HEAD PORTING & DYNO TESTING
- Thread starter waldo786
- Start date
Head porting with not much additional mods such as headers, larger camshaft, better ignition and normal hop-up goodies will be of little benefit by itself on an otherwise stock engine. Plus the log head is very limited as to how much you can even do on the intake ports, since they are concealed inside the log. There are however better versions of the log head that are more desirable than others, so this might prove to be a more beneficial swap for your application.
Howdy Waldo:
I'm in agreement with Joe. Know that the biggest return will be the work done within an inch either side of the valve seat- with the valve and valve seat most critical. The improvement will be avaiable and noticeable from idle to max rpm. A prioritized list of specifics to improve flow would be-
* A performance three angle valve job. A stock OEM head has a valve seat of one 45 degree angle.
* A 30 degree backcut on the upstream side of the intake valve.
* Blending the transition edge from as cast to machined in the valve pocket.
* Smoothing the combustion chambers and removing sharp edges.
* Removing casting flashing and irregularities from the ports.
* Rounding short turn radius'.
You may have noticed that I did not list opening and/or polishing the ports. This is the lowest priority and only useful in high rpm applications. Shaping to help flow, control heat, and support efficient combustion is the goal.
You said "a basic port job?' What does a basic port job entail?
Adios, David
I'm in agreement with Joe. Know that the biggest return will be the work done within an inch either side of the valve seat- with the valve and valve seat most critical. The improvement will be avaiable and noticeable from idle to max rpm. A prioritized list of specifics to improve flow would be-
* A performance three angle valve job. A stock OEM head has a valve seat of one 45 degree angle.
* A 30 degree backcut on the upstream side of the intake valve.
* Blending the transition edge from as cast to machined in the valve pocket.
* Smoothing the combustion chambers and removing sharp edges.
* Removing casting flashing and irregularities from the ports.
* Rounding short turn radius'.
You may have noticed that I did not list opening and/or polishing the ports. This is the lowest priority and only useful in high rpm applications. Shaping to help flow, control heat, and support efficient combustion is the goal.
You said "a basic port job?' What does a basic port job entail?
Adios, David
David,CZLN6":38spyufo said:
Here is some food for thought. On another forum, we just concluded some very extensive and exhaustive dyno testing on a Chebby 292 engine, where we tested among other things, 6 different cylinder head combos. All of which had different levels of porting and valve sizes. We discovered that there were several urban myths revealed that had long been thought to be true, when if fact, they were only a myth. The very first test we conducted, was with a bone stock 292 GM camshaft and a stock head(no porting) with stock size valves. We then swapped to another head that had the same size valves, but had the intake bolt bosses removed w/mild porting and bolt-in lumps installed into the ports, everything else remained the same as the first test(intake,carbs.cam,etc..). Now we knowingly made an increase in airflow from one head to the other of over 40 CFM just on the intake ports alone. The urban legend we later proved to be a myth, was that because you had a gain of X amount in the airflow, that there also an exponential gain in HP. After 8-10 dyno pulls with the improved head with adjustments and tweaking, we saw absolutely no gain in HP whatsoever, not even 1 single HP of gain. It wasn't until we made changes in the camshaft deparment that we begin to see any benefits from a better flowing cylinder head. We also discovered, that at best, you might gain 1HP for every 4-5 CFM gain in airflow, when you do see an increase in power from cam changes and valves sizes.
'68falconohio
Well-known member
CNC-Dude,
More questiosn for all.
Your statements have confused me. If the ports on the lumped 292 heads were able to flow more volume per unit time than stock heads, with the same camshaft why didn't they allow more charge to go into the cylinder. Thus, make more HP. What about the Tq figures? If it was truly a basic port job, wouldn't the velocity stay really close, maybe increase? because the CSA wasn't altered much but the transitions were improved.
How much can we actually draw from the 292 dyno results for our ford sixes? Namely, how can we know that the bowl work doesn't do anything for our ford sixes since the ports are generally pitiful? Maybe we don't get any peak HP gain but earn a little more usable RPM with the same HP? I havn't seen the 292 data yet since I missed the boat. Not trying to dismiss your comments, I just have A LOT of questions.
Stephen
More questiosn for all.
Your statements have confused me. If the ports on the lumped 292 heads were able to flow more volume per unit time than stock heads, with the same camshaft why didn't they allow more charge to go into the cylinder. Thus, make more HP. What about the Tq figures? If it was truly a basic port job, wouldn't the velocity stay really close, maybe increase? because the CSA wasn't altered much but the transitions were improved.
How much can we actually draw from the 292 dyno results for our ford sixes? Namely, how can we know that the bowl work doesn't do anything for our ford sixes since the ports are generally pitiful? Maybe we don't get any peak HP gain but earn a little more usable RPM with the same HP? I havn't seen the 292 data yet since I missed the boat. Not trying to dismiss your comments, I just have A LOT of questions.
Stephen
Stephen, you are absolutely right in your inquiry. But that is one of those myths that reared it head. For so many years, people have always assumed that just because you have a gain in one area, you will also see a gain somewhere else. That just isn't always true, as we showed in the dyno testing. Too many people have a "flowbench fixation" when it comes to head porting, and we also were able to show, that just because you have a 40+ CFM gain, not to always expect a proportional jump in anything else. With a stock camshaft, I think it showed that even with a better flowing head with a lot of extra bells and whistles, the engine didn't need anymore air, and the stock head was adequately supplying the demands it needed, so more air wasn't any additional benefit to it. But, once we did step up to a more aggressive cam profile, then we say dramatic increases in both HP and torque with the better heads. I am currently doing a log head for a member on here, and am looking at doing some over the top stuff to it. I expect to be able to share the findings here when I finish it up. But on an engine with a stock camshaft, I think doing an elaborate port job isn't going to be of much benefit, unless you plan to make other changes at a later time to the cam and induction system.
8) airflow does funny things, to an extent cnc-dude and czln6 are both right. you can see power gains through porting, but port shape is just as important as increased airflow. this is especially true on small displacement engines, like our sixes. another thing that is very important is port wall finish. take the 2.3l ohc pinto engine and a 5.0 V8 for instance. if you treated the head ports on the pinto engine like the 5.0 engine you will gain airflow, but lose power because the 2.3 wants the airflow moving around differently than the 5.0 engine does.
as for port wall finish, many uninformed hot rodders think you want a mirror finish on the port walls, and that is furthest from the truth. what happens when you run dry air through a port is one thing, but when the air is wet with fuel you have a completely different animal. if the port walls are polished to a mirror finish, you will find that fuel will actually stick to the port walls, and a for a short time you will have a lean mixture, then the fuel will run into the ports in a liquid form and now you have a rich mixture, and in both situations you have lost power. a rough port finish will create a situation where the fuel and the air is tumbled in the ports, and the fuel remains in suspension, and the mixture will remain closer to what the engine wants.
as you can see there is more to porting that just increasing airflow, shape and finish also play a big part.
as for port wall finish, many uninformed hot rodders think you want a mirror finish on the port walls, and that is furthest from the truth. what happens when you run dry air through a port is one thing, but when the air is wet with fuel you have a completely different animal. if the port walls are polished to a mirror finish, you will find that fuel will actually stick to the port walls, and a for a short time you will have a lean mixture, then the fuel will run into the ports in a liquid form and now you have a rich mixture, and in both situations you have lost power. a rough port finish will create a situation where the fuel and the air is tumbled in the ports, and the fuel remains in suspension, and the mixture will remain closer to what the engine wants.
as you can see there is more to porting that just increasing airflow, shape and finish also play a big part.
Howdy All:
first off, apologiese to Waldo for hy-jacking his thread. Then thanks to CNC for sharing this interesting bit of info on the siamized chevy port head. It got me to thinking. I've never done just a performance port job on an engine and then bolted it together to try it out. In my mind a performance port job would include the valve seats, valve backcut, blending the transition and smoothing the chambers. When I do a head it also includes milling to raise CR, adding an exhaust port divider, and shaping the exhaust ports. In all cases it included an improved exhaust, but not always a header, and usually an increase in carburetion. So, the increase that is noticeable may come from some other factor, or, more likely, all of them.
I have read/seen articles in Hot Rod on budget porting as well as backcutting valves, but all were in terms of CFM. None were quantified with dyno comparisons, so your assertion that increased air flow does not necessarily equate to HP is valid from my POV. Is data gathered on the chevy head going to be applicable to ours??? But until someone can empirically prove these steps useless, I'll keep doing them.
Another factor is the unique porting configuration of a chevy six. While much has been done with them to improve performance, they are nothing like the ports of our sixes. The straight shot from the log to the valve back and high velocity characteristics of the fairly small ports are totally different. Different as they may be, the question remains- does increased cfm equal an increase in HP?
This topic should possibly be moved to the tech section. Again, sorry Waldo.
Adios, David
first off, apologiese to Waldo for hy-jacking his thread. Then thanks to CNC for sharing this interesting bit of info on the siamized chevy port head. It got me to thinking. I've never done just a performance port job on an engine and then bolted it together to try it out. In my mind a performance port job would include the valve seats, valve backcut, blending the transition and smoothing the chambers. When I do a head it also includes milling to raise CR, adding an exhaust port divider, and shaping the exhaust ports. In all cases it included an improved exhaust, but not always a header, and usually an increase in carburetion. So, the increase that is noticeable may come from some other factor, or, more likely, all of them.
I have read/seen articles in Hot Rod on budget porting as well as backcutting valves, but all were in terms of CFM. None were quantified with dyno comparisons, so your assertion that increased air flow does not necessarily equate to HP is valid from my POV. Is data gathered on the chevy head going to be applicable to ours??? But until someone can empirically prove these steps useless, I'll keep doing them.
Another factor is the unique porting configuration of a chevy six. While much has been done with them to improve performance, they are nothing like the ports of our sixes. The straight shot from the log to the valve back and high velocity characteristics of the fairly small ports are totally different. Different as they may be, the question remains- does increased cfm equal an increase in HP?
This topic should possibly be moved to the tech section. Again, sorry Waldo.
Adios, David
David your right, we many times get lost in the mix as to what mod is actually contributing the most to the gains we see. We had a solid 2-1/2 weeks of parts swapping and testing, because there were several things we had an idea were actually "urban legends" instead of real facts, that we wanted to either prove or disprove as such. We were able to isolate and compare single changes, such as only the effects of CFM gain on a certain combo with everything else remaining the same. We knew that there are instances where a gain in CFM alone will yield a pretty significant gain in HP, and others where you get little or no gain at all. We were trying to profile the most common engine components that enthusiasts regularly swap and replace in an effort to gain more performance, so that these enthusiasts can make good sound purchases and make better modifications, instead of making choices that might not yield the best gains for the buck. We had several guys over there that also prepped the Chebby heads and sell them on ebay regularly, and keep getting into contests about whose heads flow the most and which one is better than the other. And this whole time(7-8 years), all this conjecture was only based on flowbench data alone. When I approached Hot Rod about doing a series of articles about a head porting series on the 6 cylinder heads based on this data, I was told by the editor, that flowbench data without any dyno results to corraberate or confirm the results was worthless. As we saw conclusively in our tests, there was a lot of truth to that statement. And relying solely on a flowbench alone will easily make a person have a false sense of accomplishment, because just a gain in airflow by itself, wont always guarentee you will have a gain in anything else. I think it would be a good project for some of the guys on here to do the same thing with some of these engines. That way, you also will discover things that you always held onto as fact will be seen to be not so accurate as you thought, just as we did. It turned out to be such a huge success that we are going to do another series of tests in February with another engine and a whole list of different parts and components. Im sure you could get enough interest on here to do the same thing.
I'm assuming a "Basic Port Job" is referring to the description on the CI website.
Our "Basic Port Job" includes a light clean up and flash removal, smoothing the combustion chambers, blending the transition from the valve seat into the port bowl area, as well as gasket port matching of both the intake (OZ and CI heads only) and exhaust ports. Emphasis is placed on velocity and how the air enters the combustion chamber, rather than simply increasing air flow. In my opinion, it's well worth a $100 bucks.
A three angle valve job is included with our Standard and Performance rebuilds, while back-cutting is only included with the Performance rebuild. However you can opt to have the valves back-cut on a Standard rebuild, for an additional $45 bucks. Maybe I should including back-cutting with the Standard rebuild, and bump the price accordingly? Either way, it's well worth the money spent.
In the near future, we're planning to test various cylinder heads (stock rebuild, our Standard and Performance rebuilds, and a 2V conversion) on a freshly rebuilt motor. I currently have both a 200ci and a 250ci at the machine shop, so I can use either one for testing? We were going to use a mild cam for our test, but maybe I need to reconsider and think about testing with a stock cam as well? The only problem is, it will more than double the amount of time required on the engine dyno, which isn't cheap.
We also hope to test a couple heads with, and without, a port divider. Personally, I think port dividers are a waste of money. However, that's just my opinion and I may be wrong. My head porter believes Ford intentionally designed the log head with Siamese ports, for two reasons. First to help scavenge the exhaust from the center two ports, and secondly to assist in cooling. Not to increase power..... As such, the installation of a port divider may be detrimental, rather than beneficial? However this is just an assumption. Do they really make a difference? We'll find out.....
Excellent topic.... very interesting.
Our "Basic Port Job" includes a light clean up and flash removal, smoothing the combustion chambers, blending the transition from the valve seat into the port bowl area, as well as gasket port matching of both the intake (OZ and CI heads only) and exhaust ports. Emphasis is placed on velocity and how the air enters the combustion chamber, rather than simply increasing air flow. In my opinion, it's well worth a $100 bucks.
A three angle valve job is included with our Standard and Performance rebuilds, while back-cutting is only included with the Performance rebuild. However you can opt to have the valves back-cut on a Standard rebuild, for an additional $45 bucks. Maybe I should including back-cutting with the Standard rebuild, and bump the price accordingly? Either way, it's well worth the money spent.
In the near future, we're planning to test various cylinder heads (stock rebuild, our Standard and Performance rebuilds, and a 2V conversion) on a freshly rebuilt motor. I currently have both a 200ci and a 250ci at the machine shop, so I can use either one for testing? We were going to use a mild cam for our test, but maybe I need to reconsider and think about testing with a stock cam as well? The only problem is, it will more than double the amount of time required on the engine dyno, which isn't cheap.
We also hope to test a couple heads with, and without, a port divider. Personally, I think port dividers are a waste of money. However, that's just my opinion and I may be wrong. My head porter believes Ford intentionally designed the log head with Siamese ports, for two reasons. First to help scavenge the exhaust from the center two ports, and secondly to assist in cooling. Not to increase power..... As such, the installation of a port divider may be detrimental, rather than beneficial? However this is just an assumption. Do they really make a difference? We'll find out.....
Excellent topic.... very interesting.
That is what most head porters forget, VELOCITY.AzCoupe":21kl6swy said:
While dyno time is not cheap, it may answer a lot of questions. Can the stock log head be improved with the log still attached? If so how much? Is it worth the effort?In the near future, we're planning to test various cylinder heads (stock rebuild, our Standard and Performance rebuilds, and a 2V conversion) on a freshly rebuilt motor. I currently have both a 200ci and a 250ci at the machine shop, so I can use either one for testing? We were going to use a mild cam for our test, but maybe I need to reconsider and think about testing with a stock cam as well? The only problem is, it will more than double the amount of time required on the engine dyno, which isn't cheap.
This is another thing that needs a definitive answer. Does the port divider work as advertised? Is it worth the effort?
Rbohm, you hit the nail on the head. Head porting alone rarely yields the same benefits as when done in conjunction with other mods. Porting complements and adds additional gains when done with other improvements, like larger valves, bigger cams, better induction, etc. The same holds true for the enthusiast looking to put a 4 bbl. carb and intake on a stock engine with no header and stock camshaft. He might see some gain, but not as much as if he had added supplementary components along with his intake and carb swap.rbohm":3l2aijg3 said:
Improvements to the log can be made without removing it from the head, but you have to get creative. I'm doing one now for a board member here. With his permission I can post pics of it, or he can post them. I'm sure he would like to share with everyone here.
We plan to start with a stock log head with a 1V, then test a 2V adaptor. This would probably be a good time to install the port divider, and see what happens, as well as headers. Next we'll test an identical head, but with larger valves. Then one with larger valves and a little port work. Or maybe do those two steps in reverse, test the ported head first, then one with port work and larger valves? The final step is to test a converted head, with and without larger valves, ported and unported. I'm guessing this will take two or three sessions, unless I have a bunch of heads lined up and ready to go.
We also want to test stock and high ratio rocker assemblies at some point, I'm just not sure when. Would it be better to test on a stock head, or a converted head? If I have enough time (cash), maybe I can do both.
Both blocks will have a performance cam already installed, so adding a stock cam into the mix really adds to the complexity. Basically we'd have to test the above head variations with the stock cam, then start all over after we installed a performance cam. If we wanted to make things really crazy, we could add a bigger cam and/or different lobes centers.
If I counted correctly, we'd need seven different heads, and two cams, for a total of fourteen pulls. Add two more pulls (once on a stock motor, and once with the converted head) for each of the following; port divider, headers, rockers, and ignition, and we have a grand total of twenty two pulls, with fourteen head swaps and a cam change.
I've heard of guys using the "seat of their pants" method for gauging improvements, but I think the only thing I'm going to feel in the "seat of my pants", is a lighter wallet.
I guess it really doesn't matter which way we do it, as long as we reach our intended goals. We already have a pretty good idea of the differences between a 2V adaptor and a converted head, and the ignition systems, we just want to confirm them. We also know the what happens when you install a set of high ratio rockers, on a fairly stock motor. Therefore our primary goals are to see what happens with larger valves, a little port work, and a port divider, on a stock motor and a mild performance motor.
Anything else? As if this isn't enough.....
We also want to test stock and high ratio rocker assemblies at some point, I'm just not sure when. Would it be better to test on a stock head, or a converted head? If I have enough time (cash), maybe I can do both.
Both blocks will have a performance cam already installed, so adding a stock cam into the mix really adds to the complexity. Basically we'd have to test the above head variations with the stock cam, then start all over after we installed a performance cam. If we wanted to make things really crazy, we could add a bigger cam and/or different lobes centers.
If I counted correctly, we'd need seven different heads, and two cams, for a total of fourteen pulls. Add two more pulls (once on a stock motor, and once with the converted head) for each of the following; port divider, headers, rockers, and ignition, and we have a grand total of twenty two pulls, with fourteen head swaps and a cam change.
I've heard of guys using the "seat of their pants" method for gauging improvements, but I think the only thing I'm going to feel in the "seat of my pants", is a lighter wallet.
I guess it really doesn't matter which way we do it, as long as we reach our intended goals. We already have a pretty good idea of the differences between a 2V adaptor and a converted head, and the ignition systems, we just want to confirm them. We also know the what happens when you install a set of high ratio rockers, on a fairly stock motor. Therefore our primary goals are to see what happens with larger valves, a little port work, and a port divider, on a stock motor and a mild performance motor.
Anything else? As if this isn't enough.....
'68falconohio
Well-known member
Would there be anything to gain by testing a solid lifter cam? Maybe the CSC-278-SST-10?
Mike, I know that you know this, so don't think I am telling you what or how to do your thing. But, when comparing the gains from head to head with different valve sizes for instance, make sure you keep the combustion chamber sizes the same, so that a rise in compression from one head to the next wont skew your results, and the gains you see will be soley from the difference in valve size, and not other variables.
No worries.CNC-Dude":pxwxi0go said:
I got to thinking about this last night and decided to add log size into the mix, but I'll only test the small log stock and fully modified. Therefore I'm going to need ten cylinder heads. Plus I'd like to test the final variation with three different cams, and maybe a few different carbs (32/36 Weber, 240 Autolite, and 350/500 Holley). The first step, once we have all the heads, would be to size and shape the combustion chambers so they are identical.
- Small log 1V - stock (test with 1V and 2V adaptor)
- Small log 2V - converted with port work and valves
- Large log 1V - stock (test with 1V and 2V adaptor)
- Large log 1V - with port work (test with 1V and 2V adaptor)
- Large log 1V - with larger valves (test with 1V and 2V adaptor)
- Large log 1V - with port work and valves (test with 1V and 2V adaptor)
- Large log 2V - converted
- Large log 2V - converted with port work
- Large log 2V - converted with larger valves
- Large log 2V - converted with port work and valves (test with 264H, 274H and 278S)
Fifteen variations x two cams + options (port divider, header, rockers, and ignition) = 32 pulls. This doesn't include extra pulls if we decided to dyno-tune some of the variations, such as re-jetting the carbs and adjusting timing. I'm hoping we can average two pulls per hour, but I'm sure some will take longer. Plus we'll need to do three cam changes. So I'm guessing this will take at least three 8 hr days, which would cost $1800 bucks. This is going to cost me a small fortune, by the time I pay for the dyno, parts, and the labor to set up each head. However, the information gained would be priceless.....
That being said, I've already had one cylinder head donated, and a couple guys have offered to pitch in a few bucks. The hardest part of this, will be gathering up eight D7/D8 cylinder heads, however I already have two.
Maybe I should make this a sticky?
Waldo,
If you keep the engine stock the the gains from porting will be minimal to zero. Do port the head if your future plans include other modifications that will increase the air flow into/out of the engine. But remember, to install a new cam requires the head to be pulled, the the head will be on the bench anyway. So if a new/larger cam is in the engine's future then you could do the porting at that time. Or you might just want to port the the thing now and be done with it.
To all the rest of the guys:
I was taught/read some place the the amount of air flow into an engine is based on a bunch of things. Just like the old saying, " you can only go as fast as your slowest step", the air flow is as great as its biggest resistance/bottleneck to flow. The the largest and most critical resistance is the cam specs. While the log design is not the best in most of our opinions, I bet the cam and the size of the carb have a lot more to do with the amount of air that goes into our small sixes than the casting flash on the inside the port. Porting is nice but is only needed to support other mods or increases to air flow.
AZCoupe:
When I saw the siamesed exhaust port for 3 & 4 the first time my thought was that the roof of this exhaust port is actually the floor of the intake. My thought was that the Ford engineers designed basically a six cylinder version of an exhaust crossover. They siamesed the ports to get heat from 1/3 of the engine's exhaust up into the intake charge. Now if that heat is needed at start-up, cold weather running or help with fuel atomization during normal operatiion, I don't know.
If you keep the engine stock the the gains from porting will be minimal to zero. Do port the head if your future plans include other modifications that will increase the air flow into/out of the engine. But remember, to install a new cam requires the head to be pulled, the the head will be on the bench anyway. So if a new/larger cam is in the engine's future then you could do the porting at that time. Or you might just want to port the the thing now and be done with it.
To all the rest of the guys:
I was taught/read some place the the amount of air flow into an engine is based on a bunch of things. Just like the old saying, " you can only go as fast as your slowest step", the air flow is as great as its biggest resistance/bottleneck to flow. The the largest and most critical resistance is the cam specs. While the log design is not the best in most of our opinions, I bet the cam and the size of the carb have a lot more to do with the amount of air that goes into our small sixes than the casting flash on the inside the port. Porting is nice but is only needed to support other mods or increases to air flow.
AZCoupe:
When I saw the siamesed exhaust port for 3 & 4 the first time my thought was that the roof of this exhaust port is actually the floor of the intake. My thought was that the Ford engineers designed basically a six cylinder version of an exhaust crossover. They siamesed the ports to get heat from 1/3 of the engine's exhaust up into the intake charge. Now if that heat is needed at start-up, cold weather running or help with fuel atomization during normal operatiion, I don't know.
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