Saturday, May 27, 2006


Inconsistancy, Imbalance in carb fuelling -I was lacking some go and felt the engine was fighting itself + 1-2 plugs bit less coloured than 3-4 - problem has been found.

1.30am 8-(

I double checked my float levels when I fitted the carbs, both were 26mm as per normal so I didnt question this, however now 1-2 cylinder carb was 2.5mm down on the back one....So problem is found, basically 1 cylinder was a touch lean, not really lean but retarded and vacuum dependant - cylinder two marginal - main jets in these cylinders would have been working ok once they got running, but more retarded that 3-4, possiblt touch leaner....needing more vacuum to operate, good job I have been pottering about...

I hope for perfect clarity tomorrow.

Lesson is, triple check everything then check it again after running. As a carb "expert" I am pretty disgusted with myself.

The levels can be low and the carbs still work fine, just they need a richer setting for optimum pckup and aren't as responsive, so basically both carbs were talking a different language, here is why I felt today that the engine was a bit crap, cause it was fighting itself...Also looking at the idle screws they tell a story, 1-2 out more than 3-4....

No harm done cause once vacuum is up around 2000rpm the suction will pull fuel from the lower ducts regardless of float level till it falls so much the engine won't run and misses....being as I had no spitbacks and misses in the mid range etc there was no dangerous lean condition on 1 carb, no harm done, still annoying, dangerous lean condition would mean no power all at all and spitbacks just mild lean-ness and retarded jet action...

It's now plainly obvious why when pulling away from a stop the engine hesitated slightly before taking off, due to 1-2 cylinders needing to build vacuum before the fuel came on properly, same on the mains, my throttle response felt poor hense my futile timing fiddling.

It all adds up, tomorrow should be a big step forward and also I'd expect a fair power gain with both carbs talking to each other and big torque raise, the power I felt was missing somehow! I like simple problems!

Also the fuel level in the rear carb was 1.5mm too low...I'm baffled by this, I robbed some brand new OE spec viton 150 valves some new carbs I have.

Before I seemed to like the earlier type floats -hard plastic- but I'm on .3 -7grams this time. Experience tells me the vitons like more pressure as they seal for longer due to their soft sealing tips - they then release more fuel later on low pressure, so compared to the metal valves they can make the fuel level more choppy, I always run 2.5psi on metal and 3.5psi on viton to help them blow off earlier and keep a more constant fuel level. The metals are pants imo they wear fast hate high pressure with a light float, where as the Viton tipped ones last a decade or more...I have seen unrebuilt 45's that are 27years old on original valves that you could re-use, viton is a dogs nads!

I'll have to retune the damned idles again now!! GRRR.

Good job I found that now before, I was gonna pull the whole damned rig to pieces tomorrow anyway cause something was out of wack, but its done now! No harm done. Rain forcasted from 8am....poop.

What I still find odd is the car was ok first time I drove it, maybe the valves tips expanded or softened and gave a better seal with some use and fuel on them, they are 20+years old even as new old stock items??? It seems to have gotten worse with time, baffled I am!! Thats the conclusion I can draw cause I spent a good hr checking the levels and emptying the bowls-refilling and testing when I fitted them...

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