Timing on a 5.9 Magnum

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Lelo Dart

Lelo Dart

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What timing is everybody running on there carbed Magnum engines?
Right now I've got it dialed back to 15 initial and 28 total and vac advance 10 degrees at full advance. Using the stock springs for a slow mech advance and it's still rattling occasionally while at cruise.
 
List more engine details to get a better answer. LA or Magnum harmonic balancer and timing cover? I suspect poor quality gas, vacuum advance moving too much or connected to an incorrect source port, or mismatched timing marks so your numbers are lower than your actual timing. I use 32 degrees to 38 degrees, depending on what set up and camshaft arrangement, and not including the vacuum advance. Usually a stock compression Magnum 5.9 or even 5.2 can use 32-34 degrees total mechanical advance and still run regular or mid grade gasoline, although some gas stations have poor gas quality so grades will vary. I run 92 octane premium in Michigan when I beat on my car, or when ambient temperature is above 80 degrees.
 
Lelo Dart said:
What timing is everybody running on there carbed Magnum engines?
Right now I've got it dialed back to 15 initial and 28 total and vac advance 10 degrees at full advance. Using the stock springs for a slow mech advance and it's still rattling occasionally while at cruise.
Click to expand...

19-20 initial, 34 total mechanical and 52 all in with vacuum advance at full.
Iron heads, stock pistons 9.1:1 and 87 fuel at 5,500 elevation with normal heat range plugs.
Did you think about plugs yet?
They can cause pre ignition and engine run on when shutting down.
 
TrailBeast said:
19-20 initial, 34 total mechanical and 52 all in with vacuum advance at full.
Iron heads, stock pistons 9.1:1 and 87 fuel at 5,500 elevation with normal heat range plugs.
Did you think about plugs yet?
They can cause pre ignition and engine run on when shutting down.
Click to expand...
Yes, cold plugs Autolite 3922. Been fighting this for a while.

Bobzilla said:
List more engine details to get a better answer. LA or Magnum harmonic balancer and timing cover? I suspect poor quality gas, vacuum advance moving too much or connected to an incorrect source port, or mismatched timing marks so your numbers are lower than your actual timing. I use 32 degrees to 38 degrees, depending on what set up and camshaft arrangement, and not including the vacuum advance. Usually a stock compression Magnum 5.9 or even 5.2 can use 32-34 degrees total mechanical advance and still run regular or mid grade gasoline, although some gas stations have poor gas quality so grades will vary. I run 92 octane premium in Michigan when I beat on my car, or when ambient temperature is above 80 degrees.
Click to expand...
LA timing cover with Magnum balancer. 92 alcohol free gas. Timing marks checked with degree wheel. Checked and set vacuum advance with manifold vacuum. Plugged in timed port on carb.
 
Rattling in cruise, on a slight uphill, on a acceleration, not wot? could be as getting colder need a little more fuel, enriched a little. Or may be a little bit bigger pump shot on carb. in winter months because of winter fuel blends, have to usually decrease 2 degree's and richen it a little.
 
spl440 said:
Rattling in cruise, on a slight uphill, on a acceleration, not wot? could be as getting colder need a little more fuel, enriched a little. Or may be a little bit bigger pump shot on carb. in winter months because of winter fuel blends, have to usually decrease 2 degree's and richen it a little.
Click to expand...
Never in town or slow driving, only hwy speeds with less throttle. If it starts to ping a press of the gas and it stops. Was rattling bad at WOT until I cranked back the total to 28. Using a wide-band A/F gauge and am running rich most of the time. I think I almost got it licked but I don't think I should have to run so little timing to make this thing stop rattling. Don't know why the same combo is working for some people and not me. Iron heads, stock .020 over pistons, RPM intake, Holley carb and electronic ignition.
:wtf:
 
What distributor are you using and was it modified at all? How long has the engine been running in this configuration? Does it handle more timing under acceleration with the vacuum advance disconnected? A fresh, clean Magnum engine with no carbon buildup and verified timing marks should not have any real tendency to rattle like this, in my experience.
 
Bobzilla said:
What distributor are you using and was it modified at all? How long has the engine been running in this configuration? Does it handle more timing under acceleration with the vacuum advance disconnected? A fresh, clean Magnum engine with no carbon buildup and verified timing marks should not have any real tendency to rattle like this, in my experience.
Click to expand...
Stock distributor using a FBO timing plate limiter. Left the stock springs. Can't have 2K on the engine since rebuild. Been trying with vac advance disconnected before taking the distributor out.
 
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