531 vs 405

smithy · 05-07-2012, 08:32 AM

Is there any advantage in using a 351 head over a 405. the ports looks the same. The combustion chambers look a bit different. I haven't cc'd them to check if they are the same size. The reason i ask this question is that i have a 405 head but i have found a 531 that is cheap.
thanks

11110000 · 05-07-2012, 09:05 AM

I don't know of any hard evidence, but the 531 is reputed to have a slightly more centered spark plug location. Also, most 405 heads are BCP, and the 531 should be a SCP head.

Other than that, really no difference to speak of.

blkaplan · 05-07-2012, 10:14 AM

Aren't the 405 heads setup for Kjet injector locations? I know the 531's are not. That would be the biggest difference i could think of.

from what i remember the 405 and 531 have very similar flow characteristics. I dont know if i would bother changing from one to another but if its cheap enough it might not be bad to get as a backup head.

towerymt · 05-07-2012, 10:44 AM

-SCP vs BCP (all 531 = SCP, 405 could be either)
-spark plug location in the 531
-k-jet holes
-a need for head mounted dizzy? only 531 can accommodate
-b21/23 block or b230? t-belt cover backing plates differ, as do valve covers, but you can still mix and match heads to blocks.

woodywhat · 05-08-2012, 02:43 AM

Quote:

Originally Posted by smithy

Is there any advantage in using a 351 head over a 405. the ports looks the same. The combustion chambers look a bit different. I haven't cc'd them to check if they are the same size. The reason i ask this question is that i have a 405 head but i have found a 531 that is cheap.
thanks

grab the531 head and deshroud the valves, skim the head.5mm. you didnt say which 405 you have 78-82 or 90-93 mods ime guesing 78-82 witch is big/w/p and if its not seeping, ide leave it on until you decide to rebuild the engine. meanwhile seach for a penta block {2.5l} to go with your tweaked 531 head and a good m47 alloy box.

woodywhat · 05-08-2012, 02:45 AM

Quote:

Originally Posted by towerymt

-SCP vs BCP (all 531 = SCP, 405 could be either)
-spark plug location in the 531
-k-jet holes
-a need for head mounted dizzy? only 531 can accommodate
-b21/23 block or b230? t-belt cover backing plates differ, as do valve covers, but you can still mix and match heads to blocks.

late 405 90-93 with blank k.jet ports run head dizy.

towerymt · 05-08-2012, 10:32 AM

Quote:

Originally Posted by woodywhat

late 405 90-93 with blank k.jet ports run head dizy.

what? never heard of such a thing. On what block? In which car?

swiggy · 05-08-2012, 11:10 AM

Pretty sure it came in euro cars, maybe australia got it too. My dad had a '90 (I think it was a '90) 740 that had a 405 head on it in the UK. May not have been stock, but it looked original. It had been on there a long time anyway, and it ran on LH 2.2 as well, the kjet ports were not drilled out. Theres some real mixing and matching and oddities in different markets..

05-07-2012, 08:32 AM	#1
smithy Board Member Join Date: Aug 2007 Location: Melbourne	531 vs 405 Is there any advantage in using a 351 head over a 405. the ports looks the same. The combustion chambers look a bit different. I haven't cc'd them to check if they are the same size. The reason i ask this question is that i have a 405 head but i have found a 531 that is cheap. thanks __________________ Smithy

05-07-2012, 09:05 AM	#2
11110000 Board Member Join Date: Apr 2004 Location: East Hartford, CT	I don't know of any hard evidence, but the 531 is reputed to have a slightly more centered spark plug location. Also, most 405 heads are BCP, and the 531 should be a SCP head. Other than that, really no difference to speak of. __________________ Sounds like some of you need handling by Rancho. - stevemd

05-07-2012, 10:14 AM	#3
blkaplan 50 shades of beige Join Date: Jul 2002 Location: Rockville, MD	Aren't the 405 heads setup for Kjet injector locations? I know the 531's are not. That would be the biggest difference i could think of. from what i remember the 405 and 531 have very similar flow characteristics. I dont know if i would bother changing from one to another but if its cheap enough it might not be bad to get as a backup head. __________________ www.BEIGEPOWER.com Kaplhenke Racing Facebook

05-08-2012, 11:10 AM	#8
swiggy ---------- Join Date: Jan 2011 Location: Victoria, BC	Pretty sure it came in euro cars, maybe australia got it too. My dad had a '90 (I think it was a '90) 740 that had a 405 head on it in the UK. May not have been stock, but it looked original. It had been on there a long time anyway, and it ran on LH 2.2 as well, the kjet ports were not drilled out. Theres some real mixing and matching and oddities in different markets.. __________________ 79 poo brown 245 - B23E/M46 swap. 405 head, K cam @ 4 deg adv. Bil HDs, dual sways, 2.5" exhaust etc. 5% tint, loud stereo and some sketchy wiring 82 yellow 244 - Slow as **** but nice and clean, gfs car

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05-07-2012, 10:44 AM	#4
towerymt the real Towery Join Date: Sep 2002 Location: VA, USA	-SCP vs BCP (all 531 = SCP, 405 could be either) -spark plug location in the 531 -k-jet holes -a need for head mounted dizzy? only 531 can accommodate -b21/23 block or b230? t-belt cover backing plates differ, as do valve covers, but you can still mix and match heads to blocks.