531 head question

How much better is the 531 head then the 530 head? I am going to do a canadan junkyard run in the next week or so. I plan on trying to find one for my 85 744ti. my car has the 530 right now, would it be a noticable difference with the 531?

PM Philip Bradley. He gave me a lot of info on this head. I got one from a friend of mine, and I'm debating on what level of porting I want to do on it. Supposedly the intake is incredible on this head, and benefits from polishing alone. The exhaust needs work however, and will really benefit from larger exhaust valves. I just need to find out which size to use.

I think the 531 did not come to North America at all on cars. Perhaps you are thinking of the Kjet 405 heads, which are available in Canada.
531 are available on some Penta engines, but which ones I'm not sure...

yeah, call around some boat junk yards looking for a AQ151, should have a 531 and V cam, NA didn't get them at all on cars, only the BCP405's.

while over on this side of the pond we got

531 with A cam (B230ET)
531 with VX(3?) cam (B230FB)
BCP405 with H and K cam (79-84 B23E)
SCP405 with B cam (B23ET)

They didn't come on car engines in North America.

The intake is better than the 530 (same valve size, though). The exhaust side is the same. The spark plug sticks out more into the combustion chamber.

If you wanna pay the nice shipping I would gladly send you a 531 head

shipping: 150$

head: ~265$

totals: 415$

benboy said:

I think the 531 did not come to North America at all on cars. Perhaps you are thinking of the Kjet 405 heads, which are available in Canada.
531 are available on some Penta engines, but which ones I'm not sure...

Click to expand...

This is what I have been finding as well. I tried finding one of these heads for a few years up in Canada, but to no avail. I did however have not too much of a problem finding the 405 heads. However, I have modified a 530 head that will completely outflow a mildly ported 531!

For what it's worth. It would be good to look for a 405, or if you are going to be near any marine yards, you might find one of these heads on an AQ151 (I think that's the 8 valve version...)

Good luck!

Eric

towerymt said:

They didn't come on car engines in North America.

The intake is better than the 530 (same valve size, though). The exhaust side is the same. The spark plug sticks out more into the combustion chamber.

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but the exhaust ports are not the same because I have a 398, a 405, and a 531 head in my garage, and on the 405 and 531 you can see about a 1/4" of exhaust valve guide into the bowel, whereas on the 398 the port is smaller and the valve guide is flush to the port in the bowel. So the exhaust ports are slightly larger too.

The 530 and 531 ex ports are the same. 160 looked close, too.

531 has a sweet intake port.

Agree w/ coondog. Ex ports aren't the same. I keep hearing people say they are, and then corrected, and back and forth. Anyways they look different to me- 405/531 having a better bowl. Not majorly different like the intake but different.

What is better. Ha. For what? Define "Better". Loaded question imo.

i can vouch for the two heads mikep had at his shop... both exhaust ports are the same. is the 531 you have from a penta mike? maybe the auto variety is different?

I'd rather have kenny's worked 398 then a 531 for the price though - its all in the numbers

heads

In Mike Aaro's article here on the site he only mentions a plateau difference in the exhaust ports between the two head types. http://www.turbobricks.com/specs.php?content=sohc_heads It sounds like a very subtle difference.

Best regards,

Do the heads you guys are comparing have valves in them? The difference is at the bowl- it would be hard to see otherwise.
I've ported a couple of each now and in my limited experience having only ported maybe 4 or 5 heads they're different- but you could make a 530 exhaust port like a 531. It isn't major but out of the box the 405/531 I've seen have been better all around even if just in terms of casting quality so to call the port the same is in my opinion misleading to someone who plans to just bolt a head on. Just my experience.

My 531 core was 200 canadian plus some old 164 parts, and my scp 398 was 100US. IME there's no real price difference if you source a penta one stateside. In terms of a major project I consider 100 or 200 bucks to be fairly negligible but that's just me. Sourcing one from europe definitely ain't worth it- if that's your only option then mod a 530- but their availibility here in the penta stuff makes them a pretty viable option these days. When i had no option, I spent 900 bucks to have a 398 ported. On my new project I had the option of a 531, so I took it. Cleaned up by myself and with new seats and bronze guides and oversized valves, the total price should be similar but the 531 should have a slight edge on flow and a definite edge in terms of durability and detonation resistance.

you can often find them cheap enough in the Uk that it isn't that bad to sell them over there.

i think i sold mark one for ?195 shipped, which at that time was about $300, and Dlot a SCP405 for less then that.

the last one i had was ?1.20 off ebay (yeah i know +?20 traveling to pick up) which i put some money into in skimming and cleaning and parts and sold to griz for ?60

heads

I have to second Kenny's comment about the casting quality. I bought some of these heads now and everyone of them looks like higher quality metal. Pierre mentioned this to me and his comment was that when polishing the combustion chambers the 405 would polish up much higher/brighter than the metal used for the 160/398. The cost for getting a better base to start with is worth the extra effort it might take to buy one of these heads.

Best regards,

tryckj?vel said:

i can vouch for the two heads mikep had at his shop... both exhaust ports are the same. is the 531 you have from a penta mike? maybe the auto variety is different?

Click to expand...

Yes, it came from a boat, and had a V cam.

NChoy said:

PM Philip Bradley. He gave me a lot of info on this head. I got one from a friend of mine, and I'm debating on what level of porting I want to do on it. Supposedly the intake is incredible on this head, and benefits from polishing alone. The exhaust needs work however, and will really benefit from larger exhaust valves. I just need to find out which size to use.

Click to expand...

I should really slap the big Valve 531 head i aquirred on a car to see what the difference is i guess.

The valve Sizes are 38mm Exhaust and 46mm Inlet. Hope this helps Nick.

I have had one stock 530 head flowed, one with just a 5 angle valve job, one with moderate porting and 38.5/44 mm valves, and one with moderate porting and 40/45 mm valves (my current head and the shop was happy enough with the results to do another one just like it for another customer). I have seen numbers for two 531 stock heads, and think the numbers I have seen for the two 531 heads are reliable because they were consistent with each other and with what I had heard and read in general.

Based on these numbers, the stock 531 head flowed dramatically better than a stock 530 head on the intake side and almost exactly the same (within 1-2 cfm) on the exhaust side. Thus, whatever perceived casting advantages there may be in the exhaust ports, in stock form, the 531 EXHAUST FLOW IS THE SAME AS THE 530 EXHAUST FLOW. The stock 531 head is a great starting point, but I would recommend investing some time and money on the exhaust side. With a street driven turbo motor, it is generally advisable to tighten up the intake to exhaust flow ratio over that generally advised for a non turbo motor.

Note that Volvo did not do any porting or change valve sizes for the turbo motors. The intake to exhaust flow is already less than ideal for the turbo motor. Obviously you can still make good power with it and run reliably for years, but there is power and efficiency to be had if you are willing to spend some time and money.

A 530 head can be made to flow like a stock 531 head on the intake with relatively minor work. I assume, but do not know, that a 531 head can be worked to flow much more due to the different casting. However, why do even the minor work necessary to make a 530 head flow like a stock 531 head if you have access to a 531 head in good condition?

The 531 head definitely should get larger exhaust valves if used on a turbo motor and the 530 head should if it is being more than very lightly modified. The exhaust flow is valve limited much more than port limited. Port all you want, but you still cannot get more than about 123 cfm of air through a 35mm valve according to Superflow.

As I understand, once the 530 combustion chamber is opened up to the 531 size, the 531 will take no bigger valves than the modified 530. Neither can be opened further due to the piston bore size. The advantage in the 531 is that the intake flows more and perhaps that the intake and exhaust will both take more porting. The walls on a 530 definitely have limits and it is possible to hit water without too much effort. Maybe someone has details on the 531.

For the money that you will invest to make a nice bigger valve 530 or 531 head, you could probably do a 16V head. I bought one fully rebuilt on the internet for $275 and one used but verified to be good for less than $100. Even a stock 16V head will outflow a moderately worked bigger valve 530 head. I think, but cannot be certain, that it will also outflow a moderately worked bigger valve 531 head. I suspect that in stock form, it will outflow all but the most seriously worked big valve 530 or 531 heads. Pretty impressive. But you need a $100 tensioner from Dick Prince (or buy the Penta part or adapt your own) and a $150 manifold adapter or $300 log header or $600 custom header to use the 16V head and you have to factor those costs into the conversion cost. Since I had a shop work the head, I spent a lot and would have done better with the 16V conversion.

Don't be unhappy with your 530 or 531 head. You can still make great power with them, perhaps have better low end torque if the porting job is well done and the cam well chosen, have a much simpler and less expensive valvetrain, and you can always turn up the boost a little to compensate.

Philip Bradley

pbonsalb:

Do you have any flow # for the 531 you can post?

I cannot seem to find them, but I did find some for a 405, which is reportedly very similar. The numbers are about the same as for the 531, to the best of my recollection. All cfm are at 28 inches of water, but I don't know whether the rest of the details were consistent with what my shop used when doing work on my 530. Things like the bore tube, the intake, the exhaust, and the seals can all be important and create large variables. This is why you have to be careful comparing flow numbers when the tests were not done by the same person on the same bench. Before and after tests by the same person on the same bench are the best.

Here is data for a 405 head that seems to be reliable and comparable based on what I have seen for 160/398/405/530/531 over the years:

intake with lift at .1/.2/.3/.4/.5 inches flowed 51/102/146/161/169 cfm, respectively

exhaust with lift at .1/.2/.3/.4/.5 inches flowed 39/78/100/108/114 cfm, respectively

The 530 intake will more or less top out in the .350 range in stock form. The 531 keeps flowing like this 405. On the exhaust, both the 530 and 531 crept up in flow right to the end, like this 405.

With my current 530 head with moderate porting and 40/45 mm exhaust/intake valves, the flow at 28 inches of water was

intake with lift at .1/.2/.3/.4/.5 inches flowed 54/113/156/164/168 cfm, respectively

exhaust with lift at .1/.2/.3/.4/.5 inches flowed 48/83/107/125/135 cfm, respectively

Again, what is most important is not these numbers I have supplied, but what your head flows now based on your testing methods and what it flows afterwards. My gains were generally in the 10% to 20% range. The other important thing to remember is that flow numbers do not necessarily translate into driveability. You could hog out ports, lose velocity, get great flow numbers, and create an engine that is really inefficient in daily driving and that runs poorly everywhere but in a narrow, elevated rpm range. Numbers are not everything. There is a science to it, which is why good shops get $75 per hour and say they need to spend at least a day on your head slicing up old heads, mocking up ports with clay, doing numerous flow bench tests, and so forth. A "fluff and buff" that is pretty much light clean up work without fitting larger valves will help a little and is much cheaper. You could probably do this yourself without much risk

In my view, the multi angle valve job is the best bang for the buck, and costs not much more than a regular valve job, yet might get you 10+ cfm at some lifts on the intake. But before pulling your head and spending any money on it, try a performance cam -- it will make much better use of what you have (but will trade low end for top end).

Philip Bradley