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Is it worth porting and bigger valves on a built 531 turbo motor?

dannyman742

dannyman742

Member
Joined
Jun 17, 2021
I am building a Volvo 240 for 30 or so pounds of boost on e85. It will be a drift car and as such, I was wondering how much restriction there is in the stock 531 head with a turbo setup? I don't want a HORRIBLY laggy setup after all, though I understand some lag is inevitable. So to my understanding porting and bigger valves reduce velocity to the turbine causing more lag, and porting isn't all that useful unless you have bigger valves to compensate. So how is the stock 531 head under 30 psi, because say I decide to turn up the boost down the line, when does it become a real bottleneck in there? And how much would I seek to gain by adding say 38 and 46mm valves and porting it to hell
 
There are very good gains to made in porting a stock head and using stock sized valves.
You can also make serious power on an untouched 8v head, especially with e85.
 
culberro said:
There are very good gains to made in porting a stock head and using stock sized valves.
You can also make serious power on an untouched 8v head, especially with e85.
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-and with a 530 head. Bigger valves help if you are after serious power. If your just wanting a strong daily, I wouldnt mess with buying a 531 head and the bigger valves. Just my opinion.
 
culberro said:
Nope.
The 531 has a better intake port and combustion chamber (slightly more opened up).
The 530 and 531 both have the same terrible exhaust port.
Click to expand...

So what can be done about the exhaust port, is the stock exhaust port a major restriction on this set up? And what do I sacrifice by making it bigger?
 
The 531's are also prone to cracking into the spark plug port, where the 530's aren't.

Having run a stock 530, a mildly ported 530, and a mildly ported, big valved 531 on the same bottom end, the 531 was just a touch more laggy but it didn't have the slight compressor surge the stock valved head had, and it also didn't hit the wall around 5500 like the stock head did. If you're going for a drift car that's high boost, you really won't notice the lag down at low rpm's most likely, but there's a key detail you left out. You have a boost number, no other info on supporting work, or what size turbo. 30psi from a stock 13c vs 30psi from a GT35 are 2 entirely different ballgames.

In my case, 9:1 build, IPD cam, around 18-20psi from a GT2871R back when I had the big valved head. The new motor will be running the current GTX2867, still 9:1, but with an SPM Stage IV head (530 casting, heavily ported, 46/38 valves).
 
gsellstr said:
The 531's are also prone to cracking into the spark plug port, where the 530's aren't.

Having run a stock 530, a mildly ported 530, and a mildly ported, big valved 531 on the same bottom end, the 531 was just a touch more laggy but it didn't have the slight compressor surge the stock valved head had, and it also didn't hit the wall around 5500 like the stock head did. If you're going for a drift car that's high boost, you really won't notice the lag down at low rpm's most likely, but there's a key detail you left out. You have a boost number, no other info on supporting work, or what size turbo. 30psi from a stock 13c vs 30psi from a GT35 are 2 entirely different ballgames.

In my case, 9:1 build, IPD cam, around 18-20psi from a GT2871R back when I had the big valved head. The new motor will be running the current GTX2867, still 9:1, but with an SPM Stage IV head (530 casting, heavily ported, 46/38 valves).
Click to expand...

Heres some info on supporting mods, enem k15 cam, 30psi from an he341, yoshifab built bottom end 8.55 compression, d088 2.5 inch intercooler piping, kl racing intake and turbo header, on a haltech1000. Oh and of course e85. Well and a cd009 to hold it all ;).. Does this change your opinion at all?
 
That's a lot of air from that HE341. I did run one of those prior to the Garrett on mine, definitely glad I had the big valved head at that time. With a 9:1 bottom end, it was a little laggy below around 3k but some of that could have been dialed out with custom tuning I suspect (I wasn't doing my own tuning at the time, just relied on box tunes).

Personally I would go for a big valved 530 with some serious port work, or a big valved 531 with port work. That turbo will have a little compressor surge with the smaller valves, definitely did on mine.
 
gsellstr said:
That's a lot of air from that HE341. I did run one of those prior to the Garrett on mine, definitely glad I had the big valved head at that time. With a 9:1 bottom end, it was a little laggy below around 3k but some of that could have been dialed out with custom tuning I suspect (I wasn't doing my own tuning at the time, just relied on box tunes).

Personally I would go for a big valved 530 with some serious port work, or a big valved 531 with port work. That turbo will have a little compressor surge with the smaller valves, definitely did on mine.
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I think i will go big valves and make it live higher in the rev range lol. But you mentioned that the 531 is prone to cracking spark ports? Ive never heard that, wondering how prone and how badly?
 
dannyman742 said:
Heres some info on supporting mods, enem k15 cam, 30psi from an he341, yoshifab built bottom end 8.55 compression, d088 2.5 inch intercooler piping, kl racing intake and turbo header, on a haltech1000. Oh and of course e85. Well and a cd009 to hold it all ;).. Does this change your opinion at all?
Click to expand...

Are you using the cheaper welded KL intake or the more expensive cast 2-piece one?

Now that we know a bit more about your setup, it's a bit easier to give you some guidance or direction.

The KL intakes have a larger flange area than a stock intake, which is a good starting point.
No matter what valve size you use, you will want to reshape the intake side of the port from the flange side to the valve. The 530 head has a particularly steep taper in the first 2-3" of the port. The 531 is better in this regard.

For the exhaust side, you will want to widen the port but don't raise it. This is especially important in the turn area. Then make the radius on the turn as big as possible, stock they are a sharp edge. This is about the best you can make the stock ex port without welding and moving it.

Edit: You will also want to unshroud the chamber on the exhaust side on either head (530 or 531). The intake side of the chamber on the 530 can also get some reshaping as well.

If you go with OS valves the seat ID needs to be opened up to ~85+% of the valve diameter, and carry this through the bowl area and turn (using a slight taper). If the bowl and seat ID are not enlarged, you are wasting money and time by installing OS valves. This is because you haven't removed the flow restriction in the head.... It's not the valve diameter :)
 
Last edited:
culberro said:
Are you using the cheaper welded KL intake or the more expensive cast 2-piece one?

Now that we know a bit more about your setup, it's a bit easier to give you some guidance or direction.

The KL intakes have a larger flange area than a stock intake, which is a good starting point.
No matter what valve size you use, you will want to reshape the intake side of the port from the flange side to the valve. The 530 head has a particularly steep taper in the first 2-3" of the port. The 531 is better in this regard.

For the exhaust side, you will want to widen the port but don't raise it. This is especially important in the turn area. Then make the radius on the turn as big as possible, stock they are a sharp edge. This is about the best you can make the stock ex port without welding and moving it.

If you go with OS valves the seat ID needs to be opened up to ~85+% of the valve diameter, and carry this through the bowl area and turn (using a slight taper). If the bowl and seat ID are not enlarged, you are wasting money and time by installing OS valves. This is because you haven't removed the flow restriction in the head.... It's not the valve diameter :)
Click to expand...

Dude thats awesome info! Im using the 2 piece cast intake. I was wondering if you had any pictures to accompany your descriptions? I hate to admit im kinda new to this lol
 
dannyman742 said:
Dude thats awesome info! Im using the 2 piece cast intake. I was wondering if you had any pictures to accompany your descriptions? I hate to admit im kinda new to this lol
Click to expand...

I also edited my post with some info about opening up the combustion chambers, the exhaust valve is heavily shrouded.


Erland Cox is a huge library of information, and also has plenty of pics as well as flow data on the heads. He has ported some of (if not THE) heads for the fastest redblocks in the world. He also does street ports and everything in between:

http://www.topplocksverkstan.se/toppar.html

Here is another great read on head flowing and porting. Lots of good info here! http://www.topplocksverkstan.se/fyrtaktintroduktion.html

Here's a link to some of the work that I've done: https://flic.kr/s/aHsmEJbbuo

There's heads, as well as fabrication work in this album. Some pics have descriptions, some don't. I'll also be uploading some pics later today of a head that had 48/40 valves installed with no porting that was done by another shop and the issues with the head. So check back later as well.
 
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