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Author Topic: Timing out of wack  (Read 1365 times)
68Zproject
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« on: August 24, 2014, 10:14:10 PM »

Recently got my engine back in and running.  The weird thing was when I had the total set to 36, the car wouldn't idle so I thought the carb might be messed up.  I set the timing by ear and drove to an old performance mechanic who checked the timing and reset the carb.  I was at 76 degrees total timing.  Neither one of us could believe it would run.  But every time I tried to bring the timing down the car would die.  So I thought I had too much advance in the mechanical and put in one stiffer spring and limited the travel in the slot.  Car ran great and idled great, but when I checked the timing, the mark was 180 degrees off the 0 mark on the timing tab.  So I took out the distributor and reversed it thinking I found the answer and some how it ran 180 out.  Not so.  I had to turn it around again.

So:  The question is:  What is the best explanation for this?  Is the cam timing off enough to do this or is my carb just plugged up and I need to idle it up at 36 total?  My idle is set at 1 1/2 turns off fully closed.  Is this in the ballpark for most?  68 302 with all stock stuff except the cam.
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68Z28
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« Reply #1 on: August 25, 2014, 06:50:38 AM »

Sounds to me that the outer ring on your balancer has shifted. Pull #1 spark plug, get piston to TDC and see were your timing mark is. George
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Stingr69
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« Reply #2 on: August 25, 2014, 11:05:25 AM »

My guess - Re-clock the distributor to where it should be and verify the wire positions on the cap.  Put your finger in the #1 spark plug hole and crank the engine to verify #1 TDC firing position - it will blow your finger out. This situation is probably not as messed up as you think it is. Some times people drop a distributor in after a cam swap in what they believe is the right #1 TDC Firing position but it is actually at #6 TDC.  Happens ALL the time.

-Mark.
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68Zproject
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« Reply #3 on: August 25, 2014, 12:12:58 PM »

I checked the balancer.  It's right on.  The firing order has been checked by 3 different people and is correct.  The engine runs, but at 75* advanced. I cant get the car to even run if I get the line anywhere near the timing tab.  Can't figure out how it runs at all this advanced.

So Mark, would the car run if I had it 180 out?
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68Z28
Stingr69
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« Reply #4 on: August 25, 2014, 01:55:32 PM »

It will not run 180 out.  The shear key might be missing but I suspect this is not the problem.

How did you verify the balancer?  How are you checking the timing?  Where does the rotor point when the engine is on #1 TDC Firing position?

Which tower are you using for #1 cylinder?  Firing order is probably fine if it ran well.

-Mark.
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68Zproject
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« Reply #5 on: August 25, 2014, 02:47:29 PM »

I pulled the bolt off the balancer and felt the keyway and it lined up with the timing line on the balancer.

I have a basic timing light and when I check the timing the line is above the top mark on the tab by about 2 inches so I can't even see it.  If I bring the timing back it wont idle and stalls.  So I'm still wondering if the carb could be plugged, but why would it idle fine when I'm way advanced?

#1 is at about 7 o'clock if your looking at it from the front of the car, top down.  Rotor is past #1 at tdc .
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68Z28
Fred Mertz
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« Reply #6 on: August 25, 2014, 02:50:37 PM »

Sounds to me like the timing chain was put on with the cam and crank not indexed correctly.
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cook_dw
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« Reply #7 on: August 25, 2014, 04:27:40 PM »

Maybe a dumb question but are you plugging off your vacuum advance when setting timing?
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Darrell Cook

1967 LeMans Blue SS/RS L35 clone
1968 Rallye Green SS L78 - unrestored original
1968 Matador Red Z28
vtfb68
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« Reply #8 on: August 25, 2014, 04:58:41 PM »

correct timing chain cover?
    VT
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05C LA RS/SS U2 712 L34 M21 BR
08E LA RS Y2 749 L30 M35
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Stingr69
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« Reply #9 on: August 25, 2014, 05:24:04 PM »

The keyway is located something like 9 degrees off the TDC mark on the balancer.  Balancer timing mark will line up with timing tab at #1 TDC AND at #6 TDC.

The crank can't be wrong.  if you are actually at #1 TDC FIRING position, the timimg mark will match up with the timing tab (at maybe 2:00).  Anything else (IE 7:00) is not possible. If the keyway is near 7:00..... the #1 piston is at the BOTTOM of the cylinder.

Distributor can't be installed right. You can't move the keyway that is cut on the crank, right?

Go back to post 2 - Pull the distributor out and put your finger over the spark plug hole while someone else bumps the engine.  When the air puffs out you line up the timing marks on the balancer and the timing tab then drop the distributor down in place with the rotor tip ending up roughly pointing at the battery. See the chilton manual for the cap wiring firing order and correct distributo tower to start the firing order.  Be sure to get that distributor all the way down where the oil pump shaft lines up and the distributor is all the way down on to the intake manifold. 

This has got to be the issue.

-Mark.
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69Z28
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« Reply #10 on: August 25, 2014, 09:25:20 PM »

Here's a pic I got years ago from JohnZ, I believe, that shows where the wires should be positioned on the distributor from the factory.

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GaryC

'UNRESTORED' 1969 Cortez Silver X33D80 Z28
z28z11
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« Reply #11 on: August 25, 2014, 09:54:50 PM »

One other question - did you build/rebuild this distributor, or remove the distributor gear during assembly of the distributor (did you use a Pertronix, or did you build this one from parts ?).

Regards - 
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1968 Z28 BRG/W
1969 Z28 X77 LeMans/W
1969 X66 L78 Cortez/BVT
1969 Z11 L48
JohnZ
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« Reply #12 on: August 26, 2014, 10:04:26 AM »

On a '68, the timing index line on the balancer outer ring will be exactly in line with the keyway (that relationship didn't change until '69, with the new alternator-on-the-right accessory drive system). First thing I'd do is to verify true #1 TDC firing position - get a piston stop tool and mark the true TDC on the balancer outer ring.

The engine will NOT run at 75* advance - that's not what you have.
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'69 Z/28
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68Zproject
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« Reply #13 on: August 27, 2014, 01:57:30 PM »

I have confirmed that the line on balancer at 0 on timing tab is tdc.  I think there are two things going on.  The distributor lost the bushing on the mechanical advance and had way too weak springs and that combo gave way too much advance way too early.  I fixed that and got the initial to 10, but I had to really bring up the idle.  Now I feel its something in the carb.  Almost acts lean.  Some research makes it sound like the power valve.
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68Z28
bcmiller
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« Reply #14 on: August 27, 2014, 03:27:03 PM »

Any idea what is inside the carb for jets and power valve now?
« Last Edit: August 27, 2014, 04:09:23 PM by bcmiller » Logged

1968 Camaro SS - now 468 BBC, M21, 12 bolt.
Bryon
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