Guys I need some help I just picked up a 67 Cutlass with the 330 in it and here is the situation:

The car starts fine and runs, around town it is pretty good but once I get to a certain RPM ( I cannot tell cause i do not have a tachometer) I hear a rattling noise coming from the passenger side I let off the gas and lower the rpms and it goes away.

Now I thought is may be a rod knock but it is not consistent all the time ONLY when I get up to certain RPMS, and if I am driving it on the freeway I can sometimes hit just the right spot (certain RPMS and I don hear it as much you can feel the power go up and down as if the lifter may be bleeding off?.

I am thinking it could possibly be a bad lifter or a worn cam lobe? I am thinking that it may be something where I do not have to replace the motor, any help would be greatly appreciated if you need more info ask away.

Thanks in advance

 

Unfortunately this is hard to diagnose long-distance. Could be anything from an internal engine problem to trans cooler lines vibrating together.

 

Thanks Joe i have eliminated the trans line cooler, the idle is a little rough and upon initial start up I hear the rattle for a brief second and then goes away, I can rev the motor up to what i can only assume to about 2-3k RPM with no signs of rattling. But only under load and on the freeway it starts to rattle

 

Do those have a heat riser valve on the passenger's side exhaust manifold? A broken spring can let them flop back and forth and rattle sometimes. Exhaust leaks can rattle too.
It is a tough one.

 

I thought about that, but for an Olds the heat riser will be on the driver's side.

 

A slight rod bearing knock can sometimes be pinpointed by running the engine and one by one pulling a plug wire off, and listen for the knock to cease. Sometimes rev-ing the engine with no load on the cylinder can pinpoint which rod is knocking.

 

That sounds like a good start I will try that tonight! I really appreciate all who have replied

 

don't shock yourself

 

yeah that is not the greatest feeling in the world. lol

 

Check the damper pully as well. In another recent thread the rattling sound was the because the rubber in the damper pully failed.

 

Will do thanks!

 

If you hear the sound under heavy engine load but not at idle or while revving in neutral it could be detonation. Detonation sounds something like a bunch of pennies being shaken inside a coffee can. When my engine was detonating it sounded like it was coming from the passenger side. The detonation in my 350 completely destroyed my pistons. What grade gasoline are you using? Is your timing set correctly? If your timing is set correctly you may want to try running premium fuel and see if you still hear the noise. 330 engines in 1967 came with either 9:1 compression or 10.25:1 compression. If your engine is the higher compression type, you will need to use premium fuel or retard your timing a ridiculous amount to avoid detonation.

 

Ahhhh.......I found out what it was, my water pump was bad and the rattling was coming from the internals it gave way in my driveway and i had to order one, but I found the "mystery" knock!

Also I had a slight hesitation on accelerating and I changed my cap, rotor, points and set the dwell to 30 degrees and also put new plugs and wires........................................ is all I can say!

I thought I was going to have to pull the motor and whatnot, but through the perseverance and a little logical deduction this cutty is runnin smooooooth!

I really appreciate all the help you guys offered me as well good to know you can come to web and get a wealth of knowledge from people who know their s**t!

 

Glad to hear everything worked out for you!!

 

i am having almost the exact same problem... it just happened today while driving on the highway. i have a 1971 455 though. but same thing, i feel like something happened when i was going about 80 mph and then slammed on the gas... after that when i was going about 65-70 mph and would be pushing the throttle more (going up a hill / going a little faster) i would get this slight inconsistent knock. it was only when i throtttled it more ( same thing about the tachometer though) i can only guess it was at 3000-3500. when i would cruise at lower speeds i wouldnt hear it but now im afraid to let loose off the line for fear of breaking something more or hurting the engine. i am going to try some of these things you guys suggested and see if i can find the problem but if anyone else has any other suggestions of what it might be, im all ears!!

another quick note, i used to run the car on only 89 octane and i was cruising with a buddy that said no dude you have to put premium in these cars ... so i did but then this happened, it might be a coinicidence but i thought i might mention that...

the sound sounds like a loose single penny hitting the inside of a valve, sometimes it makes a soft sound and other times a real loud one... very inconsistent though... and its really only when i have the gas pedal down from 1/3 to 1/2 way down... im afraid to push it farther.

thanks for any more suggestions!

Jay

 

Jay, although a new thread for your problem would have been warranted here. You may have run across a station with older fuel, which generally has attracted moisture. I would start with the basics, check your engine tune. Once you have established everything is set right, functional, take it for another ride and see if it is still present.

Report back with your findings, and engine settings.