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Setting Dwell??

Posted: September 30, 2017, 3:40 pm
by Mr. Jones
Bought a Bosh timing light at O'Rielly's,instructions say to set dwell before timing...I have a dwell meter and have never used it...so what's the procedure for setting dwell...
Thanks
Dan

Re: Setting Dwell??

Posted: September 30, 2017, 3:58 pm
by ThinLizzy13
Dan,
To hookup dwell meter attach red to the negative coil post and ground the black. Typically I set my gap with the feeler gauge then fire the truck up and read the dwell meter. I then adjust the gap according to the reading and repeat.

Re: Setting Dwell??

Posted: October 1, 2017, 7:27 am
by Day 2
Same here... also, if you have dual points, stick a piece of paper between one set and read one set at a time.

Robert

Re: Setting Dwell??

Posted: October 1, 2017, 8:51 am
by FarmMotorSports
A pull tab from a beer will set point gap perfectly. :D
The hard part is finding a pull tab. :cry:


I haven't set points since highschool,
so the tab in the top of my tool box should last a lifetime...

Re: Setting Dwell??

Posted: October 1, 2017, 11:03 am
by slick4x4
A guy told me to set em with a dime
I didn't have a dime so I used 2 nickels

Re: Setting Dwell??

Posted: October 1, 2017, 12:23 pm
by ThinLizzy13
Gotta be careful with that technique. Don’t wanna shortchange your dwell gap.

Re: Setting Dwell??

Posted: October 1, 2017, 2:51 pm
by Mr. Jones
Found the dwell meter instructions and read their How to....dwell read out about between 37 and 41,points were set at .025...... no timing mark on crank pulley...pulled about 11 1/2 on vacuum and backed to a little over 10 not sure if that's enough any thoughts on that.....brake booster is creating a vacuum leak, disconnected and plugged the hose, got it to idle about 650 and drove thru town to a job that's starting tomorrow......performance was not great but got it there......tearing off a plastic shingle roof I installed 12 yrs.ago and replacing with a similar product.... me and one helper his buddy cracked a rib and is out for a while....two story and steep should be a fun week...
Brandon thanks for the input
Dan

Re: Setting Dwell??

Posted: October 1, 2017, 3:35 pm
by ThinLizzy13
I don’t remember if you have a 352 or a 240/300 but for a 240/300 your dwell is ok. For a 352 points should be gapped at .017 and dwell should be around 26-31. Your vacuum reading seems very low. You should be in the 15-18 range. The 352 in my 67 w/ 78k original miles sat at 15-16ish.

For timing with no marks on the pulley I would pull your dizzy and set the engine to TDC. Mark the pulley with chalk (I’m assuming you still have the markings on the engine block side). If you don’t have timing marks at all on the engine side the pulley should have a slightly raised line on it. If you don’t have any of this at all you will have to set engine to TDC and set timing with a vacuum gauge.

From here reinstall the dizzy with the rotor pointing at 1. Then set timing at the spec (if you have markings). Personally I like to set timing to spec then hook up my vac gauge. If you go this route advance timing until the highest vac reading that the engine begins to stumble at. I then back it down 1 or 2 readings on the vac gauge. After this I will take it for a drive and back the timing down if I get any spark knock.

I also suggest tuning your carb with a vac gauge while doing this.

That sucks about your job. Hopefully you can get the truck dialed in and have one less thing to worry about.

Re: Setting Dwell??

Posted: October 1, 2017, 6:24 pm
by Toyz
Dan, do you still have the Loaf o Matic dist/ carb setup? If your dwell is moving around that much; sounds like your distributor is quite worn. Alway set for the minimum specified dwell; as everything wears in the dwell increases, just the opposite of points.
Paul

Re: Setting Dwell??

Posted: October 2, 2017, 5:49 am
by Mr. Jones
Brandon,
About the low vacuum,anyway to increase it without a total rebuild?

Engine is a 240/300.....carb is a Holly/Motorcraft 1940 New kit installed last weekend

Paul,
Not a Loaf-A-Matic.......and was replaced a couple yrs.back.....less then 5K.miles on it
Dan

Re: Setting Dwell??

Posted: October 2, 2017, 6:17 am
by ThinLizzy13
You mention performance wasn’t great. I’m thinking your timing could be off which could give you a low vacuum reading. Try tuning the timing with the vacuum gauge and see if you can get the number up a bit.

I hope I don’t have the retard/advance backwards, but when I retarded the timing my vac reading drops; when I advance the timing my vac reading goes up.

Not really sure where to go if your vac ends up being that low after dialing it in. If something is worn internally, how the needle moves on the vac gauge can shed some light on the issue :2cents:

Re: Setting Dwell??

Posted: October 2, 2017, 7:34 am
by Mr. Jones
Brandon,
One more question,when the timing is advanced does that change the point gap when it fires.......should I recheck dwell and reset points for the change after resetting the timing......
Thanks
Dan

Re: Setting Dwell??

Posted: October 2, 2017, 7:47 am
by ThinLizzy13
Nope. Set the dwell then the timing. Timing shouldn’t affect it.