Thursday, December 4, 2008

Rich running update

Ok a little update on why I think the engine is running richer then required. I've taken a picture of the spark plug. A little out of focus, macro photography is not my forte, need to get a macro lens quick...


I have the carb jetted currently this way at sea level(H30/31, I believe this is has a 25.5mm throat), also checked the float level and installed the right washer under inlet valve(1.5mm), fuel pressure is right at 2.8PSI...

Main Jet 125 (Most people are running 127.5 on 1600s, even at a step lower it's still running rich)
Idle Jet 55 (I can get the idle right, no smelling of gas out the exhaust at idle)
Air Correction 125 (Stock unit, not even sure I can get anything bigger/smaller to replace this with)
Power Jet 50 (Stock jet, I think I'll mess with it later after I've got the main jet right)

I originally thought maybe with the A/C on I might be sucking a larger vacuum then usual, thus leading to the rich running. Not so though, I tried running it without the A/C and still the same results.

I'm guessing because of the higher local temperatures (it's like 30deg C or 86deg F here on average), I can vapourise more fuel in the intake manifold, talk about free lunch hah, but this also means with the current fuel tank vent system (straight vent to atmosphere), the car will loose more fuel to evapouration...

Now to try a 122.5 or 120 main jet...

2 comments:

Anonymous said...

My '74 sedan came with an H30/31 with a 140(!!!) main jet. Talk about running rich and fouling plugs! Long story short, I tried a 135, 130, and 127.5 before finally getting advice on the Samba and took it straight down to 120. It ran great, good power and economy and no more fouling plugs.

Gang said...

What sized engine did you have on it?
I'm getting 122.5s and 120s to test it out.

Will probably put the rest on sale somewhere or something, not much use sitting in my drawer...