Concern using a vacuum gauge to time my 1956

[Hillbillycat]

Hi everybody, this is my first post after reading A LOT on this great forum.

Finally had the guts to fiddle with the timing on my 365 using a vacuum gauge, trying to find my engine´s sweet spot. Had the timing set on the "A" mark with a light when I had bought the car 2 years ago but always had the feeling it lacked power. Switched from 95 octane to 98 and 102 (all 5% ethanol) this year but that didn´t change nothing. Then I found the superb instruction on how to time an engine with a vacuum gauge on this forum and went for it. Before anybody asks: The Carter WCFB carburetor had been rebuilt and ultrasoinc cleaned, distributor cap is new, as well as points and condenser, spark plugs, wires and coil. Power brakes work, no evidence of a vacuum leak. Washer motor is the only thing that doesn´t work. Wipers do but not that great (motor is rebuilt).

I get low vacuum about 14-15Hg with timing set to the "A" mark at 1522ft.
I can get nearly 20 Hg before the engine starts to act up using my vacuum gauge. But then the pointer is about 1 1/2" advanceed from the "A" mark. That concerns me. The rubber on the harmonic balancer is very likely still the original one from 1956. Could that cause such a mismatch?
I hear no pinging (maybe don´t know how that should sound) at all. Engine seems to run smoother and purr with 18Hg and I get more low end torque and more punch above 60mph, plus the wipers actually work way better. More than 18Hg and I get hard starts like the piston is kicking back. That tells me it´s too far advanced.

I´m afraid to set timing too far advanced and ruin my eninge. Should I go back to  the "A" mark? The car runs well with that timing but is rather lame. I know they are heavy whoppers and no sports cars. Like I said- I just want to find the sweet spot for best engine performance.

[David Greenburg]

When using a vacuum gauge, I dial it back about 1” from max vacuum.  Old timers told me years ago not to worry too much about the timing marks on an older engine; things slip and wear, and the vacuum gauge approach compensated for this.

[fishnjim]

Have to ask yourself, best performance for what?   
We used to give the distributor a twist, if we were running what we brung at the drag strip, but if you want it to start, run, and have decent fuel mileage and drive train life it's probably best left stock timing.   That's the way it was designed to run*.   The torque curve, etc is based off the gearing and throttle rpms.
Remember the vacuum advance is tied into all that, so you're distorting the advance curve at the same time, and some of these have a vacuum assist pump for wipers, so if you don't do it right, you're just kidding yourself.   You really need a good compression test before you can rely on absolute manifold vacuum readings.   That's one of the "fallacies" of early motor thinking, that the vacuum would tell all.   I don't know of any made today that adjust on vacuum.   It was quick and dirty art.
Invest in a timing light and dwell/rpm meter and set it were it's supposed to be and drive it.   Then you can sneak up a bit, drive for a tank, and see what impact.   If you want it to launch off the line, you wont save fuel.  And that puts extra wear and tear on the drive line.   You really have to take it out and put on a dyno if you want to maximize your engines output.   With those set transmission shift points, I don't think it'll optimize anyway.   Today's computer controlled everything, you can adjust the trans and motor.   Mechanicals are mechanicals and do one job real well.   You'd have to recurve the advance and up the spark energy if you really want that boat to ski and then why not put a hot cam, re-jet the carb, and other things in, and you'll never be satisfied with it but spend a load of money.   aka hot rodding.
* - I used to troubleshoot equipment, and I'd say 90% of the issues were they were running outside of what it was designed to do and just needs to be set back to "normal".   

[D.Yaros]

I agree with DG.  Go with sound and performance.  The timing mark is your "starting point".

[J. Gomez]

Here is one reason you are seeing a low manifold vacuum if your camshaft is the original OEM, there was a changed made with a new camshaft after engines 4X-22787 and 4XK-7452 per the MPL and note under the 1956 February Serviceman. 

[cadman56]

I have rebuilt 4 365 engines.  In all of my cars I set them up this way.
Set dwell to low side of 30 degrees to allow for rubbing block wear and base engine timing to 8 degrees advance at idle in drive.  Vacuum line to distributor is off.  reconnect the distributor after setting timing .
I hook the vacuum gauge to the vacuum pipe that is under the intake manifold and connects directly to the carb.  I then adjust the idle mixture screws to get the best vacuum and idle speed then readjust the carb to good idle speed.  I adjusted mine just hight enough to keep the GEN light from flickering.
When all done I would see between 19-20: Hg at idle in Park and then it would drop a bit when in Drive.  I am in S. Central Kansas so your vacuum readings will probably be a bit different.
I used 91 octane with ethanol gas and mixed Marvel Mystery oil in the tank.  Mixing ratio is on the back label.
I ran my cars hard and when normal driving on highway I would see 16 mpg.

[walt chomosh #23510]

Hillbilly Cat,
  May I suggest you have your harmonic dampner rebuilt before it totally fails on you before timing the motor. I'm with fishinjim and suggest you don't get too far away from factory recommended timing. (your not running any drag races) My 1955 dampner was totally shot when I sent it out to a shop in North West and was VERY pleased. (turn around was quick!) The dampner can be shipped via USPS for a reasonable price....walt...tulsa,ok

[cadman56]

Yes, iit is always prudent to check the harmonic balancer.  All my engines were new rebuilt, by me, and all the harmonic balancers were in good shape and always read correctly at TDC.  In my case, the extra 3 degrees advance gave better performance and drive-ability and mileage with nary a spark knock or engine rattle.
Your case may be different.

[Hillbillycat]

Hi,
thanks for all the answers.
I checked the engine # this morning and it acutally is a later digit with 13-15Hg vacuum being normal. Thank you very much for this specific info. It was the low vacuum reading that made me think my timing was too late in the first place.

I´m living in Germany and will have to see where I can find someone who rebuilds harmonic balancers over here. Is there a way to check if it is deteriorating or having been rebuild in the past. The engine itself had once been sprayed over (in the wrong blue of course :-)), but hadn´t been removed for this purpose - you can detect spray mist on the firewall from improper masking. So I assume it hadn´t been rebuild.

I plan to check if TDC matches with the C mark. Then I can set it back to A and go on from there a few degrees advanced.

[J. Gomez]

If you want/need to check if the harmonic balancer marks are correct you can use a TDC tool to check if the mark are correctly position.

You can Google “TDC tool” and find several sources for them or if you are handy you can make one yourself. Also there are several sites that can provide details as to how to use the tool.

Good luck..!

[bcroe]

If you want/need to check if the harmonic balancer marks are correct you can use a TDC tool to check if the mark are correctly position.

You can Google “TDC tool” and find several sources for them or if you are handy you can make one yourself. Also there are several sites that can provide details as to how to use the tool.   Good luck..!   

I would start with verifying the TDC, as my harmonic balancers often
slipped out of position (or came completely off) after a decade.  You
might be able to make a good mark on a pulley somewhere.  I just
threw these all away and used FluiDampers on all engines, no more
failures.  Bruce Roe