Dodge 1976 Pickup

Tiny
CTRICE
  • MEMBER
  • 1976 DODGE RAM
My 1976 Dodge pickup (95K miles, 318 engine) has severe valve rattle under load or going up hills and interstate on-ramps. This only occurs after it reaches full normal operating temperature. When it is cold and warming up this does not occur and runs fine. I have tried higher octane fuel and different plugs with no change. Anything but light acceleration causes the valves to sound is if they are coming through the hood. Any help is appreciated.
Thursday, April 5th, 2007 AT 4:02 PM

6 Replies

Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
Sounds like spark knock/detonation/pinging

Check the ignition timing and EGR
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Friday, April 6th, 2007 AT 12:04 AM
Tiny
CTRICE
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The timing is correct and I agree that it is probably spark knock just dont know why it is occuring. It is much worse in warm/hot weather also.
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Friday, April 6th, 2007 AT 6:38 AM
Tiny
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You sure its not overheating-did you check the EGR it will cause detonation if its not opening-Knock sensor not retarding the timing

If the insulator is split or chipped, detonation (spark knock) may be occurring in the engine. The underlying cause here might be an inoperative EGR valve, overadvanced ignition timing, excessive compression due to accumulated deposits in the combustion chamber, or engine overheating.
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Friday, April 6th, 2007 AT 7:20 AM
Tiny
CTRICE
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I will check the EGR though I am not positive there is even one on this truck. It is 1976 and does not have a catalytic converter though it does have a charcoal canister. I heard pickups did not need emissions equipment until around 1979. I inherited it from my Grandfather who purchased it new. Thank you for the advice.
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Friday, April 6th, 2007 AT 7:28 AM
Tiny
RASMATAZ
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Do a wet and dry compression test and comeback with the results-if its higher than normal you got accumulated deposits in the combustion chamber-raising the compression to a point creating detonation

Pre-ignition and detonation is two different things
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Friday, April 6th, 2007 AT 7:44 AM
Tiny
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Will do. Thank you and I'll let you know what I find out.
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Friday, April 6th, 2007 AT 8:33 AM

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