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08-20-2011, 01:24 PM | #1 |
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Location: Miramar Beach Florida
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Engine Detonation
Hi All,
I have a 454 C-20 with automatic. I just had new plug wires,plugs,rotor cap,rotor, modula installed. I am seeing soome detonation when I stop the truck. What do you think is causing this and how do I get that stopped? Thanks in Advance |
08-20-2011, 01:35 PM | #2 |
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Re: Engine Detonation
not a real fix, but shut it off in gear and THEN put it in park....
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Dad always said, "Son, WISH IN ONE HAND, and ......." -------------------------------------- -------------------------------------- Current toy trucks: '71 GMC 1500 SUPER CUSTOM short/step, orig. dk. blue, 350/700r, ps,pb, A/C '72 Blazer 2wd, ochre & white, 454, tremecTKO 500 5spd. ps, pb, A/C, tilt Last 10yrs of hobby vehicles, had a FEW more in the 50yrs. before these: '66 Plymouth Belvedere City of Miami cop car clone. '70 Nova 406"sb, 13.5-1, solid roller, Brodix, p.glide/t.brake, back halved, 9" Ford, spool 4.88, cage,ladder bar/coilover, 10.5 tire....... SOLD!! '67 C10 short/step side mount spare -- SOLD!! '72 Jimmy 2wd, 350/350, ps, pb, fun driver, lots of bondo & a shiny red paint job..... SOLD!! '69 Nova 350, 4spd, A/C, ps, p.b, ...SOLD!! |
08-20-2011, 01:48 PM | #3 |
It's all in the timing
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Re: Engine Detonation
You say you just had these parts installed,so I assume that someone else did the work?
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08-20-2011, 02:22 PM | #4 |
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Re: Engine Detonation
maybe the carb is loose/leaking around the base gasket or intake gaskets. While the engine's idleing squirt some spray start along the manifold gaskets and carb base. If you've got a leak the idle will speed up.
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Dad always said, "Son, WISH IN ONE HAND, and ......." -------------------------------------- -------------------------------------- Current toy trucks: '71 GMC 1500 SUPER CUSTOM short/step, orig. dk. blue, 350/700r, ps,pb, A/C '72 Blazer 2wd, ochre & white, 454, tremecTKO 500 5spd. ps, pb, A/C, tilt Last 10yrs of hobby vehicles, had a FEW more in the 50yrs. before these: '66 Plymouth Belvedere City of Miami cop car clone. '70 Nova 406"sb, 13.5-1, solid roller, Brodix, p.glide/t.brake, back halved, 9" Ford, spool 4.88, cage,ladder bar/coilover, 10.5 tire....... SOLD!! '67 C10 short/step side mount spare -- SOLD!! '72 Jimmy 2wd, 350/350, ps, pb, fun driver, lots of bondo & a shiny red paint job..... SOLD!! '69 Nova 350, 4spd, A/C, ps, p.b, ...SOLD!! |
08-20-2011, 02:08 PM | #5 |
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Location: Miramar Beach Florida
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Re: Engine Detonation
Yes a mechanic who did the new transmission.
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08-20-2011, 02:18 PM | #6 |
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Re: Engine Detonation
Could be a timing issue, but the engine run-on issue could be related to carbon build-up within the combustion chamber. Did it do it before the work was done? If not, I'd be checking the timing. Still, a hot-spot on the top of a piston could be igniting some fuel vapors that may be present within the intake due to some other fault. What year engine/carb do you have? During the mid-Seventies, engine run-on was not uncommon. GM had an anti-dieseling solenoid on a lot of carbs that was designed to close the throttle plate and prevent fuel mixture from entering the intake. If you're running a Q-Jet, there could be some fuel leaking from the plugs beneath the float bowls. That's not uncommon, either.
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08-20-2011, 02:26 PM | #7 |
It's all in the timing
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Location: Lake Mary,Florida
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Re: Engine Detonation
Have you spoke to him about the problem you are having,and if so what did he tell you?
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08-20-2011, 02:28 PM | #8 |
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Re: Engine Detonation
Detonation or dieseling after the engine is shut down is usually a result of hot chambers and raw fuel. Fuel can percolate from the bowel vent and enter the throttle body. It the chambers are hot enough, it can cause dieseling. Check to see if your throttle plates are fully closed when the engine is off. Some carburetors are equipped with a solenoid actuated throttle stop (Anti-Dieseling Solenoid)that will retract when the ignition is off, allowing the throttle plates to completely shut. If, as you state, you had a mechanic install the parts, I assume he set the timing properly. It wouldn't hurt to check it. Too much advance will cause the engine to run hotter.
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08-20-2011, 05:31 PM | #9 |
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Location: Miramar Beach Florida
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Re: Engine Detonation
Have not seen any indication of a hotter engine. I will have him check timing and check the throttle body to see if it is tight. All great ideas, thanks a million.
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08-20-2011, 06:17 PM | #10 |
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Re: Engine Detonation
What is you idle RPM set at. Sounds like it is set to high.
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08-21-2011, 10:24 AM | #11 |
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Location: Miramar Beach Florida
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Re: Engine Detonation
No tack so don't know the RPM but it does not sound high. No higher than it ever has been. Going to the shop on Monday Morning.
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08-21-2011, 01:39 PM | #12 |
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Re: Engine Detonation
ya i was having problems with the dieseling and it was just because my idle was set too high, but just try turning down the idle a bit and see if that does the trick
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