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I recently decided to give my motor a tune because it had only been done by ear by a mate. I set the timing to 8 degrees of advance and turned the mixture screws in and then back out 1 and a half turns. I was previously getting 200km per 40L of fuel, now it's around 150km per 40L.
It now has a pretty bad flat spot off the mark, however the flat spot it previously had just when the secondaries open seems to have improved as long as I get some momentum up first.
With a trip from Sydney to Brisbane on the cards for during the week I want things set right so it doesn't end up costing me a fortune in fuel. Where do I start?
It's a 308 with quadrajet and M21
Thanks in advance
Scott
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Have you checked the timing marks are in the right place? Your mixture setting sounds arbitrary and wrong. Shouldn't you screw in until it starts to run rough and then back out til it clears?
Cheers, Brian
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Scott
There is a lot more to tuning a car than adjusting the timing and mixture screws. First of all your mixture screws only work at idle. As the throttle opens it uncovers the secondary idle ports in the carburettor base giving you a little more fu
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CHECK VACUUM ADVANCE CANISTER ON DISSY IS WORKING. MY OLD SANDMAN 308 GOT 22 MPG HIGHWAY WITH IT ON. 16.5 MPG OFF.
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Hi Scott.
Both Brians have explained the situation fairly well, but one simple point remains. You were getting 20L/100 km, you then fiddled with the base timing & the idle mixture screws & now you've getting 26L/100 km. You also now have a flat spot.
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Lets get back to basics.
You did 2 things only ? Idle mix and timing.
IDLE MIX - flat spots off the mark can be 2 things. Too little fuel or too much air. The 1 1/2T setting is a good start. BUT you need to find a mid point of the mix. With a warm
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Thanks for the input, BrianH, thanks heaps for that.
I did only fiddle with timing and mixture so that's what I want to stick with trying to fix. I did disconnect the vac advance when I adjusted the timing. It could be that the outer ring is out so I m
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What are you running.motor wize. i drove my mate hq to a show for him. i was crusing doing the speed limitwith 3.55 gears, 110kmp/hr almost 4000 rpm. i worked out i was using 20L/100KMS of fuel also. but i was driving a blown 350 with a 6/71 thru the bonn
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