Timing Help...
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Timing Help...
So, my truck ('86 F150, 302 w/ DSII, 2 bbl carb) is running better since identifying and fixing a couple vacuum leaks. It was stalling on acceleration but that seems to be resolved. It's still a little laggy and surges a bit while accelerating though. I decided to check the timing since the truck is new to me and I'm not sure how it was set up. I realize the lagging acceleration is most likely mixture screw adjustments but I still wanted to see what the timing was set for..
I found TDC of #1 using the piston stop method. The mid point ended up being dead on the factory 0* balancer mark. Rotor is in place at the #1 location. Unplugged and capped the vac advance from the dist and started it up. Initially I had my timing light set for 0*...couldn't even find the mark. Rotated the dist clockwise and started seeing the timing mark working its way up. I kept advancing the timing light until the mark and pointer were aligned. It indicated ~30-32* BTDC.
I intended to dial it back to ~10* but the engine knocks and barely idles when doing that. Put a vac gauge on it and I get max vacuum at the same 30-32* timing advance.
Isn't 30* too extreme....and what would that indicate?
I found TDC of #1 using the piston stop method. The mid point ended up being dead on the factory 0* balancer mark. Rotor is in place at the #1 location. Unplugged and capped the vac advance from the dist and started it up. Initially I had my timing light set for 0*...couldn't even find the mark. Rotated the dist clockwise and started seeing the timing mark working its way up. I kept advancing the timing light until the mark and pointer were aligned. It indicated ~30-32* BTDC.
I intended to dial it back to ~10* but the engine knocks and barely idles when doing that. Put a vac gauge on it and I get max vacuum at the same 30-32* timing advance.
Isn't 30* too extreme....and what would that indicate?
Post Fiend
Joined: Apr 2002
Posts: 19,311
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From: Waterloo, Iowa
You need to first measure the base or crank timing alone, without the spout connected or whatever it's called. Older trucks, would have to disconnect and plug vacuum advance. Not sure how yours is setup. In any case 30 degrees of crank timing alone won't work (if that's crank timing alone.)
Just about any V8 is going to be happiest around 36-38 "total" timing though - crank timing plus distributor advance. Stock trucks usually have this come "all in" in too late is the problem. Higher compression engines like maybe a little less total, 34-36 degrees. For more performance want to see this come "all in" between 2500 and 3000 RPM.
If you're still haulin' a load of gravel to KC now and then, that will be ping city. It's worth setting up right, you may need to limit the total advance but usually just a couple more degrees either way can make a big difference in driveability.
Just about any V8 is going to be happiest around 36-38 "total" timing though - crank timing plus distributor advance. Stock trucks usually have this come "all in" in too late is the problem. Higher compression engines like maybe a little less total, 34-36 degrees. For more performance want to see this come "all in" between 2500 and 3000 RPM.
If you're still haulin' a load of gravel to KC now and then, that will be ping city. It's worth setting up right, you may need to limit the total advance but usually just a couple more degrees either way can make a big difference in driveability.
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Junior User
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I did disconnect and plug the vac advance from the distributor before checking the timing...that's why I'm a bit confused on why the timing at idle is at ~30*. The timing does appear to advance more upon acceleration...I don't have a tach so I don't have actual numbers for rpm.
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