Timing issues - Pirate4x4.Com : 4x4 and Off-Road Forum

chev-mc · 12-09-2008, 12:00 PM

Hello all,
Thought I'd see if there is any advice to be given on this one.

78 K10 350

My truck ran great when I first got it a few years back. About a year ago when I took it off the road it ran like total crap.
I replaced the extremely worn timing chain and cogs.
Timed it and it still bogs under load and back fires.
I figured I had better replace the vacuum advance as well as it doesn't seem to be advancing when it should so that what I did today. Then timed it again. I checked the vacuum port on the Q-Jet as well and it pull vacuum when it needs to.
Its much better but far from perfect/the condition it was in when I got it. I can get it up to 4K without much problem but still get some hesitation and the occasional backfire. The last thing I can really think or would be the cap and rotor. I replaced them close to a year and a half ago. When I popped them off the brass was somewhat corroded.
Its just about 0 degrees here... I wish the truck would fit in the garage

HAPPYJOHN · 12-09-2008, 12:35 PM

Replace the cap & rotor. At the very least,
you'll eliminate them as the cause.

Keep us posted.

GMCTruxrule · 12-09-2008, 02:11 PM

Check/replace all the usual. Plugs, wires, cap, rotor.

If this motor is old(er) I'm gonna bet you got a burnt exhaust valve or flat cam lobe.

Or both.

chev-mc · 12-09-2008, 04:12 PM

Thanks for the info guys, I'll give it a whirl. I hope its an easy fix now but what can you do

mudskipper4x4 · 12-09-2008, 10:47 PM

As far as timing goes, check your harmonic balancer and make sure the outter ring hasn't slipped. This would cause the timing marks to be off. It sounds like a strange thing to happen but this is exactly what happened to a friend of mines truck.

chev-mc · 12-11-2008, 06:56 PM

Well a small update,
It's currently 7degrees advanced. I replaced the cap and rotor. It ran much better. I'm going to pick up a coil, plugs and wires tomorrow and check the harmonic balancer... Good call I would have never thought of that.

I dragged something home today for $100.00 tonight though

1990 Suburban 10bolt/Corp14SF 350/Turbo 400

Tranny is blown as well as the rear axle but hell for $100.00..... steal

Here's some pics
http://s463.photobucket.com/albums/q...rdferguson184/

kitimatdude · 12-11-2008, 11:08 PM

another thing to check is the springs on the advance weights in the distributor. I had them break/rust away on me before.

12-09-2008, 12:00 PM	#1 (permalink)
chev-mc Registered User Join Date: May 2007 Member # 91999 Location: Potsdam NY Posts: 21	Timing issues Hello all, Thought I'd see if there is any advice to be given on this one. 78 K10 350 My truck ran great when I first got it a few years back. About a year ago when I took it off the road it ran like total crap. I replaced the extremely worn timing chain and cogs. Timed it and it still bogs under load and back fires. I figured I had better replace the vacuum advance as well as it doesn't seem to be advancing when it should so that what I did today. Then timed it again. I checked the vacuum port on the Q-Jet as well and it pull vacuum when it needs to. Its much better but far from perfect/the condition it was in when I got it. I can get it up to 4K without much problem but still get some hesitation and the occasional backfire. The last thing I can really think or would be the cap and rotor. I replaced them close to a year and a half ago. When I popped them off the brass was somewhat corroded. Its just about 0 degrees here... I wish the truck would fit in the garage __________________ "I'll gladly pay you Tuesday for a hamburger today"

12-09-2008, 02:11 PM	#3 (permalink)
GMCTruxrule Registered User Join Date: Aug 2005 Member # 51243 Location: Tropical Paradise Posts: 3,410	Check/replace all the usual. Plugs, wires, cap, rotor. If this motor is old(er) I'm gonna bet you got a burnt exhaust valve or flat cam lobe. Or both. __________________ [COLOR="Lime"][B]1999 Chevy K3500, 5.7/4L80E/14FF/stock/stock/stock[/B][/COLOR]

12-09-2008, 04:12 PM	#4 (permalink)
chev-mc Registered User Join Date: May 2007 Member # 91999 Location: Potsdam NY Posts: 21	Thanks for the info guys, I'll give it a whirl. I hope its an easy fix now but what can you do __________________ "I'll gladly pay you Tuesday for a hamburger today"

12-11-2008, 06:56 PM	#6 (permalink)
chev-mc Registered User Join Date: May 2007 Member # 91999 Location: Potsdam NY Posts: 21	Well a small update, It's currently 7degrees advanced. I replaced the cap and rotor. It ran much better. I'm going to pick up a coil, plugs and wires tomorrow and check the harmonic balancer... Good call I would have never thought of that. I dragged something home today for $100.00 tonight though 1990 Suburban 10bolt/Corp14SF 350/Turbo 400 Tranny is blown as well as the rear axle but hell for $100.00..... steal Here's some pics http://s463.photobucket.com/albums/q...rdferguson184/ __________________ "I'll gladly pay you Tuesday for a hamburger today"

12-11-2008, 11:08 PM	#7 (permalink)
kitimatdude Registered User Join Date: Mar 2007 Member # 88672 Location: Ashcroft BC Posts: 635	another thing to check is the springs on the advance weights in the distributor. I had them break/rust away on me before. __________________ A... truck... kinda ... with stuff in it...

12-09-2008, 12:35 PM	#2 (permalink)
HAPPYJOHN What did you expect? Join Date: Aug 2008 Member # 119290 Location: near the 'con, CA. Posts: 1,657	Replace the cap & rotor. At the very least, you'll eliminate them as the cause. Keep us posted.

12-09-2008, 10:47 PM	#5 (permalink)
mudskipper4x4 AllUpInYourFace Join Date: May 2006 Member # 72951 Location: in a van down by the river Posts: 1,629	As far as timing goes, check your harmonic balancer and make sure the outter ring hasn't slipped. This would cause the timing marks to be off. It sounds like a strange thing to happen but this is exactly what happened to a friend of mines truck.

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