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531 head question

thanks

the way i was thinking is to pull the head and just clean up the ports, and maybe do some more work to the exhaust, IF someone can give me som pictures and explain what to do, so i don't screw things up. I figured that cleanig up the head would give med the same amount of power increase as a performance cam, but it's almost free, minus new gaskets.
 
Phil, as you mentioned, flow numbers on the exhaust side are more an an indicator of what the valve is flowing, not the head in the case of a stock valve- they both nearly max out the flow for that valve. So, if the valve is the major restriction in both cases, can we reliably say that the 531 exhaust port has the same flow? Another thought is that regardless of port shape the 531/405 are less shrouded around the exhaust valve as well and unshrouding a 530 to the same degree makes a noticeable difference from what I understand. Just a thought.

I'm not trying to argue one way or the other at all- and much thanks on posting the numbers- just saying it might be hard to compare the two when they are both being limited by the valve so much. I plan to get before/after of my 531 stock and then with 46/38mm and some porting.
 
If anyone is iterested i have a 531 head ill sell for 175 bucks or best offer plus shipping from ireland, i reckon another 150$,
I also have a VX cam which i will sell for 50 bucks plus maybe 20 for shipping,
Pm me if any of you are interested.
 
if the valve is the major restriction in both cases, can we reliably say that the 531 exhaust port has the same flow?

I would not jump to that conclusion. There are 8 cfm to be had between the stock exhaust flow of about 114 cfm and the theoretical maximum exhaust flow of 123 cfm with the 35 mm exhaust valve. If the ports were better, that gap should be diminished. 8 cfm is a lot even if it does not seem like much.

Volvo may not have bothered improving the exhaust flow because the 405 and 531 heads were fitted to non turbo motors and non turbo motors don't need much improved exhaust flow; they need much improved intake flow.

When you fit larger valves, you have to do some bowl work, so if you left the ports stock and fit larger exhaust valves, you would still be doing a little work and I would expect that flow would pick up. The only way to know for sure would be to compare a 530 and a 531 head that are both done with minimal port work and fitted with larger valves. I would not bother doing this test. You might as well do a little more port work while you are at it to get the most that is reasonably possible from the investment.

I commonly read of 38 mm exhaust valves being fitted as an upgrade. I used 38.5 on my first head, which was what Peter Linssen used. Peter had a hotshot head porter check out his head and it was what the guy recommended. My shop knew the guy -- he is nationally known. My shop thought it would have been worthwhile to try slightly larger valves, but I had already bought the same as Peter. The next time (I had a little valvetrain damage due to excessive heat -- probably lean running), we used 40 mm and the shop thought they were better. Low end flow picked up quite a bit. We probably would have used 46 mm intake valves, but we decided not to use new intake seats (for 2 mm larger valves, larger seats would probably be a good idea), so we went up just 1 mm, to 45 mm.

In short, I would say that the common 38/46 combination is a little short on the exhaust side. I would go at least 40 on the exhaust.

I am not sure at what point you start going too thin on the material inbetween. 40/46 is certainly doable. But 42/46 or 42/48 or 44/48 may require siamesed seats. More work, more money, and probably less head life.

The Turboford guys get good results using 1.89/1.60 valves, which is 48/40.5 mm. They may have more room for porting, though. We ran into water once or twice on the 530, even though we had cut up a head to check for thickness. Apparently, casting differences are common. Maybe the 531 is better in casting quality and consistency. Perhaps someone with a bad 531 would donate slices of it to the cause. A good porter would not go very far without knowing what he had to work with.

The smart thing to do is to flow your head, find out the intake to exhaust flow ratio, decide what you want for a target ratio, and then start work on the poorer flowing side -- the exhaust side. Do as much as you can there. Maybe don't buy intake valves until you are done with the exhaust. The intake will be comparatively easy to bring up. Then reflow the head and see what sort of improvements you made and choose the intake valve size as best you can.

Or do some more research on the intake to exhaust ratio theory. Maybe it is old science now and there is a new theory that would give you more flexibility if you adopted it. Sort of like turbo cam theory -- supposedly once you get EBR way down you don't really need a "turbo" cam with lots of lift and little overlap -- you can use a naturally aspirated cam with more overlap.

I am going 16V next time -- maybe in a year. I have a long way to go still to reach the potential of the 8V motor that I have.

Philip Bradley
 
"I would not jump to that conclusion. There are 8 cfm to be had between the stock exhaust flow of about 114 cfm and the theoretical maximum exhaust flow of 123 cfm with the 35 mm exhaust valve. If the ports were better, that gap should be diminished. 8 cfm is a lot even if it does not seem like much."

That flow is assuming a basically "perfect" port isn't it? Gains in port flow get smaller as you approach the ceiling-but maybe you're right. Either way I made no conclusions. It was just a suggestion. All I can speak from is my own experience having played with a few of them- that experience tells me that the port is different. Better, worse, I don't know. I just know it's different. That's what I see with my own eyes and grind with my own grinder.

Re 405/531 and turbo motors:

Where did you get that info? I'm quite certain b23et and some b230et had "big heads" but I'd call that all just speculation anyways- It's probably Volvo didn't develop the head with any specific ebr in mind- definitely not as a priority anyways.

"In short, I would say that the common 38/46 combination is a little short on the exhaust side. I would go at least 40 on the exhaust."

In the land of people without unlimited funds to spend melting drivetrains, the 38/46 represent a good improvement over stock at a good price. That's why I bought them. Besides, i'm confident they will support lots of power considering what the group a b21's made with stock sized ones.....


Re valves sizes and seats:

I know it's 90mm total diameter w/ siamesed seats... not sure what you can do in a boosted app with existing seats. I'll never bother to find out I don't think. the 46/38 combo is so affordable I'll never be able to justify anything fancier. Being that valveseat installation is beyond the ability of most- I'm sure the machine shop would advise on a per-project basis.

"Or do some more research on the intake to exhaust ratio theory."

It is valuable to me in that it gives an indication as to how the head will affect ebr- which is very important to me. Just part of the system though. the actual flow ratio needs to be measured against the whole system though which is where people misuse it imo. One needs to look at TOTAL intake pressure drop vs TOTAL exhaust side back pressure- from the air filter to the chamber, and then from the chamber to the end of the exhaust system.



"Sort of like turbo cam theory -- supposedly once you get EBR way down you don't really need a "turbo" cam with lots of lift and little overlap -- you can use a naturally aspirated cam with more overlap."

Well, that is a given, not even a "supposedly", because as ebr approaches ratios similar to those experienced in a normally aspirated engine, valve overlap and clyinder filling/scavenging act in a similar way as well. So yeah, definitely a fair assumption.

"I am going 16V next time -- maybe in a year. I have a long way to go still to reach the potential of the 8V motor that I have."

being that the record is well over 500hp, I'd say we all do. I think a guy needs to build one engine and build it right. We have both had failures due to not doing things right. My engine mated to that old m46 was a bad call. IMO your well built bottom and and nice valvetrain deserved proper engine management as you know. I think even relatively unmodified engines should make good numbers if they have the rest of the "support systems" taken care of. I have 80% of what I need to do the new engine and I'm trying to resist coblbing something together. I'm sure I could put something together and have fun with it until it turned itself into an expensive mistake, but good things come to those who wait I guess. ;)
 
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correct me if i'm wrong, but there's no reason to put in larger valves unless you also put in a larger seats? If the seat can accomodate a 46 mm valve, the ID diameter of the seat would still be the same, unless you do something to the seat? A larger valve on a stock size seat would be like putting a big lid over a small hole, obstructing flow?
 
"Or do some more research on the intake to exhaust ratio theory."

It is valuable to me in that it gives an indication as to how the head will affect ebr- which is very important to me. Just part of the system though. the actual flow ratio needs to be measured against the whole system though which is where people misuse it imo. One needs to look at TOTAL intake pressure drop vs TOTAL exhaust side back pressure- from the air filter to the chamber, and then from the chamber to the end of the exhaust system.

"Sort of like turbo cam theory -- supposedly once you get EBR way down you don't really need a "turbo" cam with lots of lift and little overlap -- you can use a naturally aspirated cam with more overlap."

Well, that is a given, not even a "supposedly", because as ebr approaches ratios similar to those experienced in a normally aspirated engine, valve overlap and clyinder filling/scavenging act in a similar way as well. So yeah, definitely a fair assumption.

I am not sure we know how much of EBR to attribute to exhaust valve size and port flow. Most of what I have read suggests problems are most common after the ports -- in the manifold and in the turbo. I have done some reading on exhaust valve flow and barely understood what I read so I won't try to repeat it except to say that there is a reason why exhaust valves don't have to be nearly as big as intake valves. The EBR is not the pressure before the valve that is trying to get past the valve, as I understand. We have no relatively easy way to measure pressure there, unlike in the manifold/header after.

My point was that maybe there is some contrarian, or perhaps simply less accepted at this point in time, theory that a small exhaust valves works fine because the air is forced past it. I don't know. I followed conventional wisdom for street driven turbo motors and went with a much bigger increase on the exhaust valve than on the intake valve (and still did not have much luck tightening up the exhaust to intake flow ratio -- the intake picked up too much even with comparatively little work).

Philip
 
the ID diameter of the seat would still be the same, unless you do something to the seat? A larger valve on a stock size seat would be like putting a big lid over a small hole, obstructing flow?

Yes, if it was that simple. Larger valves are not used without some modification. The seats are cut to fit and the bowl portion of the chamber/port is modified for the bigger valve. There is a limit to how much you should cut stock seats, so larger ones are used if you use significantly bigger valves. Retaining seat area is most important on the hot exhaust side.

This work is what you cannot really do yourself unless you are very advanced and have a nicely equipped shop. Seats have to be pressed in and out and you can wreck a head if you don't know what you are doing -- there is relatively little material to work with when using larger seats. And cutting multi angle seats is also best left to the experts. The better shops use expensive floating head valve machines like one made by Serdi.

The chamber work and port work you can do yourself if you have studied the subject in detail, have the right tools, and are very patient. Boris Mohar has some pictures of what he has done at his website. It is not a job for the hack mechanic, the guy with a filthy dirty shop, the guy without the proper tools, the impatient person, etc. And to really know whether you are doing the right thing, you should make a flow bench. There are a few books on the subject and you can make a decent flowbench with a vacuum cleaner and a manometer and a few other relatively inexpensive parts. I have not attempted this yet and it is not on my current projects list, but if I can make a "clean room" in the barn at some point, I would like to try this and also engine assembly.

Philip Bradley
 
"The EBR is not the pressure before the valve that is trying to get past the valve, as I understand. We have no relatively easy way to measure pressure there, unlike in the manifold/header after."

EBR is not pressure at all- it's just a number so I really don't know how to respond to that. One major reason we use port flow ratios is exactly because we cannot easily measure intake pressure or exhaust backpressure post and pre-valve. If for an example we say that on an imaginary engine that as intake pressure is increased by 10psi we end up with 20psi more backpressure at the header, then there is a 2:1 ebr at the manifolds. By using the port flow ratio you can then get an idea of what the effective OVERALL flow/pressure ratio is within the whole system start to finish.

It gets complicated looking at the whole system post intake valve and pre exhaust as well because then the piston induced pressures as well as post-combustion related pressures and such come into play and then end you also end up back looking at the cam lsa and etc. In reality the average enthusiast can do fine try to optimize flow in a balanced sense etc etc and this theory is overkill unless you're a sick, nerdy bastard like me and you just find it interesting. :)
 
EBR is not pressure at all- it's just a number so I really don't know how to respond to that. One major reason we use port flow ratios is exactly because we cannot easily measure intake pressure or exhaust backpressure post and pre-valve.

I think it is being overly technical to say that EBR is not pressure at all. It is the ratio of one pressure to another. Without pressure, EBR is meaningless. It is two pressures in relation to one another.

My point was that EBR seems to be affected MOST by the turbo. People who hotrod turbos and measure EBR most commonly write things like, "The EBR dropped by 50% once I went to a bigger turbo." Maybe 4:1 at 20 psi down to 2:1, or something like that. Manifolds/headers and the exhaust after the turbo are the next most common culprit.

They don't write things like, "After I ported the exhaust, the EBR dropped by 25%" or "Once I went up from 35 mm to 40 mm exhaust valves, the EBR dropped by 25%." At least not that I have read anywhere. I would love to read test results covering this. You won't get one from me because I do not yet have any back pressure ports installed. Eventually, I will install some, but I won't be installing them before the valve or after the valve in the port before the manifold/header.

Philip Bradley
 
Relative to the manifold head mods do not change ebr at all. So in that case yeah the turbo and manifold have the most effect. I was talking about the relationship between ebr as normally measured and the total effect of intake and exhaust flow at the point of combustion. Point is in the end, you cannot seperate manifold function and and head functions since the port is an extension of the manifold and vice versa. EBR and port flow ratio work together to balance the equation on the full scale.
 
So what exhaust to intake port flow ratio do we want and why?

Is it better to have a stock 530 head with the stock port flow ratio or a 531 head with a worse than stock port flow ratio due to stock exhaust port flow and superior intake flow? At what point will the 531 head become a problem? It seems to me that at some point the little exhaust valves will have so much more air pushed through them that things will no longer be very efficient and heat will increase and detonation may rear its ugly head.

For what it is worth, I tried for 90% and ended up with about 80%, which is about stock. Add 3 mm to the stock exhaust valve and just 2 mm to the larger intake valve, and you have increased the intake valve area by nearly as much as you have increased the exhaust -- the ratio won't really improve. We ended up adding 5 mm to the exhaust valve and 1 mm to the intake valve and still did not really improve the ratio. I think we reached the point where the exhaust was becoming port limited. It would be interesting to try porting a 531 head. There might be more room to port. We did about as much as we could on the 530 exhaust without investing too much in it. Obviously a master who ported a dozen heads could do better, and we could have done better if I had wanted to pay $75 per hours for a few days of work.

Philip Bradley
 
It seems to be somewhat port limited, especially the bowl, and even moreso combustion chamber limited. I think a slight diminishing return effect appears at some point in the routine of increasing valve size because the valve gets more and more shouded unless you keep opening the chamber walls up more and more- which you can only do so much.

Partially becuase of the physical bore dimensions and such, and also because you start killing squish area and so adding more exhaust valve for better exhaust/heat removal in an attempt to control detonation becomes counterproductive since you're losing squish area.

Port ratios are hard to nail down imo as an engine with bad ebr will want something like 90 and something with an ebr closer to 1 will probably want 70 or 80. But then adding a custom intake maifold reduces intake restriction and throws things the other way. I'd say those are probably average numbers though.
I'd say 80% is probably fine with a good ebr (ie staged turbine wheel, header, straight exhaust)
 
It will be interesting to see how my head turns out, as I've essentially put the focus on de-shrouding the valves, putting more focus on in-and-out flow past the valves rather than maintaining a high squish area.

I have a 405 BCP head that I will be suffering with HG issues I'm sure (am going to have to have it shaved significantly to remove scoring on the surface of the head), but I have put a lot of work into the exhaust ports, relatively... It has been a difficult balance though and I'm sure a good learning experience.

Would it be out of line to interject a question about exhaust port design here? More along the lines of the "end" of the port...
 
I have a 405 BCP head that I will be suffering with HG issues I'm sure (am going to have to have it shaved significantly to remove scoring on the surface of the head)
A friend welded up the coolant passages on a BCP head at the deck surface. You might ask an expert whether this is worthwhile -- whether it will make the surface measurably more stiff. You should check the head afterwards for straightness since welding can warp aluminum.

Philip Bradley
 
My head had good overall gains

I had my 405 head flow tested both before and after port work. They got about a 10% overall gains which I am happy with. He told me that to maximize the flow the exhaust port design is the limiting factor. At the time I wasn't familiar with optimizing the head for turbo use so I asked for an overall gain. I have a thread on CV with pictures.

http://www.clubvolvo.com/forums/showthread.php?threadid=1910&perpage=15&pagenumber=2

Best regards,
 
Dlot,
198 and 123 holy crap. Basically maxed out the valve flow. That intake flow is insane.

Erif, have the head milled as little as possible. The more material you take off of that surface the more it will want to flex. If you're doing the work yourself- cool. If you're paying big bucks, I might rethink as it'd be sad to have it all done and then have problems with it. That's why I ended up choosing an scp 398 on my last engine...
What was your question about the port?
 
198 and 123 holy crap. Basically maxed out the valve flow. That intake flow is insane.

Dave's numbers are reasonably in line with what I have seen (second hand) for 405 and 531 heads. There is always a margin of error -- different flow benches and different ways of setting the head up on the bench. But they seem in the ballpark.

Note how well and easily the intake picks up and how hard and little the exhaust picks up. Also note how easy it is to hit water on the exhaust. One of Dave's exhaust port shots shows a hole into the water jacket. This happened on my head as well -- even though we had cut up another 530 head and were not supposed to be close based on the slice of the first head.

Dave improved about 10% on the intake and 5% on the exhaust -- he is further from the goal of 80% exhaust to intake flow ratio that would be found on a stock 530 head. That ratio starts out much worse on the 405 and 531 head. Whether this will cause problems is debatable. Conventional turbo wisdom is that you want at least 80%.

If Dave's porter hit water on the 405 head exhaust port, I would be inclined to say that the 405 and 531 exhaust ports offer no advantages over stock. His porter said flow was port limited -- this is not entirely true. We got significantly more flow through much bigger valves, but it is partially true because there is a definite limit to how far you can go with the port due to the water jacket and even the largest valve fitted to a limited port won't flow nearly as well as it could.

I like the 16V head on paper more and more for turbo use -- I am being converted fast. The exhaust valves are sized to 90% of the intake valves. On the 8V head they are sized to 80%. A stock 16V flows on the exhaust about what a stock 531 8V flows on the intake. The stock 16V intake will outflow even the mildly worked 531 intake.

Philip Bradley
 
Green Death said:
Dlot,
Erif, have the head milled as little as possible. The more material you take off of that surface the more it will want to flex. If you're doing the work yourself- cool. If you're paying big bucks, I might rethink as it'd be sad to have it all done and then have problems with it. That's why I ended up choosing an scp 398 on my last engine...
What was your question about the port?

Right, I'm just going to get it shaved the minimum amount to get rid of the scoring marks on there and make sure it's perfectly flat... Though I'm pretty sure it will be a good amount to accomplish that.

I've done all the porting and CC work myself (haven't checked CC volume consistency yet, that's next on my list, looks ok though), this is a head that I got for free in the trunk of a car I purchased (along with a bunch of other goodies)... When I pay for a head, I will likely be getting a 531 from a Penta, or maybe even a Unitek cut head if things work out that way.

This one is largely for experimentation though, which is why I'm trying a lot more valve de-shrouding.


My port question..
What do you guys think about exhaust port shape towards the end of the port? Larry at TOO seems to prefer to have it taper down slightly to increase velocity... However I would think that this depends on primary tubing size largely. Taking into consideration velocity and anti-reversion, how much could/should an exhaust port taper down in size below that of the primary tube?

This is kind of frustrating for me, since the ends of the ports are most easily accessible, and it is very tempting to try to round the square a bit, especially on the top... However it seems counter-intuitive when considering anti-reversion and velocity (depending on primary size). Are there any accepted ratios here or anything like that? Or just more a factor that falls to trial-and-error?

The 850 turbo heads are a great example of this design (and likely most DOHC heads), and I am very curious as to whether it would be productive to open that up at all... And how much ;)
 
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