1965 Ignition Timing

[Brtele]

After I had the exhaust buttoned up last week, the car obviously ran much quieter, but I could now hear detonation/ping during heavy load.  I kept my foot out of the gas and got it back home to start working through items to determine causes.

 

- I'm running 91 octane no ethanol 

- Dwell is dead nuts 30 degrees and doesn't move when I blip the throttle

- Timing set to 2.5 btdc with the vacuum plugged and the idle set to 550ish - holds steady.

- I didn't run the rpms up with the vacuum disconnected from the dist to see what the mechanical advance is.

- I did connect the vacuum back up and ran the rpms up to 1,600 and got a steady timing reading of 38.  Based on the attached graph, that's pretty high for this rpm.

 

I'm going to check my vacuum advance across some points and run through what might be happening (bushings gone, etc.), but ran out of time yesterday - Chiefs game.

 

We'll see what we find, but will keep the group posted.

 

Thanks,

[Brtele]

Forgot to attach the timing graph I'm working from.

 

[gungeey]

So, all stock engine.. and yes too much total advance.Check bushing Stop and likely replace springs

[Brtele]

3 hours ago, gungeey said:

So, all stock engine.. and yes too much total advance.Check bushing Stop and likely replace springs

Yes, all stock ignition (as far as I know - don't know previous history).

 

Agree with your thoughts.  I'm going to further test today/tomorrow.

[joelj]

I would not rule out the possibility that the fuel might be the issue. When I first got my 64 I tried using 89 octane and it would ping when going uphill. When I switched to 93 octane the problem stopped. 91 with no ethanol seems pretty rare (at least in gas stations around me). Summer humidity or low turnover at the pump may be having an affect. It can't hurt o try running some of the fuel out and trying some 93 to see if it makes a difference. My humble opinion based on personal experience.

[Brtele]

Ok, I had a chance to slightly reduce my idle timing and check some various mechanical/vacuum advance points.

 

Again, dwell set dead nuts at 30.

 

Fuel is 91 octane - no ethanol.

 

Spark plugs are .035 gapped R45S plugs

 

Vacuum Blocked - Mechanical Only:

530 - hair below 2

800 - 8

1100 - 13

1600 - 19

2000 - 20 (I should've checked where the mechanical was "all-in", but let's just assume it's 2000 for s&g's)

2300 - 20

 

Vacuum Hooked Back up:

530 - 20

800 - 23

900 - 26

1200 - 33

2200 - 38

anything above 2200 was holding steady at 38.

 

Turned the car off and it started right back up no issues at all.

This morning the car was dead cold and after a single pump - it fired right off - maybe even faster than before.

 

The engine seems to be a little smoother at idle in drive.  I previously had a very slight vibration (felt like a mild cam), which seems to be smoothed out (might be placebo - who knows).

 

Acceleration performance difference was negligible - couldn't tell if it was better/worse.

 

I'm pretty sure I still had some slight detonation at 3/4 throttle when accelerating the car from 20mph to 40ish - it's not there all the time and I kind of have to work to get the engine to do it.  I'm starting to think I need to leave this well enough alone and keep my foot away from that range/situation, enjoy the car and find something else to focus my attention.

 

Please let me know if you guys/gals read anything way out of line.

 

Thanks again, 

Brandon

 

[Seafoam65]

Your car shouldn't ping on 91 octane gas.......try pouring some  B12 chemtool carb cleaner down

the throat of the carburetor very slowly while the engine is running. This will knock the carbon deposits off

the top of the pistons and may solve your detonation problem. 

[Jim Cannon]

I plotted your numbers on your timing chart.  I think you are a bit too advanced at low RPM and then your mechanical should keep going up at higher RPM (not stop at 20 deg.).

[Brtele]

10 minutes ago, Jim Cannon said:

I plotted your numbers on your timing chart.  I think you are a bit too advanced at low RPM and then your mechanical should keep going up at higher RPM (not stop at 20 deg.).

 

I agree Jim.  I might run the numbers again for a 3rd and 4th time just to make sure my numbers are accurate - it's a little tough doing it with two hands - might get the wife to come out and hold the throttle steady (yeah right).

[Brtele]

1 hour ago, Seafoam65 said:

Your car shouldn't ping on 91 octane gas.......try pouring some  B12 chemtool carb cleaner down

the throat of the carburetor very slowly while the engine is running. This will knock the carbon deposits off

the top of the pistons and may solve your detonation problem. 

I recently (1 gas tank ago) ran a can of BG 44K through the system (via the fuel tank).

[1965rivgs]

4 minutes ago, Brtele said:

I agree Jim.  I might run the numbers again for a 3rd and 4th time just to make sure my numbers are accurate - it's a little tough doing it with two hands - might get the wife to come out and hold the throttle steady (yeah right).

  Use the curb idle speed screw or the fast idle speed screw. I'm assuming you are using a dial back timing gun?

Tom Mooney

[Brtele]

11 minutes ago, 1965rivgs said:

  Use the curb idle speed screw or the fast idle speed screw. I'm assuming you are using a dial back timing gun?

Tom Mooney

Yes, a dial back gun

[EmTee]

Run a couple of tanks with Techron in it.

 

[telriv]

BG is head & heels over Techron in my opinion.

 

Tom T.

[Brtele]

Last night I was able to pull the initial timing back to 0.5-1 without vacuum.  I ran the timing up with/without vacuum, but forgot to take a pic of my readings so I could post (will post later).  The car didn't seem to "hate the 1 degree reduction, and most importantly - I no longer had detonation when loading up a hill from 20-40 mph.  I wasn't able to get it out on the highway to see what it felt like, but am very happy I'm somewhat out of a danger-zone.  

 

The car restarted a couple of times very easily.  Will be interesting to see if it still starts easily dead cold.

 

Thanks for all the guidance.

[XframeFX]

That frequent AWOL mechanical bushing. I can't remember if a brass replacement can be installed without pulling out the shaft. I have my distributor out now for heater core replacement.

Can be installed without disassembling?

[Wayne R]

Idle speed and especially mixture adjustment, iv   have noticed over the years are  way out, alot.

When i lived in Sacramento i was adjusting  Buick club friends  carbs  quite abit,.

After you have car running as best you can,  checking the idle mixture needles is  critical and  your car should be at normal operating

temperature.---turn each slotted  mixture screw clockwise one at a time until it just slightly drops in revs a fraction-- then go back turn

anti clockwise slowly until  it does the same drops a fraction .---now here is where its critical-instead of turning back to aprox the middle  halfway of 

the lean and rich,---after it just drops in revs a fraction in the anticlockwise direction, turn very slowly to clockwise direction,---until it runs  as smooth as possible--that usually is only about 1/8th to 1/4 inch of a turn.--this gives the carb the maximum fuel required .and allows for high and low speed operation  at its best in all temperatures.  i used to find alot  other friends Buicks were adjusted a little lean ,some even adjusted them so the screw slots were even.

Its easy to do, be patience  .  then just check your idle speed last.

I have owned  four nail heads  all 401ci,  and when tunned  correctly  they run as smooth as silk---Thank you.  hope this helps a few.

[OldGerman]

On 11/2/2022 at 5:24 PM, Jim Cannon said:

I plotted your numbers on your timing chart.  I think you are a bit too advanced at low RPM and then your mechanical should keep going up at higher RPM (not stop at 20 deg.).

 

Just checked my vaccum advance (1963 401 cui) with vacuum pump and timing light at idle rpm. Could only add about 15 deg advance with pumping 20HG. That seems to be a bit low advance deg. to me. There is no spec. In the Shop manual, just the Graph . The graph would tell me something between 15-20* vaccum advance at lowest rpm ( idel) without mechanical advancein Action.  Is that right ? The diaphragm seems to Hold the vacuum. 

[Jim Cannon]

6 hours ago, OldGerman said:

Just checked my vaccum advance (1963 401 cui) with vacuum pump and timing light at idle rpm. Could only add about 15 deg advance with pumping 20HG. That seems to be a bit low advance deg. to me. There is no spec. In the Shop manual, just the Graph . The graph would tell me something between 15-20* vaccum advance at lowest rpm ( idel) without mechanical advancein Action.  Is that right ? The diaphragm seems to Hold the vacuum. 

Do not use the 1965 vacuum advance chart for your '63.  Get the chart from the '63 shop manual.

 

15 degrees of maximum vacuum advance sounds about right.  It is added to the centrifugal advance at higher RPM.

 

 

[XframeFX]

1 hour ago, Jim Cannon said:

Get the chart from the '63 shop manual.

 

1963:

 

Of all varieties of vacuum advance pots, only the B1 is left in production. Luckily, this is the correct unit for the 1963 Delco 1110993 Distributor.

My test on a new B1: Starts @ 7.5 - Max @ 15.5'Hg   Total stroke is .132"

So, 15° with vacuum advance is within spec.

I hope this helps Frank

Spec:

 

[OldGerman]

@ John & Jim, Thank you, that helps a Lot !

At least I figured out vacuum and centrifugal are within spec.

Manifold vacuum is low, and break performance is weak.

Will search for a vacuum leak and test the check valve next.

[XframeFX]

14 hours ago, OldGerman said:

Manifold vacuum is low, and break performance is weak.

I too was chasing vacuum leaks. Recently discovered Felpro gasket set has steel shims for the intake manifold. Had I known, I would've re-torqued the bolts. 

The same set had composite head gaskets that were blamed for leaking at the oil ports. Composite/Steel Shims? Felpro had it backwards!