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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: njschmidt on February 21, 2017, 02:30:36 pm
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Hi all,
I was doing some maintenance on a '78 Chevy Cheyenne (v8 350 4BBL 5.7 L) I recently purchased and noticed some things that I wanted to ask about. First, I had noticed that the truck gave off quite a bit of blue smoke from the exhaust and was making a "chug-a-lug" sound, where it was delayed on the "a" (like chug-a........lug) to the point that it sometimes died, especially if it hadn't warmed up a lot. I decided to switch out the spark plugs, and am glad I did (they looked horrible ... burnt to a crisp, and two were barely even screwed in).
As it had been probably 20 years since I last changed spark plugs, I made the mistake of disconnecting all the cables at once and removing all the plugs... Without noting which cables went to which spark plugs. After consulting google, I found some references to the distributor I use and firing pattern marked on the engine... Only to discover that the previous owner had mixed the 2 and 4 plug cables! Here's a picture I made to help with labelling, as it was difficult for me to match my Delco Remy distributor with the drawings I found. Could this have been causing the problem I mentioned above? Since changing the oil and spark plugs, it hasn't died on me... But it still gives off a bit of blue smoke when I first start it cold (although not nearly as much smoke as it used to).
(https://preview.ibb.co/c245Dv/IMAG0113.jpg)
(https://ibb.co/jVbwLa)
https://ibb.co/jVbwLa
Some more googling suggests that this could be due to oil getting into the cylinders, perhaps due to piston rings wearing? I'm looking into doing a cylinder leak test, if y'all think it would be a good idea (I would do it myself, but don't have the leakdown gauge, yet).
The other thing I noticed was a lot of oil on the underside of the engine (see picture). I'm not sure what it's called (maybe y'all can help?) but it looks like there's a hole in the middle that could possibly be missing a screw, and oil is coming out of it? See the picture below (the view is from under the car, looking forward to the front of the car... The orange thing is the oil reservoir... Not sure what the black thing immediately before it with the hole is ... or if that hole needs to be plugged?). I plan on wiping/cleaning it all down and observing more carefully. It does appear, however, to be a slow leak and my oil pressure appears fine, according to the dash meter.
(https://preview.ibb.co/cC6wLa/IMAG0109.jpg)
(https://ibb.co/iVB7RF)
https://ibb.co/iVB7RF
Last thing I found was that the previous owner had dropped the radiator reservoir fluid cap, and decided to replace it with a beer can jammed in it. Don't think this did a good job, but I found the original resting at the bottom of the engine. Very little radiator fluid in the reservoir, so I will be checking that later... But so far it doesn't run hot so I'm hoping for the best for now.
Thanks for all comments/tips!
-nj
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fixed you pictures. you have to click on "embed codes" then the bbcode. or you can upload to this site
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Thank you! Hoping somebody might be able to identify what's behind the oil pan, and whether that hole should be plugged or not... otherwise at a loss for where the oils coming from.
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That hole in the trans inspection plate is supposed to be there. Pull it off and see how wet it is. Typically that is a rear main leak indication.
Are you loosing oil?
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Engine oil dripping off of the torque converter dust shield can be leaking from the rear main seal, the camshaft rear plug, the engine oil pan gasket, the intake manifold rear valley seal, a leaking oil pressure sensor/switch, and/or the valve covers. The only way you will know is by careful, patient observation with a good bright light and mirror. Bear in mind that fluids always leak downward due to gravity and are typically blown rearward by air circulation. If oil is coating everything, you may need to begin with a good steam clean or engine wash using degreaser. In difficult to diagnose cases, fluorescent dye can be added to the engine oil followed by inspection using an ultraviolet light source and colored filter glasses. If you run the engine while inspecting for leaks, be very cautious of moving parts!
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Blue smoke at start up points to worn valve guide seals. It's pretty common in old engines and not particularly a problem.
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Thanks for all the replies! Good to know what that cover is for and that the hole is intentional. Will be degreasing and cleaning to see if I can pinpoint it. Not losing a ton of oil, but enough that I want to find and address it.
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Check the obvious first. It could be as simple as a slightly loose oil filter.
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Wow, I'm really surprised it was usable with those two cylinders mixed up. It's been like that since you bought it you say?
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Wow, I'm really surprised it was usable with those two cylinders mixed up. It's been like that since you bought it you say?
I know, I'm amazed it ran. That and one of the spark plugs was barely even in... it wiggled when I just attached the ratchet wrench so I did a half turn with my hand and it just came out. Poor girl's been mistreated. I've only had her a week, last guy didn't really run her much at all (hadn't even gotten a tag for it).
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I've got to hunt down an oil leak too I think. It seems I'm pretty low on oil atm