All Small Six Which cylinder head?

[Otto]

Took the van for an extended test drive to check my work. The speedometer is now pretty durn close to the app on my phone, so I’m calling that fixed.

The engine ran well with the 160 jet size; I didn’t see any alarming lean readings from the AFR gauge and driveability was excellent. I’m thinking this setting will work for my engine. The van will get driven more when summer rolls around and more time behind the wheel will further tell the story.

Thanks to all that contributed to this project, it’s appreciated. Sometimes it takes a village…

 

[Otto]

Just to follow up with a summer driving update:
I drove the van to a local Econline-centric event at the end of June, and noticed the AFR meter was reading lower than it was when I was testing things out in January. Plus I could tell it was running richer due to the exhaust smell. Having windows that open on the rear doors tends to offer clues on what’s happening in the engine.

I got some new jets in the 1.55mm size as I had drilled the carb’s jets larger. The new jets are one size smaller than the drilled jets that were in the engine. With these new jets, I was seeing 14s and 15s on the meter cruising down the road- this is higher than before where it was only in the 13s with an occasional 14.
On the latest test drive w/new jets installed, the spark plugs look like this:



I pulled #1, 2, and 4 and they all looked very similar. This is after driving at 40-45 mph and turning the key off and pushing the clutch in, coasting off the road. I was able to pull the plugs from the driver’s seat even with a seat belt on!

Any thoughts on the plugs? It seems to run well. The engine is only happy with the idle at around 12.5.

 

[DON]

Plug looks good in the photo
With the idle around 12.5, let it idle for 15-20 minutes and check the plugs again. I would say it it is happy there, leave it and see if any negative issues arise .
Assuming all other aspects are correct- timing mostly

 

[Otto]

I’ve been driving the van a bit since summer hit and am enjoying how the van runs/drives now, but can’t help thinking there might be a bit more to achieve with it. I’m wondering if the ignition timing is optimum for the engine and did some initial data collection. With the vacuum hose disconnected and timing light hooked up, I find the initial base timing to be at 20* btc- seems like a bit much. Sometimes the starter protests when the engine pushes back when cranking.
Idle= 20*
1000= 22*
1500= 30*
2000= 34*
2500= 34*

34 degrees seems to be all the mechanical advance the engine is seeing; if I reconnect the vacuum hose and run the engine up to 2500, the engine is seeing ~48*.
In all the driving I’ve done with the van I’ve never heard it “ping” on regular gas. The engine is stock with the exception of the 2 bbl carb and the DSll distributor. I have the Mr. Gasket #925D kit on the workbench- is it worth it to try changing springs? I’ve read so many of the existing threads with various pro/con arguments that now I’m cautious to try anything.

 

[Frank]

I’ve been driving the van a bit since summer hit and am enjoying how the van runs/drives now, but can’t help thinking there might be a bit more to achieve with it. I’m wondering if the ignition timing is optimum for the engine and did some initial data collection. With the vacuum hose disconnected and timing light hooked up, I find the initial base timing to be at 20* btc- seems like a bit much. Sometimes the starter protests when the engine pushes back when cranking.
Idle= 20*
1000= 22*
1500= 30*
2000= 34*
2500= 34*

34 degrees seems to be all the mechanical advance the engine is seeing; if I reconnect the vacuum hose and run the engine up to 2500, the engine is seeing ~48*.
In all the driving I’ve done with the van I’ve never heard it “ping” on regular gas. The engine is stock with the exception of the 2 bbl carb and the DSll distributor. I have the Mr. Gasket #925D kit on the workbench- is it worth it to try changing springs? I’ve read so many of the existing threads with various pro/con arguments that now I’m cautious to try anything.

Great news!, nothing beats driving the old classics.
The mechanical advance is only 14*, which is why it needs 20* base timing. "Pushing back" while cranking is not good, it puts huge load on the rod bearings and starter. A solution (other than retarding the base timing, which it needs with the 14* timing curve) is to put the ignition on a separate toggle switch. Then crank the engine over (no spark) and flip the ignition on. The inertia of the rotation will overcome the early base timing, it will fire right up. Most race engines use this, as the timing is locked in at a high advance.

Have you looked at the springs in the distributor? I would wager there's more advance in the weights than is releasing thru the springs @ 2500 rpm. A lot of stock type distributors have a heavier second spring. On my 300's changing the heavier spring (only) for a lighter one put the curve right in the sweet spot.

 

[Otto]

I have a spare DSll and took this apart to compare and get familiar with it. The light spring had tension and the heavy spring had some slack.

I pulled the van’s distributor and installed one of the 925D kit springs in the advance mechanism replacing the light spring. According to the lore here on the page, the heavy spring’s post gets bent inward 3/32”. I did this and it took the heavy spring completely out of the picture, it was totally slack throughout the full movement of the advance- unless this is the whole point of bending the post. I pulled the post back about half of the distance bent where the heavy spring now came into play in the final movement of the mechanism.

Now the ignition looks something like this:
Idle= 14-15*
1000= 19*
1500= 30*
2000= 32*
2500= 35*

With vacuum connected, total ignition advance is at 52* at 3k rpm.
It might all be in my head, but the test drive this evening was good- very pleased with how it runs. It’s seeing basically the same curve with a lower initial setting. So I guess the kit worked, I think I’ll leave it alone for a while.

If someone sees something out of the ordinary here please let me know.

 

[gb500]

Did you run your mech advance readings past 2500rpm ?

Does it stop advancing at 2500rpm?

 

[Otto]

Yes, past 2500 rpm there’s no more advance. Stays the same.
With the vacuum connected, there’s more.