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Old 01-07-2020, 10:08 PM   #1
1crosscut
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Default High compression head choice.

I will be installing a Warford overdrive in my 29 AA. I plan to change over to a high compression head. Thoughts on going with the 5.5 to 1 or the 6.0 to 1?

Also are the high compression heads sold by Snyder's and Bert's the same? Price is markedly different between them.
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Old 01-08-2020, 12:56 AM   #2
Russ/40
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Default Re: High compression head choice.

Definitely go for the 6.0 to 1. Spectacular improvement in my light 29RPU. Also you will get the best price from Snyder, same head.
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Old 01-08-2020, 06:40 AM   #3
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Default Re: High compression head choice.

6.0 is a great head.
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Old 01-08-2020, 07:04 AM   #4
David R.
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Default Re: High compression head choice.

What are the advantages to having the high compression heads? What kind of improvements do you achieve in performance? I am currently going through my AA engine. Are there any drawbacks from deviation from stock head?
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Old 01-08-2020, 07:49 AM   #5
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Default Re: High compression head choice.

I went with the 6.0 head and immediately noticed an increase in power, I guess at least 25%. After asking and researching I opted for the 6:0 just because it wasn't that much more money. Very scientific approach I know. But was extremely pleased with the decision.
Remember with the new head you need less advance with the spark level. My 30 liked it at about the 9:30 position, a notch or two above horizonal for regular cruising. The engine temp will let you know where your "sweet spot" is.
"Enjoy the adventure"... Chap
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Old 01-08-2020, 08:27 AM   #6
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Default Re: High compression head choice.

I first went with a Snyder 5.5 head and loved the increase in performance so much that I sold it and went with the Snyder 6.1 head and that was even better than the 5.5 head.

David R, You will notice that hills are much easier to climb. There is less shifting involved becasue you are not always looking for that sweet spot where the engine runs best. Your take off speed will be faster.

You should always take the head to a machine shop and check it for being straight. Both heads had to be straightend a little.

My spark is best at 9-9:30.
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Old 01-08-2020, 09:29 AM   #7
mike657894
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Default Re: High compression head choice.

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Originally Posted by David R. View Post
What are the advantages to having the high compression heads? What kind of improvements do you achieve in performance? I am currently going through my AA engine. Are there any drawbacks from deviation from stock head?
putting more pressure in the cylinder may put more stress on the bottom end.
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Old 01-08-2020, 09:32 AM   #8
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Default Re: High compression head choice.

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Originally Posted by David R. View Post
What are the advantages to having the high compression heads? What kind of improvements do you achieve in performance? I am currently going through my AA engine. Are there any drawbacks from deviation from stock head?
Considered against the range of compression ratios used in the auto industry in the '30s, it would be more accurate to describe the "high compression" 6:1 heads as "normal compression" and the stock head as "low compression." I've never heard anyone report operational issues with the 5.5 or 6.0 heads.
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Old 01-08-2020, 10:37 AM   #9
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Default Re: High compression head choice.

Have the 6.1 running great.
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Old 01-08-2020, 10:42 AM   #10
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Default Re: High compression head choice.

I have an NOS Brumfield head. Anyone have good/bad experience with these?

TOB
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Old 01-08-2020, 12:02 PM   #11
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Default Re: High compression head choice.

Quote:
Originally Posted by David R. View Post
What are the advantages to having the high compression heads? What kind of improvements do you achieve in performance? I am currently going through my AA engine. Are there any drawbacks from deviation from stock head?
With my original stock head, I would have to plan my routes to avoid having to shift down on long or steep grades, thereby pissing off the modern cars as I crept along?

With the 6.0 head I just fly up the grades and not having to shift down any more.

With the 6.0 head just be mindful of not advancing spark to the same level as the 4.5
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Old 01-08-2020, 12:05 PM   #12
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Default Re: High compression head choice.

I have never had a problem of any kind with my 5.9 Brumfield heads . The 5.9 heads give a good increase in power and hill climbing ability , they will allow the engine to have an increase in top speed . The engine will run a bit cooler and I have NEVER needed to down shift on any hill as long as momentum is maintained . If I wanted to increase the power on an original type model A , I would use the 6.0 Snyder head because it appears to be original . If I was building a hot rod or speedster I would prefer the Lion head that doesn't appear original and has higher compression ratio .
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Old 01-08-2020, 12:19 PM   #13
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Default Re: High compression head choice.

The two quickest and easiest ways to more power in a Model A are compression and a bigger carb. Compression won't hurt the babbitt as long as you don't let it detonate, so less advance will be needed. When I bought my tudor years ago, I ran it on a F.A.S.T. hill climb in Auburn, CA. A few months later I had changed to a 6:1 Winfield head, it picked up a full second on that same course. On that same day I changed to a Stromberg 81 and picked up nearly another full second! Later I switched to a 97 carb and picked up about 3/10 of a second. That's on a 1/10 mile course of about 6% grade.
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Old 01-08-2020, 01:08 PM   #14
Purdy Swoft
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Default Re: High compression head choice.

I agree that a bigger carburetor will help a bit . I prefer to run dual model B carburetors than the later Ford or Stromberg two barrel carburetors . Updraft carburetors don't flood like downdraft carburetors can . I like the look of dual updraft carburetors . I run dual model B carbs on cast iron manifolds on two of my model A's . I'm thinking about instaling dual Marvel carbs with an aluminum Charley Yapp intake manifold on my September 29 . It will already run faster than I would want to drive it . I really don't much care if the Marvel carbs don't give a big increase in power . I'm more after the look but more carb will increase top speed a bit .
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Old 01-08-2020, 01:41 PM   #15
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Default Re: High compression head choice.

Higher compression, oversize intake valves, and a B carb make a world of difference.
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Old 01-08-2020, 02:54 PM   #16
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Default Re: High compression head choice.

One needs to realise the improvement in the quality of petrol since the Model A was new.
I run a 7:1 head, still low by todays standards and I am running it on 91 octane petrol without problems. Early pre-ignition problems were solved by fitting a Mallory distributor, which together with the harmonic balancer pulley were the two greatest improvements to the smooth running of the engine
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Old 01-08-2020, 03:03 PM   #17
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Default Re: High compression head choice.

The stock model a engine is detuned by 50 % ,low compression and low carburetor air flow are two areas with the greatest 'return on investment'.Model AA's were the first market for engine performance,truck owners wanted more power.
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Old 01-08-2020, 03:06 PM   #18
denis4x4
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Default Re: High compression head choice.

Quote:
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I have an NOS Brumfield head. Anyone have good/bad experience with these?

TOB

Started with the original B-F head and went to the B-F Super Head and never looked back. Hard to find a B-F head as Larry quit making them years ago.
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Old 01-08-2020, 09:38 PM   #19
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Default Re: High compression head choice.

What are the thoughts on the even higher compression heads? I happened to have a Winfield red head 7.1. I recently purchased an engine fully decked out in Winfield. (Almost certain its all repop). I've had it running but it's not in the car yet. It is a recently rebuilt babbet engine. Electronic 6v igniton as well. It should make my roadster a pretty fun machine. I'm pretty light on the pedal so I don't have much concern for the babbet.
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Old 01-08-2020, 09:47 PM   #20
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Default Re: High compression head choice.

Thanks for all of the input. Very interesting. I'll be going with the 6.0-1 head.
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