84 Chevy C/10 Running Rough Distributor Bad Timing?

[gconn77]

Hello everyone. I am not very advanced with working on engines. However, I do have a general ability to do average repairs, adjustments, etc.

I think my distributor is bad, or the timing might be off? I am not sure but the engine runs very rough. I created a video and uploaded it to youtube.com. In the video you will be able to hear the motor running as well as hear what happens when I turn the distributor a little bit. Which brings me to another question: Should you be able to turn the distributor by hand? Eitherway, turning the distributor doesn't really help much at all... in an idle I get get the motor to run better, however, giving it some gas and I have the same problem. If it helps any, before I ran into this problem... for some time now, after running the truck for periods of about 30 minutes or longer, after turning the truck off, it has been near impossible to re-start it. At first I thought it was the starter getting too hot from the engine.. I replaced that and added a heat shield. This did not solve the problem. That is when a friend told me that the timing might be off... something about a vacuum thing in the distributor. Now today, I can't run it on the road at all. Any help would be very much appreciated. Please click the small image below to view the video.



Thanks,
Garry

[Prerunner1982]

if the hold down bolt is loose then yes you can turn the dist. by hand, but make sure you tighten the hold down bolt up, or when you start the motor it will spin the dist out of setting.

Have you taken the dist. cap off yet and check the rotor and cap contacts? also check plugs and wires. depending on mileage and the condition of the cap and rotor, it might be worth while to go ahead and replace those.

[gconn77]

Here are a few pictures below. Where is the hold down bolt? Can it be seen in the last photo? Also I am not sure what the cap should look like as far as the condition of the contacts etc... hopefully with these pictures below it will help you help me! LOL!! The plugs and wires are good... those are new. Click the small images below to view the full size image:

[magnethead]

The hold down bolt ius under the distributor. 7/16" head, may require a distributor wrench (I was able to get a standard wrench on it on mine, barely)

you can't tell much listening to the motor. Most of the time you can tell by the exhaust how it's running.

EDIT- watched the video. Your timing is O-F-F and by a large amount! The backfiring is the easy way to tell that, but you definately need to find a timing light.

[gconn77]

Originally Posted by magnethead

The hold down bolt ius under the distributor. 7/16" head, may require a distributor wrench (I was able to get a standard wrench on it on mine, barely)

you can't tell much listening to the motor. Most of the time you can tell by the exhaust how it's running.

EDIT- watched the video. Your timing is O-F-F and by a large amount! The backfiring is the easy way to tell that, but you definately need to find a timing light.

I can get one... so how do I use it, and how do I adjust the timing? Is there a way of doing it without a timing light?

[Malo83]

Check all your vacuum lines, my 83 had the same problem, turned out to be a couple of vacuum lines had turned brittle with time and cracked causing a vacuum leak, best way to check them is to spray around the carb and lines with carb cleaner and see if you notice a change in RPM, keep the spray from going in the carb or you'll get false indications, best of luck

[magnethead]

If the light doesn't include any instructions (it should) and/or you don't have any social connections for somebody to do it for free, the large clip goes on the #1 plug, battery wires should explain themselves, and point the light at the timing indicator over the balancer (coating balancer from underneath in 3 layers of GUNK engine cleaner may be needed). The light SHOULD light up as the notch in the balancer passes between the 5 and 10 degree advance marks.

Another way to do it is pull the flexplate cover off, turn the motor using a flexplate crank until the notch lines up with about 8 degrees advanced, find the #1 plug wire on the cap, put a mark on the dizzy base that lines up with the #1 terminal, and with the cap off, turn the dizzy base until the mark on the base and the rotor line up. Put the cap back on and tighten the daylights out of the hold down bolt (without stripping it out). FYI, turning clockwise retards timing, counter advances timing.

also, make sure you don't have any crossed wires that would make a mis fire condition.

http://boxwrench.net/specs/chevy_bb.htm
http://boxwrench.net/specs/chevy_sb.htm

[cckutchma]

Hey Magnethead, I have about the same setup HEI dst etc and have been told both ways pull the vacuum advance hose and plug it to retard for timing or not to> What do you think and also NOT to crank the hold down bolt in fear of compressing the rubber gasket to far let meknow what you think.and GConn spray that carb cleaner around the base of the carb. if it sucks in and changes engine RPMs you might have to do some work with carb gasket-s I had to with my C20s

[magnethead]

Originally Posted by cckutchma

Hey Magnethead, I have about the same setup HEI dst etc and have been told both ways pull the vacuum advance hose and plug it to retard for timing or not to> What do you think and also NOT to crank the hold down bolt in fear of compressing the rubber gasket to far let meknow what you think.and GConn spray that carb cleaner around the base of the carb. if it sucks in and changes engine RPMs you might have to do some work with carb gasket-s I had to with my C20s

The engine is backfiring- fix that before anything, that's almost always bad timing or a misfire (crossed wires or wrong order on dizzy), and it's hard to diagnose anything with that going on.

I'd rather leave the vacuum advance working- I was told by somebody on here that the trucks were 5-8 degrees advanced from factory, and that would be somewhere around 10-12 with the advance (depending on canister). Also, if you take the space between plug wire posts and divide it into 5 imaginary sections, each section is 9 degrees.

I have the hold down bolt on mine pretty tight- I can still turn it (the dizzy) by hand, but it's very hard to do so. I just used a standard wrench b/c i didn't feel like searching our million drawers for the dizzy wrench.

[MylilBowTie]

The hold down bolt for the distributor is a 9/16 or 1/2 (pretty sure its the 9/16 tho). You want it tight so that it doesn't allow the distributor to turn after the timing has been set. So that way it will keep the timing it was set at and not wonder around as the distributor moves about. Have you checked to see what the spark plugs look like on the firing end?

After you get the timing right and the ignition right make another video. That would help get a better idea of what's going on.

[piecesparts]

First find out where all of the wires are going. Check the firing order that is forged into the intake manifold in front of the carb and check the wires are going to the right plugs. Next, FIND the hold down bolt. (9/16 DIZZY wrench works the best) Pull the vacuum line from the vacuum pot and plug the line (I always stick mine onto the bolt sticking out of the top of the carb, that holds the air cleaner on). Attach a timing light to the #1 plug (front driver plug) Start the motor and aim the light at the timing marks, set the timing at around 12 to 15 degrees BTDC. Now tighten the bolt snug. Check timing one more time to make sure it didn't move. Put the vacuum line onto the advance pot on the dizzy and it should be about right for daily driving. The dizzy moving will cause other problems for the engine that you don't want to get into. If it retards to much, the motor will run hot and eat itself up in a fair amount of time. If it advances to far then you will get detonation and a dieseling effect, also not good.

VERY IMORTANT--line up the timing marks with the pointer at zero and see if the dizzy rotor is pointing at the #1 plug wire on the distributor cap. This will require finding out if the #1 cylilnder is on the compression stroke. (Pull the plug and put your finger over the plug hole as you rotate the motor over by hand. The air will push out the hole when it is coming up on the compression stroke) The top of the stroke is where the pointer on the timing will line up with the zero O mark.


YOU NEED A TIMING LIGHT--buy one and use it wisely. Most good lights come with a wire that connects to the battery positive and negative posts, then the pickup sensor wire clamps over the spark plug wire for the #1 plug. When the motor is running then the light will flash in time with the #1 plug firing. The timing marks are in front of the timing chain cover (behind the water pump) Some are seen from the very top of the engine and others are from the driver's side. Your 84 should be from the top. Go under the truck and locate the mark on the harmonic dampener (crankshaft) and clean it (I usually mark mine with silver or white paint--fill the mark with the paint only) Then I take a long screwdriver and a rag soaked in a cleaner and wipe the timing tab clean, so I can see the marks and numbers on it. Once the timing light is working and the motor is idling, shine it down on the marks, as you rotate the distributor, the mark on the crank shaft will move along the marks on the timing tab. Look for the BTDC side (Before Top Dead Center) Work in that area only.

[greg0380]

It looks like you have an EST control module. The 4 wire plug going from a module under the dash to the distributor. I had an 85 305 that had trouble with that thing, sometimes it wouldn't start because it messes with the timing. There is an easy way to bypass it.. Swervin Ervin has a thread on this.

[Slonaker]

I have referred a couple of people to the article on 73-87.com for bypassing ESC. Both had problems like yours, and both fixed the problem by bypassing it.

Look at the bottom of this page:

http://www.73-87.com/7387garage/drivetrain/escrepl.htm

Slonaker