What is a 531 head?

monkeh · Jan 15th, 2011, 17:27

Whats one of them? And where can I find one? Will it fit onto a b230fk block with minimal of fuss?
What are the differences between that and the one thats fitted as standard?

wooble · Jan 15th, 2011, 17:53

'531' is a reference to the casting number on the left side of the head, which is '1000xxx', with the xxx in this case being 531.

The standard head on a late redblock is known as the 530 head. The 531 head has a better flowing intake design, better positioned spark plugs, and slightly larger combustion chambers. You'll find it on a B230ET engine in a 740 turbo, on a B230FB engine in a late 940, on the very rare B230FX engine in a late 240 or on some Volvo Penta boat engines (these are notorious for suffering from serious corrosion, though). It will swap straight on to any redblock with a 530 head.

Other casting numbers I know about are 160, 398, 405 (for the older B19/B21/B23 series engines - 405 is the hot one), 532 (16 valve head, can be fitted to a B200/B230 but requires a fair bit of re-jigging and usually some custom parts) and 631 ('heron' head, has no combustion chamber in the head, needs special pistons).

Skylaneguy · Jan 15th, 2011, 18:14

531 heads came on Penta (marine) engines and the B230ET, which is rated about 20 more horsepower than the B230FT. They flow better than the 530 heads. The 531 head is a bolt on 8 valve direct replacement for the 530 head. The combustion chamber is shaped slightly different and is a tiny bit larger, and the spark plug protrudes into the combustion chamber a little more. I must note the B230ET also has a higher compression ratio than the B230FT, 9.0:1 versus 8.7:1. Marine engines are run at higher power settings for longer periods of time than automotive engines, and it is clear the 531 head was designed for engines operating at higher power settings. To have the same compression ratio as the 530 head, the 531 head must be shaved a little. I can't say for certain, but I think it is about 0.011". I'll probably measure the cc of the different combustion chambers as I proceed with my project.

I have a 531 head being prepped for my L block B230FT as I type this. It will go on with a 0.036" Cometic head gasket to give 0.030-32" piston clearance. This is referred to as a tight squish engine. I measured the deck height on my block, and the pistons protrude 0.006" above the block, which I'm told is typical for this vintage of B230FT.

RealEstate · Jan 15th, 2011, 22:50

If the 531 head is considered to be a better design, why was it not more widely fitted?

Does it have any drawbacks?

Skylaneguy · Jan 16th, 2011, 01:52

Quote:

Originally Posted by RealEstate

If the 531 head is considered to be a better design, why was it not more widely fitted?

Does it have any drawbacks?

I'm not aware of any drawbacks. Here is a link to an old post, http://www.volvoforums.org.uk/showthread.php?t=43418

Jan 15th, 2011, 17:27	#1
monkeh Pain in the backside Last Online: Yesterday 18:06 Join Date: Mar 2007 Location: Newport	What is a 531 head? Whats one of them? And where can I find one? Will it fit onto a b230fk block with minimal of fuss? What are the differences between that and the one thats fitted as standard? __________________ 'Designed by a computer, built by a robot, and driven by a f***ing nutter' '09 XC70 SE - 2" lift, D5 225bhp, poverty spec '18 V60 Twin Engine R Design - 290bhp

Jan 15th, 2011, 17:53	#2
wooble Stay gold baby! Last Online: Jul 24th, 2022 16:15 Join Date: May 2009 Location: Bristol	'531' is a reference to the casting number on the left side of the head, which is '1000xxx', with the xxx in this case being 531. The standard head on a late redblock is known as the 530 head. The 531 head has a better flowing intake design, better positioned spark plugs, and slightly larger combustion chambers. You'll find it on a B230ET engine in a 740 turbo, on a B230FB engine in a late 940, on the very rare B230FX engine in a late 240 or on some Volvo Penta boat engines (these are notorious for suffering from serious corrosion, though). It will swap straight on to any redblock with a 530 head. Other casting numbers I know about are 160, 398, 405 (for the older B19/B21/B23 series engines - 405 is the hot one), 532 (16 valve head, can be fitted to a B200/B230 but requires a fair bit of re-jigging and usually some custom parts) and 631 ('heron' head, has no combustion chamber in the head, needs special pistons).

Jan 15th, 2011, 18:14	#3
Skylaneguy Member Last Online: Jan 27th, 2022 22:18 Join Date: Dec 2010 Location: Vancouver	531 heads came on Penta (marine) engines and the B230ET, which is rated about 20 more horsepower than the B230FT. They flow better than the 530 heads. The 531 head is a bolt on 8 valve direct replacement for the 530 head. The combustion chamber is shaped slightly different and is a tiny bit larger, and the spark plug protrudes into the combustion chamber a little more. I must note the B230ET also has a higher compression ratio than the B230FT, 9.0:1 versus 8.7:1. Marine engines are run at higher power settings for longer periods of time than automotive engines, and it is clear the 531 head was designed for engines operating at higher power settings. To have the same compression ratio as the 530 head, the 531 head must be shaved a little. I can't say for certain, but I think it is about 0.011". I'll probably measure the cc of the different combustion chambers as I proceed with my project. I have a 531 head being prepped for my L block B230FT as I type this. It will go on with a 0.036" Cometic head gasket to give 0.030-32" piston clearance. This is referred to as a tight squish engine. I measured the deck height on my block, and the pistons protrude 0.006" above the block, which I'm told is typical for this vintage of B230FT.

Jan 15th, 2011, 22:50	#4
RealEstate Master Member Last Online: Nov 4th, 2018 16:06 Join Date: Dec 2003 Location: Berkshire & N Wales View Photos By: RealEstate	If the 531 head is considered to be a better design, why was it not more widely fitted? Does it have any drawbacks?

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