Low vacuum

[Lionized]

I wanted to revive this thread as I've found my source of low vacuum. I finally got around to doing a compression check and have discovered that I have two/three cylinders which are low:

1= 90psi 2=120
3=140 4=140
5=150 6=132
7=145 8=145

Now, I'm really hoping some of you more experienced guys will chime in here. What I plan to do is get the engine up to temp and drizzle some water through the carburetor to break up any carbon deposits. I've also considered, and have prepared, a gallon jug of distilled water to take on a highway blast at around 60mph. Connecting a 6' 1/4" vacuum line to my manifold vacuum port and running through that until it's dry. I'm fairly certain it's carbon deposits and the rings are more than likely gummed up. There has been very little freeway driving done with this car...as it's never really been running properly. It's real, REAL close though.
Short of a ring job, anyone else have ideas?

 

[Randra]

Burnt valves?that was my original problem before my rebuild. Your compression test looks similar to mine before I rebuilt it.

 

[oldbee]

I was taught yrs ago to go 4 hits on checking compression; ur 2nd hit will show valve problems just like the 4th hit shows ring problems.

 

[Ranger16]

I've also considered, and have prepared, a gallon jug of distilled water to take on a highway blast at around 60mph. Connecting a 6' 1/4" vacuum line to my manifold vacuum port and running through that until it's dry.

I'm no expert, but that seems like a LOT of water. I ran a glass full through mine in the garage at about 2000 RPM and that's all it took to clear up a dieseling problem.

 

[moper]

Do not run water through it. Do make sure you're using the maniflod vacuum source on the carb - not the souce on the intake port runner. A single port will bounce the needle. You need a source at or above the intake's plenum. The carb should have one - even the choke pull off will work.
If this is a fresher engine it's running rich. That will not let fresh rings seat. IF the bores were rough (most non-performance shops will leave them too rough) the rings have to seat which takes time and miles of solid running - not hours of idling way rich. So ultimately once you get it running better, it may still need the rings replaced. It happens to the best of us...