High Compression Head

[Bill O'Brien]

Does anyone know what the horespower increase will be with the Snyders 5.5 head? I am going to install mine in the next week!

Is the stock Model A engine about 40hp? or am I wrong.. ??

This is from Bill Stipe's dyno results:


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.



however... Tom from Snyders told me I should only expect about a 5hp gain.. ?

I do have the Aries 'A Muffler' which should flow a bit better than stock.

Thanks!!

[MikeK]

Originally Posted by Bill O'Brien

Does anyone know what the horespower increase will be with the Snyders 5.5 head? I am going to install mine in the next week! . . . I do have the Aries 'A Muffler' which should flow a bit better than stock.

Only the high-performance Aries has a higher flow rate. It is slightly louder, but not too noticeable. I've run both types of Aries. The regular Aries, either in plain or stainless steel, is identical internally to Henry's original. Here's what it looks like inside:

[Purdy Swoft]

Originally Posted by Bill O'Brien

Does anyone know what the horespower increase will be with the Snyders 5.5 head? I am going to install mine in the next week!

Is the stock Model A engine about 40hp? or am I wrong.. ??

This is from Bill Stipe's dyno results:


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.



however... Tom from Snyders told me I should only expect about a 5hp gain.. ?

I do have the Aries 'A Muffler' which should flow a bit better than stock.

Thanks!!

How can I view the Stipe dyno results? Thanks.

[Bill O'Brien]

Dyno results:

http://www.snydersantiqueauto.com/up...lease-8778.pdf

[MikeK]

Originally Posted by Purdy Swoft

How can I view the Stipe dyno results? Thanks.

Here's the Stipe page with the links for two earlier dyno runs with different H.C. heads:
http://www.specialtymotorcams.com/pages/services.html

[Geo. H]

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I have two B engines with A High comp heads.

[Terry, NJ]

Originally Posted by Smitty

Are there any negative aspects to using a high compression head over a stock head? Is it all gain or are there trade-offs?
Most folks running high compression head these days?

Thanks, Steve

FWIW I had some concerns about higher bearing loads. In resonse, just about everyone who posted a response, had a HC head an was well pleased with it. There were NO indications of any problems. Only one person indicated a bearing failure that MIGHT have been traceable to the HC head. It might not also. The overwhelming majority were pleased. I had worried about this (Milling the head) because of a few posts seen I had seen over at "Yesterday's Tractors" where the practice was discouraged because of higher bearing loads. The 8N and the Mod.A engines are so similiar that I believe whats good for one will be OK for the other (Generally). From that, I had some worries about HC heads. My fears were not supported.
Terry

[marc hildebrant]

Are there some "before" engine dyno tests to see how an original motor performs ?

Marc

[just plain bill]

Originally Posted by Terry, NJ

FWIW I had some concerns about higher bearing loads. In resonse, just about everyone who posted a response, had a HC head an was well pleased with it. There were NO indications of any problems. Only one person indicated a bearing failure that MIGHT have been traceable to the HC head. It might not also. The overwhelming majority were pleased. I had worried about this (Milling the head) because of a few posts seen I had seen over at "Yesterday's Tractors" where the practice was discouraged because of higher bearing loads. The 8N and the Mod.A engines are so similiar that I believe whats good for one will be OK for the other (Generally). From that, I had some worries about HC heads. My fears were not supported.
Terry

My early 50's 8N has inserts on the rod bearings.

[Purdy Swoft]

Thanks Bill O'Brien and Mike K for the links to the Stipe dyno results. They are interesting

[gilitos]

Yeah, but the most useful dyno tests for comparison purposes for a lot of us would be with and without a HC head on a stock motor. Changes like cam, valve size, head design, carb size tend to be multiplicative, not simply additive. In other words, a HC head with a B cam (or hotter) might make a larger percentage change than when combined with a stock cam. Anybody aware of such comparisons?

-Giles in Cincinnati

[Purdy Swoft]

Originally Posted by gilitos

Yeah, but the most useful dyno tests for comparison purposes for a lot of us would be with and without a HC head on a stock motor. Changes like cam, valve size, head design, carb size tend to be multiplicative, not simply additive. In other words, a HC head with a B cam (or hotter) might make a larger percentage change than when combined with a stock cam. Anybody aware of such comparisons?

-Giles in Cincinnati

I have found that without a higher compression head the addition of a B cam ,B carb and reamed manifold will barely make a noticable difference. If a higher compression head is added they will all work together for a major improvement. I think that there is some dyno results on the secrets of speed site.

[40 Deluxe]

[QUOTE=The 8N and the Mod.A engines are so similiar that I believe whats good for one will be OK for the other (Generally). From that, I had some worries about HC heads. My fears were not supported.
Terry[/QUOTE]
Actually, it is the 239 cu. in. flathead and the 8N that are similar, NOT the Model A. Bore and stroke of the 239 and 8N are the same (8N displacement is 119.5 cu.in., exactly half of the V8). Pistons, rings, spark plugs, valves, springs and lifters interchange. The front mounted distributors are similar in design. Both have pressure oiling and insert bearings (main and rods). NOTHING interchanges from the A to the 8N! The A design is 10 years older than the 9N/2N/8N. The N starter interchanges with the 60 V8 starter.

[Terry, NJ]

Originally Posted by 40 Deluxe

Actually, it is the 239 cu. in. flathead and the 8N that are similar, NOT the Model A. Bore and stroke of the 239 and 8N are the same (8N displacement is 119.5 cu.in., exactly half of the V8). Pistons, rings, spark plugs, valves, springs and lifters interchange. The front mounted distributors are similar in design. Both have pressure oiling and insert bearings (main and rods). NOTHING interchanges from the A to the 8N! The A design is 10 years older than the 9N/2N/8N. The N starter interchanges with the 60 V8 starter.

You are correct in everthing you say! However while I was fooling around, restoring my 1952 8N, I read where , where the 9N (1939 - N) and subsequent 8N (Side distributor, 1947) were considered the next evolutions of the model A engine. I never said the parts were interchangable. Just as many parts are not interchangeable from 9N ,2N, to 8N, the concepts that created the designs, the ideas and thinking. When one is working around a N model tractor, you can't but notice the similiarities with the A. Contrast them with the Jubilee (1953 - NAA) and it's clear that some major changes in thinking have taken place.
Terry

[krswen]

OK .... some quantitative answers to your question about increasing compression ratio. I just finished tuning my Model A engine computer model. I was able to find valve lift tables in a back issue of the MARC Technically Speaking reprints. I got dyno and flowbench data from the Piranio site and scaled flow passage sizes from hardware photos and a carburetor cross-section drawing. I don't have an A of my own yet, so couldn't measure actual hardware. Nevertheless, agreement with the published dyno data at 2200 rpm is within 1%.

Let's suppose you just add a Brumfield head and do nothing else. At WOT (wide open throttle) HP goes from 41.7 to 53.1. BSFC (brake specific fuel consumption) improves by about 18%. Peak cylinder pressure goes up by 139 psi (51%) which the bearings have to be able to withstand. But experience indicates that they can.

In reality though, a better comparison would be to operate the vehicle at the same power as before (climbing the same hill at 2200 rpm that you used to have to run wide open). Now, because the higher compression results in more efficient burning of less needed fuel, only 86% as much air needs to flow through the engine. The fuel economy described above won't quite be realized because part-throttle bsfc is not as good as at WOT, but a 13% improvement could be expected.

One of the posters mentioned a cooler running engine. This is true. The heat rejection to the cylinder head and liner goes down by 3% and the exhaust port temperatures go down by over 190 degrees F.

Is there an upper limit to compression ratio? Theoretically no, although the benefits flatten out as you go higher. With "side-valve" engines like the A, the volume in the cylinder head has to meet an extra burden not required of modern overhead valve engines. The "roof" of the combustion chamber must be high enough to allow adequate valve lift AND have enough height to transfer the flow from the neighborhood of the valves over to the cylinder. I like what I see in Larry's head. He has found a sweet spot in adequate transfer area and "squish" areas for good turbulence generation (which speeds up combustion ... a good thing). So there is a geometric limit to achievable compression ratio with a side valve engine.

The other limit of course is the ability of the babbit bearings to withstand the higher peak cylinder pressures.

As an interesting aside, combustion development of side valve (also called flat head in the literature) didn't die at the end of the 50's. In the 90's, small utility engine makers (lawn mowers etc) were facing emissions requirements. At one of my former employers we did some combustion development work for them. We used specially modified head gaskets to visualize flame travel. We embedded ionization probes into the fire ring around the perimeter of the head gasket and applied a voltage. As the flame front arrived, it shorted the probe, and so you could calculate arrival time and flame travel parameters. I wasn't directly involved in the work, so can offer no specific insights into chamber optimization, but I would think someone with a dyno could use the same idea.

Ken

[just plain bill]

Boy, Ken you just kinda take all of the fun out of it!

[Terry, NJ]

Ken, I am no engineer! However, the statement that the cylinder head press goes up by 139lbs is a mystery to me. Is that what you meant or is this a typo? I have always thought that CR was a multiple of atmospheric pressure (about 14 lbs). So to get a cyl pressure of 139lbs would require a 10/1 CR. To get an increase of 139 + pre vious pressure (4.2 X 14.7) Say, 60 lbs (139+60 lbs= 199 lbs). To get this, by my reasoning it would take a CR of 14/1. Am I wrong about this? By my calculations, a Brumfield 5.9 head should produce about 90lbs of compression. as I said, I'm not an engineer so my thinking may be flawed, but this is my understanding of it.
Terry

[krswen]

Hi Terry .....

It turns out that when you compress a gas "adiabatically" (no heat loss), which is close to what happens during cranking, the pressure ratio is greater than the volume ratio. But the number I was referring to above is the peak cylinder pressure caused not by cranking compression but by the combustion event. For a stock A at 2200 rpm WOT the peak pressure in the cylinder is 274psi. With a Brumfield head it will be 413 psi. This occurs somewhat after TDC, depending on the ignition timing.

Ken

[krswen]

Also, don't forget that compression doesn't start until the intake valve is closed, which is around 50 ABDC for the stock A. So the true compression ratio, as opposed to the "geometric" CR, is even less than 4.22. Hence the cranking cylinder pressure, measured with a compression gauge will be something less than 4.22 to the 1.4 power, and that doesn't include leakage past the rings! Little wonder there's a range of "acceptable" cranking pressures. Cylinder-to-cylinder variation is more important than an absolute number when you are trouble-shooting.

Ken

[just plain bill]

I hate to think how technical your posts will be when you actually own an "A"