My engine was rebuilt in the summer of 1991. I have a little over 10,000 miles on it. It is an inline six cylinder with the Autolite 1-barrel carb. Recently I have noticed the oil pressure gauge on the low side. It used to be midway between the L and the H. Now it's more off center towards the L. Also, at idle the engine sounds like it's gonna shut off. And when shifting gears(I have automatic) there is a rat tat tat tat noise which goes away if you press on the gas pedal slightly. This started occurring about a little over a year ago. I had my coolant changed and I asked to have my timing checked. When the coolant was changed, they used a vacuum system which sucks in the new coolant. I never had this procedure done before; just the old tried and true way. Also, the mechanic revved the engine by pulling on the throttle from under the hood. Could either of these things messed up something? The car hasn't run right since. Does what I describe sound like I need a valve job or valve cover gasket replacement? Or possibly a malfunctioning oil pump? Thanks.

 

Revving the car from under the hood won't do anything

I'm not sure about any of the other stuff

 

no the vaccum / coolant system flush shouldn't of caused a problem at all...as for the noise you describe...uhhhh rat a tat tat[sm=WTFsgign.gif]kind of desription is that.... I'd say post a video of the noise to help us better understand what you hear

 

its a straight 6, i doubt there is much wrong, those engines will run forever.....and a day

 

Really sounds like oil pump, or the drive. Rata tat tat not enough oil to the rockers.

 

Possible broken flexplate.

 

i had the same noise when i had my i6. bad oil pump, not enough pressure gettin up to the rockers. change the oil pump or buy a 5.0 that already has a brand new oil pump.

 

Could it be lifter not quite up to par?

 

mine has 369000 miles on it all origanal and i have never had a rat a tat tat. might just have a valve out of adjustment. i have seen that before on the sixers

 

sounds like you need a v8...