Hot Rod Forum : Hotrodders Bulletin Board - View Single Post - 1977 Chevy K20: Engine Suffers from Hesitation/Power Loss When In Drive
View Single Post
  #108 (permalink)  
Old 06-25-2012, 04:39 PM
lt1silverhawk's Avatar
lt1silverhawk lt1silverhawk is offline
"But how do it know?"
Last wiki edit: How to rebuild a Rochester Quadrajet 4MV carbureto... Last photo:
Join Date: Mar 2010
Location: Lakewood, CA
Posts: 2,322
Wiki Edits: 132

Thanks: 143
Thanked 30 Times in 22 Posts
CORRECTION: That last cylinder listed for the compression should be #8, not #1.

Hey cobalt,

Originally Posted by cobalt327
Compression test is excellent. You propped the carb open?
Actually, the carb is off the truck. I never put it back on after installing the plastic cam in case I have to mess with the intake manifold gaskets again. Should the test have been done with the carb on?

Originally Posted by cobalt327
If the threads of the plugs are what's wet, that's usually from external oil getting down into the wells where the plugs live (often it comes from the v-cover gaskets). It's the color and condition of the electrodes and porcelain (wet [oil], dry/tannish [normal], fluffy/black [rich] or shiny/white [hot]) that's the main concern. If they are wet w/oil, you have a problem of some sort. Being as how the compression tested so good, I'd be looking at the PCV valve and the tranny vacuum modulator first.
Yes, the oil is actually limited to just the threads of the spark plugs. The electrodes and porcelain don't have anything on them and, from memory and the pictures posted, there was no dis-coloration.

I'm pretty sure the PCV valve is good because it does make a rattling noise. Not so sure on the hose, so I will check that. Yes, the transmission modulator is something I've been meaning to check, at least the small rubber hose that connects it to the metal line. Last I looked at it, it was bent into a bit of an "s" shape.

Originally Posted by cobalt327
What if anything were done w/the valve stem seals?
I never touched the valve stem seals.

Originally Posted by cobalt327
Do the plugs show more oily deposits on one side than the other?
According to one of the members, the images of the removed plugs from the first page of this thread shows that the passenger-side plugs appeared more fouled than the driver-side. This time around, it appears about even for both sides.

Originally Posted by cobalt327
If so, next time before removing the plugs (or now if they're still in order and you can put a few from each side back into the heads where they came from) you can mark the top of the plug w/a sharpie to see what the position of the plug's electrode is to the exhaust valve to see if the chambers are pulling oil past the seals. This is similar to "indexing" plugs if my explanation is unclear (which wouldn't surprise me! lol).
Yep, I didn't get it lol! I looked up indexing spark plugs and found a simple explanation in this article: "How to index spark plugs". So I am on board so far. Now, where I am needing more help is how to see the position of the electrode in relation to the exhaust valve. Will I need to removed the intake manifold and turn the engine manually to observe what's happening? The plugs are out right now, and in order.


Hey Pugsy,
Originally Posted by 123pugsy
Holy Cow Hawk!

Next time tell me to sit down before I read something this unbelievable!

You actually used the light.
God, I hope you didn't break anything. Prayers do get answered, dreams do come true, miracles do happen, and Hawk does eventually realize that the only light at the end of the tunnel, is the timing light. Eventually.

Originally Posted by 123pugsy
When you hook it up again, you can rev the engine and the display on the light will give you the rpms.
Then dial the knob on the light until the mark lines up.
I hear 36* total at about 3000 rpm's mentioned for SBC's.

Hopefully Cobalt will chime in here.
Either I missed it, or my timing light doesn't have a knob. I will check when I get home and report back.

Originally Posted by cobalt327
123pugsy, you're spot on w/the 36 degrees at 3000 rpm. You want the total (w/o the vacuum advance) all in as early as the engine/vehicle combo will allow. This is usually around 3000 rpm (or less if it'll let you) w/o pinging when under a load.
When I set the base timing at 9*, I did it with the vacuum advance disconnected. I then revved the engine a few hundred rpm past 3,000, and there were no issues that I noticed. I then hooked up the advance and took the truck for a quick spin and it drove fine. This time I'll do the entire thing with the vacuum advance disconnected.

Since I have never heared it before, what exactly does pinging sound like?

Originally Posted by cobalt327
If more info on the HEI is wanted, you can take a look here, especially the section on ignition advance.
Thanks, that's actually quite informative.

Thank you for the continued help!
Reply With Quote