2.25 petrol - changes for unleaded

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scottonthefen

scottonthefen

Well-Known Member
Posts
532
Location
England
My '69 2A still has its original 2.25 petrol engine in it. Since buying it 16 months ago I've been restoring it, so haven't driven it yet. We turned it over when I bought it, but that's all.

What needs to be changed on these engines to make them suitable for unleaded petrol, and how do I tell if it's been done?
 
I believe that the official Mod was to take the head off and remove the valves, then machine sockets for hardened steel valve seats to be pressed into. Turner Engineering and others can help you with this.

To give an alternative view, we used to run and work several 2.25 petrol's in the days when the engines were cheap and cheerful and we were not especially worried if we had to change a head here and there. Despite dire warnings that this mod should be done we ran them without, using nothing but lead free fuel. The engines were worked hard towing long distances and at high revs over 100's of thousands of miles. Never did we suffer from a burnt valve. I suspect there are still thousands of 2.25's out there chugging around on unleaded with no mod or additives. My view is that the 2.25 is such a low stressed engine that the issues with lead free fuel that affected engines of that period don't affect it. The choice is yours, replacement head or just run it as is and occasionally take the head off for inspection.
 
Clunk bucket is correct, the head has to be modified for lead free petrol. Turners charge about £400 for a replacement head. I ran mine on unleaded for a few hundred miles when I first got it, it hasn't been modified. I started getting ignition problems, backfiring etc so I started putting the lead replacement additive in. It ran OK after another 100 miles or so but I can't garentee that was the issue. I've been using the lead replacement additive ever since.

Col
 
The unleade conversions (to all engines) were to fit hardened valve seats, the idea was that the valves would pocket into the head on unleaded but I've run a lot of old engines and I've never actualy seen it happen. Even if it does the head could still them go and get machined for inserts. The main thing is to retard the ignition quite a bit. Unleaded burns much faster so it will really hammer an engine timed for leaded. Unleaded full advance could be 10-12 deg retarded from the leaded setting, it depends on the engine.
 
Colthebrummie said:
Clunk bucket is correct, the head has to be modified for lead free petrol. Turners charge about £400 for a replacement head. I ran mine on unleaded for a few hundred miles when I first got it, it hasn't been modified. I started getting ignition problems, backfiring etc so I started putting the lead replacement additive in. It ran OK after another 100 miles or so but I can't garentee that was the issue. I've been using the lead replacement additive ever since.

Col
Click to expand...
Worn valve seats would result in burning some oil and maybe slightly down on power. Unlikely to have caused ignition issues.
 
scottonthefen said:
My '69 2A still has its original 2.25 petrol engine in it. Since buying it 16 months ago I've been restoring it, so haven't driven it yet. We turned it over when I bought it, but that's all.

What needs to be changed on these engines to make them suitable for unleaded petrol, and how do I tell if it's been done?
Click to expand...
run it as is till theres an issue then all you need to do is fit steel seats to exhaust valves but most do all 8 seats but its the exhaust that are more likely suffer, i ran an old engine for years without fitting the seats and it was ok
 
Cheers all. Sounds like I'll be ok to leave it as is and just keep an eye on it - check the valve seats for wear when and if I have the head off and measure the compression once a year.?

Out of interest, what's the reason for the valve seats wearing? Is it just that it burns fast as rob described? So the valves are coming down harder because there's more power released by the combustion compared to the older fuel?
 
scottonthefen said:
Cheers all. Sounds like I'll be ok to leave it as is and just keep an eye on it - check the valve seats for wear when and if I have the head off and measure the compression once a year.?

Out of interest, what's the reason for the valve seats wearing? Is it just that it burns fast as rob described? So the valves are coming down harder because there's more power released by the combustion compared to the older fuel?
Click to expand...

The lead acted as a lubricant, no lubricant = more wear or so the thinking goes.
 
scottonthefen said:
Cheers all. Sounds like I'll be ok to leave it as is and just keep an eye on it - check the valve seats for wear when and if I have the head off and measure the compression once a year.?

Out of interest, what's the reason for the valve seats wearing? Is it just that it burns fast as rob described? So the valves are coming down harder because there's more power released by the combustion compared to the older fuel?
Click to expand...
lead protects soft exhaust valve seats ie cast iron from the hammering they get opening and closing under high temps, inlet obviously doesnt have hot gases flowing over them
 
Used to be able to get a fuel additive for this do they not do it anymore?
Works out cheap but never used it so don’t know if it actually works/helps.

I guess it would really depend an how you want to use the landie.how you can tell?
Does it look as if the engine has been rebuilt.
The only way of telling would be to take the head off and look. But as you say you are going to restore it, then chances are you will be getting into the engine anyway, so would say get the seats sorted.
If you don’t plan on getting in amoungst the engine then find some additive it won’t hurt.


J
 
Really there is no point doing anything. Chances are it’ll last and last. And sorting out later will be no more expensive than now. But you may never need to do it. It won’t damage anything to continue to run it as is.
 
Agreed, I think the whole issue got talked up when unleaded came in but its a bit of a non-event. The key is getting the mixture and timeing right for unleaded. THe main thing the lead replacement could do was reduce knock on some old high compression engines but I think retarding the ignition works nearly as well. I think they do give a bit less power. There's an intersting article somewhere about a BMW power FW190 being tested after WW2, the Germans only had unleaded so it was filled with high octane (ie very leaded) fuel and could be run at around 10% higher power without overheating. Bear in mind that octane ratings are % so anything over 100 is an extrapolation based on the lead addtitive. Aviation was 105 or more, 5* (correct me) was 101 or 102. I think we are now on around 91-92 but I see its never on the pumps. Wartime "pool" petrol was around 89 (I think) which is why old army trucks and bikes run well with unleaded. Be interesting to see what Rover designed the S1 to run on.
 
I'm not too sure of any of this. I'm not a scientist but I know there were scientists and mechanical engineers trying to get the best out of IC engines in the early days. The leading scientist and a couple of his assistants actually died of lead poisoning trying to perfect the correct fuel formulae. Engines used lead for decades until it was realised the lead in vehicle exhausts were causing harm to children and they started to phase it out in the 1980's millions of existing engines were converted to run unleaded at a cost of about £200 per engine. The company I worked for at the time had two pool cars, both vauxall caviliars. One was tidy, one was scruffy but both good mechanically. The tidy one was converted and the scruffy one was sold to an employee who didn't get it converted. He used it for a few years putting a lot of miles on it until the valve seats burnt away and the cost of repair was too much.
One day I will get a converted head for my series, until then I'll use the additive.

Col
 
Some good advice above; knock back, (retard) the ignition timing a bit. Check the valve clearances regularly because if the valves start to pocket, that is to say, they sink into the valve seats, the tappet gaps will get narrower, (tighter), giving you a warning.
 
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