Timing Question

[Burgundystang]

Hey Guys,
I just got finished rebuilding my 289 and was setting my timing and i noticed that the engine runs a lot better when the timing is set up around 25 degrees instead of 6. What does that mean? Should i still set it to 6?

 

[68GEETEE]

Idle timing is usually somwhere from 10-16 btdc. Total advance at full throttle should be around 38. I would think your engine is going to ping like crazy if you have it set at 25 at idle.

http://www.gofastforless.com/ignition/advance.htm

 

[Burgundystang]

What does btdc stand for?

 

[mustang70]

BTDC- before top dead center

 

[GaPonyFarm]

How do you know what the timing is if you didn't know what BTDC meant?

You are disconnecting the vacuum advance hose and plugging it, aren't you?

 

[6Stang7]

You HAVE to be doing something wrong here. You engine would be pining like crazy if you ran 25 degrees of advancement at idle. How did you know it is running at 25 at idle? If it was one of those digital lights, then I think you might have been using it wrong or maybe you are using a different timing cover marker with different dampener. Like everyone has said, 25 is WAY too much. Personally, I don't like setting timing with a timing light, because every motor is different. Just advance your timing until the motor starts to pining, then back her off a little. Go take the car out of a drive and stand on it to see how it runs. Make adjustments until it runs the best. This way, you are setting the timing at what the motor wants it at. Setting overall advancement is a lot harder to do.....like jetting your carb to run the best. Short of making a bunch of dyno pulls, I would say to set overall advancement to around 32 degrees. Do all this when the motor has warmed up. The higher you initial advancement, the hotter your motor will run.

-Shaun

 

[67coupe351w]

[hijack attempt]

you know I have the similar issue with my timing.

I havent gotten an oppertunity to drive my mustang since the resto becasue im not quite far enough along for that yet but...

I had the timing set to a point that I knew it would at least start and run from when I built the engine. I got my light out the other day and decided I was going to check what the timing was set at. It showed 25 degrees at idle (this was with me kinking the vacuum line). My eyes went and I started to back it down. The idle became rougher and rougher until the point that it died at 10 degrees and wouldnt start again until i increased it back up some. It runs super smooth (well at least for the cam ) at the "25". I cant figure out what in the world up.

As far as incorrect pointers go, I used Mr. Gasket timing tape and pointer and set it up when the engine was still in the shortblock stage so i am 100% sure that it is accurate.

 

[D.Hearne]

[hijack attempt]

you know I have the similar issue with my timing.

I havent gotten an oppertunity to drive my mustang since the resto becasue im not quite far enough along for that yet but...

I had the timing set to a point that I knew it would at least start and run from when I built the engine. I got my light out the other day and decided I was going to check what the timing was set at. It showed 25 degrees at idle (this was with me kinking the vacuum line). My eyes went and I started to back it down. The idle became rougher and rougher until the point that it died at 10 degrees and wouldnt start again until i increased it back up some. It runs super smooth (well at least for the cam ) at the "25". I cant figure out what in the world up.

As far as incorrect pointers go, I used Mr. Gasket timing tape and pointer and set it up when the engine was still in the shortblock stage so i am 100% sure that it is accurate.

What cam do you have in there? The bigger the cam, the more timing it's gonna take for it to idle.

 

[Burgundystang]

I havent tried to set it to 25 and drive it so i havent heard the pinging but at idle it seemed to run better there. Im driving it at about 12. I was just worried because in the book i have it says to set it to 6.

 

[67coupe351w]

D.Hearne:

Its nothing too huge, its an Edelbrock Performer RPM cam (214/224 .496 / .512 I believe).

 

[6Stang7]

I havent tried to set it to 25 and drive it so i havent heard the pinging but at idle it seemed to run better there. Im driving it at about 12. I was just worried because in the book i have it says to set it to 6.

Don't worry, factory settings are never the best. They always under-set them to insure that there are no problems. Just set it to what the motor runs best at and there it there.

 

[HistoricMustang]

Every motor is different. On a street machine do this.

Get an initial setting somewhere around 10 degrees - not important just somewhere close.

Next rev the old girl up to about 4000 RPM's and advance the distributor till she starts to cut out, then back the distributor back a notch until she no longer cuts outs.

Let her drop back and see what the initial timing reads. Remember, it is not initial timing that is important, it is the total timing! Somewhere in the 35 to 38 degree range is about right. But, motors differ.

Go here and click on the "BadAss" link and look for the timing info: www.historicmustang.com/tech.html .

You will expose the misconceptions of initial timing.

HistoricMustang
www.historicmustang.com

 

[D.Hearne]

D.Hearne:

Its nothing too huge, its an Edelbrock Performer RPM cam (214/224 .496 / .512 I believe).

12 degrees initial should be in the ball park for timing 25 degrees initial is way out there. As for optimal total timing, you'll need to add timing tape to the balancer, or use a timing light that does it for you. With that cam, your motor should be able to be idled down to less than 1000 rpms. I ran a similarly spec'd cam in a stock 400M and it would idle in park at 600-800 rpms.

 

[67coupe351w]

but its smooth at 25 dies at 10

 

[6Stang7]

but its smooth at 25 dies at 10

Ignore what it says. Just set it to what the motor runs best at; that's all that really matters.

 

[D.Hearne]

but its smooth at 25 dies at 10

If it won't idle at 10 degrees BTDC, then somethings wrong. either your balancer has slipped or you're not adjusting the carb correctly.

 

[MCABOSS]

timing

You may have gotten the distributor installed a few teeth off!