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Old 02-21-2011, 09:02 PM
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holley 670cfm fine tuning

I just replaced the discharge nozzle to a .35 tube style from the stock .31 and it seemed to help with off idle acceleration. Though when at 3/4 throttle you will feel a surge when the secondaries open up and it will put you back in your seat.
Is this normal or should it be a smoother transition when the secondaries open?
I am also using a weiand g team open plenum, single plane intake which probably wasn't the right one to use for this application. I found out later it is used for higher rpm peak power. So this probably was part of the sluggish off idle response. Just wondering if I should mess with the jettings at all to help? I am running stock power valve and pump cam on this 670 holley vacumm secondaries on a 327 .40over with a mild cam and headers, hydraulic rockers.

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Old 02-22-2011, 12:40 PM
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Well I have a history with a holley 670 but its not on my engine now cause I sold it. The holley street avengers are very very lean out of box.

You should not feel your secondaries kick in and if you do they are opening up to soon. Check and see what spring is in the secondary.

If you have the yellow one then put in the silver one and try it and see how it does. If you have the silver one in and its doing that then all you have left to use is the black spring that came with your carb. Holley makes a vacuum spring kit that allows you different options to tune with. I use a silver in mine for best overall results.

Those carbs have to be fine tuned with anything other then a stock type cam. Trust me I know I have spent countless hours last year with one and I took it off cause of other issues but my 600 1850 holley carb I have on it is basically the same carb as it uses the same metering block's and base plate and carb tower and all part numbers are the same. I really don't know how one is rated 600cfm and the other 670cfm and to me its just a marketing thing but that is another story.

I redid my 600 with a quick change vacuum secondary and also a secondary metering block to put in jets in the rear.

I had to go up two jet sizes in the front and I put 72 in the rear. Your engine will want a different tune since its less cubic inch with different heads and stuff.

So far how does it do while cruising wise with the stock jets in it? Also what do your plugs look like. You might want to check them. Mine was bone white and I am still working on fine tuning mine.
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Old 02-24-2011, 09:12 PM
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try recurving your distributor ( the mechanical weights under the rotor)
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