Volvo 260A info needed please

[CaptainCaveman]

Hi,

Does anybody know anything about this engine (Volvo Penta 260A)? I have been using unleaded of late but can it be safely run on unleaded or do I need to use LRP or some kind of lead additive? what would you recommend? any information greatly recieved

thanks
CC

<hr width=100% size=1>PRINCESS (32 large ones)!

 

[Will_M]

AQ260A
1978 - 1985 approx
5.7ltr V8
260hp @ 4400rpm

Both the 260A & later B require a fuel octane min of 91, ie they should be running leaded fuel.

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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[Chris_d]

Will, you've posted this a couple of times, but regular unleaded is 95octane so if and engine requries 91min, unleaded is alright.
The only issue is if it has hardened valve seats or not surely? and requries Lead or an additive.

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[Will_M]

You know you may be right. Unleaded is infact a 95 octane and as such would be ok. The info was taken from VP service bulletin and am woundering if it is still totally correct, further investigation on my part required I think.

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[CaptainCaveman]

So no problem with the octane levels as unleaded is 95RON and the the engine needs a minimum of 91RON, like you say its all about how hard the valve seats are? as I dont really want to take the risk I think I will start using LRP just to make sure and use a lead additive on the remaining unleaded in the tank....cheers

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[BarryH]

I wouldn't worry too much. I've been running my volvo on unleaded for years now. Thw head had to come off for a blown gasket. There was no noticeable valve seat degredation. No signs of hot spots or premature wear. Had them checked by a engineers and they passed it as healthy. I just lapped them in for good measure. In any case your 260 is based on the yank block. They were using unleaded long before the UK.

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[tr7v8]

According to the Seloc manual 260A is 350 cu in Chevy, typicl small block Chevy, 9.5 : 1 compression ratio and 91 RON min fuel. Although the manual lists leaded for some it doesn't say anything about any of the V8s.
Also bear in mind that the USA stopped using leaded in their cars around 1976 the I think it's very likely that it is safe.
Couple of points, unleaded is quite aggressive on fuel hoses so leaks can become apparent where their were none previously and it does increase running temp slightly which if the cooling is marginal could be significant.


<hr width=100% size=1>Jim

Draco 2500