Thread: Fuel usage S3 2.6 10MPG!!

Yeah, they are thirsty but not that thirsty.

What carby you running? When was the last time the exhaust valves were adjusted? What is the compression like? Running the original dizzy? - if so, what sort of spark you getting?

They used to get that sort of MPG on Fraser island pulling a trailer....

The 4 cyl was always much better,and didn't have much less go.

Sorry can't help as to yours

Originally Posted by Homestar

Yeah, they are thirsty but not that thirsty.

What carby you running? When was the last time the exhaust valves were adjusted? What is the compression like? Running the original dizzy? - if so, what sort of spark you getting?

Carb is the std Zenith Stromberg, correct jet and 4J needle. It is the non adjustable one. I checked the inlet and exhaust clearances, .010 inlet and .012 exhaust. Compressions are slightly low at around 115-120 psi.
Great spark with a GT40 sports coil. Has a Bosch army fitted distributor. Advance is as spec.

Thinking of getting an adjustable carb to try, but plugs are not black.

Terry

Put a better quality muffler on it? I've pulled off some shocking mufflers over the years, with severely reduced pipe sections just inside the spigots.

As we actually have good fuel these days - try advancing the timing - I guess until it pings and then back off a bit. The standard timing was determined based on possible crap fuel usage in the boonnies.

Garry

Only 3 degrees advance? Try 10 for starters and give it more if it doesn't ping at 10. Check that exhaust system and maybe get the local muffler shop to make up a big bore straight through. Phil Irving was adamant that a street inline six should have a split system, 1-2-3 and 4-5-6 in two separate systems, minimum 2" each. Compression is a bit low. Does it use oil? If so a set of rings may be called for. Have you done compression test wet and dry? If it still reads 115-120 with oil in the bores then a valve grind is on the cards.

Originally Posted by bee utey

Put a better quality muffler on it? I've pulled off some shocking mufflers over the years, with severely reduced pipe sections just inside the spigots.

Its a new muffler. Std offset shape with full bore in and out.

Originally Posted by Bigbjorn

Only 3 degrees advance? Try 10 for starters and give it more if it doesn't ping at 10. Check that exhaust system and maybe get the local muffler shop to make up a big bore straight through. Phil Irving was adamant that a street inline six should have a split system, 1-2-3 and 4-5-6 in two separate systems, minimum 2" each. Compression is a bit low. Does it use oil? If so a set of rings may be called for. Have you done compression test wet and dry? If it still reads 115-120 with oil in the bores then a valve grind is on the cards.

Yes I did think about 10deg. The w/s manual says 2deg after tdc, thats a bit extreme. The S1 (similar engine design) runs well at 10.
I would like a 3-2-1 exhaust but hard to justify, but the std manifold is horrible.
Uses about 1 litre in 5k km. a lot of that would be leaks. Had the head off a couple of years ago and lapped the valves. Thats only about 10k km ago. There was about .004" to .006" bore wear then.
I thought the compressions were reasonable for its age at 115-120. A good 7.8 cr engine should be 135-150