Electrical: Unstable cam angle

[christophe]

[Mike Van Veghten]

Cam Angle ?
Do you mean dwell, overall timing, mechanical timing...?

Mike

[Son O Lark]

Cam Angle ?
Do you mean dwell, overall timing, mechanical timing...?

Mike

Isn't cam angle and dwell the same thing?

[63 R2 Hawk]

If the breaker plate bushing is worn, it will tend to tilt or wobble the breaker plate when the vac servo actuates and causes the dwell angle to change. Check to make sure the breaker plate doesn't rock if you try to rock it from side to side...

[kxet]

Isn't cam angle and dwell the same thing?

Yes, disconnect vaccum advance and see if dwell stop flucuating, if it does breaker plate is sloppy. (take vaccum hose or pipe loose and plug opening)

[christophe]

[Dan Timberlake]

i think my swell dwell meter reads degrees, like this one.

http://i563.photobucket.com/albums/ss78/47redwillys/DwellMeter.jpg

The early Hemis came with dual point distributors. the then-new factory bulletins describe dwell this way -

http://www.imperialclub.com/Repair/Lit/Master/059/page16.htm

[christophe]

It never occured to me before but I'm wondering now if computing dwell in % is a french specificity.
Sorry if I mislead anyone.

[gordr]

Note that a number of distributor designs, the cam angle/dwell must change as the vacuum advance applies, since the pivot point for the breaker plate is not concentric with the distributor shaft. The Prestolite V8 distributor is one such. Presumably the specified value for dwell at idle is chosen such that dwell at cruise, with the vacuum advance mostly in, is satisfactory. Under acceleration, with fairly low vacuum, your dwell should be close to idle dwell, and it's most important to have a strong spark when cylinder pressures are high.

[christophe]