Clatter at idle?

[76 Cee Bee]

I just picked up a 76 Avenger w/ 455 olds and Berkeley pump. When you start the engine I hear a clatter noise coming from the starter area. Once you idle up the noise goes away. It's not the jet drive because I unhooked the drive line before starting it. Also it's not a rod knock (I've heard that sound before). Just sounds like something is rattling by the starter and flywheel. It's fairly loud and annoying. Unfortunately to get the flywheel cover off, it requires the motor mounts to be removed and worse yet, I need to use an engine hoist to support the engine from falling. Should I just try and change the starter first? It's a mother to get to but maybe possible without removing the engine. Just curious if I'm headed down the right path or not. Any thoughts?
Thanks,
Devin

[kp216]

Cracked flexplate?

[mdlfnsatx]

have you checked to see if the starter is shimmed properly, it could be the bendix just barley touching the flywheel when the motor is running. i would reccomend putting the thinnest shim in first and see if that heads you in the right direction.....good luck

[76 Cee Bee]

does it have through transom exhaust? My buddies sounded just like that and it was one of the flappers in the exhaust tips.
It does have transom exhaust. The noise is pretty loud. Not just a rattle. Enough to make you turn the engine off and go "something ain't right". I thought maybe the flexplate had some weights added when the motor was rebuilt and they could be touching the cover but with increased RPM the noise goes away. So that doesn't make sense. Maybe the flexplate is warped and with RPM it straighten's out enough not to rub? I've driven the boat on the lake and it works fine at speed but damn cruising through the 5mph zones clattering is embarrasing.

[76 Cee Bee]

have you checked to see if the starter is shimmed properly, it could be the bendix just barley touching the flywheel when the motor is running. i would reccomend putting the thinnest shim in first and see if that heads you in the right direction.....good luck
So I agree that would make the noise I'm hearing but why at increased RPM would it go away? If it's touching the noise should increase with speed. That's what has me worried. Shimming the starter would be a nightmare because of how hard it is to get too. I hope that's not the case.

[rerfert]

Cracked flexplate?
If it is a cracked flex plate...and you have the starter out rotate the engine and tap the flex plate with a hammer in a few positions....a crack will sound rather tinny/hollow?

[beerjet]

How are the rocker arms doin . You might hear one if it aint done right or comein loose.
-beerjet-

[BLOWN JOB]

Its an olds. No but seriously i would check the fly wheel

[Cas]

a flywheel bolt could be loose (or more than 1). At idle there's enough vibration for the bolt to shake and the sound is resonating thru the flywheel. When you rev it up, there's less vibration thus no sound. Ok, it's a stretch but you just never know.

[centerhill condor]

these flywheel guys get my vote! loose bolts, cracked, the starter work isn't that bad if you lie on the engine with one of those "ass pads" from the race track between you and the engine. the spare mirror helps you get a better understanding of what your hands are doing. Works great for me. Remove the dipstick and tunnell ram for best results! BTW I use no shims. best of luck.

[Keithb87]

We had the same kind of issue. It was the starter/ key switch. The key would not turn back from start to run and was leaving the starter Engaged.
The noise was terible at idle and calmed down at speed. But the starter did not last very long.

[ultra tweaker]

I had a bumpping rattly sound out of my brand new 509. I called several old timers in the so. cal. area and my machinest was very worried(fifth motor, to long a story to tell) I took the boat to a race engine builder here in Hemet he used his trained ear and said that it was normal because the sound went away when you revved it up. I spoke to another old timer who new this guy. He said that if that was what he had said it was true because if the guy with the trained ear could sell a job if he would. It is cam bump. Boat motors have wide tolerances. This motor is a full roller solid lifter deal and he said boats don't have rubber motor mounts so you hear things you wouldn't in a car. Hope this helps.

[76 Cee Bee]

these flywheel guys get my vote! loose bolts, cracked, the starter work isn't that bad if you lie on the engine with one of those "ass pads" from the race track between you and the engine. the spare mirror helps you get a better understanding of what your hands are doing. Works great for me. Remove the dipstick and tunnell ram for best results! BTW I use no shims. best of luck.
Turns out it was the driveshaft hub bottoming out in the crankshaft snout before it could press tight against the flywheel. So the flywheel could rattle a little bit. I machined a little off the driveshaft hub and problem solved. Too bad I had to use an engine hoist to lift the engine while I removed the flywheel cover. Fun job. Thanks for everyone's help.

[jetboat]

seams thers a few avengers out there with some of the same problems.after putting a new starter on the old flex plate went missing teeth with the power of the new starter.although you have a olds vs my 460 still have to lift the motor.we'll be doing that next week.