Flathead porting?
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GOSFAST
Well-known member
Hi Roger, not sure Goodson even has the bowl-hogs anymore??
But if so, the smallest one they had, the DCW BH-25 is actually still somewhat large for the "standard" 1.500" Flathead valves. The way the seats are installed in the block from the factory leaves little material "hanging" inside the throat area. The bowl-hog would most likely remove very little material with the stock valve sizes.
Having said that, if you choose to install o/size valves you'd have a better chance of them working!
Below is a shot of them from Goodson along with the "driver"!
Thanks, Gary in N.Y.
P.S. One of the reasons Goodson MAY have dropped those tools is the same operation can be performed with the assortment of blades available for most head machines, conventional or CNC. We have both setups available here.
But if so, the smallest one they had, the DCW BH-25 is actually still somewhat large for the "standard" 1.500" Flathead valves. The way the seats are installed in the block from the factory leaves little material "hanging" inside the throat area. The bowl-hog would most likely remove very little material with the stock valve sizes.
Having said that, if you choose to install o/size valves you'd have a better chance of them working!
Below is a shot of them from Goodson along with the "driver"!
Thanks, Gary in N.Y.
P.S. One of the reasons Goodson MAY have dropped those tools is the same operation can be performed with the assortment of blades available for most head machines, conventional or CNC. We have both setups available here.
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Ol' Ron
Well-known member
I think porting and bigger valves are overkill for a street engine. However, when building engines I did use a bowl mill in all my engines and some port reshaping. The bowl mill I made was for a 1.5 valve and I used it on most of the engines I built. I had another reamer for the 1.6 valve. Here's the rub. The blocks have allot of core shift in this area. in some blocks very little material was removed, in others only one side maube removed and I did have a break through in one block. The engine in Richards engime is the only engine I'm familiar with that is built up 276 with a completly stock valve assy and needlessly to say one of the better preformers I've ever driven. BUT, It is a street engine in a heavy car and a good port job with large valves may have improved the WOT acceleration,, but he doesn't do that very much.
GOSFAST
Well-known member
Hi Ron, exactly right, on most blocks this is what we've seen!
Thanks, Gary in N.Y.
P.S. It it was a "very serious" build for race-only I would look into having it extrude-honed. Would be somewhat expensive but it would work. We do exhaust manifolds on occasion where class rules dictate the program.
Ol' Ron
Well-known member
Pet that's abeautiful job, I took pride back in the early days at the quality of my porting and relieving. I realize now, after muck testing with a flow bench, releving was wrong and you can't improve flow very much after 10 minutes in a port with a carbide. I wish someone would dyno test a block before and after just to see how much it improves the output.
PeterC
Well-known member
Re: Flathead porting/Relieving?
Well Ron .. your raise an age old question which I certainly will not argue one way or the other - below is an interesting article in Street Rodder Magazine way back in 2009 that covers the subject but I am sure does not settle it.The Truth About Ford Flathead Engines- Destroying Flathead Myths
Written by Ron Ceridono on May 1, 2009
View All 4 Photos
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1/4 Joe Abbin at Roadrunner Engineering has spent years collecting flowbench and dyno results on Flatheads. That huge amount of data allows Joe to make extremely accurate computer simulations for his customers.
Given the fact that the first Ford Flathead engine was produced 77 years ago, and hot rodders have been tweaking them since day one, it would seem we would have learned everything there is to know about one by now. But during the time hot rodders have been building Henry's venerable V-8, more theories have been advanced and more myths have been created about them than any other engine.
One of the reasons so many misconceptions exist about these engines is that early on much of the speed equipment was developed with seat-of-the-pants evaluations, and if a certain combination won races or set records, it was deemed a success. Another reason is that many of the engine builders who have amassed a large amount of comparative data on modifications and combinations of components haven't been willing to share the information. Not many engine builders who have spent untold hours on the flow bench and in the dyno room are willing to tell all. Joe Abbin of Roadrunner Engineering is one of the few exceptions.
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2/4
We first worked with Joe on our "One Last Flathead" series in 2004. At that time, many engine builders were denying the effectiveness of the classic relief, but his research convinced us that was definitely not the case--Flathead myth number one is that reliefs don't work. The second conclusion Joe came to contradicts conventional engine building wisdom, and has to do with compression ratios. With most engines, increasing compression results in more power, but with a Flathead there is a point not only of diminishing returns, but a point where power is lost--and it's lower than you might think. Flathead myth number two: the higher the compression, the more power the engine will produce.
Since we first collaborated with Joe, he's gathered more flowbench and dyno information to confirm his earlier findings, and has followed up his first book, Blown Flathead, with his new 335hp Flathead Ford V-8 Performance Handbook (available from Roadrunner Engineering). He was gracious enough to pass along some of the myth-busting information he's collected.
3/4
Optimizing The Flathead Ford
Relieving And Compression Ratios Versus Air FlowLike any engine, the Flathead will benefit from a good porting job. Increases in intake and exhaust airflow translate directly into increased power. Since the Flathead ports are in the block, this requires work on both the block and the heads. The Flathead has a very restricted flow path, with the valves being next to the cylinder rather than over the piston. This relatively complex flow path presents several areas that require attention. Airflow can be greatly improved by moderate porting and intake and exhaust airflow can be increased 35% or more with a corresponding increase in power.
The merits of relieving a Flathead have been vigorously debated in recent years. At one time, all serious Flatheads were relieved, and with good reason. My flow testing of both relieved and unrelieved blocks has clearly demonstrated that relieving substantially improves flow. Even low compression cylinder heads with very large combustion chambers and large transfer areas (between the valves and cylinder bore) will show substantial gains from a moderate, 0.125-inch deep, constant-depth relief. As noted above, mild "street" porting and relieving job can increase flow and therefore horsepower 35% or more. Since relieving provides the major part of this gain it is highly recommended. The traditional constant depth (0.100-0.125-inch) relief to the head gasket boundaries is very effective. The constant depth relief flows substantially more than the ramp type (where the relief does not go into the cylinder bore). The only bad news is that relieving does remove material from the combustion chamber and lowers the compression ratio. The good news is that not much material (about 3 cc) will be removed, which typically lowers the compression ratio only a small amount, about 0.2 to 0.3 point. Lowering the compression ratio 0.3-point reduces power about 1%, which is more than made up by the greatly increased airflow that relieving offers.
4/4
Removing material in the combustion chamber for any reason always lowers the compression ratio. In the case of relieving (area C) there is only a small penalty in compression ratio and the net result is increased power from the additional airflow.
The result of removing material at "A" is not nearly so clear-cut. Removing material in this area modestly increases airflow, but can substantially lower the compression ratio. (Cleaning up areas B and E and valves with reduced stem diameters (D) also helps airflow.) Knowing where and how to remove material in the heads for maximum benefit is covered in detail in my new book, 335hp Flathead Ford V-8 Performance Handbook.
In the Roadrunner Engineering study, published in the December 2002 and March 2003 issues of STREET RODDER article "Revival of the Fittest," the computer analysis was based on a 276 cubic inch Flathead with a "3/4 race" cam and typical intake and exhaust systems at sea level conditions. Actual flow test data and combustion chamber volumes for representative test head configurations were then used for input into Engine Analyzer Pro. The results were the higher compression engines dominated power projections at lower engine speeds, but then ran out of air at higher speeds. The lowest compression engine improved relative to the others as engine speed increased, but the improved flow never produced higher peak power than the others. Simulated and actual test results indicate that the optimum compression ratio for peak horsepower for a normally aspirated street Flathead is about 8:1 to 9:1. Going with the low side of this range has the advantage of requiring lower octane fuel with minimal loss of low-end torque and mileage. Years of street driving experience validate these results. These results were also validated in a second similar study that included the buildup of an actual engine, documented in the July 2004 issue of STREET RODDER in the article "Out with the Bad Air, In with the Good." It's also been found that supercharged street Flatheads perform best with lower compression ratios, as discussed in the books referenced above.
Well Ron .. your raise an age old question which I certainly will not argue one way or the other - below is an interesting article in Street Rodder Magazine way back in 2009 that covers the subject but I am sure does not settle it.The Truth About Ford Flathead Engines- Destroying Flathead Myths
Written by Ron Ceridono on May 1, 2009
Share This Article Facebook Twitter Google+ Email
1/4 Joe Abbin at Roadrunner Engineering has spent years collecting flowbench and dyno results on Flatheads. That huge amount of data allows Joe to make extremely accurate computer simulations for his customers. Given the fact that the first Ford Flathead engine was produced 77 years ago, and hot rodders have been tweaking them since day one, it would seem we would have learned everything there is to know about one by now. But during the time hot rodders have been building Henry's venerable V-8, more theories have been advanced and more myths have been created about them than any other engine.
One of the reasons so many misconceptions exist about these engines is that early on much of the speed equipment was developed with seat-of-the-pants evaluations, and if a certain combination won races or set records, it was deemed a success. Another reason is that many of the engine builders who have amassed a large amount of comparative data on modifications and combinations of components haven't been willing to share the information. Not many engine builders who have spent untold hours on the flow bench and in the dyno room are willing to tell all. Joe Abbin of Roadrunner Engineering is one of the few exceptions.
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2/4 We first worked with Joe on our "One Last Flathead" series in 2004. At that time, many engine builders were denying the effectiveness of the classic relief, but his research convinced us that was definitely not the case--Flathead myth number one is that reliefs don't work. The second conclusion Joe came to contradicts conventional engine building wisdom, and has to do with compression ratios. With most engines, increasing compression results in more power, but with a Flathead there is a point not only of diminishing returns, but a point where power is lost--and it's lower than you might think. Flathead myth number two: the higher the compression, the more power the engine will produce.
Since we first collaborated with Joe, he's gathered more flowbench and dyno information to confirm his earlier findings, and has followed up his first book, Blown Flathead, with his new 335hp Flathead Ford V-8 Performance Handbook (available from Roadrunner Engineering). He was gracious enough to pass along some of the myth-busting information he's collected.
3/4 Optimizing The Flathead Ford
Relieving And Compression Ratios Versus Air FlowLike any engine, the Flathead will benefit from a good porting job. Increases in intake and exhaust airflow translate directly into increased power. Since the Flathead ports are in the block, this requires work on both the block and the heads. The Flathead has a very restricted flow path, with the valves being next to the cylinder rather than over the piston. This relatively complex flow path presents several areas that require attention. Airflow can be greatly improved by moderate porting and intake and exhaust airflow can be increased 35% or more with a corresponding increase in power.
The merits of relieving a Flathead have been vigorously debated in recent years. At one time, all serious Flatheads were relieved, and with good reason. My flow testing of both relieved and unrelieved blocks has clearly demonstrated that relieving substantially improves flow. Even low compression cylinder heads with very large combustion chambers and large transfer areas (between the valves and cylinder bore) will show substantial gains from a moderate, 0.125-inch deep, constant-depth relief. As noted above, mild "street" porting and relieving job can increase flow and therefore horsepower 35% or more. Since relieving provides the major part of this gain it is highly recommended. The traditional constant depth (0.100-0.125-inch) relief to the head gasket boundaries is very effective. The constant depth relief flows substantially more than the ramp type (where the relief does not go into the cylinder bore). The only bad news is that relieving does remove material from the combustion chamber and lowers the compression ratio. The good news is that not much material (about 3 cc) will be removed, which typically lowers the compression ratio only a small amount, about 0.2 to 0.3 point. Lowering the compression ratio 0.3-point reduces power about 1%, which is more than made up by the greatly increased airflow that relieving offers.
4/4 Removing material in the combustion chamber for any reason always lowers the compression ratio. In the case of relieving (area C) there is only a small penalty in compression ratio and the net result is increased power from the additional airflow.
The result of removing material at "A" is not nearly so clear-cut. Removing material in this area modestly increases airflow, but can substantially lower the compression ratio. (Cleaning up areas B and E and valves with reduced stem diameters (D) also helps airflow.) Knowing where and how to remove material in the heads for maximum benefit is covered in detail in my new book, 335hp Flathead Ford V-8 Performance Handbook.
In the Roadrunner Engineering study, published in the December 2002 and March 2003 issues of STREET RODDER article "Revival of the Fittest," the computer analysis was based on a 276 cubic inch Flathead with a "3/4 race" cam and typical intake and exhaust systems at sea level conditions. Actual flow test data and combustion chamber volumes for representative test head configurations were then used for input into Engine Analyzer Pro. The results were the higher compression engines dominated power projections at lower engine speeds, but then ran out of air at higher speeds. The lowest compression engine improved relative to the others as engine speed increased, but the improved flow never produced higher peak power than the others. Simulated and actual test results indicate that the optimum compression ratio for peak horsepower for a normally aspirated street Flathead is about 8:1 to 9:1. Going with the low side of this range has the advantage of requiring lower octane fuel with minimal loss of low-end torque and mileage. Years of street driving experience validate these results. These results were also validated in a second similar study that included the buildup of an actual engine, documented in the July 2004 issue of STREET RODDER in the article "Out with the Bad Air, In with the Good." It's also been found that supercharged street Flatheads perform best with lower compression ratios, as discussed in the books referenced above.
Ronnieroadster
Well-known member
Im proud to say I had a hand in that or should I say both hands at times.
Ronnieroadster
Ol' Ron
Well-known member
I like to say that I agree with most of this. When I wrote my book. I'd made a homemade Flow bench that I calibrated in percentages, because I had no way of converting the results into CFM. This can become addictive, because I was looking for the holey grail of flow. During this time I tried everything I could think of including grinding into the water jacket and making a port out of Bondo. What I learned was a relieved block did flow better than a non relieved block, so I thought. However i haden't taken into consideration of the shape of the combustion chamber. I then found that changing the angle of the transfer area had a major affect on flow and the best angle was 11/12 degrees. Unfortunately there isn't enough material in the heads to acheive this so I setteled on an 8 degree angle. Now the exit of the transfer area comes into play here as well and I use 60 degrees. By using Offy heads which are thicker thasn others I can carve a very nice combustion chamber thaat doesn't need a relief, I didn't stop there. I found that by making a piston with a 7 degree top sinilar to the old 409 chevy and a combustion chamber with an 8 degree angle we get a higher compression ratio with bwtter breathing. I don't have any sientific answers here.
Now the ports. By removing the hump on the top of the post and removing some of the material from the guide ares by aprox 3/16" wou will increase the bottleneck between the port and bowl. This takea about 10 to 15 minutes with a good carbide. This will increase flow about 15/20%. Now you can spend the rest of the day there and not gain a great deaal more.
Exhaust
I spent a good deal of time moving the exhaust ports so they come straight out. I find that by squareing up the port and placing a 45 degree angle in the outlet, you can achieve aproxamately the same flow rate. I wanted to do some dyno testing on this subject when I wrote my book, but ran out of money. BUt somehow I can't believe you can get 35% improvement in flow, I guess I just like to see where I'm wrong.
Some pics to follow when I can find them. Please excuse the spelling
Now the ports. By removing the hump on the top of the post and removing some of the material from the guide ares by aprox 3/16" wou will increase the bottleneck between the port and bowl. This takea about 10 to 15 minutes with a good carbide. This will increase flow about 15/20%. Now you can spend the rest of the day there and not gain a great deaal more.
Exhaust
I spent a good deal of time moving the exhaust ports so they come straight out. I find that by squareing up the port and placing a 45 degree angle in the outlet, you can achieve aproxamately the same flow rate. I wanted to do some dyno testing on this subject when I wrote my book, but ran out of money. BUt somehow I can't believe you can get 35% improvement in flow, I guess I just like to see where I'm wrong.
Some pics to follow when I can find them. Please excuse the spelling
Kahuna
Well-known member
In my opinion,
the question of relieving vs not is directly related to the combustion chamber design of the cylinder head used. Most all early and later aftermarket head designs were meant to increase the compression ratio. In these, relieving may help, because of the loss of flow.
But, with a Ford designed head, I can see no way that a relief would be of any benefit.
This type of argument/discussion reminds me of the 45 degree vs 30 degree valve seat angles
the question of relieving vs not is directly related to the combustion chamber design of the cylinder head used. Most all early and later aftermarket head designs were meant to increase the compression ratio. In these, relieving may help, because of the loss of flow.
But, with a Ford designed head, I can see no way that a relief would be of any benefit.
This type of argument/discussion reminds me of the 45 degree vs 30 degree valve seat angles
THANK YOU TO ALL who replied, Maybe I didn't explain myself properly but in JWL's book he makes a longer valve guide to turn the flow in to the chamber. If you look at the the valve pocket the flow comes in and runs into the wall this would cause turbulance maybe cutting down the volume that goes into the cylinder. The aim would be to keep the velocity of the flow high to get more into the chamber. Just my ideas!! ROGER