Bigfella237
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- Joined
- Mar 14, 2015
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- Far South Coast of NSW
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- More cars than I've got space to park!
There's no way a different octane fuel alone could have "cleaned out" a carb, although I'm not sure about any additives that may have been added? It's more likely that a bad batch of fuel fouled something up, or stirred something up in your tank.
The only thing you can actually "adjust" on a 350 Holley are the IDLE mixture screws on either side of the metering block and the stop screw on the throttle shaft (idle speed adjustment). Everything else requires changing hard parts like jets, power valve, etc. In fact, if you have the idle speed set high enough, you'll find that adjusting the idle mixture screws does next to nothing because fuel is flowing through the main circuit as well as the idle circuit.
I would suggest you go back to basics and reset your base tune before doing anything else, it sounds like you've been adjusting everything randomly and have no idea where you're at with anything?
Check the plug gaps and condition, check the condition and attachment of the plug leads and, this may sound silly but, recheck your firing order.
If you had points you would set the dwell angle next (aka points gap), then set the base timing at idle RPM, then verify that the mechanical advance is working (timing should advance with RPM while the vacuum advance is disconnected), then verify that vacuum advance adds timing when re-connected.
Also check the timing is stable, Holden V8's with stretched timing chains tend to have the timing jump around, especially while cranking on the starter.
Then check your float level (verify it isn't too high with the engine off, otherwise you'll pump fuel everywhere, then re-check while idling). You may have a spec of crap holding the needle & seat open and making the carby flood? Do you have a fuel filter inline? Might be worth checking that too.
{Insert EDIT: If still flooding you may have to remove the float bowl and check that the float still actually floats, I've seen a couple of Holley floats over the years which leak, fill up with fuel and, well, sink}
Then set your idle RPM, then adjust the idle mixtures and idle speed together (changing idle mixtures will change idle speed). I usually adjust idle mixtures by ear using a length of plastic hose (I shouldn't have to say this but don't stick it all the way in your ear or you'll suck your brains out). With the air cleaner removed, listen to each barrel and adjust the idle screw for that barrel, you'll hear it 'spluttering' when it's too rich, then the sound should 'clean up' when the mixture is about right. I usually leave them just on the clean side of the transition.
Once you're back on track with the tune, you need to be able to duplicate the original problem, when it happens again, a timing light while cranking will tell you whether you have spark, so it would be useful to carry one with you.
No matter how complex, any engine only needs three things to run... fuel, compression and ignition... all delivered at the right time of course. It's a simple process of elimination.
Andrew
The only thing you can actually "adjust" on a 350 Holley are the IDLE mixture screws on either side of the metering block and the stop screw on the throttle shaft (idle speed adjustment). Everything else requires changing hard parts like jets, power valve, etc. In fact, if you have the idle speed set high enough, you'll find that adjusting the idle mixture screws does next to nothing because fuel is flowing through the main circuit as well as the idle circuit.
I would suggest you go back to basics and reset your base tune before doing anything else, it sounds like you've been adjusting everything randomly and have no idea where you're at with anything?
Check the plug gaps and condition, check the condition and attachment of the plug leads and, this may sound silly but, recheck your firing order.
If you had points you would set the dwell angle next (aka points gap), then set the base timing at idle RPM, then verify that the mechanical advance is working (timing should advance with RPM while the vacuum advance is disconnected), then verify that vacuum advance adds timing when re-connected.
Also check the timing is stable, Holden V8's with stretched timing chains tend to have the timing jump around, especially while cranking on the starter.
Then check your float level (verify it isn't too high with the engine off, otherwise you'll pump fuel everywhere, then re-check while idling). You may have a spec of crap holding the needle & seat open and making the carby flood? Do you have a fuel filter inline? Might be worth checking that too.
{Insert EDIT: If still flooding you may have to remove the float bowl and check that the float still actually floats, I've seen a couple of Holley floats over the years which leak, fill up with fuel and, well, sink}
Then set your idle RPM, then adjust the idle mixtures and idle speed together (changing idle mixtures will change idle speed). I usually adjust idle mixtures by ear using a length of plastic hose (I shouldn't have to say this but don't stick it all the way in your ear or you'll suck your brains out). With the air cleaner removed, listen to each barrel and adjust the idle screw for that barrel, you'll hear it 'spluttering' when it's too rich, then the sound should 'clean up' when the mixture is about right. I usually leave them just on the clean side of the transition.
Once you're back on track with the tune, you need to be able to duplicate the original problem, when it happens again, a timing light while cranking will tell you whether you have spark, so it would be useful to carry one with you.
No matter how complex, any engine only needs three things to run... fuel, compression and ignition... all delivered at the right time of course. It's a simple process of elimination.
Andrew
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