I ran the DC292/292/108 cam. I didn't like it and it wasn't in my 360 for but one summer.
I initially ran it in at 108LSA; for the topend and Effective overlap. And it was awesome.
But with just 11.3Scr the bottom was soft.
So I advanced it 4* and got some bottom end,
but with a starter gear of just 2.66 x 3.55= 9.44, the bottom was still soft.
Well; I live 20 minutes from the nearest city, and at that time, I drove to work every day, so 3.55s were kindof my limit.
I advanced it sumore, and things were improving, but now the top end was gone.
I realized that I had made a mistake, and later in the year, I sold the slightly used cam.
>Here's what I learned;
That cam wanted a lot of bypass air. At one point, I was up to 1/8th inch holes one in each primary. Eventually I figured out that this was too much. So I soldered them up, moved over, and went back to 1/16. which was too small. 3/32 was about right.
1) Convention says that cam needs 20ish degrees. But, at 20*, I couldn't drive that cam slow enough to parade with it.
2) here's what happened to me at 20.
The engine made so much idle power it was crazy. But, she wouldn't idle down until the throttles are nearly closed. So then 800rpm was 6.8 mph, and that was as slow as I could drive without riding the brakes. But when I rode the brakes, the engine pulses were so strong that the chassis began bucking, and it could get violent.
I wanted to get down to at least 4mph, which would be 470rpm.
3) I pulled the "standard A833" and swapped in the "overdrive box", to see what a 3.09 low would do. That got me to 5.85mph at 800
4) by now, I knew I was never gunna get there with 20* of Idle timing. So, in the interest of expediency, I reset the timing to 5* advance; yes, 5*..
This got me down to 550rpm=4.0 mph/ close enough; in gear, the engine had just enough power to pull itself on hard, level, flat ground with not much extra, and, the bucking was gone.
Of course, at 5*, I had to open the throttles quite a bit to idle on, and that's when I discovered that two of 1/8th " holes, one in each primary was too big. I fixed it.
So now I could parade.
But the risk of stalling in traffic was too high, so, as a daily, I ran it at 12 to 14.
The thing is, that I had discovered that at 550 rpm, that 292 cam was sounding mightyfine.
5) My solution was to procure a dash-mounted, dial-back, timing module. Which I set so that I could electronically add up to 9* of retard to 6* of advance, on top of where the Distributor was set, right from the driver's seat, which did NOT affect the T-slot sync. This solved two problems for me;
I got down to 4mph for parading, and I now had the possibility to run up to 60degrees of cruise-timing. UP TO.
6) But I had already decided that this 292 cam was not for me, so, as Winter approached, I pulled the Powertrain.
***********************************
7) if you've paid attention, you should have heard me say, that my 367 at 11.3 Scr and the 292/108 cam, would in fact idle down to 550rpm, in gear and pulling itself, with just 5*..
With an automatic, you don't have to go that low; but, I guarantee that if you did, it would END your rpm drop.
Personally
I would start at 10 degrees and retune the Idle-circuit, to work with that, with the idea that, if you can make that work, try 2 more degrees. BUT
8) the ONLY reason to run lots of Idle Timing, is cuz it makes low-rpm power, in cylinder-pressure handicapped engines. That's it.
But you have a 3000stall, and 3.91s so then, yur engine NEVER has to pull from a low rpm. SO then, there is NO logically justifiable Reason to run so much initial..
9) Here's what I did, to get the low-rpm power back;
I installed a 2-Step timing curve that jumps the timing up fast, from 900 to 2800, then slows down to end at ~3400, so that I can run 87E10 gas full-time. AND
I modified my VA to bring in 22 degrees , fast and hard. This works really well with retarded Idle timing, which already has a large amount of throttle-opening, so, the Spark-Port is activated quite early, in time. Thus, at Part Throttle, My engine could be seeing up to 42* at 2000 rpm, 50* by 2800. My engine is NEVER lazy. It never detonates, and now, with a smaller cam (230/237/110) it still goes 93 in the Eighth at 3457 pounds at 900ft elevation. This engine now has over 100,000 miles on it.
10) the point I'm trying to make is this; How much is a new convertor gunna cost. versus retarding the timing to no more than 14Idle.
11) don't forget, that if you change your Idle-Timing, you will need to at least check your Power-Timing.
12) if you have iron heads, you may not get away with less than 91 gas, at WOT. This will be heavily dependent on your Effective cylinder pressure.
Happy HotRodding.
