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Old 05-27-2010, 05:31 PM   #21
Brad in Germany
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Default French dual spark plug head

At Rétromobile in Paris, France last year I saw this rather interesting Model A head. It was made by the "Etablisement Veyet", Lyon, France.


What does the extra set of spark plugs do? I believe it might have been an attempt to squeeze a little more power out of the smaller AF engine that it is mounted on.

The engine is located in central France. His asking price for the entire engine as pictured is 1500 Euro ($1875.-) and he does not know what the condition of the engine is....

Fordially,
Brad
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Old 05-28-2010, 05:09 PM   #22
Bick in New Zealand
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Default Re: High compression heads?

Bassman,

I'm running a Winfield head, and have been very pleased with the performance and reliabilty.

Cheers
Bick
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Old 05-28-2010, 05:13 PM   #23
Jason in TX
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Default Re: French dual spark plug head

Brad - My guess would be that the engine you are looking at was either originally a fancy speed (they have been made with dual spark plugs for speed. Look at the modern Lion Head)

OR an airplane engine head. redundancy is nice to have in the air, and airplanes had two sets of magnetos. One electrical system goes out, switch over to the other and keep 'em flyin'

I also found this on a Harley website: Interesting Info:

Quote:
In 1917, Liberty Aircraft discovered that simply adding another spark plug to the opposite side of the combustion chamber and increasing the voltage at the plugs would cure detonation and increase power.
The same dual plugging solution was incorporated by Continental and Lycoming in the 1920s and 30s. Primarily used as a safety factor, it also reduced spark plug fouling and detonation and increased RPM..
For exactly the same reasons, your Harley motor can benefit from dual plugging. Dual plugging will “undo” the problems with its combustion chamber design and help your Harley run happily on unleaded gas.
Dual plugging alone of a stock motor will eliminate most detonation, stop plug fouling and hard starting, increase horsepower by five percent or more, increase gas mileage, double spark plug life, and lower emissions. Some tuners have reported six to eight percent increase in gas mileage.


Quote:
Originally Posted by Brad in Germany View Post
At Rétromobile in Paris, France last year I saw this rather interesting Model A head. It was made by the "Etablisement Veyet", Lyon, France.


What does the extra set of spark plugs do? I believe it might have been an attempt to squeeze a little more power out of the smaller AF engine that it is mounted on.

Fordially,
Brad
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Last edited by Jason in TX; 05-28-2010 at 05:31 PM.
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Old 05-28-2010, 05:54 PM   #24
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Default Re: High compression heads?

Quote:
Originally Posted by Elrod View Post
I'm a fan of the Thomas head, but mine has what appears to be a Brumfield profile. Runs great. The carbs need just little more tuning but I like the power that it puts out!
That appears to be an original Thomas head as opposed to a Dan Price reproduction.
Dan told me how to modify one of his heads to get 10 to 1 compression.
After welding the chamber up completely you machine it to look exactly like a flathead V8 Edelbrock head chamber.
I ended up with 11 to 1.
Here's a pic of the V8 chambers..The 4 bangers looks identical.
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File Type: jpg Heads.jpg (10.2 KB, 137 views)
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Old 05-28-2010, 06:47 PM   #25
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Smile Re: High compression heads?

I just put on the Snyders 6:1 head with a touring cam. I can run 65 mph all day and not hear the motor run. Best money ever spent. I also run a 4 speed overdrive.
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Old 06-09-2010, 03:30 PM   #26
Larry Brumfield
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Default Re: High compression heads?

In reference to (#11) Aerocraft's comments above concerning a Brumfield Head, go to and please read my posts numbered 10 and 12 on the thread entitled RE: Rear End Noise Update, June 9, 2010. Thanks

Larry Brumfield
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Old 06-09-2010, 05:10 PM   #27
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Default Re: High compression heads?

Quote:
Originally Posted by Bick in New Zealand View Post
Bassman,

I'm running a Winfield head, and have been very pleased with the performance and reliabilty.

Cheers
Bick
Hi Bick,
Are you the owner of the coupe with 16's, and twin carbs etc?
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Old 06-09-2010, 05:16 PM   #28
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Default Re: High compression heads?

Larry, Nice to see you posting on the "Barn" again. Have missed your posts.
Paul in CT
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Old 06-09-2010, 05:38 PM   #29
Bob A.
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Default Re: French dual spark plug head

Quote:
Originally Posted by Brad in Germany View Post
At Rétromobile in Paris, France last year I saw this rather interesting Model A head. It was made by the "Etablisement Veyet", Lyon, France.


What does the extra set of spark plugs do? I believe it might have been an attempt to squeeze a little more power out of the smaller AF engine that it is mounted on.

The engine is located in central France. His asking price for the entire engine as pictured is 1500 Euro ($1875.-) and he does not know what the condition of the engine is....

Fordially,
Brad
I have dual plugs on my wife's "Hemi" engine. As far as I'm concern,"It squeezers more money out of my wallet" when I have to do a tune up.
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Old 06-09-2010, 10:50 PM   #30
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Default Re: High compression heads?

i have tested for compression on 3 different heads .
stock - 55#
5.5 - 75#
6.1 - 85#

hope this helps .......... steve
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Old 10-11-2018, 06:54 PM   #31
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Default Re: High compression heads?

Quote:
Originally Posted by Jason in TX View Post
I'm a fan of the Thomas head, but mine has what appears to be a Brumfield profile. Runs great. The carbs need just little more tuning but I like the power that it puts out!







Are they 94 Holleys and what jet cofigurations are you using. I have a Riley 2 port head and having trouble tuning them. I've been told that the power valves are the wrong size
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Old 10-11-2018, 07:05 PM   #32
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Default Re: High compression heads?

Quote:
Originally Posted by Lawrie View Post
What sort of cranking pressure do you get with the 5.5 head.
Lawrie
In my tourer, which you know, Lawrie, I get more than others here have said they get - high 90's. Very close to 100 psi in each. That's higher than I would have expected from 5.5:1 compression ratio but that's what it is! Bores are 60 over, FWIW.
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Old 10-11-2018, 07:40 PM   #33
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Default Re: High compression heads?

Quote:
Originally Posted by Niggled View Post
Are they 94 Holleys and what jet cofigurations are you using. I have a Riley 2 port head and having trouble tuning them. I've been told that the power valves are the wrong size
Those appear to be Stromberg's.
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Old 10-11-2018, 08:28 PM   #34
Tom Foster
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Default Re: High compression heads?

Compression (PSI) / 14.7 = compression ratio. Good for rough estimate, no lab glassware needed.
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Old 10-12-2018, 12:11 AM   #35
old31
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Default Re: High compression heads?

Quote:
Originally Posted by karsyn View Post
I just put on the Snyders 6:1 head with a touring cam. I can run 65 mph all day and not hear the motor run. Best money ever spent. I also run a 4 speed overdrive.
x2 with karsyn.
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Old 10-12-2018, 11:57 AM   #36
Jim Brierley
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Default Re: High compression heads?

Just a comment, the pics posted by Jason, niggled, etc. appears to be more like a Winfield chamber. The original Thomas tended to detonate, Winfields did not. On dual plug heads, I ran a big Hall-Scott (5 3/5" bore) on a chassis dyno years ago. They had dual plugs, one on the left side of the head (OHV) one on the right. Each bank was on a separate switch. At idle there was a difference in RPM when one bank was shut off, at full throttle there was no difference in power!
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Old 10-13-2018, 11:47 AM   #37
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Default Re: High compression heads?

Quote:
Originally Posted by Tom Foster View Post
Compression (PSI) / 14.7 = compression ratio. Good for rough estimate, no lab glassware needed.
Fearless
That would be a very rough estimate! Nowhere near accurate! Compression pressure is dependent on several variables such as when intake valve closes, cranking speed, engine temperature, and rate of leakdown.
Compression ratio, on the other hand, is based on two simple measurements: the volume of the combustion space with the piston at BDC, and then the combustion volume with the piston at TDC. Then simple division gives you the correct ratio.
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