Strange Engine Pinking / Knocking - 1950s 2L Land Rover

[jtay2024]

Hi All!

I am hoping to gain some knowledge from the smart bunch on here!

My Dad has a 1950s Land Rover. Some times it has quite a bad habbit of excessive pinking / knocking.

We have tried multiple times to change the timing, and using the highest octane fuel we can it still occurs. (99 UK Octane).

Symptoms

- High RPM wide open throttle.
- Doesn't seem to occur when at lower RPM.
- Seems worse when driven short journeys for a period. (For example, much worse on my long drive to work, much better on way back).

Now, with those weird symptoms the only thing I can think is that maybe we are carboning up the cylinders and causing glowing hot spots. That would explain why the journey home from work it almost entirely disappears?

Does it sound like I'm on the right path here or is my logic off?

If so, are there any cylinder / piston cleaning fuel additives we could use to help mitigate this on the shorter trips it frequently does?

Thanks!

 

[CharBaby]

I think you're on the right path. You may want to use a dose or even several doses with any PEA fuel system cleaner.
I don't know what is available to you in your area. There are plenty of over the counter fuel system cleaners from...
Chevron Techron, GumOut, STP, RedLine SL-1

 

[PontiacHO]

What type of ignition advance does it have? If any, I imagine it’s a centrifical (mechanical). Could be sticking and/or extremely weak springs. Can check that by pulling the distributor cap and manually rotating the rotor to evaluate the engagement of the advance process.

 

[Astro14]

I was thinking ignition advance problem as well. Weak springs. Or, perhaps a distributor that is curved for vacuum advance, but doesn’t have the advance connected (which would throw off the curve)?

Is this the original distributor? Was it ever rebuilt? Was it perhaps from a later model, and curved for EGR (which takes a lot more advance at high RPM) and you have a non-EGR manifold?

When you’re setting timing - what is the specification?

 

[LvR]

Knocking at high RPM and not low?

Wanna say that is not when knock is usually to be expected - especially on such a low compression engine.

Sure its knock (as in spark) and not as in mechanical (gaga oil pump?)

 

[Devo242]

Have a friend with a '61 MGA 1600 who had similar issue with the engine breaking up a bit at the higher end of the RPMs, and given his driving habits it was quite frustrating. He had tried adjusting timing, valves, using fuel system cleaners, and as a habit had been using 93 octane fuel (99 RON equivalent), all without any change. Given the low compression of the motor I suggested he try lower octane fuels and with nothing to lose he did, and surprisingly it cleared the issue up.

Also, it seems the UK moved to E10 fuel a few years ago, if possible try and locate ethanol free fuel.

E10 Petrol - Fuel Industry UK

www.fuelsindustryuk.org

Personally, I do not like fuel containing ethanol for use in motors not designed for it. The '59 MGA in my signature uses 89 octane ethanol free (E0) exclusively, it lives in the upper RPM band and has never experienced any issues.

 

[Passport1]

My 1959 Bugeye Austin Healy Sprite needed occasional 'de-coking'. Early English cars got that service often.

 

[Trav]

IIRC these old timers had a vacuum advance, check for a broken/leaking hose, hose in the correct location and test the vacuum advance with a hand vacuum pump. It would be no surprise to find a defective advance.
Depending on the distributor it may need ported or manifold vacuum, make sure it is in the proper location.

 

[tnt_motorsports]

IIRC these old timers had a vacuum advance, check for a broken/leaking hose, hose in the correct location and test the vacuum advance with a hand vacuum pump. It would be no surprise to find a defective advance.
Depending on the distributor it may need ported or manifold vacuum, make sure it is in the proper location.

My thoughts exactly is the vacuum advance is leaking or not working correctly.

It also could be "dieseling" due to build up of carbon. You could try the old Seafoam trick to solve some of that...

Just my $0.02

 

[bonjo]

If it is pre-ignition , I would look into:
Has the engine been modified to run at higher compression?
incorrect or old spark plugs
incorrect distributor
too much carbon deposit in on the pistons
engine running hot or overheating

 

[jtay2024]

I think you're on the right path. You may want to use a dose or even several doses with any PEA fuel system cleaner.
I don't know what is available to you in your area. There are plenty of over the counter fuel system cleaners from...
Chevron Techron, GumOut, STP, RedLine SL-1

Cheers. We can get Redline SI-1 here in the UK. I think that has the highest PEA concentrate in it from what I've seen of the MSDS sheets. Perhaps a bottle of that would help general running regardless of whether it's the cause of this issue.

What type of ignition advance does it have? If any, I imagine it’s a centrifical (mechanical). Could be sticking and/or extremely weak springs. Can check that by pulling the distributor cap and manually rotating the rotor to evaluate the engagement of the advance process.

It's a vacuum advance. It's all connected etc and has been the same since the engine was rebuilt years ago. I don't think we used to get the issue of knock / pinging back then but I couldn't be certain.

I was thinking ignition advance problem as well. Weak springs. Or, perhaps a distributor that is curved for vacuum advance, but doesn’t have the advance connected (which would throw off the curve)?

Is this the original distributor? Was it ever rebuilt? Was it perhaps from a later model, and curved for EGR (which takes a lot more advance at high RPM) and you have a non-EGR manifold?

When you’re setting timing - what is the specification?

The connection is attached. I believe the distributor is one off a different engine (same model and similar year), and it wouldn't have had EGR for sure.
The distributor has been rebuilt, and has electronic ignition in it now rather than points, but this issue was there before that was changed.
The timing specification was done correctly a while back, but it pinked quite a bit, so we've retarded it a bit, and it's been played around with numerous times and it doesn't seem to get rid of the issue.

Knocking at high RPM and not low?

Wanna say that is not when knock is usually to be expected - especially on such a low compression engine.

Sure its knock (as in spark) and not as in mechanical (gaga oil pump?)

Yeah that's what really puzzles me. I can go up a dead steep hill with it at a lower RPM and WOT and it'll run beautifully all the way up. If I'm going up a long shallowed gradient at a faster speed it'll start pinking. I don't think it's mechanical as it'll disappear as soon as I let off the throttle a bit.

One thing I have noticed recently when looking at the exhaust system to check for rust etc was that the rear section has a very narrow part in it. Looks like it's made badly at the factory. I am wondering whether a restricted exhaust would cause excess heat in the cylinders when at WOT and at high revs (highest back pressure).

 

[jtay2024]

Have a friend with a '61 MGA 1600 who had similar issue with the engine breaking up a bit at the higher end of the RPMs, and given his driving habits it was quite frustrating. He had tried adjusting timing, valves, using fuel system cleaners, and as a habit had been using 93 octane fuel (99 RON equivalent), all without any change. Given the low compression of the motor I suggested he try lower octane fuels and with nothing to lose he did, and surprisingly it cleared the issue up.

Also, it seems the UK moved to E10 fuel a few years ago, if possible try and locate ethanol free fuel.

E10 Petrol - Fuel Industry UK

www.fuelsindustryuk.org

Personally, I do not like fuel containing ethanol for use in motors not designed for it. The '59 MGA in my signature uses 89 octane ethanol free (E0) exclusively, it lives in the upper RPM band and has never experienced any issues.

That's very strange. I wonder how that works. The fuel I am using currently is Esso branded with 99 octane and 0% ethanol so I would have thought that would make for the best resistance to knock. Now I'm wondering whether a lower octane but with a higher ethanol content would help reduce knock due to ethanols cooling ability!

My 1959 Bugeye Austin Healy Sprite needed occasional 'de-coking'. Early English cars got that service often.

Yeah very true. It maybe time to take the head off and give the whole thing a really deep clean out.

IIRC these old timers had a vacuum advance, check for a broken/leaking hose, hose in the correct location and test the vacuum advance with a hand vacuum pump. It would be no surprise to find a defective advance.
Depending on the distributor it may need ported or manifold vacuum, make sure it is in the proper location.

I'll have a good look and see what I can find. I'll need to buy a vacuum pump and test it. I believe it's after the throttle plate but I'm not 100% sure. I'll check. I don't think there is anywhere else the pipe can be connected through from what I've seen.

My thoughts exactly is the vacuum advance is leaking or not working correctly.

It also could be "dieseling" due to build up of carbon. You could try the old Seafoam trick to solve some of that...

Just my $0.02

I'll double check all the connections of the pipes are seated and see if I can get a vacuum pump to test the advance. Cheers.

If it is pre-ignition , I would look into:
Has the engine been modified to run at higher compression?
incorrect or old spark plugs
incorrect distributor
too much carbon deposit in on the pistons
engine running hot or overheating

- Perhaps slightly, the head was skimmed during the engine rebuild.
- Spark plugs have been changed plenty. I have tried to go to a cooler running plug but that didn't seem to help.
- Distributor maybe incorrect, but it was off a model with the same engine and a very similar year (within 2 years back when things didn't change much year to year).
- Could well be carbon, that'd fit with it being more of an issue when running on choke / just after the choke has been used a lot more.
- I think the temp is fine, we have a temp gauge fitted and it's often sitting around 75c.

Thanks for all the advice everyone! I have a good few things to start checking!