I got some time to tinker with the truck this weekend, so I pulled the plugs and checked the compression.
#1 = 173 psi
#3 = 170 psi
#5 = 174 psi
#7 = 177 psi
#2 = 170 psi
#4 = 169 psi
#6 = 165 psi
#8 = 166 psi
Are those results normal for a TBI 350 or a little high?
A few of the plugs (#1, #5, #7, #4) were loose and the others were not very tight. #5, #7, & #4 had some guey, sticky leakage out of the spark plug hole. I’m not sure what it is, it doesn’t really smell like oil. I’m guessing it escaped the chamber due to the loose plugs. I ran a couple tanks of premium gas and Techron through the truck just prior to removing the plugs, if that matters.
All of the plugs had a small area on the porcelain that was burned with maybe a little glaze on some. Some also had some of the substance that ozzed out the holes. It could be oil but the truck doesn’t smoke or use any noticeable amount of oil between changes. There were a couple that had a few black specks, which I’ve read is detonation, but they weren’t bad.
I videoed each cylinder with a borescope I picked up. You can see the substance discussed above, as well as the carbon build up in the chambers. The worst was on cylinder #5. I’m not sure what a normal amount of carbon is for an engine with nearly 180,000 miles on it but I’m going to try and find some GM Top Engine Cleaner to run through it. I’ve read it works pretty well.
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I don’t know much about reading plugs, so if any of you guys can take a look at them and the video, I’d appreciate it.
https://imgur.com/a/DeDQ3Gp
I also used the borescope to verify that the timing mark on the harmonic balancer is accurate. It’s dead on 0 degrees, so I don’t think the timing is off.
I also checked for slack in the timing chain/distributor. I measured it by turning the crankshaft in one direction until the rotor started moving, marking the spot and the turning the crankshaft in the other direction until the rotor just moved. I get about ½” as measured on the balancer. I think that’s about 7 degrees. I’ve read normal is 5 degrees or less, but I’m not sure.