Inliners International Forums General Discussion MOPAR Thoughts on Porting & Polishing the flatty

Curious what the consensus is on port work in the flatty.

Some things I've read seem to point away from porting & polishing in an effort to maintain turbulence and fuel atomization.

On the other hand, I've heard of people having success with port matching...what's the general consensus?

ALso, what mods should be done to the stock cast iron head in terms of smoothing or de-burring?

Thanks,

Gary

Contrary to the way you would port and prep an OHV engine, compression in a Flathead engine will begin to restrict breathing if a head is resurfaced too much. I would keep that to a minimum. By reducing the head volume, you also make the transition area smaller as well. This is the area that is between the cylinder and valves in a Flathead. As for porting and relieving, there are many thoughts on this, some are dated all the way back to when these engines were new, and others are more modern thinking with todays technology and techniques. Tex Smith's Flathead book can give you a good baseline for beginning such a chore, I would highly recommend it. Welcome to Inliners....

CNC-Dude:

(Gary...Not trying to hijack your thread, but this sort of goes along)

Okay, I have a half and half. An F-head. Intakes in the head and exhaust in the block, as you know. Given it's stock 7-1 compression ratio I want to raise it. When the rebuild starts on the spare block I don't want to shoot myself in the foot. So... Custom pistons from Ross, or just deck the block and the head and take what I can get there? In other words..how does the transition area come into play with mine, compared to the flatty?
Also, I have been working on port matching the exhaust ports to the headers, and generally cleaning them up. How about the area where the valve guide is in the port? Can I reduce the height of that area?...the top of the guide itself to open up the area available?

Thanks:
Paul...aka xerxes

Xerxes, the thoughts that are conveyed in Tex Smith's Flatty book, seem to point to the intake breathing being affected more by making the transition area smaller, than the exhausts expelling of gases would be, in a true Flathead. I am not as familiar with an F-head configuration as I would like to be, but from pics I have seen of a cylinder head, it appears to have it own separate channel or pocket to carry the charge gases in. So it probably would not be as sensitive to cutting or milling the head surface as a conventional Flatty engine would be. If that is the same style head as the Edgy design, maybe he could be contacted to add his thoughts to this subject matter, then we all could benefit from his knowledge and expertise. I would hate to assume this to be the case with this engine, and it turn out to not be accurate info for you. But that is my off the cuff thoughts just from seeing pictures of the F-head/block configuration. Oops, forgot to finish the rest of your questions. If you did cut the head a lot to get more compression, you can always relieve the block, just in the area where the exhaust passes thru the transition part. Since it is a much narrower passage than that of a true Flatty, it might not compromise or take away from much compression you added by cutting the head to start with. Also, tapering or trimming away at the valve guides is going to improve flow also, so I would recommend doing that. If the guides are removable, or replacable, you can taper them in a lathe before you install them, that way you can keep the amount you remove from them more consistent. Hope this helps out....

CNC-Dude:

Thanks very much. That helps for sure.

Sincerely:
Paul...aka xerxes

Xerxes
What type of engine are you running...Outside of hot Model A Fords, you don't see many "F" heads! Please tell us more!

Leif

Leif:

The motor I refer to is the Willys F-head. They started making F-heads around 1950 or so, and continued to make them until the 1970's or there abouts. Mine is a six cylinder 161 cu in. Willys used it in station wagons (2 wd) and the Willys Aero cars. Kaiser also used it in some of their cars. And they (6cylinder) were used in Brazil for a number of years in cars and Jeeps. The more common F-head was the 134 cu in four cylinder used in Jeeps.

Sincerely:
Paul...aka xerxes

Very interesting!
I've been a pretty full fledged "car nut" for close to 50 years and I'm still learning about completely new stuff (like this)

I had no idea a major manufacturer was making F heads post WWII.


Thanks!

Leif

Yeah, Rover were still making them into the sixties, possibly the seventies...

The Landrover engine and their sedan range had the F-head. Rolls-Royce too, their six that was supplanted in their sedan range in 1955 by the V8 was an F-head, but it continued in production even though their cars had gone to V8 ohv.

The engines kept going in 4-cylinder and 6-cylinder form, possibly even straight 8s, in military use (Austin Champ 4WD military version, for instance) and the 6-cylinder 4-litre engine was used by Austin in their Van Den Plas Princess R from about 1964 to about 1970.

This led to the prospect of it being used in Austin-Healeys and six prototypes were laid down. Compared to the Austin-Healey 3000, the Austin-Healey 4000 was 6" wider (bodies cut up the centre and 6" added in, same with chassis), they had an improved front suspension and a Salisbury rear axle.

But Donald Healey had more in mind. They built and began testing (I believe) a full ohv head for this all-alloy engine, supposedly getting very good power out of it before the project was canned. By then three of the prototypes had been completed and they were sold off, the remaining ones were also sold and completed by private owners. So there are six Austin-Healey 4000s around the world with F-head alloy 4-litre sixes in them.

If it's of interest, the reason they were canned was because of the Leyland-BMC merger... which put 6-cylinder sports cars from Jaguar (E-type), Triumph (TR5, GT6) and MG (the unloved MG C which had an engine based on the Healey 3000 unit) under the one roof.

Now I have a rough spare 230 block I want to start experimenting with gasflow... though this will rely on my nephew being able to make time available to do it.

I'm considering that the 'transition area' is basically a part of a port which has a valve mid-way, so it becomes an important part of the detailing for port work.

Any ideas?

I ran across this releived Mopar flathead a few years back. I was told it came out of a circle racer in the 50's. It seems to me that any gain in flow would be lost to lower compression with this setup.

Could you mill the head more to bring back some compression?


MBHD

Obviously there would be milling and filling opportunities...

To be honest, I don't think there's much compression lost there, it's a fairly small area that's been relieved and it's not a deep cut.

Dan, In my way of thinking air flow is more important than compression ratio, you need air in the cylinder to compress. But the relief is old school, you need to flow air over the top of the valve to utilize the entire diameter of the valve and max flow. The combustion chamber in the head is more inportant than anything, can you post a picture of the head?

If you want to make the most HP use a turbo, flatheads really like turbos for a few reasons, one is of course to increase air flow.

Have done a few ford flatheads with turbos that made real good HP for a relatively stock design, 500HP+

Just my thoughts.

Harry

relief is old school, you need to flow air over the top of the valve to utilize the entire diameter of the valve and max flow. The combustion chamber in the head is more inportant

I agree, the relief (as shown) assumes that air will follow the floor, and drop down into the bore. IMHO the only "working" part of it is where it exposes the valve seat to the gasket surface immediately on valve opening. From there, the relief depth should decay as it approaches the bore (shallow angle to reach the seat depth and be flush at the bore edge).
I suspect that a generous radius at the bore edge (like 3/16") would improve VE and reduce pumping loss, but it does add a bit to chamber volume, and must stop at least 1/16" (more = better) above the highest point of ring travel @ TDC or the ring will overheat and lose tension.
The area above (and behind) the valve is more important, since the flows will tend to expand upward and away from the valve.
To conserve compression, the relief behind the valve can be partially filled following the general idea used in the Harley-Davidson KR diagrams.
Important: the width of the relief (deck and head) where the relief enters the bore should not be increased, this is a major part of the original Ricardo turbulent quench head. Chamber turbulence is not reduced by porting but is dependent on quench, if possible reduce the piston to head clearance to .040". Milling the head will not do this unless the piston has positive deck, you have to deck the block (or increase the rod length, stroke length, or compression distance).

I think Motor City Flathead uses a port design similar to what you describe. It is strange to think of a port design that is partly shared by intake and exhaust and must flow in both directions. Sort of like a siamese port with the valves in the middle. It seems that whatever is done to help the intake will not be good for the exhaust and vise versa. I guess that the exhaust has the advantage of help from the piston so the intake is the main concern. Maybe that is why so many of these engines have strokes longer than their bores. Once you get a flow going keep it going. Yep, they need blowers. Beater

No, it's not why they have longer strokes...

That was just the way it was done in days now long gone. There was some carryover from steam involved there too, where British horsepower ratings were calculated from the bore.

Stroke length was not (as much) penalized by older registration and tax rates (as Ray just said), but it's also the most practical way to get a long L6 engine into a small to mid-size car, which was a big sales point for Chevy and Ply-Do.
If you reduce the bore pitch and piston size to shrink the overall length and weight, stroke is what's left to make the engine big enough.
In a flathead, it also helps keep the chamber area (not necessarily volume) under control, and (by reducing the bore size to keep the same displacement) shorten the quench distance, which is typically from the plug to the opposite side of the chamber.

It seems likely to me that in adding forced induction -- turbo- or supercharging -- to a flathead, one would want to relieve the block in order to reduce compression and the opportunity for detonation, and let the increased flow do the work.

God's Peace to you.

d
Inliner #1450

With some exceptions, a stock bore and stroke L6 motor isn't going to have enough compression to limit boost, the head gasket, water jacket and lower end will limit the boost before this happens.
From what I've seen, high CR flathead engines are generally hot-rodded Ford V8s with aftermarket heads, or strokers - in which you would not want to run the 9:1 etc. they have.
Another factor is that if you reduce compression, the off-boost power really takes a dive, as does gas mileage.
I'm working on a side-valve (motorcycle) with about 6.5:1 static CR, and expect to run between 10-15 psi through it (Eaton M45).