S-10 Forum banner

1 - 11 of 11 Posts

·
Premium Member
Joined
·
210 Posts
Discussion Starter #1
I just ran a leak down test on a LM4 with unknown miles. All cylinders were terrible only got one that was crazy good with only 5% leakage. All cylinders were leaking via valves. I couldn't hear anything in the pan. So I then thought I'm not getting a true closing of the valves so I took the lowest cylinder #7 and simply loosen the rocker. now they should be closed. Same thing 85% leak by. I then lightly tapped the exhaust and it bounced up to 50%.

I haven't tried any others but obvious it is carbon build up. The plugs were brown grey no burning oil if anything it looks like it was ruining somewhat lean. I remember some where way back when that someone used Marvels mystery oil to breakup the carbon.

Any thoughts short of a valve job :)
BTW I'll be starting a build thread soon on my 2002 xtreme blazer.
 

·
94 4x4,01 Blazer
2001 Blazer 4dr 4wd LT
Joined
·
1,410 Posts
before you oil it- try feeding some water while running. it steam cleans the valve train .then do you check again.
 

·
Registered
Joined
·
2,146 Posts
It's not a bad idea to replace lifters and lifter trays on any LS before swapping it into the truck. That has the heads coming off anyway. Could use some lapping compound and a poor mans valve job to clean them up, but also worth looking around to see how much a real one would cost. Might be worth the $50-100 to let the pros give it a go.
 

·
B4U Task Force Admin
Joined
·
27,668 Posts
It's not a bad idea to replace lifters and lifter trays on any LS before swapping it into the truck. That has the heads coming off anyway. Could use some lapping compound and a poor mans valve job to clean them up, but also worth looking around to see how much a real one would cost. Might be worth the $50-100 to let the pros give it a go.
Not to mention they'll look pretty...
 

·
Premium Member
Joined
·
210 Posts
Discussion Starter #6
I decided to go through the leak down again.I lightly tap each rocker arm with a dead blow and now all cylinders are holding 4 to 7%. The intake seem to be the worst.
 

·
Registered
Joined
·
295 Posts
I still say you need a valve job.
That is unless you can find somebody to ride under the hood and play whack-a-valve as they stick.
You'd be pissed if you installed it and got the same results, then you'd get to pull heads while the engine is in place. Not fun.
If they're not seating, they're not seating. They didn't lift off the seats while the truck was parked, they were in that exact position when it last ran.

So, it's either...
There are two ways to do a thing - right and again
or
We do it right because we do it twice!

And as cheap as they are, it would be prudent to swap lifters, as others have said.
 

·
Been there Done it
Joined
·
10,514 Posts
an LM4 with unknown miles
That's probably the basis of the problem. It could have 300K+. Pulling the heads would also give you a chance to look over the pistons and cylinders.
 

·
Registered
Joined
·
2,146 Posts
This is why I sometimes just drop in the engine without checking anything lol results are often better than you expect.
 

·
Premium Member
Joined
·
210 Posts
Discussion Starter #10
This post was more of this is what I found. That is why I actually ran the test. I did not want any surprises. The intake was carbon up. Because of the results I will be pulling heads and check clearances and hopefully I can get by with a lapping. Thanks
 

·
Premium Member
Joined
·
210 Posts
Discussion Starter #11
Pulled the heads not any surprises. No broken or bent push rods. Lifters were fine. Lifter tray is ok but will be replaced with OEM. I did see some differences from the drivers side to the passenger side valvetrain. Rocker arms and push rods have a slight burnt on coating lifters did not. Where the other is fine just a darken oil appearance. I'm waiting on my order for a valve spring compressor tool to show up.Once I get it I'll know more about the valves.
 
1 - 11 of 11 Posts
Top