volvo aq 130 petrol

[chrissy]

Will this engine run on unleaded its about 1977 fitted to a princess 25.
If so do i need to make any adjustments to the ignition timing.

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[tr7v8]

Certainly when its in the car it won't run unleaded as standard. It would certainly need the compression ratio lowered and exhaust valves and seats changed.
Unlike a car where they are treated fairly gently I wouldn't take the risk of trying it either. Straw poll of club members is Millers VSP or Castrol Valvemaster Plus are the 2 additives to use. Probably cheaper than tracking down 4 star as well.

<hr width=100% size=1>Jim

Draco 2500

 

[gonfishing]

i have the same engine fitted in my fairline which i run on lrp and use an additive
i don't intend taking any chances on engine valves seizing

julian

<hr width=100% size=1>WHAT??? more petrol!!!

 

[Duncan_Hamble]

AQ130s come in A, B, C and D variants. I believe that the D and possibly the C variant can run on unleaded. The Volvo Penta manual details this. Might be worth speaking with your friendly Volvo Penta Dealer.

Duncan

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[Will_M]

Only the 130D can use unleaded, the A,B&C require a min fuel octane of 97, ie they in std form should run leaded.

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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