Rear window out.

[Mad4slalom]

I reall some years back a buddy had an AC Cobra replica with a severely 'cammed' stroker 514 cu in big block Ford engine. He was 'running' a rather silly Holley Dominator race carb too. We took a trip (with me in the Vette following him) at 50 mph or so speeds to the local car meet - perhaps 15 miles distance. His car was running so rich that when we got to the meet his eyes were bloodshot from the intensely rich mixture in the cabin. Anyone who has travelled in a Cobra cabin will be well aware that unlike a Vette you get blown to pieces by the poor areodynamics and back-draught from the side exhausts circulating excess exhaust fumes in the cabin. Me? - I learnt within a few hundred yards of following him about the exhaust fumes and dropped right back.......but even so my eyes were still red from inhaling the fumes when I got to the meet.
Mad4 - It isn't difficult to tune a Holley without resorting to using probes rammed up your tailpipe. Simply put a new set of plugs in the engine (or super cleaned ones) - once the engines warmed-up and off-choke go for a steady 50 mph cruise for a few miles - cut the ignition/engine off - knock it into neutral - and coast to a standstill (ideally in a pre-planned layby) - remove the plugs and note the condition of each one and its position in the engine. Perhaps do the same thing in urban/town use (and again try and record the colour of plugs) - do the same thing yet again at wide open throttle - obviously you'll have far less less time to do this (do it in an intermediate ratio if you have to) but the colour of the plugs should tell you if the fueling is correct. The first two tests should tell you if primary main jets are sized correctly. The third test if secondary main jets are correctly sized. If there are underlying mechanical issues with the engine these should show too.

Thanks Rossc, I gave it a good blast then popped into the garage , gave it a bottle of forte petrol system cleaner, he put his probe up after saying it smelt really rich . The analyser showed that it wasnt that bad , hydrocarbons a bit up but not too bad. He said to have a google and a tweek myself. I will pull the plugs next few days , look at them to note Which if any look oily or fouled. Will fit the new plugs and give her an oil change. Then look again as you suggest. Say for instance if the plugs look good , should I still be looking To lean off the idle mixture as that is when I am more aware of the rich smell . Just giving it a few blasts over 3 consecutive days (italian tune up) has smoothed out the bog over idle to main jet transition a lot. Definitely likes to be used than parked up so am making the best of the high pressure set fair weather while I can. Any good links to tweeking the 650 double pumper with vac secondaries welcome.
I have a bung in the downpipe but will need a meter of some sort And read I need to plug vac line with a golf tee . Have’nt touched a carb for years except for the beach buggy solex. Thank you for input snd advice .

 

[Roscobbc]

Thanks Rossc, I gave it a good blast then popped into the garage , gave it a bottle of forte petrol system cleaner, he put his probe up after saying it smelt really rich . The analyser showed that it wasnt that bad , hydrocarbons a bit up but not too bad. He said to have a google and a tweek myself. I will pull the plugs next few days , look at them to note Which if any look oily or fouled. Will fit the new plugs and give her an oil change. Then look again as you suggest. Say for instance if the plugs look good , should I still be looking To lean off the idle mixture as that is when I am more aware of the rich smell . Just giving it a few blasts over 3 consecutive days (italian tune up) has smoothed out the bog over idle to main jet transition a lot. Definitely likes to be used than parked up so am making the best of the high pressure set fair weather while I can. Any good links to tweeking the 650 double pumper with vac secondaries welcome.
I have a bung in the downpipe but will need a meter of some sort And read I need to plug vac line with a golf tee . Have’nt touched a carb for years except for the beach buggy solex. Thank you for input snd advice .

A 650 scm Holley with a vacumn secondary function.......isn't a double pumper (which has mechanically operated secondaries)
Good news its one thing less to be concerned about. And yes, Italian 'tune-ups' on old school engines are effective. Mine tends to gas-up a bit in town use if the idle speed is set too low (say 550/600 rpm) and eventually after a few weeks of this a plug or two will carbon-up and fail. I find that 800 rpm works best for my set-up. Some of the higher performance Holleys (especially race spec double pumpers) have 4 idle screws (one for each choke) and are extremely sensitive to idle screw settings and will easily over-fuel.