Dogwoodmudhole Posted July 8 Report Posted July 8 Hey Folks, I bought a very rusty 82 720 a few weeks ago and noticed a high idle. Vacuum test was steady at about 21 but replaced some egr lines and pcv valve to try to address high idle. Lots of oil pooling in air filter housing. Also we pulled plugs and both plugs on rear cylinder are very very black with lots of carbon buildup. Truck runs ok. I’ve had it up to 70 and it’s smooth. But I’m just not sure what I’m dealing with. Those plugs are more than fouled. My son thinks it’s terrible blowby and we need a rebuild. I’m not so sure. Any suggestions? Also there’s a mystery…there was a bb in one of the 1/4” egr lines we replaced. I know it didn’t grow there… Quote
]2eDeYe Posted July 8 Report Posted July 8 I would start with a compression test and then go from there. That will tell you if you have a good baseline and what to check next. 1 Quote
datzenmike Posted July 9 Report Posted July 9 Oil in the air filter is atomized oil being pushed out the valve cover vent from excessive blow by. The block vent has a screen to filter out the droplets before reaching the PCV valve. So does the valve cover, but at some point it must be being overloaded. Mark down your compression test results on a warm engine then add two tablespoons of engine oil to one of the spark plug holes and retest and record the results. If the compression went up with the added oil the rings are worn. Two adjacent cylinders with low compression could be the head gasket is blown between them. A leak down test is even better. The leak down tester has two pressure gauges. One is adjusted to 100 PSI, the piston is set to TDC and air supply introduced through a plug hole. The second gauge reads the pressure inside the combustion chamber which will be lower than 100 PSI because of leakage past rings and valves. A reading of 90 PSI is 10% and all is good. A 20% reading is not so good. Air is escaping somewhere. If past the intake valve you will hear a hissing at the open end of the carburetor. If an exhaust valve is leaking you will hear it at the exhaust pipe end. If the rings are leaking you will hear it at the valve cover vent pipe. 2 Quote
Dogwoodmudhole Posted July 9 Author Report Posted July 9 Wow. Thanks. A lot of this is over my head but I have a son and brother who are mechanics and can help me with this. I really appreciate it! Quote
banzai510(hainz) Posted July 9 Report Posted July 9 (edited) if you can get to 70mph . Is it worth rebuilding? I SAY JUST DRIVE IT!!!!!!!!!!!!!! replace plugs and get NGK wire sets. check the timing. key is make sure those motors dont over heat Edited July 9 by banzai510(hainz) Quote
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