Knoking rattling noise 69 GMC Truck

WISE651

MEMBER
1969 CHEVROLET TRUCK

Ok so when I am doing about 40 mph going up a hill lightly steping on the gas I hear a like knocking, rattling noise coming from the engine and it only does it at this time. And I have had my truck (1969 gmc shortbed) for two years now and I have heard this noise before in the past and it went away and now I belive it is getting progessivly worse. I am thinking it could be my valves. I had my exhaust just replaced as the prior one was not good, it had broken pipes and broken headers and I ran it like that for about a year and a half. So I am thinking I could have a burnt valve. Please tell me what you think.

3 Replies

MIKE H R

MECHANIC
3,094 POSTS

If it was a valve the engine would run rough, have the timing checked, check the plugs and wires. Does it sound like a octane ping.

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Monday, March 12th, 2007 AT 9:20 PM

WISE651

MEMBER
2 POSTS

No it really doesnt doesnt sound like a ping, but to be honest I am not really sure of what an octane ping would really sound like. And my truck accually runs really good. Its just under a load when I am going up a hill, lightly stepping on the gas pedal, it makes a ratting noise coming from the engine. Its not really a knocking noise. I dont know, its just so wierd becasue I have never heard anying thing like this. And its not a loud noise. When I give it more gas also, the noise goes away.
Today I am going to change the spark plugs and see what happens.