Author Topic: Timing out of wack  (Read 9664 times)

cook_dw

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Re: Timing out of wack
« Reply #15 on: August 27, 2014, 08:57:24 PM »
Acts lean at idle, cruising or WOT?
Darrell Cook


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68Zproject

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Re: Timing out of wack
« Reply #16 on: August 27, 2014, 11:32:47 PM »
Acts lean at idle, cruising or WOT?

All the above.

It has whatever was recommended on this site.  72/76 jets I believe and 65/85 power valves?  I just had it apart a few weeks ago as the bowls were leaking and the accel pump housing leaked because of a stripped screw.  I fixed the accel pump and used new gaskets on the blocks and bowls.  The kit I had, had two 65 power valves in it so I only replaced the front one.  I checked the back one and it seemed to be working.  However, with this timing thing I've had a few backfires.
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JohnZ

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Re: Timing out of wack
« Reply #17 on: August 29, 2014, 04:04:30 PM »
<< I fixed that and got the initial to 10, but I had to really bring up the idle. >>

Is your vacuum advance working (adding 15* at idle) and is it connected to a full manifold vacuum source, or to the stock "ported" vacuum source?
'69 Z/28
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68Zproject

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Re: Timing out of wack
« Reply #18 on: September 03, 2014, 09:08:32 PM »


Is your vacuum advance working (adding 15* at idle) and is it connected to a full manifold vacuum source, or to the stock "ported" vacuum source?

Yes and Yes.  I have it set up like yours, but I really need a dial back light to see how everything is working.  I also bought two new power valves and will see if that helps.
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68Zproject

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Re: Timing out of wack
« Reply #19 on: May 23, 2015, 10:21:30 PM »
I'm going to drag this one back to life.  I finally seem to have gotten this figured out.

First problem was the distributor.  The point rubbing block had worn down and even though the dwell was on, the gap was only about .009.  Also the distributor would not go down all the way on the intake.  For some reason this caused some kind of bind and the mechanical advance would stick.  I shimmed it and changed points.

Second issue was the fuel pump.  Even though lots of mechanics told me they either work or they don't, I replaced it with another Delco and it runs great.

Now the only issue I have is the power valves.  I had the 6.5s in, but I had a backfire and now I can turn the idle screws in all the way and it still runs, so I think at least that one is blown.  Also, I put a vacuum gauge on it and I'm only getting about 9-10 inches.  I'm running the Comp Cams xs 282s.  Is that the normal vacuum that this cam runs?  If so should I go to 4.5 power valves?
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janobyte

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Re: Timing out of wack
« Reply #20 on: May 23, 2015, 11:13:37 PM »




To properly size a power valve, take a vacuum reading at idle and if it is above 12" for a standard transmission a 6.5" will be safe to use. For automatic transmissions take a vacuum reading in gear at idle and if the vacuum is below 12" divide that in half for proper size. Example 9" of vacuum in gear at idle will require a 4.5" power valve.  (quoted per Holley website) My rule of thumb was size 1/2 the vacuum at idle. While you have it apart might as well install the blow out protection kit.
68 Z/28  born with: 302, drive line, etc..

68Zproject

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Re: Timing out of wack
« Reply #21 on: May 24, 2015, 02:56:15 AM »
I heard that requires drilling something out.  I don't really want to do that.  I don't think there will be any more backfires now.
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