FH high dome heads NA

[Bored&Stroked]

BTW, I have nothing against OHV Hemi Engines :

Here is a blown early 392 with Donovan 417 heads that I've built for my 34 coupe. This is just a mockup in my shop. It will have a Crower 8 port injector on it (converted to EFI). Now, if I can just get back to Ohio and find some more time (project has been in mothballs for a decade!)

Attachment 485508

Here is a look at the ports and rockers . . . some huge airflow (these were top-fuel heads). They'd only work on the street with a blower:

Rockers-IntakePorts copy.jpg

Here is the new blower/injector setup - both magnesium.

2017-12-07 23.15.49.jpg

Here is another 'Hemi' project:

Ardun-ScotBlown1 copy.jpg

And here is a new 14-71 blower design I'm working on - just about done with it. It is for high-end competition - mostly BBC and Hemi platforms. It will be whacked out of a chunk of 6061 billet aluminum. Just finishing up all the NC Toolpath work - hope to be making prototypes shortly:

NewBlower-F16-HurricaneForce.jpg

[Yoyodyne]

Nice stuff!

[21stud]

Originally Posted by Yoyodyne

How much material is there over the stock chambers in stock heads to allow for enlarging the transfer passage in stock heads?

I am sure material thickness will vary a lot, measure first, then modify. Many times core shift is possible. However, not sure what you mean by enlarging transfer passage, it is too deep most ford heads. Can't get enough compression.

My interest is about iron heads, simply stronger and not so corroded than AL.

Are those Evans heads pop-up desing original or modified? good looking chamber for sure.

Here are example of sonic test results, these are prewar 24-studders. not milled OEM. dimensions are mm:

[21stud]

B&S,

Very nice, professional stuff as allways

[Pete]

Originally Posted by Yoyodyne

How much material is there over the stock chambers in stock heads to allow for enlarging the transfer passage in stock heads?

You have it reversed for performance.
You fill the transfer passage in the head and move most of it to the block.
This shortens the fuel flow path. Also shortens the flame front travel.

[Yoyodyne]

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Originally Posted by Pete

You have it reversed for performance.
You fill the transfer passage in the head and move most of it to the block.
This shortens the fuel flow path. Also shortens the flame front travel.

Thanks Pete. In some early heads the transfer is long and narrow, and kind of deep too. I was thinking it might be good to fill it in to make it shorter and wider like aftermarket heads.

Originally Posted by 21stud

I am sure material thickness will vary a lot, measure first, then modify. Many times core shift is possible. However, not sure what you mean by enlarging transfer passage, it is too deep most ford heads. Can't get enough compression.

My interest is about iron heads, simply stronger and not so corroded than AL.

Are those Evans heads pop-up desing original or modified? good looking chamber for sure.

Here are example of sonic test results, these are prewar 24-studders. not milled OEM. dimensions are mm:

Thanks very much for that. I want to widen the narrow passage near the valves and fill in the rest over the piston. Would you weld or braze to add material?


I have a pair of repro AL 34 heads and some NOS 35 AL heads, but I'd rather experiment on iron heads first.



I found those photos on FB, have no other info on them.

[Pete]

Originally Posted by Yoyodyne

Thanks Pete. In some early heads the transfer is long and narrow, and kind of deep too. I was thinking it might be good to fill it in to make it shorter and wider like aftermarket heads.





Thanks very much for that. I want to widen the narrow passage near the valves and fill in the rest over the piston. Would you weld or braze to add material?


I have a pair of repro AL 34 heads and some NOS 35 AL heads, but I'd rather experiment on iron heads first.



I found those photos on FB, have no other info on them.

You want the transfer passage as wide as possible with straight sides. NO curves or bends. The straightest possible flow path.
Remember, all of this keen stuff works great on a race engine but just about all configurations for the street will be about the same.
I have never tried welding up a set of iron heads. Welded lots of aluminum ones with a MIG spool gun.
With the amount of welding you are contemplating you are going to have problems cleaning the scale from the inside of the water passages and bolt holes. Acid stripping will be required.

[Yoyodyne]

Originally Posted by Pete

You want the transfer passage as wide as possible with straight sides. NO curves or bends. The straightest possible flow path.
Remember, all of this keen stuff works great on a race engine but just about all configurations for the street will be about the same.
I have never tried welding up a set of iron heads. Welded lots of aluminum ones with a MIG spool gun.
With the amount of welding you are contemplating you are going to have problems cleaning the scale from the inside of the water passages and bolt holes. Acid stripping will be required.

Good points, thanks. I'm building a mild street engine with the 1007B you ground for me. so this sounds like wasted effort. Was just trying not to overlook some obvious details. I'm going to modify heads to close up the deck height w/stock flat top pistons and thought this might be good to do at the same time on the same heads.

[Henry Floored]

One little thing that I don’t think has been mentioned. The Navarro Hi-Domes are not “pop-ups” in the truest sense. The edge of the piston does not rise above the deck surface. The sphere is almost egg shaped and fits tightly in the domed portion of the head.

I spoke to Mr. Navarro on the phone about this very thing. I personally believe that the 30% airflow increase is reasonable given how much room for breathing improvement there is in almost any side valve engine.

Now 30% increase in airflow does not of course translate automatically to a like increase in power if the energy from the mixture cannot be extracted due to poor flame travel etc.

The flow path in a Flathead Ford has two bottle main necks and one other challenge. The choke point in the intake port before the valve pocket, the abrupt change of direction as the flow is forced to turn in the valve pocket and last and most importantly the slam turn the intake charge makes when it enters the chamber as the valve opens and bounces off the cylinder head and into the cylinder.

The choke point in the intake port can be mitigated by “porting”. The valve pocket can be opened up and smoothed or better yet the valve guide locked in place and epoxy or braze used to extend the port floor into the valve pocket and effectively become a ramp to get that mixture to turn more efficiently.

The problem that’s not so easy is that last 180 degree turn the mixture must make to fill the cylinders.

Barney Navarro designed the transfer area and “Hi-Dome” to gently turn the mixture around through the whole of the head which in theory will increase flow dramatically.

The Navarro Hi-Domes are not the only performance heads that may have issues with flame propagation. The first and second Gen Chrysler hemi and any big block Chevy with domed pistons need more ignition lead to get the mixture lit to compensate for less than perfect flame travel.

So really what Barney Navarro was going after was the worst part of the equation and in my opinion he was on the money.