Minor shudders at idle

[banderberg]

Hi, I've got a 3.0L with points ignition. I've got my engine idling at around 600 RPM in the video below. It has a few shudders and rattles a little and I'm not sure if this is normal or what I can do.. I'd really like the engine to idle still and without the rattles. At higher RPM it smooths out.

See my 24 second video below.

New video · Thursday, Jul 14, 2022 🎬

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[Rick Stephens]

I'd do a compression test and a hook up a vacuum gauge. Tells a bunch about condition of the motor that you cannot see.

 

[banderberg]

I'd do a compression test and a hook up a vacuum gauge. Tells a bunch about condition of the motor that you cannot see.

I did, it has 160 psi on all four cylinders

Should I also do the vacuum gauge?

 

[Rick Stephens]

Vac gauge will tell you condition of valve train and whether you have an adjustment problem.

 

[banderberg]

Vac gauge will tell you condition of valve train and whether you have an adjustment problem.

Thanks, what do you mean by an adjustment problem?

 

[Rick Stephens]

 

[achris]

Hi, I've got a 3.0L... I'd really like the engine to idle still and without the rattles. At higher RPM it smooths out.

3 litres is a BIG 4 cylinder (petrol) engine with a flat plane crankshaft. That creates a lot of secondary imbalances. It's never going idle like a 6 or 8 cylinder engine.

 

[banderberg]

3 litres is a BIG 4 cylinder (petrol) engine with a flat plane crankshaft. That creates a lot of secondary imbalances. It's never going idle like a 6 or 8 cylinder engine.

That's good to know, what do you make of my engine's behavior in my video? Any cause for concern? I really want to get the boat in the water and have some fun.

 

[achris]

That's good to know, what do you make of my engine's behavior in my video? Any cause for concern? I really want to get the boat in the water and have some fun.

Hmmmm. Something not right. Could be a valve adjustment problem, timing problem or a mixture problem...

Check the valve adjustments and the timing. If they're right, pull the carb and give it a birthday...

Chris ..

 

[Scott06]

Hmmmm. Something not right. Could be a valve adjustment problem, timing problem or a mixture problem...

Check the valve adjustments and the timing. If they're right, pull the carb and give it a birthday...

Chris ..

Agreed they are not the smoothest engines for sure, but yours could probably be improved. Chris gives excellent guidance here. Would be interested to see if you have a loose rocker arm

Are ignition components in good order ? what do spark plugs look like ?

In the end what the 3.0 l lacks in smoothness it makes up for in reliability... very durable engine. Had one for 20 years and really leaned on it tubing and skiing ...

 

[banderberg]

Agreed they are not the smoothest engines for sure, but yours could probably be improved. Chris gives excellent guidance here. Would be interested to see if you have a loose rocker arm

Are ignition components in good order ? what do spark plugs look like ?

In the end what the 3.0 l lacks in smoothness it makes up for in reliability... very durable engine. Had one for 20 years and really leaned on it tubing and skiing ...

Last week I replaced points, condenser, set the gap and adjusted with dwell meter, replaced wires, cap, rotor and spark plugs (and set the gap on those as well per the engine specs).

I have never done valve adjustments, so I am not sure how complicated that is.

 

[banderberg]

Hmmmm. Something not right. Could be a valve adjustment problem, timing problem or a mixture problem...

Check the valve adjustments and the timing. If they're right, pull the carb and give it a birthday...

Chris ..

The timing was at 12 BTDC so now it's at 8. No real difference in the behavior seen in the video.

So you would suggest valve adjustment next. That's a little intimidating. Any advice on that job?

I have a brand new carb from National carburetor sitting in a box. Just trying to decide if I really need it.

Bottom line, you would advise against taking the boat out on the water.

 

[achris]

The timing was at 12 BTDC so now it's at 8. No real difference in the behavior seen in the video.

So you would suggest valve adjustment next. That's a little intimidating. Any advice on that job?

Follow the manual word for word.

I have a brand new carb from National carburetor sitting in a box. Just trying to decide if I really need it.

Bottom line, you would advise against taking the boat out on the water.

Definitely.

 

[banderberg]

Follow the manual word for word.

Thanks, I have the manual and I read over the section on valve adjustments (engine off) but I have never done a valve adjustment, let alone taken the valve cover off of any engine.

Is this something a novice can do with the right tools or am likely to get myself into trouble?

Does the valve cover gasket most likely need replacing too?

I did order a vacuum test kit from Amazon so I can do that when it arrives (although I'll have to research that, never done it before either).

Thanks for the help!