French Model A aluminum head
 

I mainly hang out on the early V8 Forum and Swap section. A friend here in France got this head in a load of Model A junk.Its used and appears to have been resurfaced.It has 2 spark plugs per cylinder.Made in Lyon France and when I have no idea.Any thoughts? Thanks

Re: French Model A aluminum head
 

Almost feels like they took a standard head and drilled new plugs wherever there was room to put them, not like where it made sense to put them.

Re: French Model A aluminum head
 

I'd say it is aero-inspired.

I have a dual-plug Funk head in my collection that was made for use on an inverted Model-A/B engine mounted on a Funk aircraft. The compression ratio on the Vevet looks to be low which generally indicates it was not a power-adder or a racing head. Again, likely used on a Model-A powered airplane.

Re: French Model A aluminum head
 

It is interesting that there is more carbon buildup on the #1 and #4 cylinders. I wonder if it had to due with the plug placement.

Re: French Model A aluminum head
 

The nature of the flame front is going to be different in 1/4 vs 2/3, which means that it's impossible to optimize your timing. Half the cylinders will always have slightly incorrect timing, so it's not surprising to see carbon buildup in half of them.

Scalded Dog did their dual-plug head as shown below, with the aid of computers and a lot of testing, so you can imagine that a design with both plugs located at the same edge of the combustion chamber might not be the optimal arrangement.
https://2f685466824b0d462892-feca951...1608144695.jpg

Re: French Model A aluminum head
 

My guess was aircraft also. Here is a head for a Pietenpol.

Re: French Model A aluminum head
 

Dual spark plugs are fine. How do they mount the dual distributors/magnetos? Do they use a special cam shaft with dual gears? Dual mags on an engine can pick up the speed of the engine about 50 RPM. I'd really like to see one!
Terry

Re: French Model A aluminum head
 

My old single cylinder BSA motorcycle had dual plugs. It was modified. The coil had two ends. Instead of grounding one end of the secondary, it was lead to a second high voltage connection. One end of the coil when to one plug and the other end went to the other plug. They both fired at the same time.

Re: French Model A aluminum head
 

Mystery over. Not aircraft.My friend a found an ad in his search.That Mfg also made heads and intakes for the conversion for 4cyl and flathead V8.These conversions were designed for the Gazogene Conversion.Here is a link that I found on Google.


https://www.google.com/url?sa=t&rct=...Wk3umqJ-6peQdH


Here is the ad my friend found.The head has compression rating of 8 according to the ad.

Re: French Model A aluminum head
 

The combustion chamber design looks good, a modified heart.. plug placement is interesting, trying to overcome the Siamese port issue..

Ford engineering first used the heart combustion chamber design with the police head in 1931..Yapp's 'computer' designed head uses the same.. the boys at Ford designed theirs with a slide rule

Re: French Model A aluminum head
 

Terry, Running dual plugs was more common in T's than A's. Many used a Stutz distributor, they were nice looking and had 2 caps. They were driven via a side-drive setup, similar to a magneto drive.

Re: French Model A aluminum head
 

I have owned 3 dual plug Model-A/B heads, and most of them use(d) a magneto on a side-drive (powered off the outboard side of the timing gear), and a magneto in the cylinder head in lieu of the regular Ford distributor. I had one set-up that used a Early V-8 Distributor that was mounted onto a Model-B distributor in the normal position. Since the early Ford V-8 distributers were basically two 4 cylinder distributers inside of one housing, it worked fairly well. Nissan dual plug distributors (-with leading & trailing firing) have been converted for use on Model-A/B dual plug applications however I don't have any experience with those. As Jim said above, some have used the Stutz distributer, but those things are REAL expensive when you can find them for sale!! :D

Typically, with the brass-era and A/B engines with dual ignition that I have worked on, the initial timing (BTDC) is set much closer to TDC since you don't need as much lead in the timing to account for flame travel when you have two separate spark plugs lighting the mixture. When only one plug lights the mixture, it typically has only part of that entire mixture that gets lit by the time the piston reaches TDC, so you lose some of the combustion efficiency in that situation. Therefore when all of the fuel & air gets lit, the efficiency is increased which results in a little more RPM increase.




Thank you for sharing this. I would never have thought of the gasifier. Very cool! :cool:

I will tell you that when you look at the Yapp head pictured above which supposedly has 6½ compression ratio, and compare it to the Veyet head in the combustion area and in the area over the piston, it appears the Yapp head has a smaller combustion chamber.

Re: French Model A aluminum head
 

I had a chance to buy a Vevet head several years ago at Rétromobile. Unfortunately, it was for sale with the entire Model A engine and the engine kinda exceeded my suitcase weight allowance :rolleyes:. Here are some photos of it:

https://www.fordbarn.com/forum/attac...1&d=1608286877

https://www.fordbarn.com/forum/attac...1&d=1608286877

https://www.fordbarn.com/forum/attac...1&d=1608286877

https://www.fordbarn.com/forum/attac...1&d=1608286877

https://www.fordbarn.com/forum/attac...1&d=1608286877

https://www.fordbarn.com/forum/attac...1&d=1608286877

https://www.fordbarn.com/forum/attac...1&d=1608286877

https://www.fordbarn.com/forum/attac...1&d=1608286877

https://www.fordbarn.com/forum/attac...1&d=1608286877

Brad in Maryland

Re: French Model A aluminum head
 

Brad, Very interesting! So, they just used two connectors per cylinder and it used the same source for each spark! I was imagining something quite different. Maybe a two tiered dist. cap with a longer shaft, maybe keyed, maybe square to accommodate a special rotor, with wires, not connectors and two pressed in brass "tracks" for the rotor pickups to carry the charge from the coil. Interesting problem!
Terry

Re: French Model A aluminum head
 

[QUOTE=BRENT in 10-uh-C;1963865]I have owned 3 dual plug Model-A/B heads, and most of them use(d) a magneto on a side-drive (powered off the outboard side of the timing gear), and a magneto in the cylinder head in lieu of the regular Ford distributor. I had one set-up that used a Early V-8 Distributor that was mounted onto a Model-B distributor in the normal position. Since the early Ford V-8 distributers were basically two 4 cylinder distributers inside of one housing, it worked fairly well. Nissan dual plug distributors (-with leading & trailing firing) have been converted for use on Model-A/B dual plug applications however I don't have any experience with those. As Jim said above, some have used the Stutz distributer, but those things are REAL expensive when you can find them for sale!! :D

Typically, with the brass-era and A/B engines with dual ignition that I have worked on, the initial timing (BTDC) is set much closer to TDC since you don't need as much lead in the timing to account for flame travel when you have two separate spark plugs lighting the mixture. When only one plug lights the mixture, it typically has only part of that entire mixture that gets lit by the time the piston reaches TDC, so you lose some of the combustion efficiency in that situation. Therefore when all of the fuel & air gets lit, the efficiency is increased which results in a little more RPM increase.

Here again, I'm thinking back to my days in aviation. I believe all the Continental and Lycoming engines had a dual ignition and a four position ignition switch, off, right mag, left mag, and both mags, Prior to take off, we always did a a run up. This involved bringing the engine to 1650 rpm and switching to say, left mag, check rpm (Shouldn't be lower than 1600). Right Mag (Same drop) and then back to both mags. RPM should increase to 1650. So, running on individual mags gave us 50 less rpm. I realize that the purpose of dual mags was not to gain the 50 rpm, but increased reliability and a lessened chance of engine failure due to a faulty ignition. But the dual ignition was a true dual ignition with two separate mags.
Terry

Re: French Model A aluminum head
 

When you look close at the pictures, it appears that the "Yapp" head is machined deeper in the portion over the valve heads.

Re: French Model A aluminum head
 

Interesting discussion about multi plug engines, some dyno testing has shown the Yapp Lion head likes just a bit of stagger between the firing of the plugs.

Brass era cars had multiple plugs, this is a Buddy's Pierce Arrow Roadster small inline six (540 cu in approx)
It has 3 plugs per cylinder, a mag that fires 2 and dist for 1.

Dist is used for starting and turned off once running.

Re: French Model A aluminum head
 

Terry, the difference is Redundancy vs. Complete Combustion. In an aero-inspired engine, the main intent was to have a back-up plan when the first ignition system failed. In racing and early era engines, even those seem similar by design, the intent was different. The brass-era/early-era vehicles had poor combustion chamber designs, and flame travel across a large bore piston was pitiful, -especially at low RPMs. Therefore having two separate ignition sources from opposing locations within the combustion chamber allowed for the fuel mixture to be ignited nearly simultaneously within the cylinder. This simultaneous combustion allowed the charge to provide a bigger push on the piston creating more power. The racing applications liked the dual ignition because not only for better combustion efficiency, but also the advantage of not needing to have as much total ignition timing. Less chance of detonation caused by too much ignition timing when two ignition systems are firing simultaneously but at a less total advance, especially across a wide RPM band.


I would guess the reason for the distributor is the mags were not impulse mags, and so it was easier to start with a battery supplying voltage to a coil. This is one area where a Ford Model-T was really superior to other cars who were using Kettering-based ignition systems. An early Model-T (pre-1920) was provided without any battery to aid in starting. These were started by spinning the engine where the magnets created enough AC voltage to ignite a coil. If the engine oil was thick, it hampered the mag output and made the car difficult to start. The same issue applied to a Kettering-based ignition system, however if someone had a dry-cell battery to connect to the Model-T coil box, then the coils could be fired multiple times with every ¼ turn of the crankshaft. This allowed the spark plugs to be self-cleaning when the engine was overly rich on fuel. A Model-T could be started in the coldest of temps when others could not be started in the same type weather. Henry knew this, and this is just another reason why he felt the Model-T was the perfect car.

Re: French Model A aluminum head
 

This method was common on new cars a few years ago; one coil for two cylinders. Interestingly, the spark jumps from the center electrode to the ground electrode on one plug, and from the ground electrode to the center electrode of the companion cylinder. Since the electrode that the spark jumps to wears faster, Ford (and maybe others) used plugs that had platinum on only one electrode. Half were platinum on the center electrode and half were platinum on the ground electrode. We just used double platinum tips when replacing the plugs. This system produces a "waste spark", that is,when two cylinders fire at the same time, one is on the power stroke and the other is on its exhaust stroke. The plug that fires on the exhaust stroke is called a "waste spark".
Now most cars have the coil-on-plug system and each cylinder fires independently.

Re: French Model A aluminum head
 

Having "the same source for each spark" means that only one of the plugs fired at a time, so the only advantage would be longer plug life!

With just one path from the coil to the distributor cap and only one spark being generated by the coil, the spark will only fire one of the plugs, whichever one requires the least voltage. To fire both would require a separate coil for each plug (and a modified or second distributor). Or a coil with two leads as described in my previous post.