Flathead Transition Area - What & where is it?

[wkuran]

Although I have had my flathead for many years, I am new to many of the terms associated with modifying engines. One term in particular is the transition area

The engine, a Willys Super Hurricane, is in a 1960 Utility Wagon. It runs well but this past year I have had to do some cylinder head work and that is when I started hearing about the transition area. After ready through many posts on this forum, I have an idea as to what it means but still can’t quite locate it for sure.

I assume that since it is called the transition area, it is somewhere between the valves and the cylinder bore but what does it transition?

I may be too literal but would like to be able to see the transition area. Where is it? Is it on the block deck, on the cylinder head, on both or somewhere in between.\?

If I had a photo of the block deck and cylinder head would it be possible to use a marking pen to outline the transition area?

If I can find the transition area I should be able to measure it. How big should it be and why? What shape should it be and why? How do I measure te size?

[mag2555]

Could you post up some specific examples of how the word transition was used in a sentence or two that you have read?

[wkuran]

Could you post up some specific examples of how the word transition was used in a sentence or two that you have read?

Sure . . .
"By reducing the head volume, you also make he transition area smaller as well. This is the area that is between the cylinder and valves in a Flathead." from Inliners International.
"to my best guess I tried to open up the transition area, or what I thought was the transition area." from the HAMB
"Do you actually grind into the domed area on the head and move the transition area towards the center of the dome." from The Flat Spot
". . . how do you go about relieveing a flathead ford v8 by the valves and piston ... it makes the transition area smaller and more restrictive." from the Jalopy Journal
"I think if you need more transition area it should be included in the cylinder head not the block. " from Speed Talk

[panic]

Ricardo carefully guarded details of his patented and heavily protected quench discovery (100 year ago), but did say that the transfer X-sectional area is 50% of the area above the valve seats. The restriction is necessary, how it's shaped is a different question.
One factor: are your valve stems parallel to the bore axis (Ford V8 is not, Ford photos will be very wrong if yours is not angled).

[PackardV8]

Relieving the block between the valve seats and cylinder to increase the transfer area has fallen out of favor with some of today's flathead builders with access to a flow bench.

Any grinding to enlarge the transfer area has a concomitant reduction in compression ratio. Panic is the man, but IIRC, the Harley-Davidson KR is considered the most scienced-out flathead ever. The Racing Department found it advantageous to trade compression for flow. The best examples raced at 6.5:1 compression. Maybe Panic can lay hands on some of the head photos from that era.

[wkuran]

I should have titled this post as "Flathead Transition/Transfer Are - What & where is it?" After reading a couple of replies I realize that it the the transfer area that I am interested in. But, I do see the terms used with the same topic.
Perhaps a moderator can edit the post title.

[wkuran]

Ricardo carefully guarded details of his patented and heavily protected quench discovery (100 year ago), but did say that the transfer X-sectional area is 50% of the area above the valve seats.

Can you explain what "50% of the area above the valve seats." means? I have Ricardo's book, "The Highspeed Internal Combustion Engine'" if that is what you are referring to, can you tell me to find where he discusses this concept?

The restriction is necessary, how it's shaped is a different question.

The transfer area is intended to be a restriction? Why is it necessary? What does it do?

One factor: are your valve stems parallel to the bore axis (Ford V8 is not, Ford photos will be very wrong if yours is not angled).

The valves are inclined 2.7 degrees https://drive.google.com/file/d/1EKSwDA ... sp=sharing

[wkuran]

Relieving the block between the valve seats and cylinder to increase the transfer area has fallen out of favor with some of today's flathead builders with access to a flow bench.

I don't consider block relieving beneficial either. From the photos I seen adding this feature creates a volume defined by the area laied out on the block. In this case is the transfer area actually the transfer volume?

Any grinding to enlarge the transfer area has a concomitant reduction in compression ratio.

I agree that removing material from the combustion chamber increase the volume and decrease the compression ratio. Where in the combustion chamber is the transfer area (volume?)

Panic is the man, but IIRC, the Harley-Davidson KR is considered the most scienced-out flathead ever. The Racing Department found it advantageous to trade compression for flow. The best examples raced at 6.5:1 compression. Maybe Panic can lay hands on some of the head photos from that era.

[panic]

2.7° is fairly mild, IMHO may be less than the common Ford photos. Definitely an advantage vs. parallel stems, it's a major factor in the K (KH, KR) out performing its ancestor, the 45.
Factory angled seats are inclined to the deck surface at the complement to the stem angle: 2.7° stem axis means a shallow eyebrow above and concentric to the seat, but tilted at 87.3° (90° - 2.7°).
The idea is that the valve curtain is presented to the transfer area instantly the valve cracks open, so the "relief cut" blends into the seat's top angle and blends into the deck surface toward the bore. The intake mass should have a smooth path from the seat to the bore opening (and the ledge in the head casting that directs the charge downward at roughly the mid bore).
Many engines with mileage have seats sunk by use, rust, etc. and should be restored by deepening the relief cut to just intersect the new deeper seat.
Here's a diagram of Kohler mods

[panic]

What size are the valves?
How close together are they?
What are the seat angles?
Stem diameter?

[frnkeore]

I am not a advocate of relieving blocks! But, I think what should be done, is to, radius the top of the cylinder, in the transfer area, to 3/16 - 1/4"R , depending on how far down the top ring is.

Rather than cause turbulence going over a sharp edge, the radius, could promote tumble.

Something else, if there is enough space, between valves, I think there should be a divider, extending down to the block, between valves, creating a individual "port", into the cylinder and the shape of that port could be tuned for increased flow and and increase mass, to increase compression. It would also help with managing overlap flow.

[wkuran]

What size are the valves?
How close together are they?
What are the seat angles?
Stem diameter?

Intake head diameter: 1.650"
Exhaust head diameter: 1.500"
Valve center-to-center spacing: 1.629"
Stem Diameter: 0.341"
Seat angles: see drawings
https://drive.google.com/file/d/1EdnqJk ... sp=sharing
https://drive.google.com/file/d/1WYSNQt ... sp=sharing

I'll provide any engine design details that are of interest but I'm am still hoping to get an understanding of where the transition area is located, how big it should be and why, and how to measure it.

[wkuran]

2.7° is fairly mild, IMHO may be less than the common Ford photos. Definitely an advantage vs. parallel stems, it's a major factor in the K (KH, KR) out performing its ancestor, the 45.
Factory angled seats are inclined to the deck surface at the complement to the stem angle: 2.7° stem axis means a shallow eyebrow above and concentric to the seat, but tilted at 87.3° (90° - 2.7°).
The idea is that the valve curtain is presented to the transfer area instantly the valve cracks open, so the "relief cut" blends into the seat's top angle and blends into the deck surface toward the bore. The intake mass should have a smooth path from the seat to the bore opening (and the ledge in the head casting that directs the charge downward at roughly the mid bore).
Many engines with mileage have seats sunk by use, rust, etc. and should be restored by deepening the relief cut to just intersect the new deeper seat.
Here's a diagram of Kohler mods

Not sure how much of the Kohler head design is applicable to my cylinder head but some of the design details are similar.
Clearance above the vales is more than 0.200" - I say more than because part of the valve is is closer due to be tilted. The chamber roof is 0.694" a,
bove the block deck. Valve lift is 0.410".
Clearance behind intake valve: 0.115"
Clearance behind exhaust valve: 0.095"
The Kohler head 1/4" material minimum between the chamber and stud holes. On my head the material between the chamber and stud holes is between 0.300" and 0.350".

https://drive.google.com/file/d/1JaJ9gO ... sp=sharing

Modeling shows the majority of flow is through the central and upper part of the chamber. A smooth path is important but enlarging the combustion chamber by increasing the roof height, rather than lower the block deck, will result in less pressure drop as the A/F mixture flows from the valve to the piston bore. Thick of replacing a standard 90 degree elbow in a piping system with a long sweep elbow

This flow simulation is simplified but is still shows a valid approximation from which to visualize the effects of chamber design changes.
https://youtu.be/xivNI_Pw6Jo

[frnkeore]

It looks to me, with that flow pattern, that raising the valve, to within .020 of the head would flow better.

What RPM level are you wanting?

[wkuran]

It looks to me, with that flow pattern, that raising the valve, to within .020 of the head would flow better.

What RPM level are you wanting?

RPM is between 5000 and 5500. Design piston speed is 4000 fpm at 5140 rpm.

A rule of thumb for lift is one-quarter of the valve diameter, which is 0.413 inch. I am at 0.410 lift. The intake port area is 1.60 inches.
What is it about the flow pattern that makes it likely the head would flow better if the the valves stopped 0.020" from the chamber?

Any thought on how I find and measure the transfer area?