spark knock
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New User
Joined: Jun 2003
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spark knock
Like another problem I read earlier, I get spark knock once my truck goes to closed loop while accelerating. 1990 F-150 w/302, new timing chain, new heads, new cam, and many new sensors and I still get spark knock while accelerating but not always. I checked TDC w/ the heads off and the timing marks are good. I don't know what to do next. Any suggestions are appreciated.
Senior User
Joined: Sep 2001
Posts: 282
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From: East Wenatchee, WA
Well let me ask you a couple of questions. Did you raise the compression by changing the heads? Different cc cambers or mill the head to raise it? What are you setting your base ignition timing at while at idle? I know some cams with different durations can change compression slightly. Just some things to think about. I know base timing for my 1993 F150 with a 5.0L is 10 degrees before TDC.
Elder User
Joined: Jul 2004
Posts: 757
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From: Fredericton NB, Canada
Get a timing light, and play with the timing a bit, see if you can hit a sweet spot where the knock goes away. Have you changed brands of gasoline lately, try gassing at another location. Are you putting regular in it? Try some "Plus" and see if that fixes the problem.
-Matt.
-Matt.
Postmaster
Joined: Dec 2003
Posts: 2,659
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From: S/C Texas
My truck.......91 302......knocks bad on 87 octane, even worse on cheap 87. Walmart 87, wont hardly move, or run once it does, and shifts. I started using 89 octane......much better. Then I used Chevrons 89 octane....much better. Hardly ever notice knocking.
I thought I read somewhere in my Chiltons that the timing wasnt adjustable?
I thought I read somewhere in my Chiltons that the timing wasnt adjustable?
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Thank you very much for the input. I am timing it at 10 BTC. I changed the cam because Ford told me w/out a mass air flow sensor I needed the stock cam. In the process I found I had no seat left on 2 exaust valves and bought rebuilt ones. As far as I know everything is back to stock, the compression is around 145 give or take a few but I dont know enough about what the base should be. I did drop to a lower octane when prices went up and don't know if the 2 go together but I will definetly try next fillup. Thank you again.
Last edited by sparkie182; Sep 13, 2004 at 09:22 PM.
