Originally Posted by Caballerokid
Ok... I have a chevy 360 with 882 heads, 1.6" and 1.94" valves, 1.6:1 roller rockers, crane 274H06 came and lifters (flat tappet), .125" dome pistons -3.5cc, long tube headers, edelbrock performer intake and of course a holley 4777-2 carb. I have a carter vane type electric fuel pump internally regulated 6 psi and a 4 spd saginaw with 2.73 rear end and mini spool. Ignition is all MSD with e-curve dizzy (init. 19° total 38° (any lower on init. and its no where near as responsive, I could drop the total but haven't yet).
Issue, I had a lean bog from a stop and another bog from the primary to the secondaries. I had .035" primary squirter and .025" secondary squirter in the carb, 67 primary jets and 76 secondary jets, with a 4.5" power valve, orange primary accel cam (hole 1) and pink secondary accel cam (hole 1). It was using lots of fuel and low on power as well.
Here's what I've done so far... I put the squirters back to .028" front and rear, left the power valve for now, used the blue accel cam for the primary (hole 1) and the black accel cam (hole 1) for the secondary. Adjusted the accel pump arm with a .015" shim on both primary and secondary. Took it out and drove it. It ran great off idle and from a stop still has a slight lean spot when transitioning from primary to secondary. I brought it back around and put the .025" squirter on the secondary and the lean spot decreased some. (I have an a/f gauge showing a lean condition which is how I know it's lean)
I wouldn't think I would want to go lower on the secondary squirter would I? Where should I go from here? I'm wondering if I'm squirting too much fuel to where it can't all burn showing up as a "lean" condition due to the unburnt air and raw fuel in the exhaust. Could this be the case? If so, what are some recommendations?
My 600 dp had the bog. Contrary to what most say, when I dynoed the car with A/F readout, I found that this was due to an over-rich condition.
The prior owner of the carb was obviously chasing this problem and had installed a 28 squirter in the secondaries, leaving the 25 in the primaries.
I changed both out to 21s and the bog went away based on SOP but have yet to get tthe car back on the dyno. It was especially troublesome to me because it was right where I cruise with 3.70:1 gears and the TKO-600 in OD if I kick the throttle without downshifting to 4th. Note that at the point of bog, the A/F goes as low as 10:1.
Also note that in every case, the leanest A/F ratio is giving the best torque/power. After this test, I leaned the secondaries by ~1.3 jet size.