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Old 06-21-2022, 02:17 PM   #1
shoestring
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Post Cam and I built one of these David Vizard budget flow benches

So the way these benches work is that you hook up a shop vac (the nuttiest one you have) to a "cylinder" that the head sits on, and there's a capillary tube that feeds a manometer. Ours has 80 inches of water in it. You run the vac, open the valve to say 0.300" and read the number. Say it pulls the water to the 30" mark. We started at 40" (80" in a U-shape is 40" per leg), so it's pulling 10" of water times 2 (there's 2 legs of the manometer) for a total of 20". You do some mods and remeasure. Well this time it only pulls say 9" for a total of 18. There's an obvious improvement here because the capillary tube which is located in the cylinder is seeing less vacuum (more air is cruising past the valve). It's not 10% in this example because there's some square roots involves and stuff but that's not really important and not a good idea to focus on.

And while I can't tell you exact flow numbers (because we don't know them), I can tell you that for a fact the B21F intake outflows the B230F intake by a fair margin. The head used was the one off of our LeMons car which has some bowl and valve/valve seat work but is a stock 44mm valve. There is ZERO chamber work on this head, but it is cut about 2.25mm below stock 146.1mm spec and they measure between 44 and 44.5cc.

So here's the real flow result of the head off of our LeMons race car that has the standard 44mm intake valve with a multi-angle valve job and bowl work, and a 38mm exhaust valve, also with multi-angle valve job and bowl work, some of which includes filling the long side turn. As measured at 28" on a Superflow at R&L Engines, Dover, NH:

LIFT--------INTAKE CFM---------INTAKE W/MANIFOLD & TB-------EXHAUST
0.050..............24.1........................... ...23.5.............................23.8
0.100..............52.5........................... ...49.0.............................48.5
0.150..............77.0........................... ...76.5.............................67.2
0.200............102.9............................ ..97.0.............................82.5
0.250............125.2............................ 113.8.............................91.2
0.300............148.8............................ 125.7............................100.2
0.350............163.9............................ 134.0............................107.1
0.400............168.2............................ 141.0............................111.3
0.450............171.9............................ 144.0............................114.5
0.500............173.9............................ 142.0............................116.7
0.550............175.2............................ 142.0............................117.8
0.600............175.6............................ 141.9............................118.2


As I've posted a million times before, we make 144 whp with this head and a K cam. This is not the EXACT intake and throttle body we use, but they are all stock, unmodified pieces.

Also note that this head has a 38mm exhaust valve with a strong amount of bowl work but doesn't flow a lick more than a stock valve on a stock port! Why? Valve shrouding. Again, I can't tell you exactly how much of a gain in flow it is, but I can tell you it's a LOT.

Ask away, I just wanted to get this put up, I've been sitting on the info for a little bit. the only thing I've been able to do with the intake that's worth a crap is grind out the throttle body stud bosses that get in the way of the #1 and #2 runners in the plenum. You've got to take them all the way off, like on the opposite side, and it's going to expose the studs, so you may need to pull the studs and do some vacuum-leak prevention with some sealer or something. Those bosses make a bunch of turbulence at higher (>0.300") valve lifts and removing them helps alleviate this.

This flow test also answers the question I've had as to why Volvo cams are ground either single pattern or with a little more intake lobe: they need it. There's a 75% "rule" (let's call it a guideline) for exhaust-to-intake relationship. This is lobe-to-lobe, not just a single lift point, so hopefully you have a calculus person in your house like I do. If you've got less than 75% exhaust flow compared to the intake, you need more exhaust lift/timing. The opposite is true if you have more than 75%: you need to crutch the intake. BMW S54 is a good example.

DON"T CRUCIFY ME OVER THE PREVIOUS STATEMENTS, obviously it's not necessarily that simple. It's merely meant as a conversation starter.

DISCUSS.
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Last edited by shoestring; 06-24-2022 at 04:54 PM..
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Old 06-21-2022, 03:42 PM   #2
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I had that restrictive efi intake tested when my cylinder head was modified. The efi intake took a large amount of flow away from the intake flow. After reading your post it makes sense to me that the exhaust with the 38mm valve didn't show as much improvement as I expected. I had a 405 head improved with stock valves and the 531 head got the 38mm exhaust with the same flow work. I forget the numbers but it wasn't that much more flow. It's in the spreadsheet that Gary made up.

Edit:That home brew flow bench is neat. Nice work!
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Old 06-21-2022, 04:42 PM   #3
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Can you expand on the exh valve shrouding comment? Said it flows same but then say it flows more?
So a stock exh port flows same as a bowl worked one, but deshrouding it made all the difference i take it?
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Old 06-21-2022, 04:54 PM   #4
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Affirmative. And a bigger valve in the same chamber is even more shrouded.
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Old 06-21-2022, 05:04 PM   #5
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Sure. I've had both a completely stock 530 head and then the above head professionally flowed. Same shop, same machine. The above head has an oversized 38mm exhaust valve as compared to the stock 35mm, with corresponding throat and bowl work done under the 38mm valve to take advantage. These heads have nearly identical exhaust port flow numbers, within a couple cfm at each point.

So what does that tell us? It says that the valve and throat area aren't the restriction. If you look at a picture of the combustion chamber of a 530 head, the chamber walls wrap pretty tightly around the exhaust valve for a good portion of its diameter. The only direction the exhaust gases can really get out is from the inside of the chamber. With the larger valve, the problem actually gets worse because because the diameter of the valve is closer to the walls of the combustion chamber.

We've observed that even on a stock head, no valve job, no port work under the valve, nothing, that exhaust flow improves SIGNIFICANTLY if you deshroud the valve: expose more of the diameter of the valve seat to escaping exhaust gases. Obviously, you can't go all the way around, but you can probably double the available area. Please don't read that as doubling flow.

My thought is that when we deshroud the valve, exhaust flow is going to jump a bunch. Like a Brady Bunch.

This is why I test and measure. I learned a long time ago that just because I did something doesn't mean I made it better.
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Old 06-21-2022, 05:57 PM   #6
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I like this. Looking forward to moar testing.
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Old 06-21-2022, 06:24 PM   #7
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Plus with a bigger valve you lose velocity and need to gain a lot of flow to get better or break even per se. Ive used a flow bench and once you use one you kinda dont wanna port anything without one after knowing what you find out. I need to make a homeade one though. What were your thoughts on the flow performance one?
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Old 06-21-2022, 07:02 PM   #8
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I’ve always wondered why, when this method only infers flow by measuring pressure drop- why doesn’t someone adapt an AMM to directly measure airflow
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Old 06-21-2022, 10:23 PM   #9
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What were your thoughts on the flow performance one?
It's more than the 14.99 I spent building this one? Honestly if I were to get to the point where I was really trying to port heads rather than just kind of a "let's see if this actually works" thing, it would be in the budget.
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Old 06-21-2022, 10:25 PM   #10
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I’ve always wondered why, when this method only infers flow by measuring pressure drop- why doesn’t someone adapt an AMM to directly measure airflow
This is a wicked idea, but you would have to know the exact relationship of air mass to voltage, which I do not. Maybe Cam does.
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Old 06-22-2022, 12:28 AM   #11
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I have a TON of pictures of all this. Let's start with the bench itself:

We start by drawing air through the side of the "bore", like this:



This is PVC pipe with a tube epoxied in and a cap on the bottom held in with caulk.

Along with a wooden head mounting structure, like so:



A foam head gasket type thing completes the package:



Along with a 96mm bore adapter 3D printed by my friend Zack:



Valve control is handled by a screw on the stem of the valve, which is installed with a test valve spring, like so:



The initial version measures pressure drop through the spark plug hole with the hose from a compression tester threaded in. To my surprise this does not leak.
The complete apparatus, V1:



There are some issues with the first version. There are a few small leaks which were easy to sort out. Most importantly, correlation is awful, the flow seems to hit a hard cut around .250" lift which doesn't match any big boy flow test of any 530 intake port I have ever seen. We made a few revisions before figuring it out.

First, the hose adapter was eliminated and the tubing was smushed directly into the spark plug hole:



This seemed to do nothing at all at first. So we figured there was some quirk to drawing air from the side of the "bore" and carried on cutting a hole in the bench. This was confirmed by a test wherein the head was flipped on the wooden board and flowed more air in one orientation than the other.

Bench access hole:



So the vacuum could move air from the bottom:



A typical V1 flow test showing stalling far before an as-cast port is done gaining flow:



The unit is inches of water, but it's indicated inches of water on the hanging manometer so the actual water column height is given by 2*41-X where X is the number I have written down here. Very straight forward.

During another test while we were feeling annoyed by our lack of progress I decided to just keep jamming the tube into the bore. The result? More flow!

We ended up repurposing the tube in the side as a sort of "pressure chamber", where the manometer inlet now lives. It seems that the previous location was too turbulent for proper measurement of airflow in the port. Correlation much better now.
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Old 06-22-2022, 03:33 PM   #12
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that definitely looks like a basement in Swampscott (said affectionately)
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Old 06-22-2022, 03:45 PM   #13
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that definitely looks like a basement in Swampscott (said affectionately)
Oh man is it ever
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Old 06-22-2022, 04:24 PM   #14
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Massachusetts joke noted.
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Old 06-22-2022, 06:38 PM   #15
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Cool project! May it provide many hours of entertainment and head scratching.

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Quote:
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I’ve always wondered why, when this method only infers flow by measuring pressure drop- why doesn’t someone adapt an AMM to directly measure airflow
This is a wicked idea, but you would have to know the exact relationship of air mass to voltage, which I do not. Maybe Cam does.
There are some sparse Bosch AMM (aka MAF) datasheets at: https://ipdown.net/documents.html
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Old 06-22-2022, 08:10 PM   #16
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It's been an incredible distraction so far.

edit: And the basement's just as damp as you'd imagine.

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Old 06-23-2022, 07:55 AM   #17
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I might need to build one of those with a MAF for the new garage, after I finish my other 10 projects that is

As for the porting, I collected this in my 530 porting folder and always wondered how this could be one of the better flowing heads. Any future plans to also test intake valve sizes?
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Old 06-23-2022, 12:41 PM   #18
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Any future plans to also test intake valve sizes?
Dude I wish I could tell you that we have the means to do that. Unfortunately we would have to send the head out to have that done. It's now extremely clear to me that it's the intake side, not the exhaust, that needs all the help it can get, because of the manifold.

It looks like KG Trimning offers an intake valve with a reduced stem size (from the picture). Anybody know about/have experience with this or something similar?

I'm also going to look into a flap wheel on a flexible shaft to see what can be done with these intake runners in the manifold. Where it's a dry intake I'm hoping I can pick up a little something if I make them smooooottttthhhhhhh....

I don't know. I do know that I'm kinda reinventing the wheel here and none of this will surprise most people.
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Old 06-23-2022, 01:07 PM   #19
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You could just ditch the stock intake manifold. You could have a port that moves 400 CFM; it’s still going to suck through a straw.
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Old 06-23-2022, 01:33 PM   #20
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Quote:
Originally Posted by shoestring View Post
Dude I wish I could tell you that we have the means to do that. Unfortunately we would have to send the head out to have that done. It's now extremely clear to me that it's the intake side, not the exhaust, that needs all the help it can get, because of the manifold.

It looks like KG Trimning offers an intake valve with a reduced stem size (from the picture). Anybody know about/have experience with this or something similar?

I'm also going to look into a flap wheel on a flexible shaft to see what can be done with these intake runners in the manifold. Where it's a dry intake I'm hoping I can pick up a little something if I make them smooooottttthhhhhhh....

I don't know. I do know that I'm kinda reinventing the wheel here and none of this will surprise most people.
From a strength perspective, there shouldn't be any issues with the undercut valves (reduced stem). I've ran ~52mm diameter valves with 8mm/6.5mm stems at a lot of revs without issues (pushrod V8). They can help with flow, or they can hurt... but you've got the tool to figure that out!

If you need to get deep inside the intake, a 6" long extended shaft burr is the way to go. I'll send you some links for some reasonably priced ones. They can easily get out of control, but with practice and brown shorts you'll get the hang of them. I also have a bunch of extended sanding mandrels as well, very helpful!

But really I'd look at another intake manifold, unless you're realllllly working on a budget.
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Old 06-23-2022, 02:04 PM   #21
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If I had tig skills and a tig, this would be a done deal. Also, the projects we have going now require OE reliability: Cam's got to be able to drive his 944 daily, and my buddy's 244 has to have probably 4-5 days a week out of it, 3 seasons, and be able to go a couple hundred miles from home without a hitch. That means that ALL the stuff that goes along with the performance aspect has to be bulletproof. You could almost say that the performance aspect is among the last things to consider. Sounds goofy, I know, but it's self-imposed restrictions like this that force us to think harder. When I was a kid we had cars that had wires running everywhere and exhaust leaks and stuff like that, but we had time to mess with them all the time and never went more than 30 miles from the house.
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Old 06-23-2022, 02:09 PM   #22
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The Swedes have zero complaints about these: https://shop.klracing.se/sv/artiklar...m-spjall-.html
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Old 06-23-2022, 02:24 PM   #23
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We might have an appropriate application for this.
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Old 06-23-2022, 02:27 PM   #24
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I'm not sure what you have for a welder, but you can do decent work with a spool gun and a mig with aluminum. It definitely takes practice, but it's a much lower barrier to enter with.

There's not a lot of material in the stock b230f intake runners, and the injector boss area is a big (the biggest?) restriction there. Even the cheap welded KL Racing intake is 2mm larger in diameter at the port flange (40.5mm vs 38.5mm with the intakes I have here).
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Old 06-23-2022, 02:46 PM   #25
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Intake manifold swap seems outside of the scope of this (my) project. I like the cast KL one, the work and expense required is probably not worthwhile at this power level.

Depends on how in the weeds a ported B230F manifold still is, I suppose.

Either way you still have a Volvo 8V head.
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