timing light results

[joe_db]

I got my new timing light last night
The results are a bit odd though. From my initial test:
IDLE
RPM on light = 800
RPM on my tach = 1000
Advance = 16 degrees at crank

FULL THROTTLE
RPM on light = 2250
RPM on my tach = 2500
Advance = 38 degrees at crank

Besides for my tach being off calibration, shouldn't it be 0 degrees at idle I am not even sure how to fix this, if it is a problem.

[hanleyclifford]

1000 or even 800 rpm is a little high to get back to zero centrifugal advance. I find that I need to get down to 500 or 600 rpm to read zero. The springs on our distributors are a little old and sloppy.

[joe_db]

Good point - I'll have to turn my idle down some.

[JOHN COOKSON]

Originally Posted by hanleyclifford

1000 or even 800 rpm is a little high to get back to zero centrifugal advance. The springs on our distributors are a little old and sloppy.

Also there can be rust and corrosion in the advance doohickey.
Even though it may appear to be working correctly it may be hanging up a bit.
I would suggest, if you haven't done so in the last year or so, take it apart and have a look.

TRUE GRIT

[Dave Neptune]

Joe, in the performance industry we did not worry about the base idle unless we had idle issues, we always set the timing at "total advance". The A-4 by the book is "zero" for base plus the 17 degrees in the dist for a total of 34 degrees on the crank. All this means is that at 38 degrees your timing is 4 degrees to advanced~by the book.

What you have is very close and if your C-adv is working at 800 it may be advancing a bit. Wear and the loosening of the springs over time is a probably all you are seeing. Another words if your adv is working freely I would set the "total timing and enjoy a liquid bread rather than tweaking or worrying!!!

Dave Neptune

[sastanley]

Oooo...ooooo...Now that I've 'solved' my electrical problems, I am ready to get back to getting all this stuff dialed in again too.

I just received my 'optical tach' last week, so that I can test the calibration of my installed tach, and I have my timing light aboard and ready. Once again the old salts (liek Dave Neptune ) re-enlightened me that 17° dizzy advnace = 34° crank advance..A quick check of my light this weekend on the crank pin was less than 17°, but it was running great so, I didn't mess with it.

I just need to get down to the boat and do some 'messing about'.

[KentB]

Cant make sense of the tach issue... Does it go all the way back to zero when shut off? Some tachs have switches that allow you to adapt them to different motors. (2 cycle vs 4 cycle) and 2,3,4,6,and 8 cylinder.
Because the ratio of error is not the same at different speeds it looks like the tach is just plain out of whack.

[joe_db]

My tach is a VDO tach that can adapt to a variety of gas and diesel engines. Someplace there is a menu you can get at to adjust it. I have to find the right combination of button presses to do it.

Originally Posted by KentB

Cant make sense of the tach issue... Does it go all the way back to zero when shut off? Some tachs have switches that allow you to adapt them to different motors. (2 cycle vs 4 cycle) and 2,3,4,6,and 8 cylinder.
Because the ratio of error is not the same at different speeds it looks like the tach is just plain out of whack.

[Ball Racing]

Unless you have a major name, high performance tach, they are off.
Teleflex seems to be off in most applications.
My teleflex- one day reads low, then the next reads high.

[KentB]

Yup. Just "calibrated one of those VDO tachs myself.
There is ONE button in the back of it. You press that while turning the ignition on and that will put it into setup mode. After that there are a series of short or long button pushes that set it all up.
Hopefully you have the instructions still but if not, you can get them online at the VDO website.
I sort of stumbled on the right setting of 4 stroke, 4 cylinder on a grey marine 60horse, after quite a few failed attempts. Its tougher than setting up an LCD digital watch (at least they usually have 4 buttons, not 1!)