Cylinder head design

[Kahuna]

I was just reading the thread about blown head gasket problems on some after market cylinder heads. An interesting discussion to me.
I currently do not own a Model A, but have had several in the past with stock heads, milled heads, Winfield, Cyclone, and an overhead conversion.
My question:
Why aren't the combustion chamber designs of the after-market flat heads more closely linked to the late model (46-53) Ford V8 flathead designs? Is it because the compression ratio would be too high? Is there a worry about the babbit in the rods and mains? Or is it something that I haven't thought of? Just wondering.
Seems that a Model A/B would be real happy with a compression ratio of about 8:1.
Maybe I'm just whistlin Dixie
Any thoughts
Thanks
Jim

[1930artdeco]

8.1 would blow the babbit right out after any length of time.

Mike

[Bruce Lancaster]

Vertical valves and huge difference in distance valve to cylinder are a differing factor here...implicit adaptation of Ricardo design, followed by lawsuit, came in V8 times...flat piston V8 heads, '32-36, are very different from the classic '37-up type and much closer to Model A/B practice...but valve placement in the V8 was substantially different than Model A in several ways.
B made about one horse per 4 cubes..V8 by 1934 made one per 2.5, huge difference in expectations. Fenderless '32-33 Fords running as stock cars in the Elgin races could hit 100MPH. How stock is an interesting question with answer hidden to us, but there was a huge real world difference in top end. Interestingly, one limit on top end power in '32-33 Fords was the whippy forged crank (sound familiar??) and those cars actually grew higher top speeds when they got replacement '34 cast cranks of same diameter!

[Jim Huseby]

I had the exact same question as you about the combustion chamber shape and after a year or two of investigation of FH chamber designs and performance on various engines, made a very simple observation. By just looking at old Motors Manuals, it's easy to calculate the HP/cu. in. for every engine listed. The latest of the Dodge and Plymouth FH's, around 1959, made the most specific HP of any FH's listed. I had a couple of those Mopars in the shop, so it was easy to copy that. Also, the junior dragsters that start out with a 5HP B&S engine are developing over 50 HP (10 times the stock engine! That would theoretically be 350-400 HP from a Model A!) and its head design was similar to the Mopar. I had an aftermarket aluminum high performance A head that had plenty of thickness for radically changing the chamber shape and then milling it back down to 7 to 1 and cc'ing. I gave lots of room and flow shape around the valves and transfer area. The shape of the flame front and its relationship to the changing shape and size of the chamber with changing crank angle was a phenomenon that I couldn't adequately model. My theory was to get as much of the explosion blown onto as much of the piston head area as possible at TDC while, at the same time, encouraging efficient cylinder filling on the intake "stroke". This, of course had to be considered with the diameter, length, constrictions, etc. of the intake system, along with a consideration for turbulence, which the A is reputed to require a lot of (I don't really know, or how to test for it). During this research and experimentation, I realized there were several varying philosophies or approaches for specific benefits that had been tried over the lifetime of the FH engine, and theories and experiments are still advancing.
On an RK engine with inserts, full pressure, Carillo rods, 1 3/4" int. valves, hot touring cam, S 94 carb, header, electronic Mallory, etc., my experimental head makes lots of whacking HP with no indication of a HP drop-off above 3000+ RPM. Now that's not a very scientific answer for you, as it hasn't been dyno'd or raced against another similar car ('30 coupe with fenders, bumpers, Zephyr gears, 3.78, etc.). There are many influencing factors that I played with and tried to balance with each other or make mutually effective. There are many factors I can't rearrange, such as the-mentioned valve angle and proximity to the cylinder, and I'm sure many that I don't understand. The Mallory as set up has too much total advance, so the engine will be too retarded at low RPM if timed for fast running, or KNOCK at above 2500 with much throttle if timed for low speed running. I'm thinking that a stock curved B distributor will have about the right amount of total advance, even though I'm aware of much of the data already out there for a set-up similar to this. BTW, it hasn't blown the Felpro dark gray head gasket with about 1500 miles, but its over-due a re-torque.

[Crazydaddyo]

Show us a picture of your new combustion chamber please.

.

[BRENT in 10-uh-C]

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Originally Posted by 1930artdeco

8.1 would blow the babbit right out after any length of time.

Mike

Mike, respectfully that really isn't a true statement based on my experiences. To substantiate this, think of diesel engines manufactured in the 30's & 40's that used babbitt, ....their longetivity was substantial with much higher compression ratios. The proper type and installation of babbitt will withstand everything we would subject it to in a Model A 'banger' engine.

Kahuna, I think the biggest thing you see with higher than an 8:1 CR is loss of volumetric efficiency, --or loading the charge into the cylinder. The other thing that kinda affects some of this is the stock siamesed intake ports where it is difficult to get #2 and #3 a full load of fuel/air. There are several good combustion chamber designs, ...and the one that I like is the one that 'Pop' Evans made that is very similar to a late flathead design. One final thought to remember is the RPM differences between a flathead V-8 and the A/B flathead 4 cylinder.

[just plain bill]

Originally Posted by BRENT in 10-uh-C

Mike, respectfully that really isn't a true statement based on my experiences. To substantiate this, think of diesel engines manufactured in the 30's & 40's that used babbitt, ....their longetivity was substantial with much higher compression ratios. The proper type and installation of babbitt will withstand everything we would subject it to in a Model A 'banger' engine.

Kahuna, I think the biggest thing you see with higher than an 8:1 CR is loss of volumetric efficiency, --or loading the charge into the cylinder. The other thing that kinda affects some of this is the stock siamesed intake ports where it is difficult to get #2 and #3 a full load of fuel/air. There are several good combustion chamber designs, ...and the one that I like is the one that 'Pop' Evans made that is very similar to a late flathead design. One final thought to remember is the RPM differences between a flathead V-8 and the A/B flathead 4 cylinder.

I have had good success with the "Crows Foot" combustion chamber as used by Winfield and others.
I would hesitate to give a limiting number to the compression ratio as there always seems to be some one that has had success with a higher compression ratio although I'm running close to 7.7 to 1 at this time.

[Crazydaddyo]

Here is a configuration that I have been thinking of:



The dashed line would be the standard chamber shape for a H/C head. The solid line outside that would be the modification.
I was also figuring that the chamber roof would be higher over the intake valve and the spark plug would be located closer to the intake valve.

.

[Crazydaddyo]

Here is what a JR. Dragster head looks like. Keep in mind they do run them on Alcohol.

[BRENT in 10-uh-C]

Originally Posted by Crazydaddyo

Here is what a JR. Dragster head looks like. Keep in mind they do run them on Alcohol.

You mean "some" JR dragster heads look like that...

.

[Jim Huseby]

Crazydaddio- I didn't take pics, but will when the head has to come off, I hope a long time away. Compared to the jr. dragster head shown, it has a little more roundness behind the ex valve so that when the ex gasses slam against the wall behind the valve, they will be smoothly routed back toward the opening. The transfer area is taller, allowing as much flow there, especially intake, as possible while keeping the C/R up. Instead of the chamber essentially abruptly ending 1/4 of the way over the piston (3/4 of the top of the piston is not exposed to the flame front at TDC in the jr. dragster chamber shown, which appears to have at least 10 to 1 C/R), I ground away the dam or ridge and sloped the chamber toward the far side of the piston top, thinking that would get pressure on the top of the piston sooner and smoother than waiting for it to travel down far enough for the expanding gasses to reach it. We do understand that with the little chamber shown, there will be lots of turbulence and that the flat area above the piston is a squish area, and that that configuration makes lots of HP in the jr. dragster and many, if not most high performance FH heads. I am not a scientist or expert in this area, but I am insanely curious, and being blessed with ADHD, did not control the urge to get out the die grinder and risk ruining a good Thomas head. I would like to hear lots more on this subject. JH

[Jim Huseby]

Hello Brent- Yeah, SOME jr. dragster look like that. The one I copied looked more like I described, but with milled ribs standing in the transfer area, I presume to take up some space without impeding the flow too much. I did not use the rib idea, and arrived at 7.1 to 1 with .080" over. Please tell us more about the performance figures of that jr. dragster as the real proof here is in the pudding and not my theories. I think it is worth the embarrasment and loss of a blown up engine, if necessary, to experiment with going faster. Would you venture to tell us how you will use this knowledge on your next secret weapon? We all know you're thinking up something. JH

[Bruce Lancaster]

The Jr. Dragster head is similar to all '37-53 Flathead heads...
The purpose of the tight area above the piston, as you note, is the Ricardo principal, essentially, the same effect exploited in most SBC heads. That are in these designs is kept as tight as possible, numbers like .040, for turbulence...the mix on compression is forced out and over toward the transition and valve area, allowing homognous mixture with lots of turbulence. One noticable effect is a simultaneous need for LESS spark advance (often taken as an indicator of combustion efficiency) combined with lowered tendency to knock...a flathead or sbc will both run higher compression with less tendency to spark knock if this area is tight, and will lose response and knock more if this area is too far from head.
A difference is that the flathead piston top and the chamber above have matching shallow domes.
Flathead valves are canted several degrees toward the cylinder (as are the valves of the circa 1932 British Ford 4 cylinder and the Ford USA N series 4 of 1939), which directs the probably circa 30 degree flow off of the seat more towards piston area. The rise in the transfer area matches this flow in stock heads.

[just plain bill]

I have noticed that the Winfield heads that I have use a different radius for the intake valve and the exhaust valve in the combustion chamber wall behind the valves. I think the JR dragster head that CDO posted looks similar to the standard Winfield pattern as to the transition to the flat area over the piston which maybe a bit shorter, Of course that just might be my old eyes.

[MrTube]

OK now I'm confused.

If Ethanol produces less power than gasoline why would you use it on a high performance engine?

[Kahuna]

The junior dragster head presented by Crazydaddio is but one of many head chamber designs and is very close to a stock Ford flathead in design. However, that design is not the type used by the successful racer. It is much more refined and used a lot in tractor pulling stuff (riding lawn mower type pulling).
Valve angles, to me, mean little, as both the Briggs and the Kohler engines do not have offset valve gear. I'm not familiar with the output of the Briggs, but the Kohler engines do, in fact, produce more than 50 HP. 50 HP is needed to be competitive. More is needed to win.
As Brent mentioned RPM, let's talk about that a little. I see no reason that a Model A/B shouldn't be able to run to 5K, properly built. Also, the Briggs/Kohler stuff is run upwards of 9K. Big difference.
My original question was really about the aftermarket. With what is known as far as "late" head design, why do the Brumfield's/Synder's just use the older designs when clearly the later stuff would be better?
Jim

[d.j. moordigian]

I asked Larry Brumfield twice about spark plug location and/or angle here on the
Barn. I thought it was a good topic for his improved combustion chamber head, but
no answer. I think plug location is a horsepower maker.
Dudley

[Crazydaddyo]

Originally Posted by d.j. moordigian

I think plug location is a horsepower maker.
Dudley

Winfield thought so too.

.

[Jim Brierley]

The late Harley racing flatheads had an interesting chamber, and ran very well. In the 30's, all this was still being developed. Things don't happen overnight.

[gilitos]

Put a little ethanol in one palm and a little gasoline in the other: the ethanol makes your hand colder as it evaporates. It has a higher heat of evaporation, meaning that it cools its surroundings more as it evaporates. In an engine, this means that you can run much higher compression ratios without detonation when running ethanol (methanol, too), which means more efficient combustion (i.e. more HP per unit of fuel). Air/fuel ratio has to be adjusted to get this potential power, though.