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Old 05-24-2021, 11:03 PM   #1
Model A Ron
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Default 5.5 Head Spark Advance

I have been finding the right spark advance position for my 5.5 head. I start in the fully retarded position and quickly drop down a few clicks. When I get to about 20 I drop it to 1/2. By keeping at a constant 45mph I advance the spark until I no longer feel an increase in power and then back up one click. What I have found is that I cannot make my car ping even with full spark advance however the car seems to now like about 3/4 advance. Going up a hill i retard the spark to 1/2 just to be on the safe side. Does this sound about right to the people with a 5.5 Head?

Also I have found that my Model A runs cooler. Its been getting into the low 90's around hear and my Motometer is just registering a tad bit when the car is running. When I turn it off it jumps to about 1/2 when hot. Shortly after starting it hot it quickly drops from 1/2 to just about showing some red. Is this what your seeing as well?

I appreciate your feedback as I value to hundreds of years of experience you all have.

Thanks
Ron

Last edited by Model A Ron; 05-24-2021 at 11:10 PM.
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Old 05-24-2021, 11:14 PM   #2
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Default Re: 5.5 Head Spark Advance

When you say "runs cooler", I assume you mean than it did before.
The higher compression head improves the efficiency of the engine some so less fuel goes to waste heat and more goes into useful power. The other common cause of unintended engine heat is running too retarded on the spark. You may be finding a better spark advance point now because you are paying attention to it more.
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Old 05-24-2021, 11:20 PM   #3
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Default Re: 5.5 Head Spark Advance

Pull the spark down until you just start to hear pinging when pulling, then lift it a click or two until it stops pinging. If you cannot get it to ping at all, with lever all the way down, id say you arent hearing it or your lever/timing needs adjustment.
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Old 05-24-2021, 11:24 PM   #4
Model A Ron
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Default Re: 5.5 Head Spark Advance

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Originally Posted by GeneBob View Post
When you say "runs cooler", I assume you mean than it did before.
The higher compression head improves the efficiency of the engine some so less fuel goes to waste heat and more goes into useful power. The other common cause of unintended engine heat is running too retarded on the spark. You may be finding a better spark advance point now because you are paying attention to it more.
GeneBob
You are right that I am paying more attention to it. With the stock head I ran 1/2 advance and bumped it a few clicks down when I went over 40 and just above full spark advance between 45 and 50. The weather was 10 to 15 degrees cooler and my Motometer would be between 1/3 to 1/2. Now its showing 1/8 maybe a tad bit more but not much at all.

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Old 05-24-2021, 11:29 PM   #5
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Default Re: 5.5 Head Spark Advance

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Originally Posted by eagle View Post
Pull the spark down until you just start to hear pinging when pulling, then lift it a click or two until it stops pinging. If you cannot get it to ping at all, with lever all the way down, id say you arent hearing it or your lever/timing needs adjustment.
I have an open car and to be honest its loud once you get moving. I have been listening and I just do not hear a ping. When holding 45 and advancing without giving any more gas I can feel the power increase once I do not feel an increase I back off one click. When I look I am at 3/4 spark advance.

I guess what I am saying is that I now use the spark advance by feel and I did not do that with my stock head. Is my method sound?
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Old 05-25-2021, 06:14 AM   #6
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Default Re: 5.5 Head Spark Advance

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Ron, You are doing all the right things with the spark advance. My only advice is that you are being too conservative when going up a hill and should search for the sweet spot (knee) like you do on the level.

My hearing is almost gone so there is no listening for pinging for me. I just search for the sweet spot like you do.
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Old 05-25-2021, 06:23 AM   #7
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Default Re: 5.5 Head Spark Advance

Ron, my roadster has a 5.5 Snyder head. It is bored out 125 thou, giving an increase in CR to about 6:1.
I was running it up to a very audible ping and then back 1 click. This was about 28 deg on my strobe light from memory. I dropped the sump to check bearings after 25000 miles on an engine built by Shwalms.
Babbitt mains were good but every rod babbitt was cracked on the top thrust side. One rod had a loose piece where the tinning had not taken on the rod. I sent photos to Snyders and the comment back from Ora Landis at Schwalms was "you may wish to back off a bit on your ignition timing".
I ordered new Snyders rods with shells, adjusted the caps half a thou closer to get 0.0015 inch bearing clearance instead of the 2 thou when first fitted. I then changed my timing procedure to advance until no more power was felt on an uphill pull at 55 mph. This turns out to be 23 degrees advance and I have since found others on forums stating this is enough too. It is quite a way back from "just less than pinging"
Since then I also tried 95 or 98 octane fuel and the engine feels even happier on hills in top gear at 35 mph.
I have always changed into 2nd overdrive from top non o/d (Mitchell o/d) before I reach 30 mph so as never to lug the engine.
Static timing is set at 5 deg after tdc to avoid busting 6 voltstarter drives and the lever is above 9 0'clock on the quadrant.
Car is a 1930 roadster with B carb, drilled out A manifold to suit carb, and Stipe IB330 camshaft.
I retard the ignition at traffic lights then advance to the limit-stop I put on the quadrant at 23 degrees and then don't touch the timing again from 30 in top to max speed, which is more than 75 mph. I backed of at 75 and only do this to check carburettion by doing a plug chop.
Car runs below 160 deg always and has a 160 thermostat.
Our Tudor is similarly tuned and set, but bore is 60 thou over and cranking pressure about 85 psi. Roadster is 95 psi.
All only my opinion of course but based on careful observations, and monitoring of things like exhaust valve temperatures with various settings etc etc.
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Old 05-25-2021, 07:26 AM   #8
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Default Re: 5.5 Head Spark Advance

I have the centrifugal advice in my car so I don't have mess with my spark control, but
my car does run cooler with the 5.5 head. Here in Florida we are seeing the high 90's degree and an occasional 100 degrees. My Moto Meter shows about 1/4 red on the road @ 45 to 55 MPH and just showing red @ speeds below 45 MPH. Love it.
John
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Old 05-25-2021, 07:45 AM   #9
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Default Re: 5.5 Head Spark Advance

Raising compression raises efficiency, your engine converts more of its heat into power. I run mine in 100 degree plus heat. never have an issue..7.5 to 1 compression..

2 misnomers about correctly increasing a model a engines power...one? its bad for babbit, two? it runs hot.
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Old 05-25-2021, 08:12 AM   #10
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Default Re: 5.5 Head Spark Advance

Quote:
Originally Posted by GeneBob View Post
The higher compression head improves the efficiency of the engine some so less fuel goes to waste heat and more goes into useful power.
This really does not make an engine run cooler, ...actually it makes the engine run hotter due to more fuel being completely burned inside the combustion chamber -and thus creating more BTUs. The major reasoning behind a high-compression head running cooler is the roof of the combustion chamber is lowered which allows for for water passage capacity above the hottest portion of the chamber. This allows for better heat dissipation into the (additional) water.



Quote:
Originally Posted by Model A Ron View Post
GeneBob
You are right that I am paying more attention to it. With the stock head I ran 1/2 advance and bumped it a few clicks down when I went over 40 and just above full spark advance between 45 and 50. The weather was 10 to 15 degrees cooler and my Motometer would be between 1/3 to 1/2. Now its showing 1/8 maybe a tad bit more but not much at all.
It has been my experience that preignition sounds on a L-head (flathead) are different sounding than an OHV engine, therefore many people never recognize a squeaking noise that is the sound of detonation. I would suggest for the interim until you are very familiar with your vehicle's engine, that you step up to using mid-grade or premium fuel. You can probably get away with 5 degrees or so of more advance when using a fuel with an octane rating over 90. This should put you into a safe zone until you have 3-4 thousand miles on your vehicle and can discern a change from normal if you were to use a lower octane fuel.

With regard to your Motometer readings, I am going to suggest reading above about increased BTUs and below about Motometers. It has always been my experience (...and we have installed a bunch of H/C heads over the years) that just installing a H/C head does not drastically lower water temps to the level you are suggesting as indicated on your Motometer. Something else changed if that is happening.



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Originally Posted by jayvee34 View Post
I have the centrifugal advice ( advance ???) in my car so I don't have mess with my spark control, but my car does run cooler with the 5.5 head. Here in Florida we are seeing the high 90's degree and an occasional 100 degrees. My Moto Meter shows about 1/4 red on the road @ 45 to 55 MPH and just showing red @ speeds below 45 MPH. Love it.
John
Again, the high-compression heads do run cooler simply because of more water capacity, ...and not really because of a centrifugal advance.

John, I realize a Motometer is a unique novelty however they are about the worst temperature indicator that someone can use. Most people experience the similar readings with their Motometer simply because at higher speeds/RPMs, the water pump is slinging more water upward into the upper water tank. At those higher RPMs, that water actually splashes onto the bulb of the thermometer which creates a higher reading than just water vapor & air that is surrounding it at lower speeds.


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Old 05-25-2021, 08:36 AM   #11
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Default Re: 5.5 Head Spark Advance

200 HP of gasoline at 20% engine efficiency => 40 HP motive work + 160 HP of waste heat
200 HP of gasoline at 23% engine efficiency => 46 HP motive work + 154 HP of waste heat
or it could be an extra cup of water in the head.
I strongly suspect it is more attention being paid to the spark advance leading to less heating due to spark being retarded.
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Old 05-25-2021, 08:50 AM   #12
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Default Re: 5.5 Head Spark Advance

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Originally Posted by BRENT in 10-uh-C View Post
This really does not make an engine run cooler, ...actually it makes the engine run hotter due to more fuel being completely burned inside the combustion chamber -and thus creating more BTUs.
So wait, your argument is that the stock head runs cooler than a HC head because a stock head experiences higher rates of incomplete combustion? Isn't that a function of the air supply rather than the compression ratio?
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Old 05-25-2021, 09:02 AM   #13
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Default Re: 5.5 Head Spark Advance

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Originally Posted by jayvee34 View Post
I have the centrifugal advice in my car so I don't have mess with my spark control, but
my car does run cooler with the 5.5 head. Here in Florida we are seeing the high 90's degree and an occasional 100 degrees. My Moto Meter shows about 1/4 red on the road @ 45 to 55 MPH and just showing red @ speeds below 45 MPH. Love it.
John
John
Mine seems to be running cooler as well and we are seeing about the same on the Moto Meter but Brent is saying it should run hotter but has more water. I guess we must be doing something different.

We are just not right in the head lol
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Old 05-25-2021, 09:07 AM   #14
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Default Re: 5.5 Head Spark Advance

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Originally Posted by alexiskai View Post
So wait, your argument is that the stock head runs cooler than a HC head because a stock head experiences higher rates of incomplete combustion? Isn't that a function of the air supply rather than the compression ratio?
No, not at all. A stock head does not necessarily run cooler than a H/C head. For the sake of this discussion, the piston is likely going to draw the same amount of air/fuel no matter which head is used, so the BTUs of the fuel mixture is comparable, however several things play into this such as latent heat when the combustion is made which changes because a higher compressing of air increases its heat value. That alone coupled with the burning fuel makes a higher BTU value. Therefore a higher compression head runs hotter inside of the combustion chamber ...however the additional water capacity (of the high compression cylinder head) moving in the head's passages allows for that energy to dissipated much better.
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Old 05-25-2021, 09:09 AM   #15
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Default Re: 5.5 Head Spark Advance

John, I realize a Motometer is a unique novelty however they are about the worst temperature indicator that someone can use. Most people experience the similar readings with their Motometer simply because at higher speeds/RPMs, the water pump is slinging more water upward into the upper water tank. At those higher RPMs, that water actually splashes onto the bulb of the thermometer which creates a higher reading than just water vapor & air that is surrounding it at lower speeds.


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[/QUOTE]

Your explanation sounds reasonable. As long as I don't see it boiling over I
will have to assume it is running cool. I am going to get a laser temp gun and check for the true running temperature. Thanks
John
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Old 05-25-2021, 09:17 AM   #16
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Default Re: 5.5 Head Spark Advance

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Originally Posted by Model A Ron View Post
John
Mine seems to be running cooler as well and we are seeing about the same on the Moto Meter but Brent is saying it should run hotter but has more water. I guess we must be doing something different.

We are just not right in the head lol
That sounds reasonable too!! Especially your last sentence

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Old 05-25-2021, 09:30 AM   #17
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Default Re: 5.5 Head Spark Advance

And here I thought HC heads run cooler because higher combustion pressure the quicker the gases want out. So now I'am wondering just how much more coolant is in a HC head ? A gallon, quart, pint, soup spoon ?
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Old 05-25-2021, 09:33 AM   #18
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Default Re: 5.5 Head Spark Advance

My my...let's review basic internal combustion engine 101..heat is a byproduct of an engine,its power..wasted,not transfered into usable power for driving the car.By raising effciency of the combustion process by increasing cylinder pressure,a higher percentage of combustion effciency is achieved,resulting in less heat needing to be dissipated.

Oh,and my babbit comment? Take a minute and research 'hydrodynamic principle' and see for yourself,its the formula for all journal bearings regardless of composition.
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Old 05-25-2021, 10:17 AM   #19
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Default Re: 5.5 Head Spark Advance

Quote:
I have been listening and I just do not hear a ping.
Could you hear it ping before you replaced the head? Maybe your hearing is like mine, I can't hear the higher frequencies, happens to a lot of us old farts.
I'm considering putting a knock sensor and an indicator light on my CCPU.
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Old 05-25-2021, 10:27 AM   #20
Model A Ron
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Default Re: 5.5 Head Spark Advance

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Could you hear it ping before you replaced the head? Maybe your hearing is like mine, I can't hear the higher frequencies, happens to a lot of us old farts.
I'm considering putting a knock sensor and an indicator light on my CCPU.
I think I have good hearing but then again I could not hear it ping when it had the stock head as well. Maybe I will try to hear it with the car parked in neutral.

The PO timed the can just before I got it and he told me it was timed to TDC
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