Series IIa Petrol Engine "Chatter"

[warrenperkinson]

Hi All,

I've got a 1970 Series IIa 88" with a 2.25 standard petrol engine running 91 octane petrol.

When the engine is running at highway speeds it emits what can best be described as a chatter. The noise kicks in around 45 - 50MPH in 4th gear with overdrive engaged - but can also occur around the same RPM in other gears (not sure of the exact RPM, but at the higher end of the scale for a Landie).

I've recently I replaced all the ignition (including installing an electronic ignition), sparks, leads etc. Also had the (zenith) carb fully reconditioned and had the timing done. Also new oil in the engine, and I've checked all the oil levels in the usual places.

The sound is a little like pinking, but as I've had the timing done, I'm assuming that it's not that... a "chatter" is the best description I can give it...

Does anyone have any suggestions as to what this could be? Tappets? Valve guides? Where should I look first?

Thanks in advance for any pointers...

Warren.

[SafeAirOne]

What is the condition of the timing chain and tensioner?

[stomper]

I would start by dropping back to regular 87 octane, and resetting your timing. As the octane increases, the fuel may be precombusting at higher RPM. The new Pertronic system may have changed the spark timing enough to bring this issue on.

[warrenperkinson]

I would start by dropping back to regular 87 octane, and resetting your timing. As the octane increases, the fuel may be precombusting at higher RPM. The new Pertronic system may have changed the spark timing enough to bring this issue on.

Hi Stomper,

In New Zealand the lowest octane rated petrol that is commercially available is 91 octane unleaded petrol - so dropping back to a lower rating isn't an option.

I had the timing done after I installed the electronic ignition. Both the timing and the carb were done at the same time. Do you think I need to recheck the timing?

Cheers,
W.

[warrenperkinson]

What is the condition of the timing chain and tensioner?

Hmmm... do you think it could be the tensioner? I've not checked that...

How do I check that....?

[warrenperkinson]

Just a thought... could it be that my vacuum advance is blocked/not working (and therefore causing pinking at speed)?

[I Leak Oil]

First off are you sure it's the motor???? Sounds like very specific conditions you're hearing it in.

Anyway, perhaps I missed it but did you adjust the valves while doing all the other tuneup stuff? The valve train in these motors aren't exactly modern quiet to begin with.

[canyonero]

I had a similar sounding situation a while ago, and although it resolved itself, there was a theory floated that it could be the rotor in the distributor getting out of whack...

[warrenperkinson]

Here is an update on my situation...

I had advice that this is likely to be pinking as the advance gets too far ahead at speed (read: high revolutions). So, I retarded the timing a little. After some experimenting.... no change.

By this time though, I had figured out that the vacuum advance on the dizzy was kaput, and in addition, my series IIa was running an older DM2 distributor (from a series I).

So I purchased and installed a new Lucas 45D4 distributor and replaced the vacuum advance pipe (old one was copper, new one is plastic).

Reset the timing using the old adjust and drive (and repeat) method. The spark is as retarded as it can be at idle before it starts to miss (at idle).

Engine runs heaps better now (I have engine braking again!)... but still the same clatter at high speed.

So I can now safely rule out pinking as the source of this clatter.

I'm thinking that next I should check my valve clearance....? Any other suggestions?

Cheers...

[JimCT]

higher octane precombusts less

that is wrong, higher octane gas is harder to precombust, that is why it is needed for high compression engines. In a series engine it is just a waste of money , but does no harm

I would start by dropping back to regular 87 octane, and resetting your timing. As the octane increases, the fuel may be precombusting at higher RPM. The new Pertronic system may have changed the spark timing enough to bring this issue on.

[o2batsea]

And it's not valve train noise? Not a water pump about to explode? Not loose stuff rattling at a harmonic that matches the engine RPM? Not the bonnet about to fly off its hinges? Not a bottle of brake fluid you keep tucked under the bonnet that begins to jump around when the truck gets going fast? Not a loose wheel?
Can you post up a viddy with the truck doing this?

[CKubinec]

I have actually had both water pumps, alternators and fan belts make chatter sounds although not always at higher RPM. It would be pretty simple to pop the fan belt off and run it for a short while to see if anything changes. So long as the engine is cold to start there shouldn't be any harm. Good luck.

[warrenperkinson]

Hi All,

I've found the source of the problem! Although it sounds very much like pinking from the engine, it turns out, after much experimenting, that this noise is caused by the overdrive lever rattling at 50MPH and above.

It's a Fairey overdrive.

I've yet to resolve the noise, but I now know with certainty where it is coming from (light forward or sideways pressure on the overdrive lever completely eliminates the "chatter").

I just thought I'd close this topic out in case anyone else out there comes across a similar issue.

Cheers,
Warren.

[I Leak Oil]

First off are you sure it's the motor???? Sounds like very specific conditions you're hearing it in.

I can't stand random noises in my vehicles so I've spent copious amounts of time chasing them down and that's why I suggested it wasn't the motor from what you originally described. My old Fairey O.D. lever being one of them by chance!!!! One down many to go!

[stomper]

Yeah, mine rattles too. A nylon washer and torquing that big shoulder bolt tightly, but not too tight so that you can't shift it in and out seems to work best.