Mpls Funk

Hi guys,

I have a 1970 350/350. Trying to get the timing and dwell set properly. I have a digital volt meter that has dwell meter setting...when I have tried using that, the reading bounces all over the place.

I just got a friend's old school dial/meter and connected it (negative to ground and positive to the negative lead of the coil)...and it is reading ~8 degrees! I believe this should be set at 30 degrees. I'm not sure if I should trust this meter either? Is it possible for the car to run with a dwell at 8 degrees? Or is this meter not right either?

The car tends to diesel a bit after shutting it off, and if this dwell is that far off, and then the timing is far off as well, that could explain a lot!

Big2Bird

Get a new points/condenser from NAPA. Set the gap at .018" at the cam apex, then fine tune the dwell to 30*. THEN set the timing. I would try 36* at 3000, and see how that works, vacuum plugged.

Mpls Funk

Thanks - I don't recall how many years old the points/condenser are...but they don't have hardly any miles (just not driving the car much). Can they go "bad" without being used?

How do I set the gap at .018" at the cam apex...I'm not sure what that means?

Big2Bird

You could use them, but I gave you a baseline that will get you close to 30*. You cannot set old points with a feeler gauge, only new ones.
You bump the engine to get the cam follower of the points to get max gap, or the apex of the dizzy cam lobe.

toobroketoretire

Although a dwell meter is more accurate a .019" feeler gauge is all you need because the dwell time (coil saturation time) isn't real important.

Big2Bird

Using a feeler gauge on used points introduces inaccuracy due to the pitting caused by metal transfer. They will be too open.

kanvasman

Here's my $.02 from another old geezer that used to know what points are…Turn the engine over until the apex or high point on the dist lobe is opposite the points. Use a feeler gauge to set it at about 19 ( a matchbook cover will also work enough to get it started, but then a feeler gauge will probably be easier to find nowadays than a match book), start the car then use an allen wrench ( or there are even special tools that have a spring in the shaft to enable you to FINE TUNE the dwell with the engine running. Get it to spec, then adjust the timing. And as said above, the most important thing is to plug the vacuum.

Big2Bird

Mpls Funk

Something just occurred to me....I know I need to plug the vacuum to set the timing, but do I need to plug it to set the dwell? Could that be why it read so low as I did not have the vacuum plugged when I did it?

Big2Bird

Nope.

toobroketoretire

Dwell meters usually have a 4 cylinder scale, a 6 cylinder scale, and an 8 cylinder scale and if its set to the wrong scale you'll get a wrong reading. The specs call for a dwell angle of 28 to 32 degrees so you have some leeway. With the Pertronix point eliminators being readily available and inexpensive I can't understand why people still run points. The constant side pressure of points causes upper bushing wear but the Pertronix doesn't which makes the Pertronix a nice upgrade.

Yellow6t7

My $.02, just take the car to a mechanic. Spend the $100. Think you are way in over your head.

TimAT

Vacuum has zero effect on dwell. None, nada, zip, zilch. It DOES have an effect on timing.

If you use a feeler gauge to set point gap, wash it down completely with alcohol. A trace of oil on the feeler gauge blade will very effectively insulate the contact points. And without contact they won't work.

Mpls Funk

Thanks - that's what I thought, but wanted to be sur . Thanks for the tip on cleaning the feeler gauge!

427Hotrod

That's why they make point files.

The feeler gauge will get you close....assuming there isn't a giant nub/pit on the contacts as Big2Bird mentions. If it's that bad then it's time for new points anyway.

The other old school way is to have it running...turn the adjuster in until it starts to falter/die. Back out a half turn. Still need to ck with an accurate dwell meter.

Good points will last a long time. Stay away from the cheapie stuff.


JIM

Mpls Funk

I went and purchased and installed a new points/condenser set. I still can't get my digital voltmeter/dwell meter to read anything that makes sense...it jumps all over the place, even as high as 1000. When I connect the old school dial dwell meter, I can't get it above 10 degrees. How many turns of the screw would you expect it to take to get it from 10 to 30? Is it 1 full turn? more? Would you expect that I would have to turn it clockwise or counter clockwise to get it to increase from 10 degrees?

Could my coil be bad? Or if it was bad would the car not start/run at all?

TimAT

Your dwell meter sounds a little flaky.. The colored lead from it (yellow or red usually) goes to the distributor side of the coil, and the other lead to a good ground.
Most GM points come from the store close enough to get the engine started for the final adjustment. At least the ones used since they invented the window type distributor cap

Big2Bird

Try another meter. Actron has one for $20.

Mpls Funk

Thanks guys - I agree that my electronic meter is flakey. But what about the old school dial type? Is that wrong too? Do I have two bad meters?

Gets back to the basic question - do you think the car should even run with a dwell setting of ~8-9 degrees and a timing of ~8 degrees BTDC?

I tried it again, if I turn it CCW, it would reduce the dwell a bit, and then nearly die...that was after maybe 1/2 turn? If I turn it CW about 1/2 turn, it might come up to 9-10 degrees dwell, but then if I go further it again starts to die out.

TimAT

Look at 427Hotrod's post above- Old school way to set dwell-
And both of your meters are funny. Batteries in them? Some do some don't.

IF it's running, the dwell HAS to be close- and 8* BTDC is also close.