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

sixbangr · 06-01-2010, 07:51 PM

It should be at around 11 o'lclock, it is at 9. I assume the only way for it to be this far off is for the gears to be in wrong. I tried setting it, it won't run if you lower it to the marks.

raycow · 06-02-2010, 02:49 PM

If you can't set the ignition timing on the mark, the outer ring of the balancer could have slipped. It is held in place by a rubber to metal bond and this bond can fail over time.

Pull the plug on #1, then put a pencil in the hole and turn the crank by hand to check TDC.

Ray

PanelDeland · 06-02-2010, 06:20 PM

Did you disconnect the vac advance? if not it will really mess with timing .

**mr48chev** · 06-02-2010, 08:24 PM

This a photo that 68Gmcee posted in another thread a couple of weeks ago but is a good example.

here you can see the timing mark on the damper down at about 3 oclock.

Do as Ray said and pull #1 sparkplug (the front one) and with your finger over the hole have someone bump the engine over so that it comes up on compression. when the timing mark is close to the mark on the tab you can then use a pencil or piece of welding rod (LONG enough so that it can't be lost down the cylinder) to check and see when he piston is at top dead center by turning the crank with a ratchet or flex bar and socket. Once you know it is on top dead center, check to see if the mark on the damper is or isn't lined up with the 0 on the timing tab. If it is off at that time you can put a new mark on the damper at 0 but the rubber ring between the hub and outer ring may be suspect and the damper probably should be replaced.

Once you know that your timing marks are right hook your timing light to the #1 (again front) spark plug wire and check the timing with the vacuum advance hose disconnected and plugged.

06-02-2010, 02:49 PM	#2
raycow Registered User Join Date: Mar 2003 Location: San Francisco, CA USA Posts: 2,454	Re: 250 timing marks If you can't set the ignition timing on the mark, the outer ring of the balancer could have slipped. It is held in place by a rubber to metal bond and this bond can fail over time. Pull the plug on #1, then put a pencil in the hole and turn the crank by hand to check TDC. Ray Last edited by raycow; 06-02-2010 at 08:26 PM.

06-02-2010, 06:20 PM	#3
PanelDeland I am a Referee of life. Join Date: Jun 2000 Location: Greensboro N.C. Posts: 13,993	Re: 250 timing marks Did you disconnect the vac advance? if not it will really mess with timing . __________________ The 47-present Chevrolet and GMC Truck Message Board Network,it's owners,moderators,members,and associates of any type should not be held responsible for my opinion. You can't fix stupid,not even with duct tape. "My appearance is due to the fact that "GOD" does punish you for having too much fun!" Barrett-Jackson has perfected alchemy,they make rust into gold! "You can lead a horse to water but you can't saddle a duck" "Cleverly disguised as a 'Responsible Adult' "Sometimes your Knight in shining armor is just a retard in tinfoil"

06-02-2010, 08:24 PM	#4
mr48chev Registered User Join Date: Jul 2007 Location: Toppenish, WA Posts: 15,640	Re: 250 timing marks This a photo that 68Gmcee posted in another thread a couple of weeks ago but is a good example. here you can see the timing mark on the damper down at about 3 oclock. Do as Ray said and pull #1 sparkplug (the front one) and with your finger over the hole have someone bump the engine over so that it comes up on compression. when the timing mark is close to the mark on the tab you can then use a pencil or piece of welding rod (LONG enough so that it can't be lost down the cylinder) to check and see when he piston is at top dead center by turning the crank with a ratchet or flex bar and socket. Once you know it is on top dead center, check to see if the mark on the damper is or isn't lined up with the 0 on the timing tab. If it is off at that time you can put a new mark on the damper at 0 but the rubber ring between the hub and outer ring may be suspect and the damper probably should be replaced. Once you know that your timing marks are right hook your timing light to the #1 (again front) spark plug wire and check the timing with the vacuum advance hose disconnected and plugged. Last edited by mr48chev; 06-02-2010 at 08:43 PM.

06-01-2010, 07:51 PM	#1
sixbangr Registered User Join Date: Jan 2002 Location: Texarkana, Texas Posts: 261	250 timing marks It should be at around 11 o'lclock, it is at 9. I assume the only way for it to be this far off is for the gears to be in wrong. I tried setting it, it won't run if you lower it to the marks. __________________ 1961 Apache short step.



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