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

sons65project · 12-15-2011, 03:08 PM

I have a 65 GMC with 305 v6. It has holley 550, Electronic ingnition, valves adjusted. Great truck.

Here is my questions. Sometimes it runs perfect, other times it sputters up through carburetor. Is it timing? Jetting?

Getting ready to turn it over to my 17yr old for his daily driver and want it running perfectly.

Thanks for your input

**Corts60** · 12-15-2011, 07:20 PM

sputtering through the carb is a lean condition. It could be one or several things. I would check for vacuum leaks, timing, and air fuel mixture.

Timing on the V-6's I believe is around 4 degrees. If you have a vacuum gauge, use it to set your air-fuel mixture. You want the max amount of vacuum at idle.

Hope this helps.

*HEI451* · 12-15-2011, 08:15 PM

My 305E runs at the groove on the damper, 7-1/2 degrees.

Try getting the engine into the problem zone, and doing a plug chop. Thgat is literally, getting it to do what it shouldn't, then, on a road that isn't heavily traveled, take the engine out of gear, but the ignition, coast to the side of the road and stop, pull a few plugs and wsee if it is rich or lean.

Which "electronic iginition"? If it is a PerTronix, they have a lot of 'issues'. And, drop in systems like the Ignitor MUST keep a small plugg ap, anything over .035 is begging for 'miss' issues.

brokenspoke · 12-16-2011, 07:12 AM

I like using a vacum guage for setting my timing.....Advance untill higest reading and then back off untill it just drops a pound....done

*HEI451* · 12-16-2011, 12:20 PM

NO, NO, NO, doing the vacuum reading method only over advances the engine, usually with seriously bad results.

DO IT RIGHT, PLOT THE MECHANICAL AND VACUUM ADVANCE CURVES WITH THE ENGINE RUNNING, AND SET THE TIMING CORRECTLY, WITH A TIMING LIGHT, AT IDLE.

Avoid the over advancing issues and problems, don't use a vacuum gauge to set timing.

Sorry, I've only been fixing the different ways, like this one with a vacuum gauge, for people that got into lots of trouble from setting timing incorrectly, for over 40 years so far. I build custom ignition systems for a living, and KNOW how to do it the right way, and, using a vacuum gauge to set timing AIN'T ONE OF 'EM.

sons65project · 12-16-2011, 01:59 PM

Thanks for all your help. I have a full hei ignition bought off ebay specifically for this motor. no points. most of the sputter seems to be under hard acceleration.

Maybe not enough juice going to the distributor?

Appreciate all your help. This truck is a blast. Someone even dropped a muncie 4 speed in it. pics coming.

12-15-2011, 03:08 PM	#1
sons65project Registered User Join Date: Jan 2010 Location: La Mirada CA Posts: 10	timing????? I have a 65 GMC with 305 v6. It has holley 550, Electronic ingnition, valves adjusted. Great truck. Here is my questions. Sometimes it runs perfect, other times it sputters up through carburetor. Is it timing? Jetting? Getting ready to turn it over to my 17yr old for his daily driver and want it running perfectly. Thanks for your input

12-15-2011, 07:20 PM	#2
Corts60 Just here to tinker Join Date: Jun 2008 Location: Holland, MI Posts: 3,697	Re: timing????? sputtering through the carb is a lean condition. It could be one or several things. I would check for vacuum leaks, timing, and air fuel mixture. Timing on the V-6's I believe is around 4 degrees. If you have a vacuum gauge, use it to set your air-fuel mixture. You want the max amount of vacuum at idle. Hope this helps. __________________ 78 C10 SWB Diesel #1 (wrecked)http://67-72chevytrucks.com/vboard/s...1978+silverado 78 C10 SWB Diesel #2 (sold)http://67-72chevytrucks.com/vboard/s...d.php?t=650751 60 GMC Suburban (sold)http://67-72chevytrucks.com/vboard/s...d.php?t=445526 60 GMC 1000 (sold)http://67-72chevytrucks.com/vboard/showthread.php?t=298235 67 GMC 1500 (sold) http://67-72chevytrucks.com/vboard/s...d.php?t=803695 73 Chevy C20(Daily)http://67-72chevytrucks.com/vboard/s...d.php?t=852767 86 Suburban(summer unit) http://67-72chevytrucks.com/vboard/s...d.php?t=810697 88 Suburban 4x4(sold)

12-15-2011, 08:15 PM	#3
HEI451 Account Suspended Join Date: Mar 2011 Location: Yerington, Nevada Posts: 864	Re: timing????? My 305E runs at the groove on the damper, 7-1/2 degrees. Try getting the engine into the problem zone, and doing a plug chop. Thgat is literally, getting it to do what it shouldn't, then, on a road that isn't heavily traveled, take the engine out of gear, but the ignition, coast to the side of the road and stop, pull a few plugs and wsee if it is rich or lean. Which "electronic iginition"? If it is a PerTronix, they have a lot of 'issues'. And, drop in systems like the Ignitor MUST keep a small plugg ap, anything over .035 is begging for 'miss' issues.

12-16-2011, 07:12 AM	#4
brokenspoke Registered User Join Date: Jul 2011 Location: Anderson, Texas Posts: 535	Re: timing????? I like using a vacum guage for setting my timing.....Advance untill higest reading and then back off untill it just drops a pound....done

12-16-2011, 12:20 PM	#5
HEI451 Account Suspended Join Date: Mar 2011 Location: Yerington, Nevada Posts: 864	Re: timing????? NO, NO, NO, doing the vacuum reading method only over advances the engine, usually with seriously bad results. DO IT RIGHT, PLOT THE MECHANICAL AND VACUUM ADVANCE CURVES WITH THE ENGINE RUNNING, AND SET THE TIMING CORRECTLY, WITH A TIMING LIGHT, AT IDLE. Avoid the over advancing issues and problems, don't use a vacuum gauge to set timing. Sorry, I've only been fixing the different ways, like this one with a vacuum gauge, for people that got into lots of trouble from setting timing incorrectly, for over 40 years so far. I build custom ignition systems for a living, and KNOW how to do it the right way, and, using a vacuum gauge to set timing AIN'T ONE OF 'EM.

12-16-2011, 01:59 PM	#6
sons65project Registered User Join Date: Jan 2010 Location: La Mirada CA Posts: 10	Re: timing????? Thanks for all your help. I have a full hei ignition bought off ebay specifically for this motor. no points. most of the sputter seems to be under hard acceleration. Maybe not enough juice going to the distributor? Appreciate all your help. This truck is a blast. Someone even dropped a muncie 4 speed in it. pics coming.



Register or Log In To remove these advertisements.

Register or Log In To remove these advertisements.