Ignition timing - The 1947 - Present Chevrolet & GMC Truck Message Board Network

chvtrkman · 10-07-2007, 12:37 PM

Sorry if this topic has been discussed to death. I did a search but turned up nothing specific to my problem. Here goes:

My 292 has no power above 1500 rpm. I went to check timing yesterday, I put the timing light on it....can't find a mark lining up anywhere on the timing tab on engine block.My question is, would my truck even run if the distributor were to have gotten off a tooth? I didn't pull the dizzy, but a friend who worked on it for me in my absence may have.Any clues?

BTW: the truck is a tiny bit hard to start when cold, but once it idles a minute or two it starts easily, idles ok, and revs ok. just when I drive it, it cuts out after 1500 rpm, and has little to no power to climb a grade. I haven't checked for a vacuum leak yet as I want to make sure timing is correct first.Any help is appreciated.

chvtrkman · 10-07-2007, 04:14 PM

Ok,so I reset the timing to 8 degrees BTDC. Checked for a vacuum leak....everything's good there. Tried making carb adjustments 5 times.
The best I could get before it starts to cut out is 2000 rpm. Once again, I'm baffled.

**WorkinLonghorn** · 10-07-2007, 07:37 PM

Clogged fuel filter? Severely clogged air-filter? failing fuel pump? Points or electronic distrib? If points, dwell off?,points all burnt or oily? Carb clogged with gunk? Timing weights stuck and not advancing the timing as RPMs increase?

chvtrkman · 10-07-2007, 08:02 PM

WorkinLonghorn,
Thanks for the reply. Sometimes I neglect to give info that I don't think is pertinent to the problem. For example, the carb is new(installed in May of this year), as was brand new air cleaner, fuel filter, etc. New points,plugs,condenser as well.Pretty much all that stuff is new as the truck sat for 5 yrs. out in the woods.

I went out to tinker after dinner, I reset the timing back to original setting, only this time didn't use timing light, just did it by listening as I turned the distributor. That, in combonation with the leaner carb adjustment made a big difference, but it's still not 100%.At least I can drive up a mild grade now. I still haven't checked the fuel filter ( even though it's new) for debris clogging it up. I think I've narrowed it down to either that, or a bad vacuum advance. Tomorrow I will see if our local auto parts store will have one. If not I can order one from a supplier on the "net".Thanks again.

**68 Stepside** · 10-07-2007, 08:20 PM

My 66 3/4 ton had a leaky vacuum advance, it was a total dog until I fixed that. Fortunately it had 4.57 gears

, so I really didn't have a lot of problems with grades anyway...

**WorkinLonghorn** · 10-07-2007, 08:40 PM

The vac advance only affects part throttle operation (if installed correctly).So if you floor it going up a hill and the engine misses or runs real weak,it's not the vac advance (but it could be the centrifical adv.).Apply a partial vacuum with your mouth to the vac-line and you should see the points rotate counter-clock-wise.
If you have an old gas tank,it could very easily clog the filter in no time at all.I had to mount a huge filter on mine about the size of a lawnmower muffler to get some serious use from my old '69 between fuel filter changes!

DavesRide · 10-07-2007, 08:58 PM

Here is a good trick to find if fuel is an issue. Take one of those small propane touch bottles and take off the tip. Put a piece of hose on it long enough to reach carb from drivers seat. drive vehicle and when it malfunctions turn on propane and if it runs better it has a fuel delivery issue. I did this to an old quadrajet and figured out my metering rods were not raising up to deliver fuel once the secondary flaps opened. Just a thought. Dave

Sport/Truck · 10-07-2007, 09:09 PM

Quote:

Originally Posted by DavesRide

Here is a good trick to find if fuel is an issue. Take one of those small propane touch bottles and take off the tip. Put a piece of hose on it long enough to reach carb from drivers seat. drive vehicle and when it malfunctions turn on propane and if it runs better it has a fuel delivery issue. I did this to an old quadrajet and figured out my metering rods were not raising up to deliver fuel once the secondary flaps opened. Just a thought. Dave

Good tip, just be careful. The tube runs where on the carb? The top?
The nice thing about that idea is if it's not a fuel issue, you can end your problems with the torch in you hand.

s/t

DavesRide · 10-07-2007, 09:49 PM

Yes, very true. Be safe. I ran mine into the top opening of carb and held it in place so it did not go anywhere else. If the truck in question is missing under load then do look into ignition system. If it feels like it just holding back still on 8 cylinders then check into fuel. Yes, do not set it on fire.

Alex Hayley · 10-08-2007, 10:05 AM

Did you check for a stuck mechanical advance? I just worked through that issue a couple of weeks ago.

**WorkinLonghorn** · 10-08-2007, 10:35 AM

Quote:

Did you check for a stuck mechanical advance?

I already mentioned that twice.
Here;

Quote:

Timing weights stuck and not advancing the timing as RPMs increase?

and here;

Quote:

but it could be the centrifical adv

10-07-2007, 12:37 PM	#1
chvtrkman Registered User Join Date: Sep 2007 Location: PA. Posts: 178	Ignition timing Sorry if this topic has been discussed to death. I did a search but turned up nothing specific to my problem. Here goes: My 292 has no power above 1500 rpm. I went to check timing yesterday, I put the timing light on it....can't find a mark lining up anywhere on the timing tab on engine block.My question is, would my truck even run if the distributor were to have gotten off a tooth? I didn't pull the dizzy, but a friend who worked on it for me in my absence may have.Any clues? BTW: the truck is a tiny bit hard to start when cold, but once it idles a minute or two it starts easily, idles ok, and revs ok. just when I drive it, it cuts out after 1500 rpm, and has little to no power to climb a grade. I haven't checked for a vacuum leak yet as I want to make sure timing is correct first.Any help is appreciated. __________________ _____________________________________________ 69 C-20 292, 4 spd O/D, 4:56 rears. No a/c p/s p/b p/w......restoration project,"Operation:Stovebolt" 78 C-10 305 TH350 new (old) daily driver 02 Suburban Z71 a.k.a. the family truckster 99 Silverado 1500 Z71

10-07-2007, 04:14 PM	#2
chvtrkman Registered User Join Date: Sep 2007 Location: PA. Posts: 178	Re: Ignition timing Ok,so I reset the timing to 8 degrees BTDC. Checked for a vacuum leak....everything's good there. Tried making carb adjustments 5 times. The best I could get before it starts to cut out is 2000 rpm. Once again, I'm baffled. __________________ _____________________________________________ 69 C-20 292, 4 spd O/D, 4:56 rears. No a/c p/s p/b p/w......restoration project,"Operation:Stovebolt" 78 C-10 305 TH350 new (old) daily driver 02 Suburban Z71 a.k.a. the family truckster 99 Silverado 1500 Z71

10-07-2007, 07:37 PM	#3
WorkinLonghorn Senior Member Join Date: Dec 2006 Location: Studio City, Calif. Posts: 2,883	Re: Ignition timing Clogged fuel filter? Severely clogged air-filter? failing fuel pump? Points or electronic distrib? If points, dwell off?,points all burnt or oily? Carb clogged with gunk? Timing weights stuck and not advancing the timing as RPMs increase? __________________ '69 GMC C2500 Custom Camper, 8 1/2' bed, New GM 350, NP 435 Close Ratio 4spd. Trans., 3.73 Dana-60 open.Camper and Trailer wiring, PS, PB, AC, tach , three gas tanks, stereo speakers, 2nd owner, Work-Truck supreme. Last edited by WorkinLonghorn; 10-07-2007 at 07:39 PM.

10-07-2007, 08:02 PM	#4
chvtrkman Registered User Join Date: Sep 2007 Location: PA. Posts: 178	Re: Ignition timing WorkinLonghorn, Thanks for the reply. Sometimes I neglect to give info that I don't think is pertinent to the problem. For example, the carb is new(installed in May of this year), as was brand new air cleaner, fuel filter, etc. New points,plugs,condenser as well.Pretty much all that stuff is new as the truck sat for 5 yrs. out in the woods. I went out to tinker after dinner, I reset the timing back to original setting, only this time didn't use timing light, just did it by listening as I turned the distributor. That, in combonation with the leaner carb adjustment made a big difference, but it's still not 100%.At least I can drive up a mild grade now. I still haven't checked the fuel filter ( even though it's new) for debris clogging it up. I think I've narrowed it down to either that, or a bad vacuum advance. Tomorrow I will see if our local auto parts store will have one. If not I can order one from a supplier on the "net".Thanks again. __________________ _____________________________________________ 69 C-20 292, 4 spd O/D, 4:56 rears. No a/c p/s p/b p/w......restoration project,"Operation:Stovebolt" 78 C-10 305 TH350 new (old) daily driver 02 Suburban Z71 a.k.a. the family truckster 99 Silverado 1500 Z71

10-07-2007, 08:20 PM	#5
68 Stepside huh? Join Date: May 2000 Location: Washington, Illinois Posts: 5,690	Re: Ignition timing My 66 3/4 ton had a leaky vacuum advance, it was a total dog until I fixed that. Fortunately it had 4.57 gears , so I really didn't have a lot of problems with grades anyway... __________________ Someday when I'm lonely, Wishing you weren't so far away, Then I will remember Things we said today. RIP El Jay

10-07-2007, 08:40 PM	#6
WorkinLonghorn Senior Member Join Date: Dec 2006 Location: Studio City, Calif. Posts: 2,883	Re: Ignition timing The vac advance only affects part throttle operation (if installed correctly).So if you floor it going up a hill and the engine misses or runs real weak,it's not the vac advance (but it could be the centrifical adv.).Apply a partial vacuum with your mouth to the vac-line and you should see the points rotate counter-clock-wise. If you have an old gas tank,it could very easily clog the filter in no time at all.I had to mount a huge filter on mine about the size of a lawnmower muffler to get some serious use from my old '69 between fuel filter changes! __________________ '69 GMC C2500 Custom Camper, 8 1/2' bed, New GM 350, NP 435 Close Ratio 4spd. Trans., 3.73 Dana-60 open.Camper and Trailer wiring, PS, PB, AC, tach , three gas tanks, stereo speakers, 2nd owner, Work-Truck supreme. Last edited by WorkinLonghorn; 10-07-2007 at 08:44 PM.

10-07-2007, 08:58 PM	#7
DavesRide Registered User Join Date: Oct 2007 Location: Garageless, Missouri Posts: 408	Re: Ignition timing Here is a good trick to find if fuel is an issue. Take one of those small propane touch bottles and take off the tip. Put a piece of hose on it long enough to reach carb from drivers seat. drive vehicle and when it malfunctions turn on propane and if it runs better it has a fuel delivery issue. I did this to an old quadrajet and figured out my metering rods were not raising up to deliver fuel once the secondary flaps opened. Just a thought. Dave

10-07-2007, 09:49 PM	#9
DavesRide Registered User Join Date: Oct 2007 Location: Garageless, Missouri Posts: 408	Re: Ignition timing Yes, very true. Be safe. I ran mine into the top opening of carb and held it in place so it did not go anywhere else. If the truck in question is missing under load then do look into ignition system. If it feels like it just holding back still on 8 cylinders then check into fuel. Yes, do not set it on fire.

10-08-2007, 10:05 AM	#10
Alex Hayley Registered User Join Date: Jul 2000 Location: NC Posts: 987	Re: Ignition timing Did you check for a stuck mechanical advance? I just worked through that issue a couple of weeks ago.



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