Points gap and dwell, non-Camaro - Team Camaro Tech
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post #1 of 13 (permalink) Old Jun 4th, 12, 07:33 PM Thread Starter
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Steiner
 
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Points gap and dwell, non-Camaro

I recently purchased a '49 Pontiac Chieftain business coupe with rebuilt original straight 8 and what appears to be original distributor body. Unfortunately the timing tab is MIA.

Anyway, the car starts pretty good and runs OK. While going through the ignition to correct the previous owner's botched 12V conversion I ran into a little issue. I'm reading about 42 degrees dwell angle and the gap seems OK on the points. Spec is start with 0.016" point gap and set dwell no more than 30 degrees. These things idle at only 400 RPM and if I rev the engine dwell reading will drop a little but not much.

However, I can't get the car to start if I move the point set either way. The previous owner said it burned up a couple sets of points but I believe it was because he wasn't using a ballast resistor at first and the coil was a NAPA model that required one. When he did add one, he had the ignition power wired to the negative side of the 12V coil, and then a ballast resistor between the positive side of the coil and the distributor. (!). I initially rewired the existing components correctly with ballast resistor between ignition power and coil positive and drove for a while like that. This weekend I changed out the coil for one with internal resistance (no ballast resistor needed) and changed out the condensor to a 12V model to be sure that was correct. I also pulled the points and they looked OK but I went ahead and installed a new set.

I fooled with the "gas selector" to advance and retard the dizzy since I know a dwell change will affect the timing but regardless of where I set it the car just would not start if I changed the point gap. It started and ran fine with 42 degrees dwell but wouldn't start if I changed the gap at all regadless of gas selector position. Does anyone have any input on this? My thinking is that as long as the gap is within spec to prevent arcing or burn that maybe the dwell angle isn't a big issue.

Thanks.

'69 Camaro
Dart 400-AFR 195-224/224 HR-Powerjection III TB with F.A.S.T. Sportsman XFI
TKO 600-Moser 3.42-Detroit Truetrac
500hp/538lbft

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post #2 of 13 (permalink) Old Jun 4th, 12, 09:44 PM
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Phil McCullough
 
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Re: Points gap and dwell, non-Camaro

My first suspicion would be your replacement coil/condensor. Is there spark at the plugs only at the 42 degrees dwell angle? I suppose longer dwell allows longer saturation time for the coil/condensor to produce it's energy for spark making. Maybe changing the point gap allows allows contact to ground somewhere? Luck to ya. PRMc
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post #3 of 13 (permalink) Old Jun 5th, 12, 12:10 AM
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Re: Points gap and dwell, non-Camaro

I know this sounds ...well basic....u did change the cylinder section on the muti meter to 8 cyclinder?

Why did you convert theign system to 12v, not ballast?
I would have left it orginal.
If the whole vechice was still 6 Volt yep would upgrade that to 12V, but still retain a ballast ign......
Reason..its a bitch to dial the correct condesor in to stop pionts or make pionts last a long time as they should....simple things like changing the wire or lentgh the between coil and dizzy messes this up..

OH a thought...one can do a 100 set of pionts and not wipe the contacts before install..then get that one which has that bit heavier oil anti corossion stuff on..it burns and caused issues....always wipe the pionts on the cardboard backing of the box they come in... long shot.

Quote:
I'm reading about 42 degrees dwell angle and the gap seems OK on the points. Spec is start with 0.016" point gap and set dwell no more than 30 degrees.
What is the dwell at 16/1000 ?
15/16 thou is what u would set pionts at on most pionts dizzies if you dont have a manual around and they will run.
And 8 cylinder does have 45 degs fires, 42 degs seams a very long satruation time thats just over 90%

Quote:
These things idle at only 400 RPM and if I rev the engine dwell reading will drop a little but not much
Most dizzies will, it indicates some wear in the shaft /bushes...u many notice the total timing if graphed, goes up to spec then and 700 1000 rpms abovethat pull another few degrees.

My Spelling is not incorrect...it is creative

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post #4 of 13 (permalink) Old Jun 5th, 12, 12:49 AM Thread Starter
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Re: Points gap and dwell, non-Camaro

Steps,

As I said, the car was already converted when I bought it. It had a NAPA 12V universal coil (resitor required model), ballast resistor, and unknown condensor. Dwell was about 35 before I touched it. I gapped the plugs down to spec since they were a little wide and that's about it.

Since there have been so many little gremlins so far, I changed everything out yesterday to:
New cap and rotor;
Matched 12V coil and 12V condensor for 1970 Alfa Romeo Spider (internal ballast coil);
Cleaned and checked point gap on existing points which were fairly new;
Got 42 degrees dwell with point gap set were I could get it to start.

Changed out the points to a new set, cleaned them, same thing, 42 degrees dwell when set where the car would start.

The meter is not adjustable. It has a graph for each 4, 6, 8 cylinder.

Ah ****. As I'm sitting here thinking about it I think I know what the problem is. I was just thinking about how I couldn't get the meter to read at all if I grounded the coil wire and hooked up the meter to check dwell just by spinning the engine over, it would only read with the engine running. My meter just has a ground lead and test lead. In my mind I can see myself hooking the ground lead for the meter to alternator output stud instead of the alternator case. ****. That'll do it. There's a couple of hours I'll never get back.

'69 Camaro
Dart 400-AFR 195-224/224 HR-Powerjection III TB with F.A.S.T. Sportsman XFI
TKO 600-Moser 3.42-Detroit Truetrac
500hp/538lbft

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post #5 of 13 (permalink) Old Jun 5th, 12, 04:01 AM
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Re: Points gap and dwell, non-Camaro

http://www.secondchancegarage.com/public/615.cfm another place: www.classiccardatabase.com
Point gap: 0.035"
Meter hook-up can always bite you.
Check timing by aligning the circle or steel ball on the flywheel to the pointer above the starter.
6.5:1 static compression, 375 rpm in Drive, 425 in neutral.

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post #6 of 13 (permalink) Old Jun 5th, 12, 01:00 PM
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Re: Points gap and dwell, non-Camaro

Meter hook up...yep number times thats had one scratching the head, and a deep frown, over the years.
Thu since gone digital multi meter dont seem to do it....thu miss the anolge, espec when they have separate 'graphs' marking lines like Steiners.....thu didnt like over lapping tach ranges.. mine did it around the 3500 and thats a bitch ..too close to the low 3000 rpms when graphing up a cent curve.

My Spelling is not incorrect...it is creative

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post #7 of 13 (permalink) Old Jun 5th, 12, 01:35 PM
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Re: Points gap and dwell, non-Camaro

Quote:
Originally Posted by Everett#2390 View Post
http://www.secondchancegarage.com/public/615.cfm another place: www.classiccardatabase.com
Point gap: 0.035"
Meter hook-up can always bite you.
Check timing by aligning the circle or steel ball on the flywheel to the pointer above the starter.
6.5:1 static compression, 375 rpm in Drive, 425 in neutral.
I thought I remembered something like this to set timing on the 39 Pontiac I worked on. Ya beat me to it!

Jeff
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post #8 of 13 (permalink) Old Jun 5th, 12, 06:52 PM Thread Starter
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Steiner
 
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Re: Points gap and dwell, non-Camaro

Hey, thanks for the links Everett. I've got a reprint of the shop manual so all that stuff is in there but I don't remember seeing anything about alignging the flywheel with a mark. That will sure help if I have to make my own timing pointer.

'69 Camaro
Dart 400-AFR 195-224/224 HR-Powerjection III TB with F.A.S.T. Sportsman XFI
TKO 600-Moser 3.42-Detroit Truetrac
500hp/538lbft

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post #9 of 13 (permalink) Old Jun 5th, 12, 06:54 PM Thread Starter
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Steiner
 
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Re: Points gap and dwell, non-Camaro

I think the problem was that I was on autopilot with a short circuit. Had been troubleshooting the fuel and temp sending units and gauges and fixing the bad charging system with the DMM. Switched over to working on the ignition with the dwell meter and there you go.

'69 Camaro
Dart 400-AFR 195-224/224 HR-Powerjection III TB with F.A.S.T. Sportsman XFI
TKO 600-Moser 3.42-Detroit Truetrac
500hp/538lbft

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post #10 of 13 (permalink) Old Jun 6th, 12, 03:07 AM
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Re: Points gap and dwell, non-Camaro

You're welcome,
1- Early 1949, IGN mark. Late 1949 and 1950-54, first line to come under pointer
is for standard heads , second line for high compression heads, third line is TDC.

Pointer is on pass side, rear of block. Reason I remember is Grandparents had a '48 and a '52 Chieftain's with straight 8's.

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post #11 of 13 (permalink) Old Jun 7th, 12, 06:29 PM Thread Starter
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Re: Points gap and dwell, non-Camaro

Quote:
Originally Posted by Everett#2390 View Post
You're welcome,
1- Early 1949, IGN mark. Late 1949 and 1950-54, first line to come under pointer
is for standard heads , second line for high compression heads, third line is TDC.

Pointer is on pass side, rear of block. Reason I remember is Grandparents had a '48 and a '52 Chieftain's with straight 8's.

Yep, it's got the three marks on the balancer and specs are 3 degrees or 6 degrees depending on head for base timing. Then loosen the clamp for the "gas selector" arm on the dizzy and hammer it down the road adjusting the dizzy for gas quality until it starts to knock and then back it off a little and clamp it down. There's a bump cast into the engine block where the arm bolts and the arm has 20 degrees incremented on the end of it....10 advanced to 0 to 10 retarded....final setting timing is your base timing plus or minus whatever number on the gas selector arm lines up with the bump on the block. Trick. I figure with 87 octane she ought to take some timing....

I found someone parting out a straight eight and asked them if they had the tab and wanted to sell it. If not it shouldn't be hard to run a bolt down in the #1 hole as a stop to find TDC and make a pointer. Well, it may be a little difficult....the balancer is like an inch away from the radiator.

'69 Camaro
Dart 400-AFR 195-224/224 HR-Powerjection III TB with F.A.S.T. Sportsman XFI
TKO 600-Moser 3.42-Detroit Truetrac
500hp/538lbft

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'02 Z/28 vert-stock-sold and totaled
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post #12 of 13 (permalink) Old Jun 8th, 12, 05:47 PM
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Re: Points gap and dwell, non-Camaro

Just something temporary until you put the 540 in, right?


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post #13 of 13 (permalink) Old Jun 8th, 12, 05:51 PM Thread Starter
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Re: Points gap and dwell, non-Camaro

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Originally Posted by BPOS View Post
Just something temporary until you put the 540 in, right?
Ha. Yeah, and while retaining the single bail four wheel drum brakes of course. Funny thing is that I could go to a big block to save some weight. It's a moot point now though....found an Ignitor kit for it.

'69 Camaro
Dart 400-AFR 195-224/224 HR-Powerjection III TB with F.A.S.T. Sportsman XFI
TKO 600-Moser 3.42-Detroit Truetrac
500hp/538lbft

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