb spray while flicking the cam with your finger. Also, check for vacuum leaks using the carb spray. If those fail, disconnect the throttle cable from the carburetor to see if that makes any difference.
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Normal idle is about 7 or 8 hundred rpm's. According to the repair manual.
1 John 2:15-17
Jeremiah 17:7
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the engine dies under 1200 rpms, I've backed out the high idle screw pretty far but if i step down the idle screw to around 800 or so it'll idle really rough and eventually die, the truck is a 83 k10 with a sm46
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Does the choke plate open completely as the engine warms? Is it puffing any smoke out the exhaust? Any backfires through the intake or popping out the exhaust? Have you removed and inspected the spark plugs?
Verify the firing order. Check for vacuum leaks using Berryman's B12 or similar carburetor spray. Check the idle mixture adjustment.
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I wouldn't worry about the psi as long as it doesn't rattle or knock
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chokes all the way open, I've checked timing, no backfire of any sort
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1) The timing might be very retarded if it won't idle below 1200. What does everyone think about that?
2) What weight oil are you using now?
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sounds like a vacuum leak? but 6 psi @1000 rps?
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timings at 8 degrees btdc, 15-40 oil, and just dropped the pan and the pickup is stopped up near where you can't even see the screen, yet i can't get the pickup tube out it will rotate tho, should i go ahead and replace the pump as well?
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Yes. Oil pumps are cheap insurance. Not worth trying to clean it out. You can clean it but I would just replace it. It's easy and doesn't take much time, since you already have the pan off. Probably have much better oil pressure when your done.
You will need:
-oil pump, standard pressure is fine for a stock engine. A Mellings brand or simular is good, AC Delco is even better if you can but not required.
-oil pick up tube
-plastic oil pump drive shaft retainer ring (this usually comes with the new pump)
-oil pick up tube retainer of some type. Also very cheap insurance. Prevents the tube from rattling out from vibration.
The pick up screen should be flat and parallel to bottom of the oil pan.
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i went ahead and replaced the oil pump and the oil pickup, now all i have to do is fill with oil
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Don't forget to put the pan back on first haha.
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and oil drain plug
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and oil drain plug
That being the most important.
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haha i did, i tell you what one piece oil pan gaskets make life a lot easier when the motor is in the truck, will update y'all tomorrow on the oil pressure and idle issues, thank y'all again
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Yes they do.
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update, i was able to get it to idle at 800 but it is extremely rough idling, timing is at 8 degrees btdc. and idle mixture screws are 1&1/2 turns out, any ideas of why its running so rough? valve adjustment? i checked for vacuum leaks but couldn't find any, and now my oil pressure is roughly 10-12 hot psi at 800 with is better than 6, but i may add a quart of 20-50 to bring it up a little more, what do y'all think?
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anybody?
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You have already gained double your old oil pressure reading. Again, as long as it's not making noise, be responsible with your oil changes. There should be no need to add 1 quart of oil that is different than the rest of the oil in the engine. Drive it, monitor your pressures at various rpm ranges, check to see that it matches the 10 psi per 1000 rpm guideline or is pretty close.
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update, i was able to get it to idle at 800 but it is extremely rough idling, timing is at 8 degrees btdc. and idle mixture screws are 1&1/2 turns out, any ideas of why its running so rough? valve adjustment?
Have you checked for a fouled plug(s), sticking lifter(s), plug wire not seated, corrosion of terminals in distributor?
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plugs are brand new, there is a ticking noise but I've figured it was a exhaust leak because I've adjusted valves 3 times, all spark plug wires are seated, and no corrosion on terminals
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still can't get it to idle smooth at 800, very choppy idle
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If you hover the carburetor with a rag, does the idle smooth out? Any chance the 'tick' is a plug wire arcing to ground?
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i can't comment on hovering with a rag due to it raining outside right now, and i don't believe so
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Man! The entire country is washing away while California looks like a dried grape! No puns, please....
You might also check for a cracked plug porcelain when you get the opportunity.
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Red or green grape? Lol
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it sound like the driver side has a valve out of adjustment or missing just a hair, I'm gonna double check the valves, then spark plugs then timing again
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update, found why i could idle it down but when you gave it gas it would idle back up to 1000. my quadrajet carb base plate throttle shaft is worn and has a huge vacuum leak, you couldn't hear it until you were under the hood and wiggled/moved the throttle. looks like i will be sending my base plate off to cliffs performance to put bushings in for the throttle shaft, thank you guys for yalls help
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Welcome
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Glad you got her figured out
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now i jus gotta ship it to get it rebuilt and it should be running smooth