70s Marina rolling resto / running repairs

[Misterg]

...the timing setting is 5 degrees atdc.

Our '71 bay was the same. You need to have the original distributor for it to work - there's some sort of additional vacuum advance thing going on.

 

[colnerov]

You can't stick religiously to the original setting because the fuel used back in the day is not the same as the fuel available today. You need to try different settings to see which setting the engine is happiest with.

 

[Jack_K]

It isn't really possible to properly time an unloaded engine by advancing or retarding at either high or low speeds and watching for the rpm drop. The mixture is different unloaded which has a totally different timing requirement for maximum rpm. That's why vacuum advance exists. If the mixture is set incorrectly, so will your timing if it is done by ear.

The advance curve could also be wrong and you'd then be on a path to engine destruction.

So many supposed cooling issues turn out to be a poorly tuned engine, especially the timing. I've watched many people spend heaps on cooling system "fixes" with no success until they finally listen to me.

 

[minimutly]

It isn't really possible to properly time an unloaded engine by advancing or retarding at either high or low speeds and watching for the rpm drop. The mixture is different unloaded which has a totally different timing requirement for maximum rpm. That's why vacuum advance exists. If the mixture is set incorrectly, so will your timing if it is done by ear.

The advance curve could also be wrong and you'd then be on a path to engine destruction.

So many supposed cooling issues turn out to be a poorly tuned engine, especially the timing. I've watched many people spend heaps on cooling system "fixes" with no success until they finally listen to me.

Finally someone with some sense. The only way to check and set ignition timing is with a timing light. You set the max advance, check the idle advance, then re attach the vacuum pipe. Doing it by ear is asking for melted pistons. You may have done it and got away with it, you may have got it right, but the method is flawed.

 

[bricol]

I think you are confusing "tuning" and "tuning" a standard engine on standard bits to run well in use.

On the simple engines I used it on, they run fine, develop power and torque, and the one in my competition car is coming up for 21 yrs . . .

Would I use it on a more modern (1991 ) turbo-charged, injected engine in my Lancia . . .no.

You can't use a timing light to set dynamic timing on some Triumph engines - there is no spec to work to. I have a timing light - the times I've used it, there's not been any need to make adjustments.

 

[Melvyn Best]

Interesting comments re the timing positions,my air cooled VW,has a 1971+ engine with the AH code,even has a female diagnostics socket! A USA engine possibly California,the timing setting is 5 degrees atdc. Never heard of it,presumably to reduce emissions,runs awful at that position probably going to waste fuel ,not save the planet,it runs sweet at 10,as others have said adjust by ear and feel,no lumpiness and quick pick up on throttle response.

That engine probably had a distributor that had a double vacuum advance /retard unit originally?

 

[nickk]

That engine probably had a distributor that had a double vacuum advance /retard unit originally?

Wouldn’t know how to recognise one.

 

[Melvyn Best]

Finally someone with some sense. The only way to check and set ignition timing is with a timing light. You set the max advance, check the idle advance, then re attach the vacuum pipe. Doing it by ear is asking for melted pistons. You may have done it and got away with it, you may have got it right, but the method is flawed.

I remember my old foreman adjusting the timing on a Bristol 410 with a newly rebuilt engine, 500miles later it had a hole in a piston !

 

[Melvyn Best]

Wouldn’t know how to recognise one.

Look at the vacuum advance unit, it probably has 2 vacuum pipes going to it? Think they are NLA.? One mod that air cooled VW owners do is to fit a readily available 009 distributor which does away with vacuum advance, from memory the timing is set to around 30deg before TDC at 3500 RPM . Better performance and economy

 

[nickk]

Look at the vacuum advance unit, it probably has 2 vacuum pipes going to it? Think they are NLA.? One mod that air cooled VW owners do is to fit a readily available 009 distributor which does away with vacuum advance, from memory the timing is set to around 30deg before TDC at 3500 RPM . Better performance and economy

Wouldn’t that stress the big ends?

 

[Melvyn Best]

I’ve worked on VW air cooled engines for nearly 50 years, I’ve known problems with main bearings on occasion but can’t remember a single case of big end failure. Probably the biggest problem is dropped valves on no 3 cylinder due to the oil cooler restricting cooling air to that cylinder ? Adjusting the exhaust valve clearances to 0,008” rather than the recommended 0.006” helps.Even after a dropped valve the big ends don’t seem to suffer. Obviously lack of oil or oil changes can cause problems on any engine. Cracked heads , heads blowing between the barrel and head joints are another couple of problems . The reason for setting the timing at 3500 RPM is at that speed the timing is at full advance which would be the same with the original distributor. Once at idle the timing retards closer to TDC.

 

[dobbslc]

My missus Beetle had a valve guide bobbing up and down with it's valve once and about an inch of crankshaft end float!
The thing still run though.

 

[Misterg]

can’t remember a single case of big end failure.

The 1600 in our '71 bay had thrown a rod when we got it.

 

[Melvyn Best]

My missus Beetle had a valve guide bobbing up and down with it's valve once and about an inch of crankshaft end float!
The thing still run though.

As a young apprentice I owned a split screen type 2 that had loads of end float, I measured it then “ adjusted” using shims only to find the crank was locked solid! What I didn’t realise was the main bearing itself was floating in the crankcase accounting for most of the end float . Ended up having to rebuild the engine

 

[Melvyn Best]

The 1600 in our '71 bay had thrown a rod when we got it.

Like I said, lack of oil or oil changes will wreck any engine.

 

[dobbslc]

As a young apprentice I owned a split screen type 2 that had loads of end float, I measured it then “ adjusted” using shims only to find the crank was locked solid! What I didn’t realise was the main bearing itself was floating in the crankcase accounting for most of the end float . Ended up having to rebuild the engine

She got a refurbed engine from that place on the A1 in Highgate.

 

[Jack_K]

Finally someone with some sense. The only way to check and set ignition timing is with a timing light. You set the max advance, check the idle advance, then re attach the vacuum pipe. Doing it by ear is asking for melted pistons. You may have done it and got away with it, you may have got it right, but the method is flawed.

I just had this same discussion on a FB group. I put up how to properly time them. A supposed expert for the cars it was about thinks that doing it by ear is the way and that's what most others were saying. I'll just let people melt their pistons.

You can't use a timing light to set dynamic timing on some Triumph engines - there is no spec to work to.

many manufacturers before the 60s didn't specify a dynamic timing value as timing lights were uncommon at the time. Only a static value was given and the advance curve was expected to be tested on a distributor machine.
To calculate the dynamic value, look at the distributor advance curve data and choose one of the data points. Double the distributor rpm and degrees values and set the timing on the car at that speed and degrees. Make sure the vacuum advance is disconnected when doing so. I normally set the timing above 1000 engine rpm. The high rpm timing is more important than idle but that doesn't mean the idle timing can be ignored, the curve needs to be roughly correct.