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Old 06-03-2009, 06:29 PM
Johan Lokander's Avatar
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Tuning a Holley

I have my 454 running now and it works cuite good, but i have some carburator tuning to do to gett it perfect, and sens my experiens whit Hollys are limeted I have some cuestions.

When I first started the engine I had the idel mixure screws ca. 2 turns out, and when I tried to adjust it it dident sems to be mutch difrent when i turnd it in or out.
If I turned it in mutch the engen died but ther wasent anny RPM encres when I turnd it out.The idel whas bad and the engine culdent idel for werry long befour it died, and I had to be werry gentel on the trottel befor i had get the RPMs up a bitt, our the engine died.
Then I turnd the mixture screws out more, dont know how manny turns, but I wold say I cant turn them out mutch more, and the idel RPMs whent upp and the idel gett mutch more stabil.But when I have the car in gere I stil have to be werry gentel on the trottel our the engin bogges out...

I have some experiens in Weber carbs, and if i wold have the same problems on a Weber, I wold have change the idel jet to have the same idel mixture I have now but whit the mixure screws 1,5-2 turns out insted of nerly all the way aut, and then the mixure wold be better when the transfer slots opend, but as I anderstand it Hollys dont have idel jets...

The Engine is a .030" over 454 whit oval port heads.
10,25-1
270 degre cam whith .538" lift
and the carb is a Holley 750 vac
Thanks!

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Old 06-03-2009, 08:30 PM
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inside the left bowl there should be 2 jet that screw in. might be on bowl side bowls on your carb, go to advanced and order like 2 sizes above yours, in increaments of 5, switch them out about 10 more then what you have stock, that should fix your lean problem
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Old 06-03-2009, 08:45 PM
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Before you change much more make sure the all of the air bleeds are clean. Inside of the choke horn there are two brass jet type plugs (8 in all), spray some carb cleaner through them all with the idle mixture screws removed and see if that helps. I start at 2 turns from bottom on the mixture screws and most times on gas it is a good starting point. Make sure the transfer slots are not covered up by the throttle blades as well this will make a bog between idle and part throttle.


I am also not against drilling the front throttle blades to help clean up the idle a bit.
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Old 06-03-2009, 09:51 PM
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Quote:
Originally Posted by 85 k5 mud truck
inside the left bowl there should be 2 jet that screw in. might be on bowl side bowls on your carb, go to advanced and order like 2 sizes above yours, in increaments of 5, switch them out about 10 more then what you have stock, that should fix your lean problem
There couldn't be any worse advice than this . Main jetting has nothing to do with idle rich/lean conditions.

Are you familiar enough with the Holley to know what your transfer slot to throttle blade relationship/setting is now? This goes along with what Mike said in the previous post, may need to drill the primary blades if you have the throttle too far open and too much transfer slot is exposed.
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Old 06-03-2009, 10:34 PM
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Quote:
inside the left bowl there should be 2 jet that screw in. might be on bowl side bowls on your carb, go to advanced and order like 2 sizes above yours, in increaments of 5, switch them out about 10 more then what you have stock, that should fix your lean problem
LOL

LOL

I forgot what I was going to say...
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Old 06-04-2009, 12:31 PM
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Yes 10 jet sizes will cure any lean issues but not anything below about 1500 RPM or so.

I don't think my Cummins smokes as much as this thing would with a 10 jet size incerase.

Keep at it and you will get it leaned out at idle.

How much converter does the car have in it, how much does it pull down when you put it into gear? Also what is base timing at? I would likw to see at least 10-12 degrees with 40 or so total with good fuel in it.

Mike
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Old 06-04-2009, 12:58 PM
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One of the biggest things that is overlooked is the accelerator pump lever adjustment. It should be between .015-.020 and must be set at WOT. Evidently you don't set it when the motor is running. But you must have the throttle at WOT with motor off, and push down on the lever and see what the adjustment is between the lever and the bottom of the screw with the spring. Then adjust accordingly with a feeler gauge as you would with setting a valve lash.
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Old 06-04-2009, 01:11 PM
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your biggest problem is not enough ignition timing.

advance the timing at idle to 15 degrees then plug the vacuum advance into a manifold vacuum source. timing should come up to around 30 degrees at idle with the vacuum advance connected.

then turn the idle down to 900 rpms and adjust the idle mixture screws for best idle (highest vacuum and highest idle).

More timing increases the rpms at idle which allows the throttle blades to be closed further which will put the carb back into the idle circuit.
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