Flathead combustion chamber profile...Q

Does anyone have profile drawings of flathead combustion chambers?
Just wondering what profile breaths the best.
I'm particularly interested in the area around the valves.

 

Maybe this will be alittle closer. Although probably not what your looking for.

 

Of "production" aftermarket heads, Weiands are some of the best flowing heads. Offys ain't bad either - especially for mass-production heads.

Don't know that there's "one" profile that works.

 

Look at an EAB head; may give you some good ideas.

 

A lot of people are looking at various stock heads nowadays.
Flatdog, perhaps the deepest combustion chamber flogger on here, rummaged through my head pile looking at chambers. Weiands were dismissed as so-so...he liked the 81AS semi stockers and the C7RA (real ones, not Weiand) Canucks.

 

So, no drawings?
There must be some info out there on flow and quench in an L-head engine.
Maybe I'll wander over to a Jr Dragster sight and see what's happening.

 

There is a classic Isky drawing of flathead chamber and ports, reproduced in many books, and of course the excellent Ford cross section drawings in the service bulletins.
Quench is roughly the outer 2/3's of the piston dome, rest of that neighborhood is the flow area.

 

I had this written down when I was deciding which head to go with, just not sure it came from one source.

Best flowing to worst flowing heads

#1 Baron racing head
#2 Motor City head
#3 Navarro high flow head
#4 Baron street head
#5 Norman Frick head
#6 Hansen racing head (like the Sharp head with relief on exhaust valve side)
#7 Flatattack high flow head
#8 C81T Ford head

Picture is of my Norman Frick 2piece head. Combustion chambers are 78cc for the blower motor.

 

I knew a guy that was looking into flow on flatheads with a flowbench. This was quite a few years ago.
The problem was the area over the cylinder wall acting as a restriction to flow. By opening up the head there, even tho compression was lost, the flow was so much better that the higher rpm power improved, and the low speed wasn't noticibly hurt.

A quick fix was to slide the head down and out, actually kinda shrouding the valves. But not much is going around the valves up there anyway. We found that .070 moving of the head gave a significant improvement.

This involved ovaling the head stud holes in the head by that amount. You need to be careful that you don't uncover a water port or have the valves actually hit the edge of the head.

Reducing the OD of the valve as much as possible. this is getting the valve seat closer to the edge. This provides less restriction as the valve is opening and closing.

This is from way back when stock parts were required and supposed to be "non-modified"

Every time there are racing rules, ya gotta figure a way around them.

Frank

 

Ricardo wrote a book about this in the 20s.

 

By the way, Flatdog was seemingly intrigued by the '32 type chambers for flat pistons, the ones with a sort of heart shaped chamber...I think he saw similarities to some of the odd flows he had seen in his testing. Wish he was still alive, and willing to show me one of his race chambers!

 

That's what I'm talking about.
When the valve is open(Up) how much air(Combustion products) is actually moving around the side away from the valve?
Do you have any profile pictures of the are over the cylinder wall?
Did you just raise the roof of the combustion chamber in that spot?

 

Anybody have a copy?

 

as Ernie stated, there may not be a combustion chamber that "is the one".
there are SCHOOLS OF THOUGHT when it comes to flathead fords, its best to find a philosophy and stick to it... or, if you've got a better idea, put it to practical use and prove your point.

Joe Abbin and Mike Davidson's flathead books are an excellant source of info... Tex Smith's flathead how-to book has some insightful interviews about flow.

i personally do not have a favorite just yet, but i take great interest in what Kong, Navarro and Tony Baron have to say about piston design and flow.

 

There are as many opinions on this as there are flathead nuts on this site (myself included). One thing to think about is what the application is. Opening up the transfer area (between the valves and cylinder) can really help flow, but your compression ratio will suffer. Everybody knows that higher compression REALLY helps a flathead on low-end power . . . so going this approach may work well for Bonneville, but will make a street car a real dog coming out of a stop light. The Baron high-flow head uses a big flat-top pop-up piston and has a huge transfer area . . . great for a blown application and high rpm power, not worth much for a street engine. The Navarro High-dome head is as close of a copy of the Harley KR racing head as is possible (given the cylinder stud location on a Ford, the intake valve sizes, ports, etc. The Navarro head uses a high-dome piston - can't remember the dome radius, but it is much smaller (higher dome) than Ford.

There are also many opinions on the value of relieving the block - which opens up the transfer area. Back in the day, just about everybody who raced flatheads relieved them -- some don't today. The Harley KR did relieve the cylinder, had a large transfer area and only had a CR of about 7.0 to 1. The BIG difference in a Harley KR (which makes more HP per cube than any other NA flathead) is that they have very well designed intake and exhaust ports, they have long-duration roller cams . . . and they rev them very high. Also, Harley used both flat top as well as domed pistons on their factory KR race bikes - can't remember which one was the last design they used?

What are you trying to accomplish in your quest? Street motors? Blower motors? Bonneville motors?

Flatdog and I spent many hours talking about combustion chambers and the many different types of chamber designs. If you want some pictures, I can dig up a few - including the Harley KR heads.

 

I'm doing a KR upper on a regular 45 lower with stroker wheels, about 57 cubes

Really there is no comparison between the flow of a K and a ford, it is redicuios the ports are Twice the size and valves are HUGE. the race KR's had something like 60hp from the factory WAY OVER 1 hp per cube

As for compression with the valve size on a harley it is really limited but as of 1968 when they stopped racing them there was no better flathead

But a v-8 puts the cylinders far too close togather to put valves like that in

 

I agree with plan9, you really need to read the article by Barney Navarro in the Tex Smith/Ron Cerrillo Flathead book. Barney Navarro was very knowledgable about flatheads and head design.

 

You're 100% correct! One of my mentors used to build race KRs - he was making almost 1.5 HP per cube on the dyno . . . with a 55 inch stroker. Which KR roller cam pattern are you using? I used to borrow his KR cylinders, heads and cams and ponder what I could apply to a Ford flathead. Wouldn't it have been cool if the Ford flathead had the breathing capability of the KR (or you could carve it to be)! Even the likes of the new Motor City blocks will never compare to the Harley design - just not enough room and the dang exhaust in the block makes the pattern designs so damn difficult.

 

http://www.jockeyjournal.com/forum/showthread.php?p=19665#post19665

I'm not sure on cam yet probably a tom sifton grind though, kinda got sidetracked

 

Might be worth your while to take a look at what the Jr.Dragster builders
are doing.They were making about 50hp with a 3.5"X3" on alcohol when
I got out 3 yrs. ago.Remember though we were twisting them 8500 to
9000 rpm and I've seen 10,200 on the telltales when a chain broke.

 

Wow, now this is the conversation I was hoping for.
The engine in question is the Pontiac straight eight I picked up last year.
For now, I'll just get it running, but with a Mallory dual point on the shelf and a couple turbo's to play with, well...a mind gets to wondering what could be done.
It would be interesting to see what I could get out of it with nothing but a gasket set and some innovation.

Every once in a while I like to post something to mine a little info and provoke a little thought.
Thank you all for your input.
This was fun.

Steve

 

Bruce,

I've got to ask, was it dismissed based on chamber shape, or flow bench data? The Weiands flow comparatively better than any other mass produced aftermarket head. By mass produced, I don't necessarily mean Navarro, Kong, or Baron.

The differences in flow were actually relatively minor in the grand scheme of things. I'm sure there's as many poofteenth's power avail with chamber design as there are in the minor flow differences, so the best power may not necessarily be the highest flow - but flow is your greatest enemy in a flatty.

A .100" relief improves flow on every single head tested - granted it was relatively minor on some (like Baron Hi-Flow), and probably at the upper RPM ranges, but the tradeoff in CR (approx .3 on a "standard" 276) would seem to be worth it.

The Barons also produce almost a point lower CR than they advertise due to the way Baron measures them...so be advised.


If money were no object, I'd like to do a pop-up design. But that will have to wait until I win the lottery...

Other tidbit - current Edelbrock machined chambers do not flow as well as their older cast chambers - although QC & consistency is radically improved - probably a welcome trade-off for most. The difference is a minor one at higher lifts.

Abbin now recommends a shallow, radiused plunge cut directly above the intake to help get the flow. Just watched a dyno run of one of his customer's engines today - very impressive numbers (can't say until he informs his customer as technically, they're proprietary) - better than the numbers the Honest Charley engine pumped out (but different cam).

Joe has a new book coming out - lots of dyno runs to back up the flow bench & theory - plenty of drag runs to back up the dyno runs.

 

Curious, are you talking about a radius in the area behind the valve - instead of a straight vertical valve pocket wall? On my racing heads, I cut a radius into the wall to help "turn" the intake charge on the back of the valve - over the top of the valve and toward the bore. This only helps during the mid point of the lift - where I want to redirect some of the intake charge over the top of the valve. The thought (as much speculation as fact) is that it is beneficial to flow some intake charge on the back and side of the valves and help it move around the back of the chamber and either toward the bore (intake) or from the bore to the exhaust port. I'm sure there is just a small potential for this to help flow, but when dealing with Ford flatheads . . . every little bit can help.

This is the same approach that I've seen on many of the KR Harley heads that were winners on flat track. My friend Don 'Snuffy' Smith modified all his KR heads in this manner.

If anybody wants pictures, let me know . . .

 

Love to see your pics.

Think of a fly cutter, but with a radius on the edge, plunge cut directly above the valve. Joe has flowed this out & his engines are making the power.

 

I'll be out in the shop this evening - will take some combustion chamber pictures for yah and post them.

 

Thanks guys.
This is really interesting stuff.
You guys are right on target for the area I was wondering about.

 

Although not a car flathead I do dabble in small single cylinder flatheads on my flowbench. I have cut a clear acrylic head so I can actually see what was going on inside as well as using velocity probes to actually measure localized velocity profiles.

Using a simple piece of string one is able to see the flow, the "conventional" thoughts are the flow takes a line-of-sight into the chamber when in fact there is ALOT more flow going over the short side (top) than most think. I've been machining my heads with an angle over the piston back towards the valves this leaves very little squish/quench area if any. This has been a big help on flow and allowed me to make the chamber even smaller. The area over the intake valve is a place flow can be found. To little hurts flow to much hurts compression.

Releiving the block has done nothing for flow, as the flow comes out of the port and over the seat it "humps up" and totally misses the relieved area. 30* seats worked better than 45*, wide seats and narrow faces with a nail head on the valve flowed the best but this is all specific for the application. Narrow valve faces will not live on the street. You have to efficiently turn the flow from the port into the chamber! A simple cut on the top of the valve above the margin stopped some serious reversion on the backside of the valve/short side turn at mid lifts. I was actually seeing the flow move backwards over the top of the intake valve.

I'm working on a wetflow setup now for my bench that will allow me to use a solution with dye in it to do some video work. I attached a picture of one of my blocks on my flowbench you can makeout the size of the chamber in the side view. Since flathead engines sell for some serious $$$$'s in the tractor pulling venue I'm not at liberty to post more detailed pictures on a public forum.

 

The Ricardo book is "The High Speed Internal combustion Engine" it is considered one of the best works on combustion. As far as I know it has never been reprinted. Depending on condition expect to pay $100-$300

 

Those are actually pretty cheap prices for one...especially an early edition.

I believe it is being reprinted in the UK, but they're still very expensive.

 

it really comes down to how fast do you want to go and how much money do you want to spend.