TBucket Engine Project (Dart SHP)

Indycars

Administrator
Staff member
Wanted to check the ignition rotor phasing, so I drilled the old distributor cap I had just replaced
so I could see terminal #1.

Trying to figure out why the rotor does not appear to move when the RPM changes. If I go directly
to the Fluidampr without stopping the engine and check timing, it moves with RPM, just like you
would expect.

So why does the the rotor not appear to move???

 

Maniacmechanic1

solid fixture here in the forum
Wanted to check the ignition rotor phasing, so I drilled the old distributor cap I had just replaced
so I could see terminal #1.

Trying to figure out why the rotor does not appear to move when the RPM changes. If I go directly
to the Fluidampr without stopping the engine and check timing, it moves with RPM, just like you
would expect.

So why does the the rotor not appear to move???

No Problems there today.
Its not supposed to bounce around the rotor.

Look into a vacuum leak again for a misfire problem.
 

Maniacmechanic1

solid fixture here in the forum
Paint a white line on the rotor and check again if you want to.

To see accurate it needs to be tested on a Sun Distributor machine or it should.
Hold any rpm desired steady as a rock testing.
No danger of the engine overheating or other things.
 

JohnHancock

Well-Known Member
The rotor doesn’t change. The timing plate under it changes That is why the rotor blade is so wide. The spark can jump anytime it gets there.
 

Loves302Chevy

"One test is worth a thousand expert opinions."
Thanks!

I've looked and don't find such a part.

Do you have a part number? I'm using the MSD 8360 Pro Billet Ready to Run distributor.

I did find this, but it's listed for HEI.
https://www.summitracing.com/parts/msd-8412/overview/

HUH, you're right. I guess that can only be done with an HEI cap.
Sorry for the confusion.
The center bushing is part of the cap with the smaller diameter caps.
 

Indycars

Administrator
Staff member
HUH, you're right. I guess that can only be done with an HEI cap.
Sorry for the confusion.
The center bushing is part of the cap with the smaller diameter caps.

I did go ahead and check the resistance thru the center of the cap and got 1.1 ohms.

Is that low enough?

FP03_DistributorButtonResistance_00874.jpg
 

Indycars

Administrator
Staff member
I tried it again today, but this time I connected the vacuum advance. This time the rotor did move
when watching it with the timing light.

Since the rotor and reluctor both move together with the mechanical advance, then the rotor does
not move while watching it with a timing light thru a hole in the distributor cap. The difference comes
in because the vacuum advance moves the plate that the magnetic pickup is mounted on.


FP04_DistributorRotorPhasing_00879.jpg

FP04_DistributorRotorPhasing_00880.jpg
 

Indycars

Administrator
Staff member
.035-1.2 ohms is generally the range, the less ohms resistance the better/

I checked several times and it would start out at .2 ohms and then rise up to 1.2 ohms. It seems to
have a capacitive component to it's resistance.

Where is Mathieu (mathd) when you need him?
 

Maniacmechanic1

solid fixture here in the forum
Ideally you want to check the Secondary KV pattern.
Raster pattern
Parade pattern.
Super imposed pattern.
Actual Dwell time per cylinders all 8.
Rise time.
Ignition firing time.
Have my Snap On CRT Counsler Digital Ignition Storage Oscilloscope.
It was about $10,000 new .
1990 vintage.
Bought it from a Friend that closed down his Auto shop.
Still paid good money to make it mine.
$600 back 2001.
 

Maniacmechanic1

solid fixture here in the forum
Some checks can be made with a standard CRT oscilloscope.
One mistake though and it will blow up from the High Kv secondary ignition voltage.
 

Maniacmechanic1

solid fixture here in the forum
If you found no vacuum leaks at all then install the ebay distributor you have from testing back 1-1/2 years ago.
See if it hits clean on all 8 cylinders again.

Substitution testing.
 

Indycars

Administrator
Staff member
.
My ignition timing is stable now compared to the video I took on Feb 20, 2016. Shown below.


The MSD module has changed, I read on YouTube that someone had the same problem with stability
and I had changed it after the video. So I can't say for sure if that cured the problem or the change below.

This winter I changed from a cheap Professional Products damper PN#: 8002 to a Fluidampr 62260D 6-1/4" OD Gold Harmonic Damper.
https://www.summitracing.com/parts/pfs-80002/overview/
https://fluidampr.com/chevy-small-block/

Below you can see how the ignition timing has stabilized. At about 7 seconds it will clear up, look for the black dot at 36°.

https://fluidampr.com/faqs/
.
 

Maniacmechanic1

solid fixture here in the forum
I won't have time till this weekend.
Have to make a video again.
Show how my Snap On Counsler Ignition Oscilloscope works.
Connect to my 1987 Corvette.
It also works on my Vertex Magnetos.
Spin test a Chevy & Pontiac V8 Mags in my SUN Distributor machine.

Absolute Best way to test for unusual ignition problems.
 
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