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14/05/2003 16:46:16   Paul   I'm just about to buy a 1977 96V4. The current owner has been using LRP. What are the views on whether I could safely use unleaded, or should I use LRP, or unleaded plus an additive.  
14/05/2003 18:27:00   ian   The conventional wisdom is to use unleaded fuel together with an additive (combined octane booster & lead substitute).

LRP is being rapidly phased-out in the UK. One of the problems with LRP is that the petroleum industry never agreed on a single formula and that the lead substitute varied from company to company. Some of the substitutes actually caused harm to the engines. I believe that there might have also been an incompatibility between several of the additives, meaning that you couldn't mix petrols from different chains unless you knew that had used as the replacement for the lead.

If you are intending to run on straight unleaded you should really have hardened exhaust valve seats (and valves) fitted to the heads and adjust the timing accordingly.

When 4-star was originally dropped there was a great deal written about 'lead memory' which referred to the existing build-up of lead on the valve/seat meeting surfaces being able to protect the valve seats from damage for quite a long time after you'd stopped using 4-star provided you did not thrash the car for long periods or had recently re-ground the valves/seats. I'm not sure whether the same applies to cars that have run on LRP for a while. 4-star is available in certain garages for a premium.
 
14/05/2003 18:36:37   Alec   I totally agree with Ian. I use unleaded with the Castrol Valvemaster additive. There are 2 versions of this, I use the one with added Octane Booster and the car runs well on it with no pinking or valve problems to date. That is good considering I tend to drive the car flat out all the time!  
14/05/2003 20:32:10   curtis muir   I agree also , and also use the Castrol Valvemaster plus additive . No problems to date and driven hard every day.  
15/05/2003 03:14:34   Paul (a different one)   Like Alec, i've been using Castrol Valvemaster, but my engine recently recently broke a piston ring and when i took it apart to rering it, i discovered the piston tops was caked in black flakey stuff. I know that this had built up within a year and whilst using the additive as i had removed the head the previous summer to redo the head gasket.
One chap who saw the engine and who i spoke to said that this build-up was because of the additive and advised me to stop using it altogether.
I am rebuilding my engine now and have shelled out for some unleaded heads to put on, so i don't have to think about this question anymore...  
16/05/2003 08:32:46   Alec   Paul,

Maybe you need to give it a bit more welly!!  
16/05/2003 23:04:39   louis   Carbon deposits is a sign of rich mixture and there for not to hotter running the problem is that excess fuel will wash oil off the cylinder walls and wear the engine prematurely... Try getting the timing and carb spot on thats the key to clean combustion!  
21/05/2003 11:36:15   Alistair Philpott   Don't forget, depending on where you live you can still get leaded petrol from Bayford Thrust, there's a website somewhere with their locations, probably find a link on the SOC site.

I'm lucky in that there's one just down the road from me, but unlucky in that I've not got a car to take advantage of it!!! Not yet anyway...  
23/05/2003 22:25:54   melissa   if you have the briquot balls in the tank would you, add an additive..?and either way is 6 degrees btdc stuck to even though unleaded is used?has anyone tested the ron of petrol in a briquot tank?or with the valvemaster?  
26/05/2003 19:39:40   louis   Balls in the tank is a load of ***** if you get my drift...  
30/05/2003 14:40:44   Steve H   Dont worry, there are two solutions that I see.
Take the heads off now and get hardened valves and inserts put in by someone like Gosnays (about 100), or run it on unleaded untill the valves start burning and performance starts to slowly decrease and then...take the heads off and get hardened valves and inserts put in by someone like Gosnays (about 100). Personally, im lazy and would do the second unless you there is another more pressing reason to take the heads off now such as new valve oil seals etc.

I would agree that balls and additives are balls.  


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