? about dwell and points

L

LAC_STS

Master Chief Petty Officer
Joined
Jul 1, 2010
Messages
895
I have been reading up on how to do a tune up on a points dist.

I have a ? though.

It says:

As point gap increases dwell decreases

As point gap decreases dwell increases

But isnt the point gap supposed to be set exactly to what the manual says?

So if I set the gap to what my manual says then the dwell is off some, Im supposed to change the point gap to compensate?

but doesnt this make the gap wrong?

Am I just confused?


Any tips for a first timer are so greatly appreciated.
 
Don S

Don S

Honorary Moderator Emeritus
Joined
Aug 31, 2004
Messages
62,321
Re: ? about dwell and points

Dwell is an exact measurement, Gap with a feeler gauge is a method to get close.
If you do enough of them and get good at "Feeling" the proper gap, the gap and dwell will both coincide.
 
L

LAC_STS

Master Chief Petty Officer
Joined
Jul 1, 2010
Messages
895
Re: ? about dwell and points

So basically I will be getting close by using the feeler to set the gap and then using the dwell to get it exact?


thank you
 
Silvertip

Silvertip

Supreme Mariner
Joined
Sep 22, 2003
Messages
28,762
Re: ? about dwell and points

That's how it was done for decades before dwell meters became available. As was pointed out, if you do it right with a feeler gauge, dwell will be correct as well. You do the same thing using either method. A feeler gauge adjusts the point gap mechanically. A dwell meter measures the degrees of distributor rotation which accomplishes the same thing. To change the dwell you adjust the point gap. To make you think even more, when doing a tune up you must set the dwell/point gap first then set the timing. Why?? Because dwell affects timing but timing changes do not affect dwell.
 
A

a70eliminator

Captain
Joined
Sep 9, 2007
Messages
3,696
Re: ? about dwell and points

I just did a tune up Friday and had my timing light light hooked as well as my tach and dwell meter, at one point my dwell was 22 I re-set gap and it went to 34 then on the third try finally got it to spec of 28 degrees, I loosen up the screws to just a little less than snug and use a screwdriver in the pry slot, you have to watch when tightening the screw that it doesn't drag the points back open.
I was keeping a close eye on ignition timing between adjustments and it never even changed enough that I could detect with a strobe light, 10 degrees BTC start to finish.
 
L

libellav15

Petty Officer 2nd Class
Joined
Jul 3, 2010
Messages
177
Re: ? about dwell and points

a70eliminator said:
I just did a tune up Friday and had my timing light light hooked as well as my tach and dwell meter, at one point my dwell was 22 I re-set gap and it went to 34 then on the third try finally got it to spec of 28 degrees, I loosen up the screws to just a little less than snug and use a screwdriver in the pry slot, you have to watch when tightening the screw that it doesn't drag the points back open.
I was keeping a close eye on ignition timing between adjustments and it never even changed enough that I could detect with a strobe light, 10 degrees BTC start to finish.
Click to expand...

If you had dwell mearurements ranging from 22 to 34 then the timing will DEFINITELY have been changing.
 
A

a70eliminator

Captain
Joined
Sep 9, 2007
Messages
3,696
Re: ? about dwell and points

Oh yes definately the timing does change I understand that, it just didn't change more than the width of the chalk mark I applied maybe half a degree?
I was wrong to say it didn't change.
 
L

libellav15

Petty Officer 2nd Class
Joined
Jul 3, 2010
Messages
177
Re: ? about dwell and points

i see what you mean :D

quite enjoying discussing dwell/timing/points at the moment

got my engine rebuild finished last week, and for the first time ever i got the timing marks to line up at the correct 6btdc at 650rpm in gear

only a small thing to most - but having the little adjustments to dwell and dizzy position actually do what they were supposed to do was a blast :)

the old balancer had slipped (front surface slipped from rear) and the marks were well off - previous owner had various white marks on the balancer from over the years - but i need it to be right every time - in theory now if dwell is correct the timing will be too.

lets get the boat wet :)
 
A

a70eliminator

Captain
Joined
Sep 9, 2007
Messages
3,696
Re: ? about dwell and points

My timing reference point hunts just a little, (width of my chalk mark) distributor shaft bushing is worn, but so is the rest of the motor.
I also have to use the same line of sight when viewing referance marks because because 10 looks like 12 from above and 8 from below, it's kinda hard to view it from straight on.
 
L

libellav15

Petty Officer 2nd Class
Joined
Jul 3, 2010
Messages
177
Re: ? about dwell and points

a70eliminator said:
My timing reference point hunts just a little, (width of my chalk mark) distributor shaft bushing is worn, but so is the rest of the motor.
Click to expand...


going a bit floppy with age - but aren't we all :D:D
 
You must log in or register to reply here.
Top