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Author Topic: 7043240 Set up  (Read 1947 times)

Offline qjetman

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7043240 Set up
« on: October 14, 2012, 04:19:41 PM »
Cliff ,
 Looking for advise on calibrating a 7043240 800 cfm Buick qjet on my 350 chevy. Engine is 10.5 to 1 , hydro roller 236/240 520/540 , Performer RPM air gap and 2.02 / 1.60 aluminium heads ( Pro topline)  Thinking of using 71 jets 41 rods and CD rear rods. What do yo uthink is a good Idle tube size and channel restriction along with idle mixture screw hole size?
Thanks
Dave
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Offline 77cruiser

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Re: 7043240 Set up
« Reply #1 on: October 21, 2012, 07:15:53 PM »
How much vac. do you expect it to idle with? 10-12
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Jim

Offline qjetman

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Re: 7043240 Set up
« Reply #2 on: October 23, 2012, 02:49:03 PM »
Well car has 12 in vac at idle . I started with idle tubes at .037 and channel restrictions at .050. Mixture screws are .089. Seems to idle good, maybe just a tad rich but I think it will work just fine. Was thinking of opening up the idle bypass from stock .108 to .110 to lean idle out
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Offline Cliff Ruggles

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Re: 7043240 Set up
« Reply #3 on: October 26, 2012, 09:30:50 AM »
Who recommended 71 jets and 41 metering rods.  That's pretty lean in that particular carburetor.

On the big 455's they used 73 jets and 44 or 45B rods in them.

Idle bypass isn't use to lean out the idle.  It is used to reduce throttle angle to prevent "nozzle drip".

With a 236/240 cam in a 350 engine, it will want a lot of idle fuel, and idle bypass air.

I'd look at the 3rd recipe in our book, in the upper range of what is recommended.....Cliff
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