Thread: 355 engine rattling while idling

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Hello All

I am new to the forum, and just have a question for you guys. I know it may be hard to diagnose not heaaring the car, but thought I might find some advise.

We recently bought an 85 olds cutlass, it has a new 355 in it with just 2800 miles on it. Yesterday I let my wife drive it, we went about 2 miles on the interstate. As my wife got in the passing lane and gave it a little gas there was a moment of hesitation. As we got off at the exit and began to slow down I noticed a rattle coming from the engine, I could hear it in the car.

SO we stopped and got out, the rattle sounds like it is coming from the top of the motor almost like something was loose. I realized it is only doing this at an idle, when you give it the gas it stops. I called the guy we bought it from who built the engine, he said it needs a valve adjustment. Does this sound right? Or does somebody have any other idea?

Thanks,

John

Sounds like a good possibility, bring it back to him for a valve adjustment if he built it and sold it, hopefully that is all it is

As far as the hesitation you mentioned, that is carb/timing related - have him look at that too while he is adjusting the loose rocker arm(s)

Might check the oil level. Sounds like low oil pressure to me.............

Thanks for the response. I have checked the oil level and it is good. The car still ran fine coming back home, but sounded horrible when idling. I am not a mechanic and just don't know what to look for. My main concern is that it is nothing major, being that I just bought the car! Hopefully I can get it taken care of this week!

John

Vary possible it could be a cracked flex plate. If it was replaced when they did the motor.There is a lot of aftermarkets made in rice land that aren't too good. I have seen 3 or 4 of them .......ted

yes the flex made by gm are not very good either i went through 3 of them untill i got one that was not cracked.all bought from a top chevy dealer.could the parts people putting bad parts back in the system? i worked for a big gmc dealer in northern va. and they had some mach.spin main and rod bearings using a screw driver and hammer.so the customer could get a new engine under warrenty because the current engine was not powerfull enough.no wonder gm went under.dishonest dealers and bad products

We determined that the rattle is coming from the area of the torque converter. You can actually move the flywheel back and forth, but the crank doesn't move. The torque converter to flywheel bolts were tight, could the bolts on the other side be loose?

Very possible bolts are loose and egged out the bolt holes,or center of flexplate simply cracked out.

Ok, all of the bolts were loose and one was backed out quite a bit! Took the flexplate/flywheel off and found that it was warped. Went got a new one and new bolts, put it all back together and it is running great!!

Thanks to all for your help!!

John