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Asking the brain trust here; how can you adjust the idle speed in your motor down after you’ve bottomed out the adjustment? The car seems to idle nice when first started at around 900 but as it warms up the idle speed gets higher to around 1,100 to 1,200 rpm. I want to take it down a little to maybe 900 max. Both carbs are synchronized to around 6 with the synchro meter tool. The jets are 140 mains, 60 idle, 180 air correction with the correct 9164.1 emulsion tubes. My car has a 1915 cc with ported CB 044s with 40 and 35.5 valves, stock cam with 1.25 ratio rockers, SVDA distributor from with a Pertronix electronic ignition module and Vintage Speed sport exhaust with 1-12” Dansk heater boxes. The car’s timing seems spot on at 7.5 BTDC at idle as instructed by the distributor’s instructions from Valves were just adjusted at zero loose lash (it has Gene Berg chromoly pushrods). Thank you in advance.

Last edited by Impala
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@Impala posted:

Never thought about that. Great suggestions, I will check that throttle cable to see if it’s overly tight. When driving around at stoplights if I find the rpms a little high I kick the accelerator pedal rapidly and the rpms come down. Sometimes they go up again gradually but sometimes stay low. Will check on that. Thank you.

Could be an indication there's something hanging up there. I forgot to mention to check where the throttle cable exits the Bowden tube and where it exits the shroud. Lots of places to get hung up. A dry graphite type lube may fix some of those issues.

Last edited by Robert M

I ran 8-9 degrees at idle with the Megajolt. No trouble with idle speed at all. If the distributor advance plate is hanging up, yeah that would do it.

I did have my cable set with ZERO play cold when I first built the car, and when the engine warmed up, so did the throttle housing. All the sudden it was idling at 1500-1800. I loosened the cable and it permanently fixed it.

Disconnect the cable and see what happens when it's hot, if the idle goes down. If you can't get it to idle low close the darn idle air bypasses. Either that or you have a vacuum leak. I'd rock the intake manifolds and see if they've worked loose.

Great suggestions. Originally timing was set at TDC at idle and it was still doing the same thing. We set it up to 7.5 BTDC as per instructions on the SVDA; the advance is working fine as advertised when taken to higher rpms. The car seems to work a little better than before. I will loosen the accelerator cable a little bit and experiment with that too. Thank you all.

I gave the accelerator cable some slack. Didn’t change much except take the accelerator pedal lower to the floor. I will check on those idle air bypasses. When I got these carburetors from Gabrielle in Italy he expressly directed not to touch those as they came calibrated with factory equipment that he has. I recall they even came with some paint on the screws. I will look into that.

“When I got these carburetors from Gabrielle in Italy he expressly directed not to touch those as they came calibrated with factory equipment that he has.”

That’s great, (he might even use a flow bench) but once you place them on the intake manifolds, everything has now changed to what your engine is doing, not his “factory equipment”.  Everything I’ve read and experienced with my Dells is start with the air bypass (bleed) screws all the way in and then adjust them out individually, as needed, as you sync all four throats.  

You’ve convinced me, guys. I will try that now. I have the Dellorto Book from CB Performance as backup too. I’ve also been talking with John Connoly from about getting a crisper response on the pedal and solving a sporadic spitting issue through at least one of the carburetors on occasion when shifting from 1st to 2nd and even 3rd and he suggested installing an anti pulse valve between the carburetor and the vacuum advance of the distributor to smooth out the vacuum signal. Apart from that and looking at my engine specs and compression ratio (around 8.5:1) he suggested downsizing the idle jets from the 60’s I have now to 55’s.

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