Question about ignition timing on 327

[Metalaroundstone]

Attachment 1187607I have a question about the proper timing spec for the 327 engine in my 1966 c10, which has a 4GC carburetor and no air injection reactor. Right now I have it at 8 degrees BTDC, with vacuum advance disconnected and port plugged. However, when I look at the specs in the service manual addendum for 1966, it says the timing should be set at 2 degrees BTDC. The 1963 service manual, on the other hand, says it should be 8* BTDC. My truck doesn't seem to like a 2* BTDC reading. I would appreciate any advice any body has on what the ignition timing ought to be and why these two spec sheets are so different for the same engine?

[Rich 5150 69]

Is the engine original, has the heads been changed, camshaft, vaccum advance have the correct vaccum dashpot, distributor mechanical advance working correctly no broken springs, not sticking or worn advance stops, a lot of variables here.. give us some history...

[Wrenchbender Ret]

You need to go with what works good. Like Rich says, there are variations. I would try about 10-12 degrees. If it runs smooth & doesn't ping on hard acceleration, or try to kick back when starting , this will work good. If not move it back to 6-8 degrees.

[Metalaroundstone]

Originally Posted by Rich 5150 69

Is the engine original, has the heads been changed, camshaft, vaccum advance have the correct vaccum dashpot, distributor mechanical advance working correctly no broken springs, not sticking or worn advance stops, a lot of variables here.. give us some history...

The engine block is original, the heads are 1968 factory replacement heads, the distributor is the original (with points) and it is in excellent shape-no broken springs etc. The vacuum advance dashpot is new from NAPA. I assume it is the right one for the truck as that is what I asked for. I hope this helps.

[OsOdeDIABLO]

Originally Posted by Wrenchbender Ret

You need to go with what works good. Like Rich says, there are variations. I would try about 10-12 degrees. If it runs smooth & doesn't ping on hard acceleration, or try to kick back when starting , this will work good. If not move it back to 6-8 degrees.

I agree, I usually start at factory and bump it up from there ,the motor will tell you what it likes.Jimmy

[brokenspoke]

I use a vacum guage to set timing

[Irishbleueyes]

The more advance you put in it ( to a certain point ) the better it will perform and better gas mileage as well. I have a 283 with stock HEI and with the vacuum connected its at 52* at idle. But the vacuum cuts out and the mech side takes over as soon as I crack the throttle. The engine runs amazing now, its low compression so it doesn't ping. Adjust it to your engine, seat of the pants, if you do have a vacuum gauge and it starts bouncing at idle you've gone too far advance.. I know original dist with points is cool but it will run better with an HEI, keep the engine chambers cleaner, smell better, start easier, better mileage and probably more timing that will wake that small block up!

[Metalaroundstone]

Originally Posted by Wrenchbender Ret

You need to go with what works good. Like Rich says, there are variations. I would try about 10-12 degrees. If it runs smooth & doesn't ping on hard acceleration, or try to kick back when starting , this will work good. If not move it back to 6-8 degrees.

I will experiment with the timing as you suggest. When you say 10-12 degrees, is this with the vacuum advance disconnected?

[Metalaroundstone]

Originally Posted by Irishbleueyes

The more advance you put in it ( to a certain point ) the better it will perform and better gas mileage as well. I have a 283 with stock HEI and with the vacuum connected its at 52* at idle. But the vacuum cuts out and the mech side takes over as soon as I crack the throttle. The engine runs amazing now, its low compression so it doesn't ping. Adjust it to your engine, seat of the pants, if you do have a vacuum gauge and it starts bouncing at idle you've gone too far advance.. I know original dist with points is cool but it will run better with an HEI, keep the engine chambers cleaner, smell better, start easier, better mileage and probably more timing that will wake that small block up!

I would like to replace the points with HEI. I was thinking about a Pertronix unit that fits inside the original distributor. I wonder if this would achieve any of the results you mentioned in your post.

[Captainfab]

The initial timing isn't as important as the total timing. You want about 34-36 degrees at 3000 rpm with the vacuum advance disconnected. I would try connecting your vacuum advance to manifold vacuum and see how it likes that. There are quite a few threads about setting your timing, in the 'Engine and Drivetrain' section here on the forum.

[R_W]

Originally Posted by Captainfab

The initial timing isn't as important as the total timing. You want about 34-36 degrees at 3000 rpm with the vacuum advance disconnected. I would try connecting your vacuum advance to manifold vacuum and see how it likes that. There are quite a few threads about setting your timing, in the 'Engine and Drivetrain' section here on the forum.

I agree completely. I have a 327 in one of my other vehicles, I set it up about 10* BTDC no vac advance. Mechanical advance with the distributor has it another 20* by 3K. Vac advance adds another 10* or so. You will know if you add too much initial timing as it will be hard to crank warm. Vac advance direct to manifold so it is in at idle.