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Old 04-15-2021, 11:41 PM   #1
Model A Ron
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Default SNYDER’S 5.5 head vs 6.1

Below is what Snyder's has on their sight. I see 54.6 HP for the 5.5 head and 57.5 for the 6.1 head. Does that make any real difference in what you will feel when driving?


The A-6010-HC 5.5:1 High Compression Head made 38.16 HP @ 1400 RPM and 143.15 ft lbs of torque and
54.6 HP @ 2500 RPM and 114.7 ft lbs. of torque with the A carburetor.

The A-6010-HC6 6:1 High Compression Head made a little flatter torque in the low range from 42 to 47 HP @
1500 to 1700 RPM and 146.4 ft Ibs of torque and 57.48 HP @ 2500 RPM and 120.75 ft lbs. of torque with
the A carburetor.
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Old 04-16-2021, 12:02 AM   #2
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Default Re: SNYDER’S 5.5 head vs 6.1

Most folks say the difference between the two is not noticeable for normal driving. The only caveat is that the higher the compression, the more critical your timing is, so if you're a set-it-and-forget-it guy on the advance lever, the 5.5 will be more forgiving.
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Old 04-16-2021, 06:15 AM   #3
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Default Re: SNYDER’S 5.5 head vs 6.1

no question- I would go with the 6. still pretty mild.
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Old 04-16-2021, 07:27 AM   #4
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Default Re: SNYDER’S 5.5 head vs 6.1

I have the 5.5 and am very pleased. 28 Special Coupe. 3.70 rear, Mitchell OD. Older rebuilt motor in good shape. Happy cruising at 45/50 with plenty of power. It will go faster but why? 7:00-16 rear tires. Tillotson carb most of the time, Stromberg 97 on a burns intake
just for fun.
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Old 04-16-2021, 07:49 AM   #5
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Default Re: SNYDER’S 5.5 head vs 6.1

5.5 is a copy of the only performance combustion chamber design by Ford engineering for the model A.6.0 is a modified heart design combustion chamber.

The stock model a ford engine suffered from two issues, low compression and inadequate fuel.Building true performance is a sum of all parts,the head will wake it up,a single V8 down draft carburetor (Holley 94 or Stromberg 97) flows air (CFM) at the same rate the engine does,matching CFM flow rates insures adequate fuel at all rpms. A late model B camshaft increases actual valve lift by over .030 and by design builds torque to 2900 rpm,as opposed to the stock A's 2400.

The engine in stock form is pleasant to operate, low rpm torque is what makes it feel good,hop it up? the torque rises right along with it. with a mitchell gear splitter I can be in 'full pull' from ten to fifty miles an hour, you can actually school some folks in traffic
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Old 04-16-2021, 08:15 AM   #6
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Default Re: SNYDER’S 5.5 head vs 6.1

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Originally Posted by Jack Shaft View Post
5.5 is a copy of the only performance combustion chamber design by Ford engineering for the model A.6.0 is a modified heart design combustion chamber.

The stock model a ford engine suffered from two issues, low compression and inadequate fuel.Building true performance is a sum of all parts,the head will wake it up,a single V8 down draft carburetor (Holley 94 or Stromberg 97) flows air (CFM) at the same rate the engine does,matching CFM flow rates insures adequate fuel at all rpms. A late model B camshaft increases actual valve lift by over .030 and by design builds torque to 2900 rpm,as opposed to the stock A's 2400.

The engine in stock form is pleasant to operate, low rpm torque is what makes it feel good,hop it up? the torque rises right along with it. with a mitchell gear splitter I can be in 'full pull' from ten to fifty miles an hour, you can actually school some folks in traffic

So if you could find 5.5 head for a bit less money would you go with that or is the 6.1 worth it? I really do not have the funds for a head right now but I would sure like to have one to go along with the Mitchell that I have on order.
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Old 04-16-2021, 10:26 AM   #7
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Default Re: SNYDER’S 5.5 head vs 6.1

5.5 especially if you are using the stock distributor

Last edited by Jack Shaft; 04-16-2021 at 10:35 AM.
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Old 04-16-2021, 11:13 AM   #8
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Default Re: SNYDER’S 5.5 head vs 6.1

I have the 5.5 head. That's all that was available 11 years ago when I needed one. It replaced a Police head that was on the engine when I bought the pickup.
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Old 04-16-2021, 11:38 AM   #9
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Default Re: SNYDER’S 5.5 head vs 6.1

Do you need to shave /surface the 5.5 or 6.1 prior to installing?
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Old 04-16-2021, 12:33 PM   #10
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Default Re: SNYDER’S 5.5 head vs 6.1

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Do you need to shave /surface the 5.5 or 6.1 prior to installing?
No. It needs to be heat cycled first so the casting with move all it is going to move.

I am not here to dispute what John is saying regarding using a stock distributor, -however the 6:1 head is very, very similar to the 5.9 head that Larry Brumfield produced for years and years. These heads were used by folks with stock Model-A distributors for years. No one ever complained about having detonation issues. IMHO, most of this stuff is 'he said/she said' where someone said you need to have a centrifugal distributer with your 6.0 head or you will blow up your engine. Nothing could be further from the truth.

I have sent a bunch of engines out the door, an every one of them use a Snyders 6:1 that we re-machine the surface (-generally about 0.005") and install. Back when Larry first introduced those heads, 98% of all engines they were installed on were cast bearings. The only bearing failures that were talked about on the forums (Ahooga and the original Fordbarn) back then were generally attributed to poor quality babbitt work. Today, using a 6:1 head does not need anything different than a 5.5 head.
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Old 04-16-2021, 12:56 PM   #11
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Default Re: SNYDER’S 5.5 head vs 6.1

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Back when Larry first introduced those heads, 98% of all engines they were installed on were cast bearings. The only bearing failures that were talked about on the forums (Ahooga and the original Fordbarn) back then were generally attributed to poor quality babbitt work. Today, using a 6:1 head does not need anything different than a 5.5 head.
I mentioned in another thread, back in the '30s 6:1 on poured bearings was the way cars came from the factory, there's nothing weird about it. I agree that the conventional wisdom that HC is bad for bearings assumes that the engine has bad or worn-out bearings to start with.
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Old 04-16-2021, 01:11 PM   #12
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Default Re: SNYDER’S 5.5 head vs 6.1

Ron, the 6.1 head is a no brainer choice. The distributor is not the issue. Knowing how to drive it is. Run your timing the way your engine wants it. Which is the way to drive an A, no matter what head you use. Buy the 6.1, or you will always wonder what your missing. Same price for both.
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Old 04-16-2021, 01:57 PM   #13
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Default Re: SNYDER’S 5.5 head vs 6.1

+/- $30
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Old 04-16-2021, 04:20 PM   #14
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Default Re: SNYDER’S 5.5 head vs 6.1

The tolerance for timing deviation decreases when compression is increased, the 'hammer' effect of detonation increases when you raise compression and efficiency. Detonation can lead to bearing failure. Those are facts, actual practice and anecdotal evidence as Brent cites should bear weight in the decision as well. Me? the overall advantage of running a centrifugal advance distributor is without question, but I understand the desire for the original look.

Those that opt for performance increases without performing all maintenance requirements are asking for trouble and when it occurs they often blame the performance parts for the failure.
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Old 04-16-2021, 04:57 PM   #15
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Default Re: SNYDER’S 5.5 head vs 6.1

5.5 vs 6.0:1 is low, timing isn't an issue at this low of a compression if it's properly timed. If it were a single cylinder flathead, you'd have no problem pull starting it without a compression release valve. Most of you have once in your life while starting your lawn mower.

57 or 54 horsepower, why is this even a discussion? The price is the same. The 3 hp difference is 5%, why would you leave 3 extra hp on the table when you're only dealing with an engine producing hp in the 50's? You'll notice the difference at some point.

A lot of people will pay big $$$ to increase their engine hp 5%.
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Old 04-16-2021, 05:31 PM   #16
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Default SNYDER’S 5.5 head vs 6.1

I have run the 6.1 and the 5.5 Snyder head. I personally prefer the 5.5 for a inexperienced model a driver. The 6.1 runs good but I have to retard the timing a bit more here and there, my “a’s” have the 6.1 with stock distributors Aries exhaust and one has a stipes cam. The Snyder’s head is the best bang for your buck for a model a.


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Old 04-16-2021, 06:47 PM   #17
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Default Re: SNYDER’S 5.5 head vs 6.1

What Brent, and Alex said....go 6.1
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Old 04-16-2021, 08:10 PM   #18
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Default Re: SNYDER’S 5.5 head vs 6.1

So the higher the compression the less spark advance you need and you will need to drop it more when going slow. Basically run the spark in the position the car like.......did I get this right?

Ron
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Old 04-16-2021, 08:31 PM   #19
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Default Re: SNYDER’S 5.5 head vs 6.1

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So the higher the compression the less spark advance you need and you will need to drop it more when going slow. Basically run the spark in the position the car like.......did I get this right?

Ron
Yes and no, it’s not that simple.

You need to meet up with a local Model A club or owner and tour or ride along with them. They’ll give you a lot more hands on info based on real experience, than any website will.
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Old 04-16-2021, 11:16 PM   #20
Model A Ron
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Default Re: SNYDER’S 5.5 head vs 6.1

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Yes and no, it’s not that simple.

You need to meet up with a local Model A club or owner and tour or ride along with them. They’ll give you a lot more hands on info based on real experience, than any website will.
I agree with first hand experience but when deciding on if to get a head and if so a 5.5 or a 6.1 some high level pointers would be appreciated.

Ron
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