Valve Shape & Seat Angles
- Thread starter maineSS
- Start date
Vergil
Senior Member
danliveshere
Well-known member
Does anybody still relieve the block anymore?
From what I've read so far, block relieving will always be controversial. In my case, the Dodge valves wouldn't really benefit. I think I'd look very carefully at where the flow wants to go thru a transparent head before cutting on increasingly rare parts.
I found another post on Speed Talk about tractor-pull Kohler engines that may help with Ford flow. The Kohler valves are inclined towards the cylinder at 4 deg, and National-level players are getting 45-50 hp, not too shabby for a single cylinder flathead. Cost for National level performance is $5- 10K, so they're pretty secretive about their work.
The post is at http://speedtalk.com/forum/viewtopic.php?f=1&t=23998&start=15 . Check out page 2, brucepts, kahuna, & panic. Kahuna mentions using kitty litter introduced into the airstream to view flow around the valve with a clear head. I think it might be a little big and heavy, but plastic microspheres might work better. Smoke would likely hide everything. Brucepts also mentions a flathead wet flow attachment, which would be interesting to see (if he actually made it).
One of the posts on GoFastNews I'd meant to link to had an good example of what correct valve seat angles & widths can do. Since it looks like GFN is history, I'll briefly quote from it.
"I've done back to back tests over the years on a number of occasions, and increasing the seat width can literally transform how an engine runs. More torque at low/mid rpm, better emissions, and a big boost at the top end.
Many years ago, I had a customer come to me with a short (1/4 mile) oval track Pinto 2L motor that had to stay in one gear throughout the race, Corner speed was about 50% of the speed at the end of the straight, which meant a good spread of torque was needed over about half the engine's rpm band. His problem was the cam they were using to get good top end power and straightline speed wasn't pulling out of the corners. They asked me for advice on a milder cam choice.
I said first thing let me look at the head and see what's been done for you. As expected it had very narrow seat wdths per most race engine builders over here who think narrow seats are the real deal. There was enough material left to recut them from 1mm to 2mm wide (42 mm inlet valve), and a minor bit tidying up in the throat area.
Next race day I got a very excited call from their mobile phone. The engine now had not only more top end bhp but so much low rpm grunt that it wasn't just pulling out of the corners, it was spinning the wheels out of them. They eventually went to a higher diff ratio to get more speed at the end of the straight. The cam choice they had didn't need looking at.
Valve seats are about the most critical part of the cylinder head as far as power goes. Flowbenches are part of the story, but sometimes you have to go past what they tell you to get engines to work at their best."
I found another post on Speed Talk about tractor-pull Kohler engines that may help with Ford flow. The Kohler valves are inclined towards the cylinder at 4 deg, and National-level players are getting 45-50 hp, not too shabby for a single cylinder flathead. Cost for National level performance is $5- 10K, so they're pretty secretive about their work.
The post is at http://speedtalk.com/forum/viewtopic.php?f=1&t=23998&start=15 . Check out page 2, brucepts, kahuna, & panic. Kahuna mentions using kitty litter introduced into the airstream to view flow around the valve with a clear head. I think it might be a little big and heavy, but plastic microspheres might work better. Smoke would likely hide everything. Brucepts also mentions a flathead wet flow attachment, which would be interesting to see (if he actually made it).
One of the posts on GoFastNews I'd meant to link to had an good example of what correct valve seat angles & widths can do. Since it looks like GFN is history, I'll briefly quote from it.
"I've done back to back tests over the years on a number of occasions, and increasing the seat width can literally transform how an engine runs. More torque at low/mid rpm, better emissions, and a big boost at the top end.
Many years ago, I had a customer come to me with a short (1/4 mile) oval track Pinto 2L motor that had to stay in one gear throughout the race, Corner speed was about 50% of the speed at the end of the straight, which meant a good spread of torque was needed over about half the engine's rpm band. His problem was the cam they were using to get good top end power and straightline speed wasn't pulling out of the corners. They asked me for advice on a milder cam choice.
I said first thing let me look at the head and see what's been done for you. As expected it had very narrow seat wdths per most race engine builders over here who think narrow seats are the real deal. There was enough material left to recut them from 1mm to 2mm wide (42 mm inlet valve), and a minor bit tidying up in the throat area.
Next race day I got a very excited call from their mobile phone. The engine now had not only more top end bhp but so much low rpm grunt that it wasn't just pulling out of the corners, it was spinning the wheels out of them. They eventually went to a higher diff ratio to get more speed at the end of the straight. The cam choice they had didn't need looking at.
Valve seats are about the most critical part of the cylinder head as far as power goes. Flowbenches are part of the story, but sometimes you have to go past what they tell you to get engines to work at their best."
Kahuna
Well-known member
As Flathead mentioned, flatheads are very different from any OHV engine. I have great respect for most everything David Vizard has done and written about, but it's not about flatheads, and most doesn't relate.
Look at that Speedtalk post and note what Panic wrote about some of this stuff.
My thoughts are that he's pretty much right. I took the same approach on my engine re valve angles. I used a protractor to come up with what I thought was the optimum angle for the gasses to flow into the combustion area and then "Bounce" off the head and into the cylinder. That angle is 45*. Anything less may be good for a tractor, but it isn't beneficial to a higher rpm Flathead Ford (Don't know anything about a Dodge). I also believe that relieving the block is a waste to time, and I don't think it's of any value to do a huge porting job (at least on a Ford). The limiting factor in the port is not the valve, but the pinch area in the port itself. It simply cannot be made large enough without hitting water. What value is there to make the ports large, when you are limited to a small pinch area? All you do is slow the port speed and make a lazy engine that has poor off-idle response.
Just my thoughts. Not trying to start an arguement with anyone.
Jim
Just thinking that there are some that could overcome the port water issue, but I don't have that skill
Look at that Speedtalk post and note what Panic wrote about some of this stuff.
My thoughts are that he's pretty much right. I took the same approach on my engine re valve angles. I used a protractor to come up with what I thought was the optimum angle for the gasses to flow into the combustion area and then "Bounce" off the head and into the cylinder. That angle is 45*. Anything less may be good for a tractor, but it isn't beneficial to a higher rpm Flathead Ford (Don't know anything about a Dodge). I also believe that relieving the block is a waste to time, and I don't think it's of any value to do a huge porting job (at least on a Ford). The limiting factor in the port is not the valve, but the pinch area in the port itself. It simply cannot be made large enough without hitting water. What value is there to make the ports large, when you are limited to a small pinch area? All you do is slow the port speed and make a lazy engine that has poor off-idle response.
Just my thoughts. Not trying to start an arguement with anyone.
Jim
Just thinking that there are some that could overcome the port water issue, but I don't have that skill
Last edited:
Bruce Lancaster
Member Emeritus
I have no way to prove anything about flow, but relieving puts the flow are at an extreme angle to the way flow comes off of seat (using seat area flow info culled from Vizard and Yunick books!)
If you look at Ford heads ('37-53) and at cross section engine drawings, the raised area Ford put into the roof of the transfer area is right where the off-the-seat angle should be putting the flow...and of course, that area is missing on most aftermarket heads because that's where they chose to fill to get compression.
This is perhaps a relic of the past--? The common heads got their basic design back when it was expensive, difficult, and unusual to build flatheads much bigger than stock. After the '49 merc stuff became available, 4 and 4 1/8 strokes became cheap and easy, and we can get compression without massive change to chambers.
Remember the great 3-part flathead build by Don Francisco in HRM in 1956? He was one of the best thinkers of his time. Biggish displacement, allowing by deliberate choice the use of stock heads and no need to relieve.
I've carefully saved numerous plans for flow benches, but doubt I'll ever have the time to get into real science.
Flatdog, a natural self trained scientist of the first order, got into serious flow work so: Elmo Rodge showed him how to make transparent shells from his experimental chambers, and a killer industrial vacuum cleaner allowed him to flow using kitty litter to make things visible.
He always used to quote a professional port guy he worked with: "Air don't like to turn."
Keeping that in mind, shove a piece of rod through a flathead intake and out through the valve area...everyone ends up fascinated with that little narrow linear path and with improving/filling the floor at the outlet area...
The pinch area in port is killer, of course...and the SBC has a similar issue to a smaller extent. The amount of work that chevy people have done to move over pushrods and such to make room for more port there is astounding.
Another flathead issue is that though there is apparently some limited flow all around, only a small part of the curtain area (on that straight line!) carries most of the actual flow.
If you look at Ford heads ('37-53) and at cross section engine drawings, the raised area Ford put into the roof of the transfer area is right where the off-the-seat angle should be putting the flow...and of course, that area is missing on most aftermarket heads because that's where they chose to fill to get compression.
This is perhaps a relic of the past--? The common heads got their basic design back when it was expensive, difficult, and unusual to build flatheads much bigger than stock. After the '49 merc stuff became available, 4 and 4 1/8 strokes became cheap and easy, and we can get compression without massive change to chambers.
Remember the great 3-part flathead build by Don Francisco in HRM in 1956? He was one of the best thinkers of his time. Biggish displacement, allowing by deliberate choice the use of stock heads and no need to relieve.
I've carefully saved numerous plans for flow benches, but doubt I'll ever have the time to get into real science.
Flatdog, a natural self trained scientist of the first order, got into serious flow work so: Elmo Rodge showed him how to make transparent shells from his experimental chambers, and a killer industrial vacuum cleaner allowed him to flow using kitty litter to make things visible.
He always used to quote a professional port guy he worked with: "Air don't like to turn."
Keeping that in mind, shove a piece of rod through a flathead intake and out through the valve area...everyone ends up fascinated with that little narrow linear path and with improving/filling the floor at the outlet area...
The pinch area in port is killer, of course...and the SBC has a similar issue to a smaller extent. The amount of work that chevy people have done to move over pushrods and such to make room for more port there is astounding.
Another flathead issue is that though there is apparently some limited flow all around, only a small part of the curtain area (on that straight line!) carries most of the actual flow.
Something that will always retard progress is a preconceived notion that things will always act a certain way. A classically trained aerodynamic engineer can mathematically "prove" that bumblebees can't fly- their wings are too small to generate the required lift. If you were to accept that notion, and started stomping a bumblebee nest, you'd find that bumblebees can fly faster than you can run, and can keep going quite a long ways. The reason why they fly is their wings operate in the "unsteady aerodynamic" region, and can generate about 2 1/2 times the lift that manmade wings can- a fact discovered by scientists researching dragonfly flight.
Now the popular rationalization is that "flatheads are different" leads to the idea that flow will somehow behave differently- it won't. Flow does not know, or care, whether it's in a flathead, an OHV, or a gas turbine. It will behave in fairly predictable ways when it meets with obstructions, and by observing the flow, you can figure out what's going on.
Now with respect to the "pinch" area in the Ford, if the dia of the pinch compared to the valve is less than the recommended 86-7% ratio, it's a problem. If not, leave it alone- something else is the problem.
One of the things Joe Mondello did under a Briggs contract was to dimple the intake port. The idea was to steer flow thru the port by pulling it towards the dimpled surface. It outflowed any other Briggs port he did, but it required quite a bit of work to figure out the correct dimple dia, depth, and arrangement. Now think about the floor of the Ford intake port- it's a dead area, and even filling it doesn't seem to do much. Go here http://olskoolrodz.com/forum/showthread.php?t=33527&highlight=siamesed+intake+port , post # 47 by Hudsonator. This is a very long thread that covers a lot of Flathead flow stuff, well worth downloading.
Anyone besides Bill Boomer have a copy of Ron's book for sale? Still can't get Bill's email to work...
Now the popular rationalization is that "flatheads are different" leads to the idea that flow will somehow behave differently- it won't. Flow does not know, or care, whether it's in a flathead, an OHV, or a gas turbine. It will behave in fairly predictable ways when it meets with obstructions, and by observing the flow, you can figure out what's going on.
Now with respect to the "pinch" area in the Ford, if the dia of the pinch compared to the valve is less than the recommended 86-7% ratio, it's a problem. If not, leave it alone- something else is the problem.
One of the things Joe Mondello did under a Briggs contract was to dimple the intake port. The idea was to steer flow thru the port by pulling it towards the dimpled surface. It outflowed any other Briggs port he did, but it required quite a bit of work to figure out the correct dimple dia, depth, and arrangement. Now think about the floor of the Ford intake port- it's a dead area, and even filling it doesn't seem to do much. Go here http://olskoolrodz.com/forum/showthread.php?t=33527&highlight=siamesed+intake+port , post # 47 by Hudsonator. This is a very long thread that covers a lot of Flathead flow stuff, well worth downloading.
Anyone besides Bill Boomer have a copy of Ron's book for sale? Still can't get Bill's email to work...
Vergil
Senior Member
Has anyone used a Rim Flow valve in a Flathead? Been reading some about them and looks like it might help in a NA flathead with bigger cam to save some of the charge from going back into the intake on cam overlap. Used on the intake but not the exhaust. Pic below. Read about then in one of DV's books.
I got a rimflow valve from APT to test along with my stock valves and the popular Street Flow Manley SBC valve. It's slightly bigger in dia, and shorter in length, so it'll never be a drop in replacement- I'll have to copy it if it turns out to be a winner. They are available as an exhaust valve, but the intake side is likely where they'd be best. They have a large margin area compared to normal valves, which I think would not help flow over the top at low lift. We'll just have to flow it and see what happens.
I located a junk 230 block in the Boston area, so I'll be doing a road trip soon. I have a friend who's a head porter, so at some point I'll get set up on the flowbench to get some data.
For those who are wondering where post #47 in my last link is, go to page 5- it's at the end of the page. Another interesting port floor mod can be found at www.ls1tech.com/forums/advanced-engineering-tech/1202820-golf-ball-effect.html -post #20 by Coreyc619. He used slots cut in the floor of a Harley intake manifold to improve wet-flow characteristics. The siamesed intake port of the dodge resembles the Harley manifold, so I may try dimpling/slotting during my testing. Also, www.popularhotrodding.com/tech/0912phr_dci_455pontiac_engine/index.html shows a dimpling treatment that gained ~40 Hp in the combustion space. Go the Homepage, search, then go to to engine Photos 4 and 10- I wouldn't expect results like this in a flathead, but it might give you an idea of dimple size/spacing.
I located a junk 230 block in the Boston area, so I'll be doing a road trip soon. I have a friend who's a head porter, so at some point I'll get set up on the flowbench to get some data.
For those who are wondering where post #47 in my last link is, go to page 5- it's at the end of the page. Another interesting port floor mod can be found at www.ls1tech.com/forums/advanced-engineering-tech/1202820-golf-ball-effect.html -post #20 by Coreyc619. He used slots cut in the floor of a Harley intake manifold to improve wet-flow characteristics. The siamesed intake port of the dodge resembles the Harley manifold, so I may try dimpling/slotting during my testing. Also, www.popularhotrodding.com/tech/0912phr_dci_455pontiac_engine/index.html shows a dimpling treatment that gained ~40 Hp in the combustion space. Go the Homepage, search, then go to to engine Photos 4 and 10- I wouldn't expect results like this in a flathead, but it might give you an idea of dimple size/spacing.
Last edited:
Here's an interesting series of photos from www.diyporting.com/thread.html - check out the low-lift valve flow pics, especially from .1-.300". For those who persist in thinking flathead flow thru the valve area is somehow "different", the Ford GT40P OHV head was well-regarded in its day (now come and gone). Note in the drawing how much of the valve area has poor flow, and where the strong flow area is.
I don't think too much Kitty Litter will get past the valve seat area at low lifts, but hopefully the thread will be visible when I add a clear plastic head. It will also be interesting to see if flow follows the deck at low lift- these pics seem to encourage reliefs...
I don't think too much Kitty Litter will get past the valve seat area at low lifts, but hopefully the thread will be visible when I add a clear plastic head. It will also be interesting to see if flow follows the deck at low lift- these pics seem to encourage reliefs...
Bruce Lancaster
Member Emeritus
I suspect the limited good flow area is actually common on typical OHV engines...apparently it takes a larger than common, usually aftermarket, Bowl to allow significant downward turn of the flow from port axis toward valve, according to Yunick.
From this I suspect LOTS of OHV engines have much of their flow in a straight line out the far side of valve....
Once turning is achieved in a huge bowl, much further development goes into tuning and turning that flow toward center, away from the chamber side restrictions...we don't need to worry til someone figures out how to grind a flathead bowl out to the size of a baseball...and then imagine what the CHAMBER would have to look like on a flathead if you could get flow all around the valve!
From this I suspect LOTS of OHV engines have much of their flow in a straight line out the far side of valve....
Once turning is achieved in a huge bowl, much further development goes into tuning and turning that flow toward center, away from the chamber side restrictions...we don't need to worry til someone figures out how to grind a flathead bowl out to the size of a baseball...and then imagine what the CHAMBER would have to look like on a flathead if you could get flow all around the valve!
As a general rule, anything within 1/2" of the valve will affect flow. Another interesting thing is that low valve openings have high depressions-(as low as 100 in water @ .070 for SBC), and high valve openings have low depressions (around 10-12 in water at .650 for SBC. This will definitely change flow characteristics as it exits the valve, and may explain why deck reliefs in the Ford block seem to work better at higher rpms, from what I've heard. GFN had an excellent article about using "Floating Depression" flow testing, where readings were taken according to valve lift depression, not at a standard 10 or 28". I don't know what depression the pics shown in the DIY porting article was, but it's quite possible that it wasn't 60 or 100" water.
It's possible to use Floating Depression testing with a common vacuum cleaner, and pull 60" at low valve lifts. Vizard's GFN article also showed how to convert FDP readings to 28", using an orfice plate and graph. It works even better with Audie Technology's Flow Quick, and if you're thinking about setting up a bench, that would be the cheapest way to get computerized professional capabilities at a rock-bottom price (~$700 vs $10K). I was able to find an archived version of the GFN article at www.eurospares.com/graphics/engine/Vizard/Porting%20School%20%232%20%-%20Super%20Cheap%20Flow%20Bench%20 ..., hopefully this link works, if not Google it.
It's possible to use Floating Depression testing with a common vacuum cleaner, and pull 60" at low valve lifts. Vizard's GFN article also showed how to convert FDP readings to 28", using an orfice plate and graph. It works even better with Audie Technology's Flow Quick, and if you're thinking about setting up a bench, that would be the cheapest way to get computerized professional capabilities at a rock-bottom price (~$700 vs $10K). I was able to find an archived version of the GFN article at www.eurospares.com/graphics/engine/Vizard/Porting%20School%20%232%20%-%20Super%20Cheap%20Flow%20Bench%20 ..., hopefully this link works, if not Google it.
Last edited:
Vergil
Senior Member
MaineSS I couldn't get the link to work but I think this is the parent directory for what you are talking about. http://www.eurospares.com/graphics/engine/Vizard/
I really like reading Davids articles, only wish he had tested as much with the flathead as he done with the OHV's. At 70 years old I hate to put time into a flowbench for a flathead but I guess it will keep me busy.
Vergil
I really like reading Davids articles, only wish he had tested as much with the flathead as he done with the OHV's. At 70 years old I hate to put time into a flowbench for a flathead but I guess it will keep me busy.
Vergil
Vergil-
Outstanding job with the directory- it has stuff I've not seen before. I downloaded some material on siamesed intakes, will look at it tonite. For those interested in the flowbench, check out Porting School #2,3 &4.
There's also good stuff concerning Turbulence & Combustion Dynamics that apply- sometimes what works in an engine is exactly the opposite of what's commonly believed, and you have to actually work with an engine to find out what's best for its particular needs.
With respect to flatheads, a lot of people go the wrong direction with respect to compression and fuel choice. The primary difference between a flathead and today's engines lie in bore/stroke ratios, these have differences most people don't even think about, but play a huge part in how well the engine will run.
Ron- do you have a working email for Bill Boomer, or an alternate source for your book?
Outstanding job with the directory- it has stuff I've not seen before. I downloaded some material on siamesed intakes, will look at it tonite. For those interested in the flowbench, check out Porting School #2,3 &4.
There's also good stuff concerning Turbulence & Combustion Dynamics that apply- sometimes what works in an engine is exactly the opposite of what's commonly believed, and you have to actually work with an engine to find out what's best for its particular needs.
With respect to flatheads, a lot of people go the wrong direction with respect to compression and fuel choice. The primary difference between a flathead and today's engines lie in bore/stroke ratios, these have differences most people don't even think about, but play a huge part in how well the engine will run.
Ron- do you have a working email for Bill Boomer, or an alternate source for your book?
Here's another post from the "Siamesed Intake Ports" thread that does a good job explaining the balance between flow and compression in flatheads- http://forum.olskoolrodz.com/showthread.php?t=33527&page=5&pp=10&highlight=Dodge=flathead (start at Post 42). Unfortunately, Hudsonater's pics got lost when his hosting service crashed, but if you can visualize what he's talking about, you'll be ahead of most people's attempts at flathead mods. The Hudson absolutely dominated early NASCAR racing- it killed the OHV competition for years.
Bruce Lancaster
Member Emeritus
There is a discussion of flow vs compression also in the classic engine book by Sir Harry Ricardo...
I have a post WWII revision no (I once had a much earlier edition) and the L-head section is I think greatly reduced to make way for all the sleeve valve and OHC late war aircraft engines. Gotta find me an early edition with more L-head stuff...he got his research start during WWI flogging some seriously poor tank engines that were L-heads.
I have a post WWII revision no (I once had a much earlier edition) and the L-head section is I think greatly reduced to make way for all the sleeve valve and OHC late war aircraft engines. Gotta find me an early edition with more L-head stuff...he got his research start during WWI flogging some seriously poor tank engines that were L-heads.