chevyo3

Finally got to the compression test I have been waiting to do since my rebuild of the LG4(305). Only did new valve seals ,and replaced the valve springs .I posted before I felt I had a head gasket problem ,because of white smoke. I figured the compression test would confirm this. When I tested cylinder #1 ,I got a reading of 0psi. All other cylinders were tested at 100psi to 150psi. I squirted some oil in cylinder #1 ,and tested again with no improvement. Could the valve be stuck open or not seating? Could this be due to me overtightening the valve lash? I cant imagine its the rings ,because it was not a problem prior to the valve job. The car did sit for about 2years. Could the rings go bad by sitting so long? This really sucks. May just trash the motor if its cronic. Besides its a crappy LG4.

JAY87GTA

If you got a spread of 100 -150 I'd say it's rebuild time regardless of the 0 in #1. It may be possible one of the valves is broke. I did mine about 2 months ago, 123.xxx miles on an L98 that's never had the valve covers off and got 165 - 173 on all cylinders, most were right at 168. Ideally you'd like to see a 8-10% spread on the numbers. Later

chevyo3

I also noticed white smoke out my exaust . I think when I did the intake manifold gasket I might not have put RTV sealant around the water ports or not enough. I think this may be the cause of my low compression readings. If a valve was broke woundnt the engine knock? If so mine doesnt. It idles fine. When driven it lacks power ,and skips. Could I have a stuck valve or a valve not seating? The heads were redone 2years ago. All I have run on them is a test drive when I put the heads back on.

JAY87GTA

White smoke generally means you're getting coolant into the cylinders. It may be possible that a valve isn't sealing, but I don't think one would knock if it was broke. Pull the valve covers and start it up for a minute. That way you can look and see if a valve is sticking open and make sure they are all opening. Later

Vader

03,

If the car sat for two years, it is very possible that you have a stuck valve or pumped-up lifter (more likely a valve stuck on dried varnish).

Do like Jay suggests - pull the rocker cover on the side with the "dead" cylinder and check the valve action on the two valves for that cylinder. Remove the rockers if necessary and make sure the valves are seated (returned to the same height). If one is stuck, try tapping on it with a rubber mallet to try to free it, You should be able to actually hear it snap shut after each blow of the mallet.

Your slightly low compression overall could be from sitting for two years and losing the polish on the bores, or could be from wear. If it is from scale from sitting, the numbers should improve slightly as you drive it. Remember that an LG4 will not have the same compression as an L98. You also need to check compression by cranking with a fully charged battery and the throttle blocked wide open.

Since the car was sitting, you should plan to change the oil a few weeks after you start to drive it to stay ahead of that scale that may get scraped off the cylinder walls.

As for the white smoke, it may be the intake sealing or even a head gasket. Just make sure you keep the antifreeze ouy of your oil or you will be junking the engine.

chevyo3

How can I tell if the head is blown or the intake gasket? Its easier to change intake manifold. I hope I dont need to do both.
Also the heads were done 2years ago(seals ,and three angle valve job,plus new valve springs.) ,and I havent really drove the car since reinstalling the heads ,just up the street ,and back. Thats when I started haveing problems with white smoke ,and skipping. I'm pulling the valve cover off on the dead cylinder side as soon as the weekend gets here. When I crank the engine over you have any ideas on avoiding oil getting all over? :hail:
I appreciate the help guys. Wanna get this thing going before summer.

chevyo3

Today I pulled the valve cover off on the dead cylinder side. I cranked the engine ,and watched the valve action. They were working on the cylinder that was dead. I then took the rockers off on the two valves ,and rapped them with a rubber mallet. They snapped shut each time. What else can I do? They seem to be OK. Should I check compression again? Please help

Vader

03,

Reassemble the rockers on the two valves, but don't set the lash to spec. Keep them a little on the loose side but make sure they still operate the valves.

Run the compression test again on that cylinder, and make sure the throttle is wide open and all eight of the spark plugs are removed. A fully charged battery is a good idea for best cranking speed (and compression results).

Waiting for new numbers...

Kwik88

Vader, How much of a difference would you expect there to be if the throttle wasn't open when testing compression?

Gary

chevyo3

Vader,
Tried what you said ,and got better results. I loosened the rockers on cylinder #1. Which was the dead cylinder. I put a better battery in her ,and blocked open the carb. All the plugs were removed ,and I tested it again. Here are the resuls:
Front of Car
#1=170psi #2=160psi
#3=160psi #4=160psi
#5=160psi #6=160psi
#7=150psi #8=160psi

I still see white smoke from exaust ,and now I see water dripping from rear of engine onto exaust pipe. Also I am getting a skip when in drive. Could this be from a intake manifold leak causing coolant to enter cylinder ,and thus causing white smoke ,and causing the skip due to spark being snuffed by coolant? Any more pointers?
:hail:

Bill Speed

Sounds like alot of work and I can imagine the $1000 cost est by my mechanic for the complete job, but a new engine can be had, via a friend of a friend for about $1400 so he tells me. if anything, that sounds very reasonable as a last resort. Though he didn't specify long block, it sounded like it as he described. I have to do my work outside in 12 degree weather right now, not much in the way of options.
Bill