Four star or Unleaded

[rjstyles]

I have a 1986 Princess 30DS fitted with a Volvo Penta 175A. It seems that all the petrol outlets in my immediate cruising area (Brixham) only sell unleaded petrol. Could anyone help with the following questions:

1 Does anyone know of a four star petrol outlet on the south coast of Devon ?
2 Someone told me that I can use unleaded for my engine - this sounds a bit iffy to me, any view ?
3 Is it possible to get some sort of additive to put in unleaded fuel that would make it suitable for my engine ?

Any advice much appreciated

Roger

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[DavidJ]

I know that a decade or more ago when unleaded fuel became widely available some of my more 'greener' friends had a conversion done (jet change and timing change I think) which left them with starting and running problems.
David


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[DavidJ]

Forgot to mention, it was a car application not a boat.

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[hlb]

Yep. You can buy an additive. Dont know if you need one or not though.

<hr width=100% size=1> <font color=blue>No one can force me to come here.<font color=red> I'm a volunteer!!.<font color=blue>

Haydn

 

[DavidJ]

Have a look at
www.marinefuel.info
You may have already seen it in this months MBM

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[BarryH]

You should be ok using unleaded in your engines. What year are they.

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[gonfishing]

hi
there was a rather indepth and definative answer to a similar question on practical boat owner to owner a couple of weeks back but can't find it on the search, but bottom line i think is something to do with which valves are fitted whether they are the modern hardened variety or the older softer type, if i'm wrong i no doubt i will be corrected!!!!!!!

julian

<hr width=100% size=1>man made it ,man can repair it, i think??

 

[rjstyles]

Thanks for the replies thus far.

Just been to Halfords and bought an additive called Castrol Valvemaster. This is a phosphorus based lead replacement designed to protect valves on older engines. Says it is compatible with leaded and LRP petrol that might already exist in the tank. Does anyone have any views on its merits or drawbacks - I won't be putting it in till next week.

for anyone interested it costs £5.99 to treat 250 litres, so not too expensive.

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[BarryH]

Your 175a's are based on the GM V6 yank lump. The yanks were using lead free way before we were over here. So unless your engines date from the early seventies, your valve gear should be ok.
The GM block was built like the perverbial brick out building, understressed and a bit of a plodder in the cars. The lead thingy is for valves seat erosion and anti "knock". I pretty sure that the engine/s you have will not be the older ones so am pretty sure you'll be OK. Its worth giving your local volvo dealer a ring just to be all clear as tp wether you can or can't. If anyone should know they will. They'll probably want the engine serial numbers though for age reference.

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[Will_M]

AQ175A
3.8ltr V6
170hp @ 4800rpm
1981 - 1985

This engine requires a min fuel octane of 91.

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[Will_M]

Sorry i've posted this once or twice before!! But may contain some useful info...

Ta, Will.


Q & A about unleaded conversion.

(Q) Why do engines need modification to run unleaded?
(A) Lead that is added during the ‘4 Star’ manufacturing process acts as a high temp lube, and stops the hot exhaust valve ‘micro-welding’ itself to its soft cast iron valve seat. The exhaust valve may operate at over 700 degrees C and 75% of its cooling is by transferred heat to the valve seat. As such the fitting of a hard exhaust valve seat and the use of suitable exhaust valve stops this ‘micro-weld’ process.

(Q) Why is the inlet valve unaffected?
(A) The inlet valve and seat are being constantly cooled by the gases flowing past them.

(Q) Do all cyl heads need to be converted?
(A) Every cast iron cyl head will need to have hard exhaust valves fitted, every alu head already has valve seat inserts fitted, some of which are already suitable to run unleaded petrol fuel.

(Q) Should the ignition timing be altered?
(A) The greater majority of engines will run on their factory settings, very occasionally it is necessary to retard the timing.

(Q) Should the compression ratio need lowering?
(A) Not normally, most engines will run perfectly well. Or though as a very rough rule of thumb is a compression ratio of up to 10.5:1 is ok.

(Q) Is there a performance down-turn using the lower octane unleaded fuel?
(A) No measurable performance down-turn, in fact you may find an increase in performance by virtue of the cyl heads been return to ‘as new’ running order.

(Q) Fuel consumption?
(A) Again, as above, there is the possibility of better/improved consumption by virtue of the cyl heads been return to ‘as new’ running order.

(Q) Cooling temp?
(A) There should be no change from the normal/correct operating temperature.

The process.
Cylinder head would be stripped back to bare casting, checked for cracks, valve guide wear etc. Valve seat inserts would then be removed.

Correct sized valve seat inserts are selected and a counterbore would be machined into the casting in the place of the original seat.

Counterbore checked for corresponding size & depth, high temp sealant applied, hard chrome-steel insert fitted and machined to match combustion chamber in shape.

An angle is machined into the valve seat, checked and then finished ready for valve fitment.

The risks.
Water cooled castings have water jackets around their existing valve seats. Considering the age of the engine and the likely hood of corrosion in and around the water jacket area. If when been counterbored this busts through the casting due to the amount of corrosion behind then it goes with out saying the cyl head is then nothing more than scrap!

Valves.
When new these valves were not expected to have to run with unleaded, although a lot of valves are made from suitable material. But you should really change the valves or have new ones machined in a known material that will be suitable for unleaded.



Most automotive engineering companies would be able to do or at least have this process done. (NB automotive engineering co, not your average spanner monkey set-up)

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[Col]

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[lanason]

Reading this got me wondering ........... the broker who sold me my boat told me it had been converted for unleaded so thats what I've been using

BUT what if he was wrong ?????

Is there an easy way to tell if it has been done ???

By the way its a AQ 170 c striaght 6 ............

<hr width=100% size=1>Adrian
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[ccscott49]

If you've been using unleaded for a while +3 months and the engine is fine, then it will be! The valve seats destroy themselves very quickly, if they aren't the hardened variety (Valve seat regression) and you run on unleaded.

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[Will_M]

(lanason)

Your AQ170C...

6cyl striaght
1973 - 1978
160hp @ 5000

If the engine is serial number 119687 or higher then from new it was ok for unleaded

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[lanason]

Serial no 4614 / 141630 so its OK - Thanks Will

Actually must be one of the last ones ???

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