My 360, after the tune, has no idle problem with any cam it has ever had from the 292/292/108 Mopar, to the 270/276/110 Hughes, to the current 276/286/110
even idling down to sub-600 in gear (manual trans) pulling itself along at ~4 mph on a flat,level, hard surface.
But I don't tune the idle with a vacuum gauge. And I don't tune it with the timing lite. And I don't use an AFR gauge.Instead, I let the engine tell me what it wants and then try to make it happen.
The only thing I insist on, is getting the Transfer slot exposure right. Then I set the idle speed with a combination of idle-air bypass and timing.
The PCV is my primary bypass, with thru-holes in the primary throttle valves as trimmers.
The trick is to not set the idle-timing with the vacuum gauge!, which leads to far more timing than the engine needs, or wants.It just makes getting the tune right ,darn near impossible.
For instance; that 292 cam wanted idle-timing deep into the 20s. But to keep the idlespeed in check, this nearly shut the transfer slots off; and in compensation I had to crank the mixture screws way out. So it idled reasonably well....... but with the transfers mostly dried up, I had a big hesitation on Tip-in.
So I pulled out timing, little by little, and the engine slowed down. Eventually, when the transfers came alive, and the fuel-trimmers back in a working range,the hesitation went away, but the engine ran out of bypass air from the PCV, and so, I figured out that if 1 PCV is not enough, then maybe 2 would be.Well that didn't work out the best all the time. But by this time I knew I was on the right track.
So I drilled the holes in the throttles, and drilled them bigger, and bigger, and suddenly more air just made the idle speed go up.
OOps.
So I soldered up the too-big holes, moved over, backed up the timing some more, and drilled new smaller holes;
Badaboom , I was back on track.
With that cam,IIRC, the idle-timing ended up at 12 to 14, and the holes ended at ~3/32 (1 in each primary).
Of course, with a manual trans, low-speed timing is far more critical than with a hi-stalled automatic; but the idle set-up for the auto is still of major importance.
For the idle-tune; on that 292, I never put a vacuum gauge on it, nor a timing light. See; I had a preconceived notion, that my engine should have a certain amount of idle-timing in or near the 20s, based on what magazine article preached. But those numbers mighta worked with the iron-headed 9.5Scr combos of the 1990s. But the iron-head tune sure didn't work on my Eddie-headed 11.3 engine.
The point is this; I learned to listen to my engine, and gave it what it wanted, not what I thought it should have. And idle-vacuum in my case, was meaningless.
I have no idea what the vacuum was at sub600 in gear, with that cam,lol.
Nor do I know what it is with the current 276/286/110, except that this cam will chug along nicely at 550/4mph. It will keep on running down to 500, but hasn't got quite enough power all the time. I almost have to toe the clutch to climb over a dime,lol. By the way,it won't do this at 14* idle-timing. I installed a dash-mounted, dial-back, timing device, and crank the timing down to ~5*. Before I had that device, at 14*, she would get to bucking like a wild horse. The timing retard tamed her.
That took care of idle-timing...........
BTW: I run the AG intake and an ancient 750DP, circa the 70s. And I just slapped on the first old used PCV that came out of the junk collection.I mean in 1999, I was none too smart,lol; not even thinking that there might be a difference among them; it fit the grommet and wasn't painted ox-blood red,or turquoise, so in it went.It's been in there ever since.
Just hoping to help.
