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    Old project/projects finally going to happen

    Back in the 90s, I had a buddy who had made his own flow bench. He used Kirby vacuum cleaner blower or blowers for the bench. I think only one, been a long time. I got to put some heads I was working on at the time on his bench, the numbers came out pretty good. He had flowed some heads on his bench, then took them and put them on a Superflow 600, the numbers were very close. So his bench was pretty accurate.

    Later on, he gave me copies of the plans he used to build his bench. In those plans, it called for a old Paxton SN-93 blower. I think those old blowers are capable of flowing around 600 CFM. Back then getting my hands on a blower was not easy and there was not much chance if I did so, that I would use it for a flow bench, it would have gone on one of my cars.

    Times have changed blowers are cheaper, and more common, with a lot of people pulling blowers to replace them with turbos. So there are a lot of older centrifugal blowers out there, that you can pick up cheaply and I have done so.

    I got the plans for the bench sometime back in the mid 90s. I had been porting heads since the 80s. I lost the plans for the flow bench sometime in the early 2000s. Then found the same info online and book marked it. Then my computer crashed and I lost everything on that computer. Then the next time I remembered to look for the plans for building a bench, they were no where to be found on the internet. I looked many times, for many hours at a time, and found nothing. Then the other day, the thought of having a bench got back in my head. So last night I searched again, right off, found multiple posts on building a flow bench. Each one, has different info, each is helpful in one way or another.

    Things are different this time, I am not just dreaming of building a bench and hoping to be able to find the pieces I need. I have the pieces and the tools and knowledge to build a nice bench. Some years ago, I picked up a Vortech S trim, for $300, came with some brackets and one or two pulleys. I found all the rest of the pieces to put it on one of my engines. I planned on putting it on my daughter's pickup. But have since decided, that twin turbos would be cooler, but then I found better heads, that I could make plenty of power with, without any boost. So boost would just result in a lot more power, than I think she would want any part of. Then I also picked up a Paxton Novi 2000, for $500. The S trim will flow 1000 CFM at 50,000 rpm. That I know of, there is no cylinder head on the planet, that will come close to 1000 CFM of air flow through one port. So the S trim is plenty big for anything I will ever flow on my bench. The Novi 2000, I have not looked up, but I know it can flow close to double what the Vortech S trim will flow. That blower, I would like to put on something, but really have not decided what yet.

    So I have a blower more than big enough for my flow bench. I need to rebuild it, but a rebuild kit for that blower is only $284. Years ago, after I lost all of the info on building a flow bench, which included what size orifices I needed to make and how to calibrate all of the pieces of the bench. So some years ago, I came up with the idea of using a MAF meter, to measure air flow. I can get air flow numbers for a given MAF sensor, then I have the ability to data log the MAF numbers. The same way I would data log the MAF numbers, I could data log barometric pressure numbers at the same time. But was not sure, those numbers would be comparable to what is produced by a production flow bench.

    So in my searching the past two days, I found one build done by some college students, who used a MAF sensor, that they were able to get the flow chart for, to measure the air flow. Then a barometric pressure sensor. Then I also found another article, that talked about adding electronic measuring devices to your existing flow bench. Those devices, included a MAF sensor, barometric pressure sensor and a data logger. They claimed the numbers they got, were very close to what was acquired by a Superflow 600.

    Then I have a mill now, so I can make the flanges I need. So I plan on building a really nice big bench. Which will be great, I have some heads, that I am going to port, that I know one of the heads, multiple guys have gotten to flow a bit over 400 CFM. The other head, is one I ported a pair of back in the 90s and got some good numbers out of, with just a little work. Those heads are considered to be garbage heads by about 90% of the guys who think they know Ford heads, but the numbers I got years ago, say otherwise. I think with the right size valves and right style valves and some good work, those heads should flow a lot of air. The good part is since, most people classify those heads as garbage, I can pick them up cheaply. So I can pick up multiple pairs to experiment with.

    So when I get this bench built, it will allow me to really have fun experimenting with heads and intakes. I used to on rare occasions take heads that I worked on, to other people to get them flowed, so it will be very nice having a bench available at anytime to check the latest work. I will probably get back to doing more porting again.

    #2
    Sounds like a fun project, I did some head work on dirt track cars in the early 90’s. We just port matched them and ground the exhaust ports a D shape, never flowed anything thou.

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      #3
      Originally posted by Bowtech38 View Post
      Sounds like a fun project, I did some head work on dirt track cars in the early 90’s. We just port matched them and ground the exhaust ports a D shape, never flowed anything thou.
      Yes, I remember some of the head porters liking the D shaped exhaust ports, mainly back in the 80s and early 90s. I think I did some D shaped exhaust ports back in the 80s. I think I quit doing that, because I kept punching through the floor corners, going too wide. Seems like that area are some of the thinnest areas of the exhaust ports on the Windsor style heads. I punched through on the exhaust ports on quite a few heads in my early years, trying to make the exhaust ports larger. I gave up on the idea of large exhaust ports. I found good flowing efficient, smaller ports resulting in very good torque and lots of throttle response and good hp. So I quit trying to make large exhaust ports, at least on the factory iron Windsor ports.

      I have spent many years reading all the theories on cylinder head flow, or air flow, then a lot of time on ram tuning and exhaust scavenging. I have built sheet metal intakes and many pairs of headers, over the years and ported a lot of heads and intakes. Gotten some pretty good results out of most of the stuff I have done. I like getting the most out of my guns and my engines/cars ECT.

      It was very nice years ago, when I had the buddy with the bench, but I think his wife decided his days of obsessing over head flow were over, or their marriage was over, that's basically what I got out of him, the last time we talked. I have not seen him around anywhere since. I think his wife has kept him on a very short leash ever since.

      Sense those days I have only taken one pair of heads to get flowed. It took almost two weeks to get the heads back from getting flowed. That makes experimenting difficult, and drags it out a long time, makes it very frustrating, having to wait that long to see how you work is going. It is not worth it at that point, then the cost of taking a head back in repeatedly, as you get farter along with the work you are doing. So I have just had to do my best guessing, on how things were going.

      In my search the past few days for flow bench info, one of the articles I read, the guy pointed out something I had not read previously. For years I have read some guys preaching that good low lift flow numbers are very important. I understand they are, but that first article I found the other night. The talks about how they tested the negative pressure/vacuum created by a 620 hp circle track engine, in the cylinder from before the intake valve opens till after the intake valve closes. What the found was that engine produced something like 122 in. vacuum as the intake valve was opening, because of the scavenging of the exhaust. Which I knew the exhaust scavenging is supposed to create a low pressure, when done correctly. But 122 in. of negative pressure is very impressive. So that gets the air flowing from the intake port while both the intake and exhaust valve are open at the same time. The point this guy was making, was that everybody uses 28" of vacuum as the standard pressure to achieve while testing the flow of cylinder heads. When the engine will actually achieve much higher vacuum when the intake valve first opens. The point where some guys spend a lot of time working on. His point was that at 122 in of negative pressure or vacuum, the air is going to flow quite a bit different, than it would at 28" of vacuum. So he was using a floating pressure style system to measure air flow, which is likely more accurate. But he was only able to achieve 60 in. of vacuum with the valve .050" off the seat. He needed a larger blower to move more air. That's where I think that me using a blower that will flow 1,000 cfm, would allow me to create a lower pressure with the valve open at something like .050".

      Most of the guys are using vacuum cleaner blowers to move air in their home built flow benches. I have either the Vortech S trim which stock will move 1,000 CFM at 50,000 rpm or I have the Paxton Novi, which will move 1,400 cfm at 55,000 rpm, stock. With both blowers I can cut the discharge and weld a straight discharge on them and increase the flow, the both have a sharp 90 degree discharge, which hurts the flow noticeably. Then the Novi, I can buy three different billet compressor wheels that each flow more than the stock cast wheel. So I can probably get the flow up to somewhere around 1,600 to 1,800 CFM. With that type of flow capability, I could pull a lot of vacuum, even with a large head, with some big valves. It will take a big motor to run that blower at those speeds. There is also a high rpm bearing kit for the Novi, that will allow it to be run up to something like 75,000 rpm. Another 20,000 rpm, plus the better compressor wheels should result in quite a bit of air flow. I am going to have to make my box and all of the pieces for this bench very strong, or the box or any weak part, will implode.


      One of my goals is to try and get my junk, factory iron heads to flow as close to 400 CFM as possible. I am pretty sure I got them up into the 380 CFM range years ago, but I never got to prove that, because of my buddy's cylinder head work coming to a abrupt stop. So I never got to flow my heads again after the last work I did on them. What I got out of those heads, with the first round of work, which was just minor work and larger valves. They flowed a lot more than people give those heads credit for. I got them up to 330 CFM on the intake and something like 220 or 230 CFM on the exhaust side. I lost those flow numbers, when I lost the info on building a flow bench. I am 100% certain, I can get the heads to flow in the 360 CFM range, but really want to believe, that 380 to 400 CFM is possible. The ports are raised up, to where they have a good angle of entry, no dead spots on the floor like the older Ford big block heads. Then they have enough cross sectional area, and can be opened up to sizes, plenty large to flow a lot of air. Then there is virtually no valve shrouding in the chamber, the big blocks have plenty of bore size. I could increase the valve size well beyond the 2.19" size I used years ago and not have any shrouding. It would be very nice to have a 400 CFM cheap budget head.

      I quit on my work on those heads back in the 90s, but have wanted to get back to where I left off a long time ago. But don't want to spend a lot of time working on those heads, without access to a flow bench. So now, I can get me a good high flowing bench. So I am plan on getting back to what I was working on many years ago. Then work on building a better intake manifold, than I built back then. I have learned a lot since those days, and have a bunch of new ideas, that I want to try out on the manifold I plan to build for those heads. So the flow bench, is just one of the many steps of my plans for some of my projects.

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