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Old 08-10-2012, 02:09 AM
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carb adjustment

i might be misunderstanding this but I need help adj. my Holley 670 street avg. carb on my engine that is a small block 350 bored .030 over with a comp cams 292-h camshaft everything throughout the valve train matches this camshaft. I am at aproxiamatly 1000 feet above sea level. dual feed single pump vac. sec.i havent got into the carb to see what the jet size is.And it has an automatic trans behind it with a 2800 stall converter. Any help in how to set this carb up and adj. would be very helpful tks.

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Old 08-10-2012, 03:14 AM
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These street avenger carbs do not work well with big duration cams.
They are made for mild/moderate motors with milder cams than the 292h.
The 292h cam needs a 10" 3500+ stall converter.

The 2800 stall may not be loose enough at idle.

But to get it to run good you need to run a lot lot lot of inital timing at idle
with the 292H cam. Lock out the distributor mechanical advance and set the locked timing at 36deg
Now remove the carb and flip it over and look at the throttle blades.
reset the pri and sec throttles so just a little of the edge of the idle transfer slot is showing under each blade.
The sec side is set by a set screw on the thrlttel base.
.020 to .030" of the slot showing.
Replace the carbs power valve with a 3.5 or 4.5" power valve.
reinstall the carb.
Fire it up , set the tining to 36deg BTDC (no vacuum advance) and let it warm up and reset the idle mixture screws with a vacuum gauge.
Should idle around 900rpm in neutral. if the idle rpm is now too low open the throttles (pri and sec throttles even) a little bit to add air flow and idle rpm. 900-1000 rpm in neutral.
make sure the PCV is connected and functional.

It is critical to get the PRI and SEC throttles idle fuel transfer slot exposure correct at idle.
(throttle open position at idle)

should not drop more than 200 rpm in gear.
Connect the vacuum advance to ported vacuum on the carb.

As I said these carbs are not a good match to that 292 cam......

This carb may need a slightly larger idle feed restriction and or a adjustment of the idle air bleed.
A clue is how many turns the idle mix screws are at best idle mix (manifold vacuum gauge)
If more than 2 turns out, the IFR needs to be larger) +.001" ,.002", .003"
You need a afr gauge to help adjust the idle air bleed size.
small changes in either if these precision orifices makes a big difference in idle AFR.

Post your results after doing this set up -(minum the IFR and air bleed tweeking)

Locked out timing is not too much for this 292H cam.

If hard to restart install a simple igniton interupt switch.
Make sure the GM OEM rear starter support bracket/brace is installed.
If yours is missing get one.

What intake manifold? what is the pri and sec jetting now?

The 670 is a wennie carb for this....
You really need a 750-800cfm carb non street avenger series.
vac sec or DP.

the 292H cam likes a 3500+ stall and big gears and rpm.
Make sure the timing tab TDC location is correct. Using a piston stop.

Last edited by F-BIRD'88; 08-10-2012 at 03:27 AM.
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