New 5.5:1 Cylinder Head Availability
 

When I bought my Model A eighteen months ago I had no idea what cylinder head it had so I wasn't looking to buy one. But I remember them being readily available at Snyder's, Mike's, Bert's, Model A Medic, etc. So now that I know I have a stock head and I'm looking for a 5.5:1 head they've been "temporarily out of stock" for many months.


Anybody out there have an idea why this is? Are they no longer being produced?

Re: New 5.5:1 Cylinder Head Availability
 

I see Snyder's has the 6.0 in stock. Maybe they are phasing out the 5.5 since they are almost the same CR and I believe made by the same person.

https://www.snydersantiqueauto.com/p...8622&cat=41686

Re: New 5.5:1 Cylinder Head Availability
 

Check with your favorite local machine shop and inquire as to having your head milled to your specifications.

Re: New 5.5:1 Cylinder Head Availability
 

Not a good idea...

Re: New 5.5:1 Cylinder Head Availability
 

You can't mill an A head to gain anything.The high-compression head has a whole different combustion chamber design.Some call it a heart shaped design.I don't have any pictures,but folks on here have posted the stock and high compression designs side by side.

Re: New 5.5:1 Cylinder Head Availability
 

That's probably what's going on. I had the 5.5 head marked on my wish lists so wasn't looking for anything else. Thanks!

Re: New 5.5:1 Cylinder Head Availability
 

Good to know. I went the mill route with my V8 heads, and it worked great, but the A head is another animal. Thanks for the clarification.

Re: New 5.5:1 Cylinder Head Availability
 

If you have an interest in a high compression head, contact Terry Burtz since he has a very good one available and I believe they are in stock. burtzblock.com


Frank

Re: New 5.5:1 Cylinder Head Availability
 

If you were considering a 5.5:1 head, a 6:1 head will not be much different. You would have a little more grunt at the bottom end of the rev range but that is about it. Just make sure you reduce the amount of ignition advance - too much is what kills bearings (and other things in there)

Re: New 5.5:1 Cylinder Head Availability
 

I put a Burtz head on and I am very impressed; my engine is .100 over. I also installed an automatic advance in the valve chamber. Limit my total advance to about 25-26 deg. engine runs great, plenty of power. Make sure your main and rod bearings are adjusted. I have a couple stock heads, and they are just dust collectors now.

Re: New 5.5:1 Cylinder Head Availability
 

No. Snyder's makes both heads, they will keep selling both.

They make them in batches. You have to wait for the time for casting, transportation, machining, etc. They will be back in stock eventually.

I recommend the 5.5 over the 6.0 head for the average driver with average original engine. It is very easy to get engine knock with the 6.0 head, and then your bearings will go south.

Re: New 5.5:1 Cylinder Head Availability
 

I have heard or read this exact thing before. Although my engine was rebuilt fairly recently I don't know if it still has babbitt bearings or if it has been converted to insert bearings. Unfortunately, the family of the previous owner was no help in answering this question. My engine starts, idles and runs very well so I'm not yet willing to open it up just to find out.

Re: New 5.5:1 Cylinder Head Availability
 

Why would that make a difference in this context?

Re: New 5.5:1 Cylinder Head Availability
 

Since there were valid suggestions of using a Snyder's 6.0 head or even the Burtz 6.5 head I felt compelled to explain why I don't consider them to be an option at this time. If and when I pull the pan off of my engine and discover insert bearings I would consider them.

Re: New 5.5:1 Cylinder Head Availability
 

The idea that Babbitt bearings can’t handle higher compression is a myth.

Re: New 5.5:1 Cylinder Head Availability
 

If it really is a myth I would appreciate any and all evidence to prove it so. Until then I can't take a chance on a Model A that I'll be handing down to my grandson some day.

Re: New 5.5:1 Cylinder Head Availability
 

Randall Strickland, you've poured your fair share of babbitt for T's and A's. What's your opinion about babbitt and higher compression?

Re: New 5.5:1 Cylinder Head Availability
 

Babbitt can’t handle high compression ??? Tell that to diesel engines that have babbitt bearings ! way more compression than a measly little 6.0 6.5 7.0 compression

Re: New 5.5:1 Cylinder Head Availability
 

Some of the large diesels have babbitt bearings in them and they have compression ratios around 18.5-1!!!

Re: New 5.5:1 Cylinder Head Availability
 

I have been running 5.5:1 and 6:1 compression ratio cylinder heads for many years successfully with Babbitt bearings. By the way, the bearing diameter determines the amount of bearing stress in the Babbitt due to cylinder combustion pressures and inertial forces.
It makes good business sense if the 5.5:1 head was discontinued because of the 6:1 head. The difference between them is only 3%.

Re: New 5.5:1 Cylinder Head Availability
 

It's not that babbit can't handle it. It can.

The problem I have experienced over and over is that the average Model A driver with the average original engine advances the spark too much on the 6.0 head and the engine knocks. The driver can't hear it knocking (for various reasons, including old age loss of hearing) and they pound the babbitt out in a short time.

Many drivers start the engine, then pull the timing lever down all the way and leave it there all the time. You can explain to them all you want about what they need to do with the timing, but they just pull it all the way down. The stock cylinder head is low enough compression that it is very forgiving to this sort of behaviour. With the 6.0 head and an engine that is timed to TDC like Henry called for, that engine won't last long.

So I mainly recommend the 5.5 head to save the driver from themselves. You get a little performance boost but less risk of hurting the engine.

Re: New 5.5:1 Cylinder Head Availability
 

I agree with this notion that people who can't be bothered to manage spark timing should not run high compression heads. I was specifically addressing the separate babbitt concern that someone else brought up.

If someone does have the skills to manage spark timing, I would actually say I think the Burtz head is the best option. Not because it has the highest compression, but because they changed the design of the water jacket. The Burtz head blocks the large central return vent in the stock head, which forces more coolant toward the rear cylinders. These cylinders run hotter in stock configurations and are more prone to gasket failure, valve failure, etc. Getting more cooling to them is an investment in the lifespan of the engine – provided that you don't undermine it by over-advancing the spark, that is.

Re: New 5.5:1 Cylinder Head Availability
 

Are the high compression heads marked in any way indicating what head/compression ratio it is?

Re: New 5.5:1 Cylinder Head Availability
 

Typically they are attempting to "pass" as stock heads, so with a couple of exceptions, the only way to know is to examine the shape and size of the combustion chamber.

Re: New 5.5:1 Cylinder Head Availability
 

I would think that they could be discretely stamped with a 5.5 or a 6.0. I would not think that there would be enough difference between the two combustion chambers to determine what it is.

Re: New 5.5:1 Cylinder Head Availability
 

If someone could post some pictures comparing the various combustion chambers that would be great. I have a head that I have been told “might be” a HC head but I have no idea if it is or not. I do not have a stock head to compare it to.

Re: New 5.5:1 Cylinder Head Availability
 

The 5.5 head has a heart-shaped chamber that projects deeper into the cylinder bore. The 6.0 head is "stubbier," more rounded.

FordGarage has a page that shows some older heads.

Re: New 5.5:1 Cylinder Head Availability
 

The 5.5 heads from Snyder's have two dots on top and they are physically smaller.
https://live.staticflickr.com/65535/...bcd8695a_z.jpg

I can't tell you about any others.

Re: New 5.5:1 Cylinder Head Availability
 

B Butturff, To tell what kind of bearing you have without opening up the engine, you can use a bore scope and insert it into the hole after you take the breather tube out. The poured bearing at the rear has a large poured flange at the forward end that is used as a thrust bearing.

The 6.0 head puts out slightly more torque and horsepower than the 5.5 head, which may be because of better breathing rather than the higher compression ratio. In my opinion the hart shaped combustion chambers do not breath as well as other designs. See https://www.snydersantiqueauto.com/c...%20release.pdf

Re: New 5.5:1 Cylinder Head Availability
 

Neil, thanks for this tip! I've never read or heard of this before and will do it very soon.

Re: New 5.5:1 Cylinder Head Availability
 

If it's insert bearings, instead of a gray flange on that rear bearing, you'll see a brass thrust washer.

Re: New 5.5:1 Cylinder Head Availability
 

Thank you too. The brass should be readily apparent with the illumination from my bore scope.