Timing Curve on 360 in an RV
If you try and set this system up in the same fashion it will not tolerate timing advance numbers much over 30* without a backfire occurring around 3K rpm’s.
If you have proved the index mark on your balancer is in fact TDC,then;
this is not likely to be a timing problem; it only appears to be. What it likely is, has already been mentioned; but here are some other possibilities, in order of most likely and known concerns are highlighted.;
As to ignition problems;
A) rotor phasing
B) faulty trigger or reverse-polarity trigger
C) Faulty cap; cracks or tracks
D) faulty coil; spark jumping to somewhere else than where it is supposed to
E) ignition crossfire from wire to wire
as to fuel problems;
F) lean AFR,or
low fuel pressure
as to other;
G) the stinking aftermarket tachometers
H) restricted exhaust
K) problems in the chamber
L) problems in the valve-opening/closings, or the timing of those events.
it could be multiple problems
But if you have proved your balancer mark, and if the computer knows that the base-timing is 12* (IIRC), then I seriously doubt you have timing issues......
If you have a Multi-Spark System, coincidentally maybe, they switch from MS to Single-Fire right around 3000.
Here's my thinking;
Every engine I have ever tuned, loved mega-timing at idle,in Neutral; mega being 20* or more. By 2800 every one of them liked high 40s to high fifties. My 367 has sometimes accepted up to 63*! while cruising! The thing is,this is cylinder pressure dependent, and the AFR has to compliment the timing.
Also; there is a specified operating fuel pressure for your system. You cannot deviate very far from the spec, without having issues. The fuel line has to be able to accommodate the flow. It doesn't take much of a restriction in a 5/16 supply line, for a return system to falter. Same goes for the filter.
Do not deviate from the installation instructions.
Also; there are two kinds of what is commonly called a backfire.
1) An actual backfire is when the A/F charge in the intake manifold catches fire. At low rpm the engine is likely to stall, as all the charge in the plenum may be consumed, and the expanding gasses may actually exit thru the throttle-body. The computer may not react fast enough to the pressure spike, so when that happens the exiting gasses may bring fresh fuel with it and then you might have a dangerous underhood fire.
What can cause a backfire, is already on-fire burning gasses getting into the intake, past an open intake valve. This is not supposed to happen, and usually signals a mechanical problem. But it can happen on split overlap, or if the chamber has hot-glowing material in it, such as carbon or metal.
2) A missfire is when the mixture never ignites at all, and passes thru the chamber unburned.This is not likely to happen with EFI.
2) If the fuel charge enters a header with an air leak, it can ignite the next time that cylinder exhausts. If it enters a log manifold, it is likely to burn as soon as it sees a flame. When the fire occurs in the manifolds or headers, this is called an afterfire.
Oh yeah, do you know how to check your rotor phasing? and trigger polarity?
The distributor towers are 360/8=45* apart. Theoretically, with precise rotor alignment, you would have a 45* window in which to fire the plug. But in reality, the spark will jump to the tower with the least resistance, so that window has to be shrunk.
Typically. a performance engine will have a 20* window, while a low-compression factory window might be 30*. We try to center the window with half the degrees before the tower and half after; that way the spark will not be tempted to jump to the next easier to fire tower.
With the D locked at 12*, the rotor should be right in the window....... but you gotta look and prove it. You do this by putting the proven crank index mark at 12*, scribing the Distributor body at the center of the #1 plugwire tower, then pop the cap off and look to see where the rotor is. If it's within say 15*, you are good to go. The closer to centered, the longer your cap will last. Mine is from the 70s, and has been on several engines, and likely has over a quarter million miles on it. If it's outta range, then you gotta re-engineer it, er I mean move it,lol.
The polarity check is easy. Just watch the index mark on the balancer as you rev up the engine. If the mark moves back and forth nicely, then she's good to go. But if it jumps around like a headless-chicken and dropping sparks, well then it ain't right.
