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I am in the process of tuning a 1800S fitted with a B18B. I had rebuilt the engine, it is a B18B bores are .040 over, slight mill on block deck, stock rebuild on head. I cc'd the head and did all the math, i am just under 10 to 1 on compression ratio. It has a "C" grind cam in with stock SU dual carbs (KD needles) and dual outlet manifold. Running on 91 octane. After break in i had the reoccurring issue of engine run on, i re checked the valves, points, base timing and played with the carbs over and over. All the systems on engine are new or rebuilt (carbs, distributor,etc.) I actually tried an "anti-run on valve" from moss motors in england, it is a solenoid that opens when engine is turned off allowing extra air into the intake hopefully leaning it out to the point of non combustible. It leaked right away creating a huge vacuum leak, i do not trust a brand new defective part so gave up on that. A last tuning effort i decided to ramp up the base timing, allowing me to close the throttle blades more at idle. BEHOLD! I can get a nice fairly smooth low idle that does not diesel. Also the car is way more powerful, actually spins the tires on hard accel. I am up to 25 degrees timing at 1500 RPM. Factory is 17-19 degrees. I do not have the vacuum advance dizzy. I also do not have any pinging at high rpms under load. I am tempted to add some more timing until i get some pinging then back off. Anyone else have this happen to them tuning one of these engines? I have done this technique on very modified engines i have built but this motor is basically stock so i stayed away from it until i was out of ideas for the dieseling issue.
Any thoughts on advanced base timing?
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