68 c10 L6 engine vibration problems

[sambudo]

What can be the cause of engine vibration? I recently tuned it up replaced spark plugs,wires, cap & rotor. Not points. It seems to be running worse then before. Any suggestions to correct this problem? I'll check to make sure i didn't cross a wire tonight.

Would a carburetor rebuild help correct this issue? Vacuum leak??

['68OrangeSunshine]

Check on your Harmonic Balancer. They can work loose over time. SMOG can accelerate the deterioration. There's only a soft rubber ring between the crank hub and the pulley sheaves. Also L6s operate in a lower RPM regime than V8s. Over-revving can bust them loose prematurely.
Is the timing mark right on or ''off''?
Does the balancer wobble at any RPM?
A loose HB can cannonball thru your radiator at freeway speeds. Don't ignore it.

If it's not that, check to see that your motor mount hardware is all secure.

[LockDoc]

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If it didn't do it before the tuneup why would you suspect the carb? If that is the case I would say it is something you changed..... Wires crossed, points not adjusted correctly, cap not down all the way...etc. Did you reset the timing after the changes?

Just some thoughts.

LockDoc

[sambudo]

Originally Posted by LockDoc

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If it didn't do it before the tuneup why would you suspect the carb? If that is the case I would say it is something you changed..... Wires crossed, points not adjusted correctly, cap not down all the way...etc. Did you reset the timing after the changes?

Just some thoughts.

LockDoc

it didn't run as rough, compression in cylinders 1 & 5 were low about 105 others around 150. Last check several months back. I need to recheck them. Wires are all correct, timing is not set where it should be. it won't run if it was. I didn't change the points.

Harmonic balancer is ok! Not sure what to do, really runs rough.

[Shaky]

Originally Posted by sambudo

Harmonic balancer is ok!

You're sure that the outer ring didn't spin relative to the inner? I'm just asking because it has happened to me on a 6.

Also, I had a 6 once where the intake manifold got so loose it was flopping around. It still ran (!) but it was rough.

[davepl]

Originally Posted by Shaky

You're sure that the outer ring didn't spin relative to the inner? I'm just asking because it has happened to me on a 6.

Wouldn't this show up on a timing light pretty quickly? I suppose it could slip only a couple of degrees and that'd be hard to diagnose, but anything more than about 20 degrees would put you so far out of whack that if you set your timing based on the timing mark you'd have really incorrect timing, your rotor would be out of phase, and the engine would shake bad. Just like this guy's truck :-)

[mechanicalman]

It won't run if the timing is set where it should be? OK I really don't know the six engines but if the timing mark is on the outer ring of the crankshaft damper (harmonic balancer) like the small block V-8s, this is possibly an indication that the ring has at least slipped, provided the wires are in the correct places.

And another possible issue, make for sure the wires went on the distributor EXACTLY where they are supposed to go, if not sure look at another engine. You cannot put the wires all 1 hole over and compensate by turning the distributor. This will put the distributor out of phase and that will not only make the engine shake but also run quite crappy. This has to do with when the points make contact, the rotor is not in phase with the electrodes on the cap and only a limited amount of distributor advance is available or possibly a weak spark at base timing (idle).

Why not new points? Recently replaced?

[hamjet]

I would pull the plugs and look at them and see if the gap didn't get closed while installing them, or maybe a piece of gunk by the spark plug hole. also look at them to see if they were firing ok. while you're at it look at the plug wire ends, ( if they were universal where you had to cut to length and add the little brass clip), even test them with a meter. If its running worse, its got to be something that happened during tune up....and yes, check the cap, rotor....

[sambudo]

What should tthe plugs be gapped at? And what is a good cyl compression 150 ?

['68OrangeSunshine]

Plug Gaps:
.035 POINTS
.045 HEI

Point gaps:
.019 NEW
.016 USED

I would be happy with 150 PSI.

[Kapote]

i have a 292 , recently i was having this problem also, here is what the problem was, the points werent tightened enough and so it would vibrate at low Rpms, but then i fixed that ad it vibrated at high Rpms, so i thought fetch now what, I thought it was the carb, i messed with that forever, nothing changed, So i timed it ( make sure your vacuum advance is OFF when timing) and pulled the cap again, with points youll get this dust in the cap, which will let the sparks jump all over at high Rpms. i cleaned that off and it runs alot better, but still new points will help. Make sure your points are gapped correctly and havent moved. also if its an old distributor it could be wobbling a little which would cause it to surge a little. hope this helps.

[sambudo]

Originally Posted by Kapote

i have a 292 , recently i was having this problem also, here is what the problem was, the points werent tightened enough and so it would vibrate at low Rpms, but then i fixed that ad it vibrated at high Rpms, so i thought fetch now what, I thought it was the carb, i messed with that forever, nothing changed, So i timed it ( make sure your vacuum advance is OFF when timing) and pulled the cap again, with points youll get this dust in the cap, which will let the sparks jump all over at high Rpms. i cleaned that off and it runs alot better, but still new points will help. Make sure your points are gapped correctly and havent moved. also if its an old distributor it could be wobbling a little which would cause it to surge a little. hope this helps.

I'm going to get points for it today. How do you adjust the points?
I know this is a dumb question. Also what about the vacuum advance where is this located? Is it on the carburetor ? Thanks

['68OrangeSunshine]

Vacuum Advance canister is a turnip-shaped item that pokes out the side of the Distributor. A vacuum hose line should run from a small nozzle on the end to the carburetor. Never seen one that wasn't silver.
To set points, one bumps the rotor until the six-sided cam is opening the points the most. Then adjust a gap of .019 for NEW and .016 for USED. A flat bladed screwdriver can be used to widen or close the gap. Then lock down the screw. V8s have a window under the distributor cap and are adjusted with an allen wrench. L6s don't. For L6s I use 2 screwdrivers. One for the lock down screw and one to adjust the gap. If you're out on the desert without everything, an old Indian trick was to use one business card [or matchbook cover] for .016 and 2 Biz cards for .019. Not exact, but you might get home.
Dwell is also adjusted by opening or closing the point gap.

[sambudo]

ok guys I'm stumped! I changed the plugs,wires cap, rotor points and condenser and a new coil and Now theres no spark!

I'm I missing something? It ran rough before changing the points. After I changed them I attempted to start it, it wouldn't I notice a slight smoke by the coil. I replaced the coil. Still no spark! Wires look good! Does anyone have any advise to what I might need todo to get this thing running again? Stumped and confused! I checked all the fuses.

[mechanicalman]

Go over everything you did, you obviously did something wrong. Probably put the coil wires on backwards. Check out the picture on this link. Keep in mind, the "resistor" on the wire from the ignition switch is built into the wire.

http://www.justanswer.com/classic-ca...968-caddy.html

Anything else you may need to know is in this link.

http://speedprint.com/deves50/doc/enginetiming.pdf

[CaptRMW]

Probably a better chance it was caused by stale air in the tires than the coil wires put on backwards..

[hamjet]

pull your cap and have someone turn the engine over to verify the points are opening and closing, its possible you may have gotten it wrong. also make sure you slipped the condenser wire behind the points spring in the right place. ( if thats how the wire connects, I'm not sure) its been a while since I've replaced points....

[hamjet]

Just thinking out loud, could it be a bad ignition switch????

[CaptRMW]

Sambudo when you checked the compression and said compression in cylinders 1 & 5 were 105 others around 150 several months back you found a problem that no ones tuneup will correct. 105 lbs of compression then was on the verge of a dead miss and if you pull the plug wires one at the time with the engine running I am sure that you can now easily find which cylinders those 105 readings came from. If your engine is not smoking and using oil then a valve job would be a good guess as to what it will take to get the compression in an acceptable range. Check the compression then put a couple of squirts of oil in the cylinders that are low and check the compression again, if the compression is still low you likely have leaking valves but if the compression come up you have leaking compression rings. Good luck

['68OrangeSunshine]

Do you have 12 VDC on the battery? Is the Fusable Link from the Pos (+) Post Lug to the terminal on the passenger side fender in good order and not open?
Does it turn over? Horn work?

[Codez67Chevy]

One thing I do suggest is checking your intake and exhaust bolts/nuts. Make sure they are to the right torque spec. I found out that mine vibrated lose over the past I dunno years. I re torqued them and it has ran really good in fact I had to readjust my carb due to them being out of spec. Just a thought.

[Alex V.]

BTW, it's possible the vibration is strictly related to ignition issues, but your low compression could cause it to shake no matter how well it's tuned up. If you get it running again and tuned properly and it still shakes (not so much a vibration, but a course, consistent shake, especially at low RPM) then it's very possible the lack of compression is the root of the problem. If it is a burned valve, it's likely an exhaust valve - a stock inline 6, when running right, shouldn't have any "lope" to speak of in the exhaust like a V-8 does. If it does, or if there's a noticeable puffing out the exhaust (once every-other revolution of the engine, to be specific), these all point to a burned valve.

[sambudo]

So here is myporlem now, I changed the points, tempted to start it and it woukdnt start. ?? Checked the spark and none. Replaced coil still no spark. All wires every thing correct. Still no spark.

so the engine was running rough, I change pointss and condensor, and it dosent start? When I turned the ignition over I did see a small plume off smoke close to where thecoil dist.located. so I thought I damaged the coil. I replaced the coil and still no spark. I put the old points and condensor back in and still nothing. I have 12v power is it possible ground wire might be faulty?

Not sure what other tests I can do at this point. I havea volt meter but not good at using it,

any suggestions?

[mechanicalman]

Use trial and error on your volt-meter by putting red wire on positive side of battery and black wire on ground side then play with it till you get an approximate 12 volt reading. Then, check the wire going from the firewall to the coil and see if you get 12 volts. If you don't, go to the fuse-box and check the spades "ign unfused" for 12 volts.

http://67-72chevytrucks.com/vboard/s...d.php?t=427012

Just for grins, is the coil wire from the ignition switch connected to the + or - side of the coil? Or what is the marking where it is hooked up?

[davepl]

Originally Posted by mechanicalman

Use trial and error on your volt-meter by putting red wire on positive side of battery and black wire on ground side then play with it till you get an approximate 12 volt reading. Then, check the wire going from the firewall to the coil and see if you get 12 volts. If you don't, go to the fuse-box and check the spades "ign unfused" for 12 volts.

Nope. You cannot diagnose resistance with a volt meter unless there's a load. You'll measure 12V on a resistance wire just the same as you would a superconducting liquid-helium-cooled monster cable.

I don't know if, with the engine running, the coil would put enough load to show up on a DVM at the coil with a resistance wire. I suspect it would not, but actually have never tried it.