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Old 05-08-2003, 05:26 PM
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Post Rattle in Engine

I've got a 1971 455 Olds V8 with headers. When the car is sitting in the driveway the engine runs and sounds healthy. But when I take it out on the road and give the engine 1/4 throttle, it will rattle. It will not rattle at any other throttle setting. The engine only has about 500 miles on a rebuild and I have noticed that the engine oil on the dipstick smells like gasoline and has a thin film of silver in it. Several people have suggested that I may have a rod bearing getting ready to let loose. I also discovered that my vaccuum advance has not been working so I'm wondering if the noise may be the valves pinging due to low octane gas combined with retarded timing. Also the rebuilt carb I have has some major problems and is allowing WAY too much gasoline into the engine at WOT. What do ya think?

Benji

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Old 05-08-2003, 05:42 PM
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if there`s fuel in the oil, it`s likely the fuel pump is ruptured internally causing a leak into the oil. Usually a engine will rattle if the timing is over advanced, not under, do you have your vacuum advance on ported vacuum? the vacuum advance is only needed as the engine revs and not needed at idle, so if it`s on full time vacuum it won`t have any advance off idle but will be advancing it like crazy at idle where it`s not needed. also check your advance curve, make sure it`s not frozen or stuck open, check the spings, if your using the lighter ones move up to heavier ones and see how it does, that or slightly retard the spark timing 2 degree`s at the time until the rattle goes away, I had a friend with a small block chevy where gas was always in the oil, lots of it, it ruined the rings in the engine and it smoked like steam train, but when we stripped it down the bearings didn`t look too bad but the rings were shot. I seen one case where a hole was in the piston allowing fuel into the oil and when he floored it, it would blow the valve covers off, so if all else fails, run a compression check. good luck.
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