5.5:1 Head or 6.0:1 Head?

Thanks gentlemen. I guess I am not the only one to experience issues with trying to see where my settings end up.

Wonder if I can do it with the engine off, and the plugs out. Since I know where my TDC is (pointer and paint on pully) perhaps I can measure how far down on pully when the rotor is in the same spot. Then divide my pullet circumfrence by 360. That will give me a measurement of every degree. Hmmmm.... We set timing statically, maybe there is a way to determine the advance statically.

My light was jumping all over the place when I tried it too.
 
alexiskai said:
I did a video a couple years ago where I explained how to set your advance to a specific number, like 21.5°. Might be useful for you.

https://youtu.be/lrEtQINvCCU?si=YbxpW3bMUO2adHXZ
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Thanks. This is a big help.

With my head I want it to be 22 degrees before when I am driving down the road. I am trying to verify that my spark advance handle stop is in the right spot for my desired 22degrees of max with new points.

My max timing is my critical value, because I do not want to "pound out my babbit".

I will need to adjust a bit for the modern points, because my wrench is not setup for them.

I have my TDC verified with a pointer already. For me I can see the shoulder of my piston with my eyeball.

So why does this BTC firing point change with more RPM? The cam and crank relationship is fixed via the cam and crank gears in the engine. And the dist drive gear is fixed to follow them via the camshaft.

I wonder if I can get my timing light to work with the positive ground to the car from my 12V battery on the garage floor. My light has the correction adjustment.
 
Gene F said:
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So why does this BTC firing point change with more RPM? The cam and crank relationship is fixed via the cam and crank gears in the engine. And the dist drive gear is fixed to follow them via the camshaft.

I wonder if I can get my timing light to work with the positive ground to the car from my 12V battery on the garage floor. My light has the correction adjustment.
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You have asked the $64,000 question, my friend!

Yes, the optimum firing point of the spark for maximum power, the timing of that spark in DEGREES before TDC, increases with RPM. (That's what leads us to use a centrifugal advance, like in the Model B distributor or in the FSI distributor.)

It has to do with the combustion process and how many degrees an engine crankshaft turns per millisecond at a given engine RPM. The fuel needs a certain number of milliseconds between when the spark fires and when the fuel is burning well, so you are timing the spark earlier and earlier at higher RPM to give the fuel the time it needs to burn. This gets the pressure from the burning fuel at the best piston position for best power. There are other things that play into it, but the relationship between timing advance and RPM that asked about is the above: crankshaft degrees per ms at a given RPM.

If you want to go down that rabbit hole, it is fun reading.

Yes, you can use a timing light powered by an external 12 volt battery. I have done it. The timing light does not care. But do NOT connect any lead to the coil post (for RPM and dwell). You need to use another external tach/dwell meter for that.
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Going back to the original topic on compression ratios and head designs, what do you think of the Burtz 6.5 head? It has a similar shape to the Snyder's 5.5 head (second image) but with a divot in the center.
 

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Mike1291 said:
Going back to the original topic on compression ratios and head designs, what do you think of the Burtz 6.5 head? It has a similar shape to the Snyder's 5.5 head (second image) but with a divot in the center.
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The primary advantage of the Burtz head for me is the redesigned water jacket which promotes better cooling of the rear cylinders. The higher compression is nice too. Users report it runs well.
 
Jim16, I have no intention of ever attempting to start the motor with a crank. I don’t even carry the crank in the car.
 
alexiskai said:
The primary advantage of the Burtz head for me is the redesigned water jacket which promotes better cooling of the rear cylinders. The higher compression is nice too. Users report it runs well.
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OK, the Burtz head center coolant passage is like the early version Ford head. Ford then added a center coolant passage claiming it would be an improvement.
If forcing more water to the rear cylinders is best, why did Ford make this change? I'm sure there were plenty of smart people working there at the time.
 
Thanks for that info on degrees Jim much appreciated.

The Snyder's 5.5 heads are 'Temporarily Out of Stock' as of July, 2026, but more are going to be made soon. They are hopefully coming yet this summer. So yes you can still 'buy' them new. They just haven't hit the queue yet.

A major national Model A engine builder told me last month that they like to put the 5.5 head on all of their rebuilds, they have 26 new rebuilt Model A engines with the three main babbitted bearings ready to ship, as soon as they get these heads from Snyders.

They have 100 heads on order!
 
Flathead said:
OK, the Burtz head center coolant passage is like the early version Ford head. Ford then added a center coolant passage claiming it would be an improvement.
If forcing more water to the rear cylinders is best, why did Ford make this change? I'm sure there were plenty of smart people working there at the time.
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The cooling passage in the center of the head was altered twice. Very early cylinder heads (pictured) had no center cooling passage. Sometime in early 28, a round hole was added. In late '29, the hole was further enlarged to an oblong shape. The Service Bulletins state that the reason was to reduce overheating.

However, Terry Burtz has stated that this is... well, a lie. Per Terry, "the sand core that becomes the water jacket needs to be held in place when the mold is filled with molten iron. The large oval hole was the result of a long strong pillar on the sand core that was used to hold the core in place." His theory is that, due to excessive failures in the casting process, Ford gradually increased the support of the sand core at that point. Rather than explain this, the service bulletin writers chose to invent an overheating justification.

Experimentation proves conclusively that, if the changes to the head were to reduce overheating, they didn't work. On the stock head design, cylinders 3 and 4 consistently run hotter (too hot) than cylinders 1 and 2. This is because too much coolant takes a shortcut route up from the water inlet, through the oblong hole, around cyls 1 & 2, and back to the water pump. Cyls 3 & 4 receive significantly less volume of coolant per minute. The Burtz head, which benefits from modern cast iron manufacturing techniques, is able to return to Ford's original, superior design.
 

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I run a Burtz head on an otherwise stock .100 over engine. I can not say enough good things about the results. It netted me an honest three miles per gallon on fuel consumption with a very noticeable power increase. It does require less advance than the stock head. I hade to deepen the recess for the waterpump to properly seat was the only issue I wan into. Dale
 
Dale'45 said:
I run a Burtz head on an otherwise stock .100 over engine. I can not say enough good things about the results. It netted me an honest three miles per gallon on fuel consumption with a very noticeable power increase. It does require less advance than the stock head. I hade to deepen the recess for the waterpump to properly seat was the only issue I wan into. Dale
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You must have gotten an early head (first 100). I had to do the same with mine, Terry Burtz was very kind and walked me through what needed to be done.
 
I have both and agree the 5.5 is ideal, but the 6.1 is fine if you manage the spark advance.The extra power is hardly noticable.
 
Interesting discussion and opinions. Some personal experience:
BF head, babbitt motor, correct head gasket from Larry Brumfileld, proper reach and heat range spark plugs, fully stock ignition. Had an FSI zipper and removed it due to major pinging climbing hills. It was ok on flat terrain. FSI said to change internal springs but found that too complicated. Balanced crank with lt.flywheel, V8 clutch. Need to listen to the motor and adjust GAV , spark advance for varying conditions. Can't set and forget the latter steps.
Adjust stock timing maybe retard rotor a degree or 2 from TDC as needed. Close point and plug gaps very slightly as recommended. Spark advance never below approximately. 9:00 on quadrant.
 
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duke36 said:
Interesting discussion and opinions. Some personal experience:
BF head, babbitt motor, correct head gasket from Larry Brumfileld, proper reach and heat range spark plugs, fully stock ignition. Had an FSI zipper and removed it due to major pinging climbing hills. It was ok on flat terrain. FSI said to change internal springs but found that too complicated. Balanced crank with lt.flywheel, V8 clutch. Need to listen to the motor and adjust GAV , spark advance for varying conditions. Can't set and forget the latter steps.
Adjust stock timing maybe retard rotor a degree or 2 from TDC as needed. Close point and plug gaps very slightly as recommended. Spark advance never below approximately. 9:00 on quadrant.
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Your experience with the FSI zipper is exactly why Detroit eventually went to a combination of centrifugal advance and vacuum advance. The centrifugal advance that you have in the FSI zipper is great for low to moderate load conditions. But you really want to back off a bit under heavier load.


Detroit figured out how to give some advance from centrifugal advance and some advance from vacuum. The nature of vacuum is that it falls off when you step on the throttle. So you lose some of the vacuum advance when the engine is under heavier load. When it’s under lighter load and the vacuum comes back, you get more advanced from that component. It’s a very clever system.

The FSI zipper does not have a vacuum advanced component. As you have discovered, you can manually retard the spark a little bit under heavy load when you use Henry’s spark advance lever. As others have said, you are the engine management computer.
 
This is all very interesting, I was just wondering about this to much compression on a stock bottom end question.


I have a fitment problem I am dealing with right now on a B motor, I acquired that is a mystery engine ( no history ) out of a '32 with a Winfield aluminum model A head with a model A water pump. I do not know what compression the head is rated at but I cant use it anyway.


I am trying to install it in a '33 and need the short water pump, I know that Dan Price makes a copy of the Thomas head that fix's this fitment problem and uses a B water pump. But here is the rub it is 7:1 compression, I am worried it is a little much for a stock bottom end.


Thoughts on this ?
 
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