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Old 05-17-2021, 08:43 PM   #1
Model A Ron
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Default High Compression Head Review

Well I took everyone's advise and drove my car along with as many Model A's that I could to help decide on what High Compression Head to get.

First off the most performance I had the opportunity to test drive was the Lion Head. This was the most power by far however it does not look stock and to be honest I was not looking to build a race car with an engine that looks modern. My vision was to drive my Model A at a constant 55 to 60mph when needed without turning the engine to fast and keep it looking stock.

Next was the Snyder's 6 to 1 and 5.5 to 1 heads. I had the opportunity to test drive both on Stock Model A's. In my opinion and remember everyone has one....I could not tell a difference between the two. I then watched a recent Paul Shinn video and he did not recommend anything higher than the 5.5 so I went with that one. Paul has done so much to bring younger people into the hobby including myself and I value his opinion.

I installed the head early Saturday morning and since then I have logged 100 miles on it. I now notice that it pulls much better from about 20mph all the way up to 55/60 mph. The engine is still turning to fast in my opinion to go a constant 55/60 but with my soon to get Mitchell OD it should have no problem.

More noticeable than the acceleration is my Model A's new found ability to climb hills. I just went for one of my standard rides through a local State Park with lots of hills. The speed limit is 25 and I always had to drop into 2nd as I would loose speed....with the 5.5 head staying in 3rd was not a problem at all.

I highly recommend the Snyder's 5.5 head and if your on the fence I hope this helps you decide.

Regards,
Ron
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Old 05-17-2021, 09:40 PM   #2
Herb Concord Ca
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Default Re: High Compression Head Review

Watch your spark rod. High compression heads don't need as much advance as a stock head.
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Old 05-17-2021, 10:35 PM   #3
Model A Ron
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Default Re: High Compression Head Review

Quote:
Originally Posted by Herb Concord Ca View Post
Watch your spark rod. High compression heads don't need as much advance as a stock head.
Funny you say that. On my first drive to a car show last Saturday with the 5.5 Head I used less spark and the car started to boil over a little. I went back to half spark advance and the problem went away. When going around 45/50mph I drop it a little more to maybe 60/70% spark and the car runs fine without any knocking or boiling over. This is the exact way I drove it with the stock head. In my opinion full spark advance is just to much for any Model A.....I think that's almost 40 deg. of Spark

Ron

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Old 05-18-2021, 04:47 AM   #4
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Default Re: High Compression Head Review

The whole thread is good, plus see the clamp I made to limit max advance:

https://www.fordbarn.com/forum/showt...el#post1872892
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Old 05-18-2021, 07:10 AM   #5
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Default Re: High Compression Head Review

Quote:
Originally Posted by Model A Ron View Post
Well I took everyone's advise and drove my car along with as many Model A's that I could to help decide on what High Compression Head to get.

First off the most performance I had the opportunity to test drive was the Lion Head. This was the most power by far however it does not look stock and to be honest I was not looking to build a race car with an engine that looks modern. My vision was to drive my Model A at a constant 55 to 60mph when needed without turning the engine to fast and keep it looking stock.

Next was the Snyder's 6 to 1 and 5.5 to 1 heads. I had the opportunity to test drive both on Stock Model A's. In my opinion and remember everyone has one....I could not tell a difference between the two. I then watched a recent Paul Shinn video and he did not recommend anything higher than the 5.5 so I went with that one. Paul has done so much to bring younger people into the hobby including myself and I value his opinion.

I installed the head early Saturday morning and since then I have logged 100 miles on it. I now notice that it pulls much better from about 20mph all the way up to 55/60 mph. The engine is still turning to fast in my opinion to go a constant 55/60 but with my soon to get Mitchell OD it should have no problem.

More noticeable than the acceleration is my Model A's new found ability to climb hills. I just went for one of my standard rides through a local State Park with lots of hills. The speed limit is 25 and I always had to drop into 2nd as I would loose speed....with the 5.5 head staying in 3rd was not a problem at all.

I highly recommend the Snyder's 5.5 head and if your on the fence I hope this helps you decide.

Regards,
Ron
Great looking engine compartment. Nice job.

Enjoy.
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Old 05-18-2021, 07:13 AM   #6
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Default Re: High Compression Head Review

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Quote:
Originally Posted by Model A Ron View Post
Funny you say that. On my first drive to a car show last Saturday with the 5.5 Head I used less spark and the car started to boil over a little. I went back to half spark advance and the problem went away. When going around 45/50mph I drop it a little more to maybe 60/70% spark and the car runs fine without any knocking or boiling over. This is the exact way I drove it with the stock head. In my opinion full spark advance is just to much for any Model A.....I think that's almost 40 deg. of Spark

Ron
I did two things to my A. 5.5 heads and the NuRex centrifugal advance kit.
My spark advance is still hooked up, and looks stock, but you do not have to
move it. The lever stays in the 0 degree' position all the time, and my temp
moto meter gauge runs at a quarter up from the bottom.
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Old 05-18-2021, 07:34 AM   #7
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Default Re: High Compression Head Review

Shinn has good videos but I disagree with the comment of going with a 5.5 and not 6.1.

I originally went with a 5.5 Snyders and liked it so much that I changed to a 6.1. Yes, you can tell the difference between the 2.

The price is about the same, so why not go with a 6.1.

Hill climbing is better and easier on the engine, your takeoff is quicker.

As far as going with a Mitchell. You might want to look at some of the other alternatives out there, F150, T5, etc. Mitchell does NOT have a first gear synchro and you need 2 separate boxes to get overdrive and Syncro and they are at least $1k over the others.
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Old 05-18-2021, 08:04 AM   #8
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Default Re: High Compression Head Review

The reason you don't see much of a difference between 5.5 and 6 to 1 is based on two reasons.. one, there isn't that much increase in compression between the two.The second is a little more difficult to explain, it involves matching all the engines systems. The model a ford engine stock was detuned, its low compression and small carburetor (flows at about 80 CFM (cubic feet per minute air flow),the engine flows at about 170CFM) work together to keep efficiency down...so to gain maximum efficiency from the compression increase, you have to add fuel as well. Efficiency as stated implies use of the power the engine is capable of.
When you do raise the true efficiency of the engine, less heat is lost. Stock model a engines have exhaust manifold issues due to this, the engines efficiency is low, and that creates high exhaust temperatures, and ultimately higher engine temperatures if the timing isn't controlled correctly.
A modified flathead A engine, where fuel, compression, timing and cam design are improved will develop about double the stock horsepower through efficient use of its displacement. As a benefit, the engine runs cooler and uses less fuel.. hard to believe but true, performance and efficiency go hand in hand. Drivability? that wonderful low end torque that makes a stock engine so nice to drive is basically doubled, and with a a B profile cam it will develop it to 2900 rpm.. power to run suburban boulevards alone, power for safety without the protection of the convoy..
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Old 05-18-2021, 08:08 AM   #9
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Default Re: High Compression Head Review

I have a "T5 World Class" transmission, 5.5 head, 3.78 rear, and it performs beatifully! Smooth shifting, can downshift into first gear at 10-12 MPH (smooth as silk), use 4th gear on local roads and 5th gear on open highways, trip MPG is 21 +, at 55 MPH in 5th gear the RPM's are at 2200, and you only have to deal with one shift lever. This is not a knock on the Mitchell as I know several "A" owners who have them and love them. I think you will be very happy with either one. Good luck! GD
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Old 05-18-2021, 08:10 AM   #10
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Default Re: High Compression Head Review

Quote:
Originally Posted by old31 View Post
Shinn has good videos but I disagree with the comment of going with a 5.5 and not 6.1.

I originally went with a 5.5 Snyders and liked it so much that I changed to a 6.1. Yes, you can tell the difference between the 2.

The price is about the same, so why not go with a 6.1.

Hill climbing is better and easier on the engine, your takeoff is quicker.

As far as going with a Mitchell. You might want to look at some of the other alternatives out there, F150, T5, etc. Mitchell does NOT have a first gear synchro and you need 2 separate boxes to get overdrive and Syncro and they are at least $1k over the others.
In my opinion nothing changes a model a more than running a modern transmission, the whole feel of it, the model a feel, is gone..oh,and there is nothing like feeling the 26% mitchell with a 3.78 rear pulling 2nd low and high..basically 5 to 45 mph (or higher) in the torque band with one quick shift..
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Old 05-18-2021, 08:17 AM   #11
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Default Re: High Compression Head Review

Quote:
Originally Posted by Model A Ron View Post
Funny you say that. On my first drive to a car show last Saturday with the 5.5 Head I used less spark and the car started to boil over a little. I went back to half spark advance and the problem went away. When going around 45/50mph I drop it a little more to maybe 60/70% spark and the car runs fine without any knocking or boiling over. This is the exact way I drove it with the stock head. In my opinion full spark advance is just to much for any Model A.....I think that's almost 40 deg. of Spark

Ron
Quote:
Originally Posted by jayvee34 View Post
I did two things to my A. 5.5 heads and the NuRex centrifugal advance kit.
My spark advance is still hooked up, and looks stock, but you do not have to
move it. The lever stays in the 0 degree' position all the time, and my temp
moto meter gauge runs at a quarter up from the bottom.

It has been my experience that controlling ignition timing is VERY over-rated on a Model-A engine. Most people do not understand the fundamentals of a Model-A engine yet tend to use characteristics and practices of a modern V8 engine tuning to dictate how the ignition timing on a Model-A engine should be done. This leads to WAY more problems than it corrects IMO!!

To begin with, most 'modern era' engines built in the last 5-6 decades have much greater (higher) compression ratios than what most Model-A engines will ever see. Additionally, the feet per second of piston travel in a typical Model-A engine are almost always one-half the speed, -and sometimes as much as one-third of the speed of a 'modern era' engine. Additional ignition timing is needed for higher compressions due to the mixture being harder to ignite and completely spread. Also, the speed of flame travel is slower when there are obstacles such as domed pistons. And, at higher RPMs the flame travel can be slower than the piston motion where a "head start" of the air/fuel ignition is needed to ensure complete ignition just as the piston has reached TDC. None of the above applies to a Model-A engine since it has lower compression (-under 7:1) where the mixture is easier to ignite, the piston does not have an obstacles to overcome which would require additional ignition time, and it is a slow-spinning engine which does not "outrun" the mixture's flame travel. This is why distributers with centrifugal and vacuum controlled advancing is required on 'modern era' engines using a much wider RPM and Power band of operation. None of these reasons for needing this apply to a Model-A engine!

There really only needs to be two to three ignition timing settings throughout the entire RPM of a Model-A engine being driven normally on streets & highways. The first one is a setting to make the electric starter easier to rotate the engine during the starting process. Many drivers omit the need for this timing location. Generally speaking, a Model-A engine will start with 15 of total timing which is the primary setting for low-speed driving (spark lever around the 9 o'clock position). At RPMs over 2,000 of operation, the driver can advance the spark lever for a total advance of around 28-30. THAT is all that is needed to have a perfectly healthy engine, ...and this even includes using a high-compression head on a Model-A engine. Any type of special distributer that advances or decreases the timing on its own is just not necessary any more than requiring an automatically shifted transmission or power-assisted braking to make a Model-A safe to drive.

One other thought to prove my point. These vehicles and their engines were designed for Ladies to operate them. As a general rule, these Lady drivers did not understand the fundamentals of spark timing location, nor how to fine-tune the Carburetor's GAV, or other facets of operation. A Lady could operate her Model-A by leaving the spark lever in one location from starting to driving without a single issue nor any harm to the engine. Today, if someone is concerned after adding a higher compression ratio cylinder head, then follow the same timing as original and just increase the octane of the fuel which will curb any detonation. Many hobbyists today try to over-think what is necessary for reliable performance and operation by trying to add all of these modifications under the mindset that they are required to be able to drive it in today's environment.
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Old 05-18-2021, 08:23 AM   #12
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Default Re: High Compression Head Review

Power assisted brakes and automatic transmissions do not improve engine efficiency, precise timing at all rpm ranges of operation offered by a mechanical advance distributor does.. perhaps this is why Ford engineering adopted it with the 'New and Improved' 4 cylinder of 1932..
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Old 05-18-2021, 08:31 AM   #13
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Default Re: High Compression Head Review

Quote:
Originally Posted by old31 View Post
Shinn has good videos but I disagree with the comment of going with a 5.5 and not 6.1.

I originally went with a 5.5 Snyders and liked it so much that I changed to a 6.1. Yes, you can tell the difference between the 2.

The price is about the same, so why not go with a 6.1.

Hill climbing is better and easier on the engine, your takeoff is quicker.

As far as going with a Mitchell. You might want to look at some of the other alternatives out there, F150, T5, etc. Mitchell does NOT have a first gear synchro and you need 2 separate boxes to get overdrive and Syncro and they are at least $1k over the others.

I realize Ron will take offense to this however I find this being the typical mindset of today. Ron has given a public review or recommendation, ...and ultimately given advice that will likely affect someone's decision in the future. Ron is a relatively new Model-A owner who IMO lacks enough first-hand experience to actually guide others in this regard. To further add to this, Ron is not an engine rebuilder or restorer who has first-hand experience with both cylinder heads where an accurate comparison can be made. Therefore, this entire recommendation IMO is based on an opinion where there is no foundation other than hearsay for comparison.
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Old 05-18-2021, 09:01 AM   #14
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Originally Posted by Jack Shaft View Post
Power assisted brakes and automatic transmissions do not improve engine efficiency, precise timing at all rpm ranges of operation offered by a mechanical advance distributor does.. perhaps this is why Ford engineering adopted it with the 'New and Improved' 4 cylinder of 1932..
John, what was the speed difference between the Model-A and Model-B? One is 60 and one is 85 mph. More RPMs to accomplish this. Higher RPMs require more total timing.
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Old 05-18-2021, 09:25 AM   #15
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We are both mechanics Brent,we both understand the combustion efficiency of proper timing at all rpms.Was the stock model a's manual advance effective? Without a doubt, it would not have endured for 90 years.Im approaching the discussion from a different view is all.
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Old 05-18-2021, 09:33 AM   #16
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Default Re: High Compression Head Review

One thing that I think can be hard for outsiders reading a discussion like this is to distinguish between someone saying "this is how I prioritize the trade-offs for this particular decision, I did it this way, and I got the results I wanted" versus "this way is good and the other ways are bad." Because the typical owner isn't going to be pushing their engine's performance limits in any way, there's a lot of room for multiple approaches that "work."
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Old 05-18-2021, 09:41 AM   #17
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Quote:
Originally Posted by BRENT in 10-uh-C View Post
I realize Ron will take offense to this however I find this being the typical mindset of today. Ron has given a public review or recommendation, ...and ultimately given advice that will likely affect someone's decision in the future. Ron is a relatively new Model-A owner who IMO lacks enough first-hand experience to actually guide others in this regard. To further add to this, Ron is not an engine rebuilder or restorer who has first-hand experience with both cylinder heads where an accurate comparison can be made. Therefore, this entire recommendation IMO is based on an opinion where there is no foundation other than hearsay for comparison.
Brent
No offense taken at all as I was expecting your comments to come. I simply took the advise to drive my car and experience the cars that different people have prior to making a decision. With this first hand experience, (Not HEARSAY) I made the right decision for myself. I was simply giving my opinion after driving cars with both heads. See my quote below from my original posting:

" In my opinion and remember everyone has one....I could not tell a difference between the two"

I am sure that someone with your experience and expert knowledge can tell the 2.75 HP difference between the 5.5 and 6.0 head and I am very happy for you. Unfortunately I could not tell the difference. If I were going for high performance based on my experience I would have went with the Lion Head however that was not the direction or vision I have for my car. We are talking about a Model A hear not a tricked out Mustang.

But what do I know? I am just a guy in my late 40's who just learned how to change my oil......for some on hear I need to point out that this is Satire

Thanks again for the expected and predictable response.

Regards,
Ron
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Old 05-18-2021, 09:54 AM   #18
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Default Re: High Compression Head Review

Quote:
Originally Posted by alexiskai View Post
One thing that I think can be hard for outsiders reading a discussion like this is to distinguish between someone saying "this is how I prioritize the trade-offs for this particular decision, I did it this way, and I got the results I wanted" versus "this way is good and the other ways are bad." Because the typical owner isn't going to be pushing their engine's performance limits in any way, there's a lot of room for multiple approaches that "work."
I agree with your statement however some people do not like the old saying of "To Each Their Own".

Some people like "My way or the Highway", if you do not like it your wrong lol
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Old 05-18-2021, 09:56 AM   #19
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Quote:
Originally Posted by BRENT in 10-uh-C View Post
It has been my experience that controlling ignition timing is VERY over-rated on a Model-A engine. Most people do not understand the fundamentals of a Model-A engine yet tend to use characteristics and practices of a modern V8 engine tuning to dictate how the ignition timing on a Model-A engine should be done. This leads to WAY more problems than it corrects IMO!!

To begin with, most 'modern era' engines built in the last 5-6 decades have much greater (higher) compression ratios than what most Model-A engines will ever see. Additionally, the feet per second of piston travel in a typical Model-A engine are almost always one-half the speed, -and sometimes as much as one-third of the speed of a 'modern era' engine. Additional ignition timing is needed for higher compressions due to the mixture being harder to ignite and completely spread. Also, the speed of flame travel is slower when there are obstacles such as domed pistons. And, at higher RPMs the flame travel can be slower than the piston motion where a "head start" of the air/fuel ignition is needed to ensure complete ignition just as the piston has reached TDC. None of the above applies to a Model-A engine since it has lower compression (-under 7:1) where the mixture is easier to ignite, the piston does not have an obstacles to overcome which would require additional ignition time, and it is a slow-spinning engine which does not "outrun" the mixture's flame travel. This is why distributers with centrifugal and vacuum controlled advancing is required on 'modern era' engines using a much wider RPM and Power band of operation. None of these reasons for needing this apply to a Model-A engine!

There really only needs to be two to three ignition timing settings throughout the entire RPM of a Model-A engine being driven normally on streets & highways. The first one is a setting to make the electric starter easier to rotate the engine during the starting process. Many drivers omit the need for this timing location. Generally speaking, a Model-A engine will start with 15 of total timing which is the primary setting for low-speed driving (spark lever around the 9 o'clock position). At RPMs over 2,000 of operation, the driver can advance the spark lever for a total advance of around 28-30. THAT is all that is needed to have a perfectly healthy engine, ...and this even includes using a high-compression head on a Model-A engine. Any type of special distributer that advances or decreases the timing on its own is just not necessary any more than requiring an automatically shifted transmission or power-assisted braking to make a Model-A safe to drive.

One other thought to prove my point. These vehicles and their engines were designed for Ladies to operate them. As a general rule, these Lady drivers did not understand the fundamentals of spark timing location, nor how to fine-tune the Carburetor's GAV, or other facets of operation. A Lady could operate her Model-A by leaving the spark lever in one location from starting to driving without a single issue nor any harm to the engine. Today, if someone is concerned after adding a higher compression ratio cylinder head, then follow the same timing as original and just increase the octane of the fuel which will curb any detonation. Many hobbyists today try to over-think what is necessary for reliable performance and operation by trying to add all of these modifications under the mindset that they are required to be able to drive it in today's environment.
In your opinion, which everybody has one. I like the difference in performance with the mods I have incorporated.
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Old 05-18-2021, 10:01 AM   #20
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Default Re: High Compression Head Review

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Originally Posted by alexiskai View Post
one thing that i think can be hard for outsiders reading a discussion like this is to distinguish between someone saying "this is how i prioritize the trade-offs for this particular decision, i did it this way, and i got the results i wanted" versus "this way is good and the other ways are bad." because the typical owner isn't going to be pushing their engine's performance limits in any way, there's a lot of room for multiple approaches that "work."
amen!!!
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