Valve Shape & Seat Angles

[maineSS]

Has any one seen any flathead flow work concerning valve shape and seat angles for better flow? Especially interesting would be wet-flowbench work, if anyone has tackled the problem of making a transparent cylinder for a flathead.

I'm presently working on a Dodge 230 6 for my Power Wagon, and have cast up some transparent heads with resin. Although Ford and Dodge flathead designs have their differences, they also share the problem of shrouded valves and sideways flow. I'm looking to keep intake velocity as high as possible, since the engine is long stroke.

I bought a new OEM intake & exhaust valve, seats, a Manley "Street-Flo" exhaust valve, and one of David Vizard's "Rimflo" valves for testing. The Rimflo was designed especially for sideways flow and low reversion in early Brit OHV engines ("A" series), and showed up to 13% greater flow than "race" valves in that application.

I've heard that one of the board members (Ron Holleran?) published a book on the Ford flathead- is it still available somewhere? Amazon lists it as "out of print".

[blown49]

Joe Abbin has done consierable flow testing. You need to oeer his book. Go to:

http:\\www.roadrunnerengineering.com (around $25.)

Jim

[Ol' Ron]

You can get the book from Bill Boomer, JWL wrote a book on this subject as well, good photos of hi flow valves. My feelings here is for street I don't feel this is necessary unless your turning hi RPM's I did find that 30* seats with some bowl work improved flow. As far as I'm concerned the valve head seat, should be as high up on the block and valve as possble. Also you should radiys the valve head to remove the sharp edg of the seat. All this does is prevent burning and should be done on a stock valve job as well.
Remember this, a 3 angle valve job is a factory valve job and you shouldn't have to pat extra for one. It's the proper way to do it.

[maineSS]

What is Bill's contact info? I did order Mr. Lawson's book.

What I'm after is getting more torque in the 1800-2000 rpm range so I can use an overdrive effectively. The early 230 cam developed peak torque ~ 1300 rpm, and about 94 Hp, later on better carburetion allowed a different grind that torque peaked at 1600 rpm and 110 hp. The truck weighs about 6000 lbs, and has 5:83 diff gears.

I have a late-model head for this engine that supposedly developed 120 hp for cars. I'm modifying 3 Keihin constant-velocity carbs used for Harley-Davidson bikes for automotive use, the HD engine and the 230 are a very close match in bore/stroke and operating specs.

I looked at the Briggs Jr Dragster racing scene, as the Dodge and the Briggs engine are fairly similar in combustion chamber shape. However, the racing associations have some very tight rules about valve angles- interesting! I'll be back with more Monday- got to head out.

[HIGHTOWER611]

Here is a copy and paste that I took off a different thread.

I ordered ol Rons book before Christmas and read it ... good info, clarifies many things.

.........I ordered from 4tford......



"With permission of the Author Ron Holleran aka Ol'Ron I have his
book Flathead book "Nostalgia" in stock. This is a printed copy same as the original except spiral wound.

Cost including postage is
$27.25 to USA ,
$23.50 to Canada and
$34.50 to the rest of the world.
paypal to me email address is fine but do not forget your postal address is needed as well. I will be shipping once a week.
For info please email me at [email protected]

For JWL's book Flathead Facts, the link is

http://www.flatheadv8.org/jwl.htm

Both are great books."

[Ol' Ron]

Sponsored Links (Register now to hide all advertisements)

I hightly recomend JWL's book. He backs uop all modificarions with Dyno runs.

[maineSS]

I read JWL's book, it was interesting to see what mods gave the most return on time and money.

The reason valves and seat angles interest me is that (a) they are the most restrictive area in the engine, and (b) they are the last chance to atomize liquid fuel flowing along the port walls.

Airflow in a duct next to the wall will tend to follow the surface if it doesn't angle away too sharply (10- 15 deg). The surface can be a continuous radius, or a series of slopes divided by edges- like valve seat angles. The advantage of angles divided by edges is that the edges will shear a fluid film passing over them if the airflow stays attached. So getting the right combination of angles to direct airflow around the seat is quite important, and usually takes a lot of work to science out.

I've been looking into the subject for awhile, and have found some interesting data on Engine Builder magazine's site, and certain BB's. An excellent EB article is at www.enginebuildermag.com/Article/16025/the_inside-angle_on_valve_seats.aspx . "How seat angles affect airflow" and Important ratios" are well worth reading- it was interesting to see Joe Mondello increase airflow thru a factory prototype Harley head by 52 cfm, and get 25 cfm of that by changing valve seat angles. Another critical area are the throat angles under the seat- the commonly used 60 deg usually isn't right in many cases. When you go from 90 deg to 60 to the 45 deg seat, you're doing a 30 deg transition- twice the 15 deg maximum for airflow attachment- from 90 to 60 degrees.

The "Important ratios" discusses throat area to valve dia- also very important. Make it too large, you'll have a lazy engine till rpm picks up.

Another good EB article on mixture velocity is at www.enginebuildermag.com/Article/1482/drag_racing_cylinder_head_selection.aspx .
The right flow at high velocity is much better than lots of CFM at low velocity. Darin Morgan's induction system design rules of Average Velocity, Instantaneous Velocity, Shape, Rate of Velocity Change, and Airflow sum things up pretty well.

Wet flow testing is starting to reveal why sometimes dry flow testing and real world results are two different things. There's still a lot to be learned about applying it, but EB article www.enginebuildermag.com/Article/1275/wet_flow_testing.aspx is a good intro.

I'll be back with more tomorrow.

[Ol' Ron]

This is very interesting, thanks. I did allot of flow testing, but never putzs with the seat angles, using a 30* seat for better flow, doesn't reaslly work well enough to measure. At least with the equipment I had. However the use of aaaaaaa duno might find some difference. Just experiment, that's wow we learn.

[Ronnie]

Do some dyno pulls and measure the difference in torque probably not a great gain considering the amount of work to accomplish it.May be worth some effort if you can do all the work yourself as JWL and a few others here have the capabilities to perform.Going to a shop and paying the labor rate will make a considerable dent in your funds account.Not to mention the dyno pulls.There are easier ways for less money to get some gains.Compression and ignition to mention a couple.

R

[Walt Dupont--Me.]

I've used 30 degree valves and seats in my 40 for 35yr's. The only thing you can say is it does open the hole up a little. Ask O-Ron how my 40 runs. Walt

[maineSS]

An excellent book I use quite frequently is David Vizard's "Tuning the A Series Engine"- 581 pages of info that goes far beyond an early Brit OHV engine. It's available for ~$35 from Advanced Performance Technology in Riverside, CA (www.aptfast.com (951) 686-0260), and worth every penny.

Vizard did a pretty thorough investigation of 30 deg valve seats, and found two problems- (1) they don't flow as well as 45 deg seats at higher lifts, and (2) cylinder leakage past the valve due to thermal distortion of the seat can negate all the low-lift gain.

He was able to solve (1) in the "A" engine with the correct series of angles- 15 deg topcut @.010", 30 deg seat @ .050", a 45 deg cut @ .020", another 60 deg cut @ .040", followed by a 75 deg blend into the port. The "A" engine had constricted flow, so this may be a starting point for the flathead.

Thermal distortion is harder to deal with. The heat from the exhaust area causes the intake seat to expand on the exhaust side, up to .004" in the "A" engine. You'll never see this effect on the flowbench, because everything is cold- and uniform. A 45 deg seat can still seal because of better wedging action, but not a 30 deg- you lose on the swings what you gained on the roundabouts. Vizard's fix is probably better for race engines that get opened up frequently than for engines that are inspected only after something breaks. He cut a "conformation groove" in the top of the valve- .025" deep x .080" wide round bottom (.040" radius) set back .015" from the valve edge. This allowed the valve head to flex slightly and seal on the seat. Of course, after a certain amount of flexing, metal will fatigue, and then bad things happen, but "that's racin'!".

I tried emailing Bill Boomer, but got a message that "mail will be delayed". Is he gone for awhile? More tomorrow.

[Bruce Lancaster]

Have Ron's book, gotta order a JWL for me and one for a friend.
Two other good theoretical reads:
Vizard's book on Chevy Cylinder heads...VERY interesting on port development, just holfd the pictures upside down so valves are going the right way. Also it is very good on fundamentals of valve seat work, effects of valve mods, general thinking. (edit...you could think of Vizard as the JWL of the Chevy, as well as of all of those ancient Anglia and Austin engines. As with JWL, if he says something is so, he has flogged it on a flowbench and dyno and seen the results in racing. He also has an earlier work on cylinder head mods, based on popular English iro but with considerable theoretical and how to info as well. It is very hard to find.)
Smokey Yunick's power secrets...complex revelations on every page on how air moves.

[John R]

The APT website now lists Visard's book at $51.95. Not quite a bargain anymore, so it would have to highly relevant to other engines to warrant buying it. However, Amazon supposedly has it for $29.33.

[Flathead]

Things don't happen the same way in a flathead as they do in an overhead.

[Bruce Lancaster]

High performance OHV heads have enough room in the bowls to allow the flow, if bowl and approach are shaped right, to turn from the axis of port into the general axis of the valve and so potentially flow (again depending on lots of things ) all around the valve coming out at an angle taking off from last exit angle grind. Smokey noted that only fairly big aftermarket heads could really do this on a SBC, bad news for us since even the crummiest stock SBC bowls are vastly bigger than those on an FH.
Flatdog found there was some feeble flow all the way around on highly developed FH's, even from the very backside of valve area, but it was close to trivial with the impostant flow almost all linear, down the port and across the back of the valve.
He evolved the same response that Bignotti seems to have mentioned in HRM, adding material at outlet side of bowl to ramp the air up and over the edge.
I suspect a lot of low perf older OHV's lack the bowl size, developed port shaping, and such to do much different than that lateral flow, and of course most such engines also have interference from chamber and cylinder walls further restricting flow anywhere but sideways and out...but of course no OHV has anything like the transfer area and attendent need for turning room up at the roof like a FH. Vizard's special valve sounds like it relates well to FH discussion...

[maineSS]

I have most of Vizard's books, they're quite good. He's also done some articles on the Go Fast News site that are excellent reading, I'll try to post the links. He's just published a book on porting that's due out Feb 13, available thru Amazon.

Raising compression is certainly helpful, I'm going from 6.7:1 to 8:1 with the 1959 head. However, the gains in a street motor will be limited, probably around 5% overall. Every little bit helps, though.

I have an older Jacobs computer-controlled ignition (the type before they started multisparking like MSD). It makes a noticeable difference on cold wet days. One area where people leave power on the table is in not recurving after engine mods. The original engine ignition curve is developed after several hundred dyno tests for a specific set of parameters anticipated by the car manufacturer. If you change engine operating conditions, fuels, driving (racing/offroad vs street use), your engine now has a new set of parameters. The success of your mods likely requires a different ignition curve. A good example is the mileage and performance problems experienced by many people on 10% Ethanol gas. Ethanol had been used in 2-5% concentration for 20 years prior to the 10% jump, with virtually no negative feedback. I'm betting that somewhere between 5% and 10% many engines see different ignition conditions.

Getting back to valves, flatheads and OHV's share the fact that the valve area is the most restrictive part of the engine- it flows maybe 1/4 to 1/3 as much as the port. High end race engines usually are planned around the valves, and typically get 10-15 hrs minimum in the valve job.

Here's some more tidbits- www.pistonheads.com/gassing/topic.asp?h=0&t=1087429&d=0&nmt= . The post by Pumaracing hits some good topics like seat concentricty, bottom cut angles, vacuum testing, etc. Especially good is his observation that "getting a perfect valve job is like winning the lottery- in fact it IS a lottery". Another post by Brucepts (#2) at http://speedtalk.com/forum/viewtopic...t=9251&start=0 covers valve head work on Kohler engines used in garden tractor pulling. He's running high rpms (9000) for short times on methanol, mainly, but has some lower rpm (4000) stuff on gas. The Kohler has inclined valves like Ford, and is a cast iron block. Post #4 by Panic may be worth reading also.

Still looking to get Ron's book- Bill Boomer's email no longer seems valid- it came back undeliverable. Be back later.

[Bruce Lancaster]

Flatdog used to follow lawnmower power type drag racing carefully, fishing for ideas, but those engine all seem to be vertical valve without the flathead cant. Does the Kohler tractor one have any valve inclination?

[Vergil]

Originally Posted by maineSS

Go Fast News site that are excellent reading, I'll try to post the links.

I tried my shortcut to GoFast News and Looks like the site may be down now... bummer

[maineSS]

I wasn't able to get into GFN, either- hopefully they haven't vanished into Hyperspace. I did download a lot of good stuff from there.

On page 2 of the pistonhead thread (www.pistonheads.com/gassing/topic.asp?h=0&t=1087429&d=0&nmt= ), Pumaracing weighs in with Parts 2 & 3 of valve seat theory, and it's pretty good. Especially relevant to flathead flow is his description of most OHV flow in Part 3- "In large part what determines the flow efficiency is how well the port guides the air to fully utilise the entire circumference of the valve seat. In nearly all cases this cannot be achieved because air travelling at high speed can't get round the short side bend in the port and just skips across the the back of the valve head and tries to exit through the long side of the valve seat. Only on the most steeply downdraft and straight ports is there such a minimal bend on the shortside of the port that the air can come close to using the full circumference of the valve seat at high lifts".

Vizard's "A" series book also goes into this with some good illustrations in his chapter on the Rimflow valve development.

Basically most OHV heads have the same valve flow direction at the seat as flatheads, but they open into the cylinder instead of a transfer slot. I'd say the depth and length of the transfer slot has a large impact- my 1959 hi-flow head has a shorter, deeper slot than previous ones.

One interesting thing I picked up from Briggs world was moving the head over towards the valves .07-.08" by slotting headbolt holes and slightly reducing valve diameter. The fellow that tried this had positive results- "these two things got us suspended from racing, and asked to never return". My '59 head also has a little more room around the valves, which looks like what he was trying to accomplish. Brucepts' post mentioned earlier also said that he gained a bit of low-lift flow over the backside of the valve by massaging the shortside radius. Kohler engines have inclined valves like Ford, so it may be worth watching what a thread does inside a transparent casting during flowtesting, which is the reason I made mine.

One of the interesting things about flatheads is their lack of ignition advance compared to OHV's. Only in the last 5 years have highly developed SBC heads come anyhere near it, and they still have a ways to go. The theory is that the extra tubulence in the flathead gives better mixture prep, resulting less spark advance. I've lugged my 230 shamelessly, and have never got it to knock, even at loads that would instantly stall an OHV engine.

I'm presently thinking that the key to more flow lies in NOT trying to bend the flow 90 deg as it leaves the valve seat. I'll have to verify this by watching my thread, but for now a deeper transfer slot seems attractive.

[Vergil]

MainSS I read the complete thread on pistonheads, good info, copied it and also the thread at speedtalk, also good. Thanks for the links.

Vergil