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

MrSteve · 05-24-2009, 10:47 PM

Hey everyone! I have an 82 GMC Sierra 2500 with a rebuilt 350. I have had a driveability issue that goes like this: I can set the timing according to spec with the advance plugged. The engine idles perfectly but when I put it in drive I move ok as long as I gently touch the throttle but If I try to drive normally it boggs and tries to die on me. I have checked all the vacuum lines and they are routed correctly with no leaks. The vacuum advance works and does move the plate in the distributor. Is it possible that the distributor is set/installed wrong? If I wanted to verify the TDC and position of the distributor and #1 how would you guide me and what steps should I proceed in? Assuming you don't have other ideas as to what could be the problem.

Steve

fiyaweed06 · 05-24-2009, 11:01 PM

to verify TDC on the compression stroke put your finger over the #1 plug hole until air pushes your finger from the hole,when this happens get your marks set to 0 on the balancer or i stick a screw driver in the hole until it reaches its top most point and stab the dizzy that should get you close enough to get it started.

James McClure · 05-25-2009, 06:55 AM

Steve, everything you have done is correct. The problem isn't ignition or timeing, but carburation. The accelerator pump isn't spraying a good healthy squirt of fuel when you snap the throttle open from an idle. With the eng OFF, look down the throttle bore and open the throttle qiuckly. What you want to see is at least 2 good streams of gas into the primary bores. Once thats' corrected you should be fine. jim

MrSteve · 05-25-2009, 01:59 PM

I'm going to check that but what I have done is moved the timing way off from spec by feel (driving and moving it till it ran better). This has allowed the truck to run fine. The problem is that I have to smog the truck and when I set the timing to spec it is barely driveable and does what I described above. Thanks for guiding me!

Steve

MrSteve · 05-25-2009, 03:44 PM

Ok... I'm at TDC (to check distributor alignement) and timed at 6 degrees according to spec. I have checked the secondaries and they are squirting fuel just fine. Starts and idles perfectly but no accerleration without feathering the throttle, and forget about flooring it... it backfires and stmbles bad. Next?

Steve

MrSteve · 05-25-2009, 08:01 PM

I just discovered I have full vacuum to the distributor. The vacuum routing is correct according to the diagram but I don't know how to test the check or temp valves.

Steve

Hottrucks · 05-25-2009, 08:09 PM

back fire though carb or tail pipe?? carb means to much advance tail pipe means to far after TDC

fiyaweed06 · 06-09-2009, 09:22 PM

steve any more info on this issue!

05-24-2009, 11:01 PM	#2
fiyaweed06 Registered User Join Date: Apr 2009 Location: tuscaloosa alabama Posts: 101	Re: Timing? Issues to verify TDC on the compression stroke put your finger over the #1 plug hole until air pushes your finger from the hole,when this happens get your marks set to 0 on the balancer or i stick a screw driver in the hole until it reaches its top most point and stab the dizzy that should get you close enough to get it started.

05-25-2009, 06:55 AM	#3
James McClure One shot, one kill. Join Date: Dec 2007 Location: Saratoga Springs NY Posts: 859	Re: Timing? Issues Steve, everything you have done is correct. The problem isn't ignition or timeing, but carburation. The accelerator pump isn't spraying a good healthy squirt of fuel when you snap the throttle open from an idle. With the eng OFF, look down the throttle bore and open the throttle qiuckly. What you want to see is at least 2 good streams of gas into the primary bores. Once thats' corrected you should be fine. jim __________________ 1984 K20 350M engine with 465,000 miles. Well, it's finally done!! Almost 2 years of work, but it was really worth the effort. Little stuff left to do is mount winch, wet sand & buff out and build belly pan\running boards. Body work takes lots and LOTS of beer!!!! God, Guts and Guns made America and God, Guts and Guns will preserve it! The worst thing you could do is get into my sights, but that don't matter, you'll never know it, cause you'll never hear the shotJim or Paladin whichever you choose.

05-25-2009, 01:59 PM	#4
MrSteve Registered User Join Date: Feb 2009 Location: Galt, California Posts: 26	Re: Timing? Issues I'm going to check that but what I have done is moved the timing way off from spec by feel (driving and moving it till it ran better). This has allowed the truck to run fine. The problem is that I have to smog the truck and when I set the timing to spec it is barely driveable and does what I described above. Thanks for guiding me! Steve

05-25-2009, 03:44 PM	#5
MrSteve Registered User Join Date: Feb 2009 Location: Galt, California Posts: 26	Re: Timing? Issues Ok... I'm at TDC (to check distributor alignement) and timed at 6 degrees according to spec. I have checked the secondaries and they are squirting fuel just fine. Starts and idles perfectly but no accerleration without feathering the throttle, and forget about flooring it... it backfires and stmbles bad. Next? Steve

05-25-2009, 08:01 PM	#6
MrSteve Registered User Join Date: Feb 2009 Location: Galt, California Posts: 26	Re: Timing? Issues I just discovered I have full vacuum to the distributor. The vacuum routing is correct according to the diagram but I don't know how to test the check or temp valves. Steve

05-24-2009, 10:47 PM	#1
MrSteve Registered User Join Date: Feb 2009 Location: Galt, California Posts: 26	Timing? Issues Hey everyone! I have an 82 GMC Sierra 2500 with a rebuilt 350. I have had a driveability issue that goes like this: I can set the timing according to spec with the advance plugged. The engine idles perfectly but when I put it in drive I move ok as long as I gently touch the throttle but If I try to drive normally it boggs and tries to die on me. I have checked all the vacuum lines and they are routed correctly with no leaks. The vacuum advance works and does move the plate in the distributor. Is it possible that the distributor is set/installed wrong? If I wanted to verify the TDC and position of the distributor and #1 how would you guide me and what steps should I proceed in? Assuming you don't have other ideas as to what could be the problem. Steve

05-25-2009, 08:09 PM	#7
Hottrucks Redefining LowBudget Join Date: Mar 2009 Location: lebanon Cow Hampshire Posts: 4,538	Re: Timing? Issues back fire though carb or tail pipe?? carb means to much advance tail pipe means to far after TDC

06-09-2009, 09:22 PM	#8
fiyaweed06 Registered User Join Date: Apr 2009 Location: tuscaloosa alabama Posts: 101	Re: Timing? Issues steve any more info on this issue!



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