How to set dwell on points?

[harrisg]

AQ125A/270, 16' Invader. My question is about setting the breaker point gap on my AQ125A. Manual says .040 mm or 0.157 in. Isn't this a starting place? <br /><br />I've been told that a dwell meter was the same as a tach like we already have on our guages and that a good way to do this was set the points at 0.157 (would 0.16 be ok?) start and check the rpm. Repeat this process until dwell gives you max rpm. <br /><br />Is there a better easier way?

 

[Buttanic]

Re: How to set dwell on points?

A tach and a dwell meter are not the same. Combination tach/dwell meters are avaiable for testing and setting dwell and idle speed but you can not use the dash mounted tach to set dwell. All though setting the point gap with a feeler gauge may or may not give you the exact dwell it is generally close enough to not cause problems. Also the timing must be checked and reset if needed after setting point gap because any changes in point gap will also change timing.

 

[Scaaty]

Re: How to set dwell on points?

Originally posted by harrisg:<br /> set the points at 0.157 (would 0.16 be ok?)

If you are just changing the points (do the condenser too) .016 just fine...get it as close as you can and if you aren't into perfect performance, the dwell will be ok too.

 

[trebor0301]

Re: How to set dwell on points?

just wanted to point out that there seems to be a difference here.Harrisg you wrote 0.16 and the spec is 0.016 dont know if it was fast typing or what.

 

[Buttanic]

Re: How to set dwell on points?

.016 is correct not .16

 

[harrisg]

Re: How to set dwell on points?

Thanks for the info. I'm looking at the vp instuction book and under Technical Data it says Distributor,breaker point gap, mm 0.40, or inches 0.157. I checked and I put the decimal in the right place. <br /><br />However, in the Seloc repair manual, it says dwell,62degrees +3 and POINT GAP .016. I think I'll go with you guys and the Seloc book

 

[Buttanic]

Re: How to set dwell on points?

I think the 62 degrees is wrong. Most engines are 28 to 32 degrees. I have found many errors in manuals over the years especially in aftermarket manuals such as Clymers.

 

[trebor0301]

Re: How to set dwell on points?

My Clymer says 62 +3 and .016 but this is the only book I have.Anybody else wanna try?

 

[rbezdon]

Re: How to set dwell on points?

I looked in my Clymers (I know but you asked). It covers only the 2.3 and 3.0 OMC engines but I would think dwell and gap would be very close. Dwell ranges between 31 and 36 +- 3 and gaps were all around 0.019. This seems logical. 0.156 is like 3/16 inch and I dont think anything runs a gap like that, not even a Stanlet Steamer!!!

 

[Dunaruna]

Re: How to set dwell on points?

0.O16 thou OR 0.40 mm. The dwell setting is 62 deg +/- 3 deg. <br /><br />Use the dwell setting, it compensates for variations in the distrubutor lobes and shaft runout.<br /><br />Initially, set the points with a feeler gauge, THEN run the dwell meter and make fine adjustments to the gap - simple - done.<br /><br />Aldo

 

[rbezdon]

Re: How to set dwell on points?

Duna, the gap must be right. .4mm converted to inches by taking the 0.039 inches per mm times .4mm gives 0.0158 inches or basically the 0.016. There is definately a decimal off in the top postings!! <br /><br />I just have a hard time believing the 62 degrees. I guess set the gap like you said. It should be close. If the dwell is near 62 it must be correct so adjust the gap until you get the 62 +- 3 but if you set the gap right and the dwell is in the 30s, I would definately question the 62 before I tried to set it there.

 

[Buttanic]

Re: How to set dwell on points?

Don't know where 62+/- 3 degrees came from but 8 cylinder is 29 degrees, 6 cylinder 31 and 4 cylinder 34. Each would be a couple of degrees more if it is a dual point distributor. How many cylinders is the engine. Even a 4 cylinder with 90 degrees between point cam lobes would have a hard time getting 63 degrees of dwell. An 8 cylinder has 45 degrees between point cam lobes so it is mechanically impossible to get 63 degrees.

 

[rbezdon]

Re: How to set dwell on points?

Tahnks for backin me Butanic. I think the dwell has to be some where between 31 and 36. No even a Stanley Steamer will run with a .156 gap or 62 degrees dwell.

 

[Dunaruna]

Re: How to set dwell on points?

O/k, you guys got me thinking that the cylmers is wrong (wouldn't be the first time) so I checked my auto manuals (NOT cylmers) - EVERY 2.1L volvo 4 banger (with points) has a dwell of 62 +/- 3.<br /><br />Thats confirmed in three seperate publications - Autotech, Rellim and Datatech.<br /><br />If a 4cyl is showing 30deg dwell, you've got the meter set wrong.

 

[Dunaruna]

Re: How to set dwell on points?

 

[Dunaruna]

Re: How to set dwell on points?

Originally posted by Buttanic:<br /> Don't know where 62+/- 3 degrees came from but 8 cylinder is 29 degrees, 6 cylinder 31 and 4 cylinder 34. Each would be a couple of degrees more if it is a dual point distributor. How many cylinders is the engine. Even a 4 cylinder with 90 degrees between point cam lobes would have a hard time getting 63 degrees of dwell. An 8 cylinder has 45 degrees between point cam lobes so it is mechanically impossible to get 63 degrees.

Although the angle of the lobes are a contributing factor, they do not dictate the dwell angle. <br /><br />The dwell angle is not a measurement of the angle of the distrubutor cam lobes, it is a measurement of the shaft rotation while the points are closed. Therfore, the fewer the lobes, the longer the duration and the angle increases. When you increase the point gap, the angle decreases because the points remain closed for a shorter period of time - That's why dwell angle adjustment is so critical.

 

[harrisg]

Re: How to set dwell on points?

The 62 degrees +3 came from the Seloc repair manual and I guess from what I see here it's in a number of other manuals also. I think what I'll do is set the points at .016 re-time to 10 degrees btdc and let the dwell fall where it may. What a great forum. thanks for everybody's help.

 

[bigbrownbuku]

Re: How to set dwell on points?

on an engine that old you are very likely going to have shaft runout, a point dunaruna was trying to make. your points gap isnt going to mean squat if you have worn shaft bearings.

 

[Buttanic]

Re: How to set dwell on points?

Dunaruna "The dwell angle is not a measurement of the angle of the distrubutor cam lobes, it is a measurement of the shaft rotation while the points are closed." <br /><br />Agreed, but there is also a number of degrees the points will be open as they ride up and down the cam lobe. The numbers I posted for 8, 6 and 4 cylinders was from the Mallory Ignition website.

 

[rbezdon]

Re: How to set dwell on points?

Bens right, gap is to get started, get close enough to run and chech dwell. Dwell is the real key parameter as it compensates for tolerances and wear. My point earlier was set the gap and see where you are. If you are in the range of 62, the manual must be right so set the dwell acordingly. If you are in the 30s with the right gap pretty sure the 62 is wrong and it wouldnt be a good idea to try to get to 62 from there, the gap would have to go way down, too small to be normal. If this is the case I would do as you suggest, set the gap to the 0.016 until you can get the correct dwell then set it.