[scotty54]

68 Sprint with auto trans and Weber sidedrafts:

The idle speed of this setup is 1100 RPM, making it impossible to set initial timing using a standard timing light.

Using the factory setting of 5 degrees BTDC at 600 RPM, can I calculate the initial timing at 1100 RPM by adding degrees based on the additional 500 RPM? Then I can use a dial-back timing light to verify initial timing.

And if I sound confused please tell me. I normally use a light to set initial timing then adjust slightly for highest vacuum. This has worked well on low compression classic V-8's.

Since I could not use the timing light, I set initial timing using vacuum alone. However a test drive revealed slower cranking and detectable pinging under acceleration, so it is too far advanced. This was all done after replacing plugs, cap/rotor, and plug wires.

[Kenth]

Instead of checking initial at idle speed, you can check centrifugal spark advance at 2000 rpm´s for 15° +- 2°.
With vacuum advance hooked up at 2000 rpm´s for 30° +-6°.

Info from Delco Tune-Up Specifications 1966-75 Manual SD-100.

HTH

[694.1]

Put the dampener at 5 BTDC. Turn on the ignition and turn the dizzy until you hear a slight TICK from the points opening.
Voila!
Then lock down the dist.

[Jeff Hamlin]

In standard configuration the Factory Specs NO LONGER APPLY most of us are running between 10 to 13 degrees BTDC

[scotty54]

Jeff - I figured I was around 10 degrees after adjusting for max vacuum. But symptoms indicated too much advance. But, I am still wrestling with the Webers and idle mixture, plus the 200-4R is shifting too early.

694.1 - Points? Hats off if you are using points. I haven't had a points distributor since 1994. Currently running Pertronix. I had not heard of your timing trick though.

Kenth - great suggestion. I couldn't find the total advance numbers so that was a big help.

[sprintbird]

Scott, initial timing should be 10 to 14 BTDC as Jeff indicated. My guess your symptoms are a result of your carbs being lean and trans shifting early. Set the timing and then tighten the trans cable very slightly so it shifts in the normal range. Then richen up your carbs.

[scotty54]

Some very confusing timing measurements today.

I have confirmed my Craftsman dial-back light is operating properly (I tested it on my 1977 Jeep Cherokee and it was spot on). I also verified all my timing marks (harmonic balancer, cam gear, and accessory gear) are all correct. Timing belt is tight. Stock dizzy with Pertronix Ignitor II.

I have made some adjustment to the TV cable and that has improved shifting. The carbs that were lean are now a bit rich, so still trying to find a happy place.

After addressing those two I went back to the timing.

1. Initially I had 40 degrees at 1000 rpm, 55 degrees at 2000 rpm. Vacuum at 1000 was 18 and steady. All timing done with vacuum advance disconnected and plugged. At this setting I was getting some audible pinging while driving, and slow cranking - both symptoms of too much advance. Rough idle.

2. Next I retarded the timing to obtain 22 degrees at 1000, 40 degrees at 2000. Idle smoothed out a little and it cranked normally. Vacuum at 1000 dropped to 11, still steady.

3. I retarded the timing further, this time to 22 degrees at 1000, 36 degrees at 2000. The idle sounded even better than setup 2, but on shutdown I got a backfire. It has never backfired before. Vacuum at 1000 dropped to 10 inches and steady.

If I retard the timing to 15-16 at 1000 I will have more problems, and that would lower the degrees at 2000 RPM to around 25-28. My next step is to return the timing to #2 and drive it to evaluate drivability.

The builder of this engine told me the idle vacuum with the 260 duration cam lowered the vacuum at idle to the point where a brake booster wouldn't work, so he installed a hydroboost. Based on this, I am not sure how to interpret the vacuum numbers. The 10-11 might be closer to normal, and the #1 test that showed 18 might be high - another sign of too much advance.

Any ideas?

[scotty54]

A follow up from yesterday's post:

More tweaking the Webers and I got the idle mixture set. A 1/8 turn on a mixture screw makes a difference!

Timing (per the timing light) is set at 30 degrees at 1000 RPM, 45 degrees at 2000 RPM with vacuum advance disconnected. Crazy numbers, doesn't make sense but the car drives good, strong throttle response and no pinging. It's the best running so far. Vacuum is 12 inches at 1000 RPM.

Connecting the vacuum advance adds 15 degrees.

I even called Pertronix and they say the Ignitor II won't cause incorrect timing light readings.

I'm stumped but happy I am getting better drivability.

[Cammer-6]

How have you verified the timing marks are correct?
Very common to have the inner and outer creep apart with age.
Pull #1 plug and find TDC

Low vacuum also caused by 6 big holes

One question thats been nagging me is the cam timing.
Do you have Robs gear?
Ive advanced/retarded cam timing via offset bushing and drilling out cam gear

[scotty54]

I have verified timing marks visually by rotating crank to TDC then confirming all 3 timing marks in proper spots, per the TSM. Rotor also pointing at #1. Arrows on the balancer inner and outer sections are aligned.

I suspected the Webers could contribute to less vacuum but wasn't sure. It makes sense.

Not familiar with Rob's gear. Is this Rob at Woodmont you are referring to?

I've never dealt with changing cam timing. I always thought "degreeing a cam" was a mod for higher horsepower engines.

[scotty54]

Woodland (not Woodmont). Sorry Rob.

[Cammer-6]

The other big question I have is your transmission cable.
Theres a ratio of cable pull to throttle opening position
that must be adhered to regardless of cable slack etc

Im pretty sure I was the beta tester for a 200-4R behind an OHC-6.
I think it was late 80s I did swap to a Monte Carlo SS(same trans as the Grand National)
I had an engine on a stand with carb set up and put the trans minus pan next to the engine.
When the pan is off you can see how much slack is in cable until it bottoms out.
I made my own bellcrank and slotted it for adjustment.
As it turns out my benchtop adjustment was spot on and havent touched it since.
Glenn(aka Birdman or Einstein) and I drove to a buddys shop with trans in the trunk.
About 4 hours later we were test driving with the ST300 in trunk.
Again the ratio of throttle opening to cable pull is paramount.
Many a trans has been fried in short order if its not correct.
Im not near my notes for that,perhaps I posted it around that time,
but PY has crashed a few times since then so may be lost.

[Cammer-6]

Originally Posted by scotty54

I have verified timing marks visually by rotating crank to TDC then confirming all 3 timing marks in proper spots, per the TSM. Rotor also pointing at #1. Arrows on the balancer inner and outer sections are aligned.

I suspected the Webers could contribute to less vacuum but wasn't sure. It makes sense.

Not familiar with Rob's gear. Is this Rob at Woodmont you are referring to?

I've never dealt with changing cam timing. I always thought "degreeing a cam" was a mod for higher horsepower engines.

Is cam stock base circle or is it a 68 4bbl cam thats been reground?

[einstein]

Originally Posted by Cammer-6

The other big question I have is your transmission cable.
Theres a ratio of cable pull to throttle opening position
that must be adhered to regardless of cable slack etc

Im pretty sure I was the beta tester for a 200-4R behind an OHC-6.
I think it was late 80s I did swap to a Monte Carlo SS(same trans as the Grand National)
I had an engine on a stand with carb set up and put the trans minus pan next to the engine.
When the pan is off you can see how much slack is in cable until it bottoms out.
I made my own bellcrank and slotted it for adjustment.
As it turns out my benchtop adjustment was spot on and havent touched it since.
Glenn(aka Birdman or Einstein) and I drove to a buddys shop with trans in the trunk.
About 4 hours later we were test driving with the ST300 in trunk.
Again the ratio of throttle opening to cable pull is paramount.
Many a trans has been fried in short order if its not correct.
Im not near my notes for that,perhaps I posted it around that time,
but PY has crashed a few times since then so may be lost.

That was a fun day!

And it performed very nicely I recall, as I got to get some miles at the wheel on a trip we took, somewhere.

[VCho455]

Have you synchronized your carbs? Getting dual Weber setups to sync up is a pain but a necessary step. Having your carbs snchronized means that both idle circuits in the separate carburetors are matched and supplying their respective cylinders the same amount of air and fuel. Otherwise the engine is running one carb and half the cylinders. When that happens and your adjusting the weak carb you will find it unresponsive then it goes over responsive and round and round you go chasing your tail.

There is lots of information on interweb about synching Webers, especially from folks with boxer engines. Those mostly run downdraft versions so you want to look to the inline engine folks as some the tools used on downdraft carbs won't work on sidedraft engines.

What are your camshaft specs? That could play into your high idle and low vacuum numbers.

[scotty54]

In reply to the most recent posts:

I am chasing multiple problems but the goal is to get good running and drivability to pursue the biggest problem - oil leaks.

The 200-4R TV cable is properly adjusted for upshifts but doesn't work for kickdown. That's ok for now, no WOT driving yet.

The cam is the 1969 "H" cam - .438 lift and 260 duration. I think the cam profile plus the big carbs contribute to the low vacuum. Normal idle for the Weber DCOE is 900-1100. And yes, I have seen many YT videos on tuning and some have been helpful. It will take time but I am learning the carbs.

The carbs do need significant work but for now was focused on the idle mixture. The mixture screws don't exhibit the proper engine response when tuning so I suspect the circuits are gunked up. 240 miles in 10 years is bad for everything mechanical but really bad for carburetors. I have been adjusting mixture then inspecting plugs.

The wild timing numbers still have no explanation but it drives good now, so time to dive into the oil leaks.

I appreciate all the replies. I am making progress and not in a hurry.

[scotty54]

Update on my excessively advanced timing:

I have made significant progress with the carbs and so far have only focused on the idle circuit. "Idle" with regard to Webers is a misnomer - they call it the "slow running" circuit and it also meters fuel well above idle until it progresses into the main circuit. Cleaning the idle circuit - jets and mixture screws and orifices yielded a significant improvement in idle quality and low end throttle response (the mixture needle were all varnished). I have also gained idle vacuum - up to 14.5 (from 12). This has also enabled me to take another shot at the timing, and at 2000 RPM I am currently sitting at 40 degrees. Not quite the 36 it should be but making progress.

[Cammer-6]

was all this happening at same time your belt came off?
I still suspect cam timing is off.
The H cam isnt a wild cam by todays standards,but in 69 it was hotter
than everything but the RAIV.
Can you choke off the opening of webers at a progressive rate to see if things improve?
Something as simple as cardboard with a hole in it?

[scotty54]

The belt was a separate problem, which occurred after removing the accessory drive to fix the oil leaks. All fixed. The timing jump was my fault. I didn't realize what I had done wrong until I was re-installing the belt.

While I was stymied by the advanced timing numbers, the car ran pretty good so I was patient while I addressed other problems. And now that I have the timing down to 40 degrees (at 2000 rpm) I am sure with a few more carb tweaks I can get it to 36 while maintaining good vacuum and idle.

I have not tried choking off the carbs and don't know what any results would mean. I have a new synchrometer now so that will tell me how well the carbs are balanced. Waiting on a Weber tuning manual.

[Cammer-6]

A carb is nothing more than a controlled leak.
you can use this trick to see if they are all balanced