Ok comp test is complete, here are my findings
Cyl#1= 80 dry/84wet
#2 = 90 dry/ 95 wet
#3 = 87 dry/90 wet
#4 = 87 dry/91 wet
#5 = 75 dry/80 wet
#6 = 78 dry/82 wet
#7 = 80 dry/84 wet
#8 = 76 dry/80 wet
They are pretty low, and have my fingers crossed that being at 8000 feet elevation will make these numbers ok. The whole pass side plugs are dirty also, while drivers side are nice and clean. Seems like that should tell me about something

 

No, those numbers are not good, even taking altitude into account. Anything below 85 psi. is considered very bad at sea level. There is a correction factor applied for altitude, but those numbers are no bueno.

Just to be clear, you had removed all spark plugs before the test? Fresh full charge battery, and blocked open the choke and throttle? If the cylinders were all even, say 110 or 120 psi, that would probably be considered pretty decent for 8k feet on a stockish engine with an expected (for example) 150 psi, some wear etc. The most important thing with a compression test is that they are all within 5 to 10 pounds of each other.

 

Yes, all plugs out, wide open throttle. I really should have done this when I first got truck, instead of putting 2500 bucks, and alot of labor into it over the past year, but it runs really good, burns no oil, so I focused on the rest of it instead. Leaned my lesson for the next one I guess. (Seem to learn alot of these lessons with this truck

 

How many miles have you put on that since it was awakened and put back into service? Said it sat for 7 years?

There might be some problems with stuck rings, from gum and carbon. This is pretty common with engines that sit for a long time. Those plugs look pretty decent actually. Is it burning oil or smoking?

Try this, you don't have anything to lose. Buy a gallon of Marvel's Mystery oil. With the engine warmed up, dribble about a pint slowly down the carb at a high fast idle, basically want to fog the motor out, but get a goodly amount in thar. Say a pint or so before it stalls out. Be careful not to hydrolock it, but get plenty in there. Then let it sit overnight or maybe a day or two and soak real good. Remove the plugs right after, let it soak, and turn engine over in a couple days or so to blow the excess oil out of the cylinders before trying to start again.

Meanwhile, add Marvels to the fuel - in to gas tank at the rate of 4 fl oz per 10 gallons of gas. Replace 1 quart out of the 5 in the crankcase oil with another quart of Marvels, and then drive it, get it good and warmed up, as in oil temperature warm, not just water temperature warm. Marvels has a penetrating oil and solvents that are made just for this kind of thing. Can't hurt, may help. If compression can bump up to say 110 on all cylinders you got a keeper. Right now though, doesn't look so good for the home team.

 

I have put about 1500 miles on it since I got it. Never really drive far as my town is about a 5 mile loop all the way around it, and next town being an hour away never felt comfortable with the truck to drive it that far across a total cell signal dead zone. ... this sucks. It is like finding out your brother has cancer, and has a month to live. I will try what you mentioned, as I am going to drive it till it blows up regardless. The truck is too nice to give up on though

 

Also. I put a scope down the cylinders, and all are shiny but the two closest to firewall have a thin layer of greasy carbon. Didn't see any gouges, or Mark's on walls or pistons, and oil changes (2 done since acquired) have produced clean, translucent oil. Never any smoke, or steam from exhaust and coolant still looks new with no loss

 

Every tune-up manual always has compression test pg.1 para 1, first thing front and center. I ignored that when I was a kid, cause I couldn't afford a compression gauge I guess, lol.

Lots of people used to perform a cylinder hone, new piston rings, and main and rod bearing overhauls with the engine installed in the car. It ain't necessarily easy, but they did it that way. I'd suggest a new timing set as well. Thing is with 180k it likely needs boring and oversize pistons. I'd still try the Marvel's though. So much for my manifold vacuum theory, I didn't believe an engine could pull a steady 15" at 8,000' if compression was that far off the beam.

 

Yeah, this is my first truck of this vintage. Had a 75 step with 351w when I was 20 but in the 2 years I had it I never had to do a thing but gas and oil. Now that the kids are older I can spend some money on it, and being 44 years old, and not knowing how to work on cars or having any tools bothered me. Now that I have horded up enough tools to fill my workshop I started learning with this one. I dont feel 100% comfortable rebuilding an engine yet, but the only way I will learn is to just go for it. Uugghh.

 

This is for a motorcycle, I think, but gives an idea of correcting compression numbers for altitude. If this chart is comparable we could use 150 or 160 as typical therefore we'd want to see around 120 psi, something like that. Maybe use .800 or thereabouts, for 8000'. It's easy to see why starting has become difficult. For the Y-block in my truck, the shop manual lists 130-170 psi as normal compression. Well altitude correction explains why the spread is so wide, now that I look at it. Those jokers living in Leadville or Quito, or Cusco, etc, screw the tables up.

 

Deep down I knew 80-90 psi was no good, but was just grasping for anything I could hold on to.the truck really does run good, so was kinda surprised by the numbers. I have been driving up some very steep fire roads lately for tens of miles with a few thousand pounds of firewood in the bed, and the truck handled it like a champ everytime. Anyhow, I really appreciate all the help on this. If it wasn't for people like you, and everyone else here this truck would have still been in the graveyard, and I still wouldnt know a damn thing about any of this

 

Have you fixed all of the vacuum leaks you mentioned earlier in the thread? I would think those leaks would effect your compression test.

 

It doesn't burn oil badly, or smoke badly? One thing with compression, it's possible to have OK compression - but poor oil control. The compression test measures just that. The oil ring is a different deal. But, I'd think it kind of unlikely to see good oil control with worn bores and compression rings? Mostly those plugs look fairly decent as far as that goes. With those compression numbers, I'd sort of expect to see oil fouled plugs & oil deposits. Real bad. Maybe all the carbon and gum is boosting compression lol. Seriously though, try the Marvel's in both the gas and the crankcase oil. Some people used to use kerosene, or ATF, I like Marvel's because I'm familiar with it, and it seems safer.

 

 

Vacuum Leaks are taken care of. It was just the tree and the rubber plugs on it. I replaced the whole 6 post tree with one that has only 2. One for the transmission valve, and one for hooking up a vac gauge when needed. Besides the brake booster, that's the only vac line there is.
Yeah no oil burn whatsoever. None. Last oil change came out clean as new oil just about. And one I did before that when I first got it was very clean and not black dark. Also put a harbor freight scope down into cylinders after doing the comp tests. And all were shiny from piston up except the back 2 sides against firewall. They had mabey a 1/16 of an inch layer of oily carbon on piston, and brownish stains on walls. But saw no scuffs, gouges, or lines on walls. I will for sure do the m.m. oil thing as you suggested, but still need to make a few more runs up the mountain to cut wood before I can think of doing anything like tearing apart an engine

 

Old Tune-Up manual, but other than the points & condenser it pretty much applies today. Not much has changed, they just put a lot more stuff in between the fenders now.