Pete :
Well, as is frequently the case, the term 'rebuild' means different things
to different people.
You're absolutely right, changing the bushing should have no impact on the
advance curve. You can just slap that puppy in there, put back the old
shaft, springs and weights and say "this has been rebuilt". (Might want to
check the old shaft for wear first)
But, springs get tired, weights and pivots wear (especially if they haven't
been lubed occasionally). I've even seen a unit where the posts that carry
the springs were bent ! To say the dizzy is rebuilt "to original specs"
means checking all these things for wear and old age, replacing or repairing
as necessary, and then measuring the advance curve to see that it's right.
Measuring the curve can be as simple as a timing light, degree wheel (or
even pencil marks on the dampener), and running the engine at various rpms.
Your mechanic no doubt has an old distributor machine that's been sitting
idle for years, and wants to justify keeping it around. (If he wants to
sell it cheap, let me know <g>)
Actually, there's even another stage beyond that, "better than original",
where you hook the engine (or car) to a dynamometer and determine the
optimum advance for each rpm, then change the weights and springs to match
that curve. Modern gasoline is very different from what they sold in the
70's, and the factory had to be pretty conservative with advance. (Advance
was also limited to reduce smog.) If your engine/intake/exhaust has been
modified in any way, this step will likely result in a noticeable
improvement. Of course, you should really do mixture the same way first,
but let's not get too deep into "Tuner's shipwright's disease" here <g>
Randall
> To my feeble brain, it would appear that to simply R & R the bushings
> in a distributor would have little or no effect on the advance curve,
> except possibly to remove play that may have altered the curve
> slightly from spec. It appears to me that the only thing that
> determines the advance curve would be the springs which are attached
> to the weights, and that if you reinstalled the same springs after
> replacing the bushings, (assuming that you had to remove the springs
> to begin with) you would have the same advance curve that you started
> with. I wouldn't think you'd ever have any reason to replace the
> weights themselves, but I guess if you did, it might have an effect
> on the advance curve if they didn't weigh the same as the originals.
> But beyond that, how could the advance curve be changed to any
> extent? How could this be that complicated?
/// triumphs@autox.team.net mailing list
/// To unsubscribe send a plain text message to majordomo@autox.team.net
/// with nothing in it but
///
/// unsubscribe triumphs
///
/// or try http://www.team.net/cgi-bin/majorcool
|