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Discussion Starter · #1 ·
Ok so I've been searching and searching and I've found that people have thought of swapping dohc heads onto b20a3's. Has anyone successfully swapped a b21 head onto a b20a4? I believe they are similar. The b20a4 is carb sohc. I have the chance to get a full swap for cheap. It has a manual tranny so I'd be swapping to manual as well. I have a bunch of b21 parts laying around. It would be going into either a 90 or 91 si. If anyone has completed this swap what kind of power are you putting out? Is there a build thread that I'm just not seeing? I searched for over an hour.
 

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Discussion Starter · #3 ·
its a whole swap at a jdm importer its been there for a while so the guy is damn near giving it away
 

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bump.....where can i find a oil pan 4 a b20a5 swap.....nd rear control arm......90 si lude..........
i have 3 in my garage... how much you wanna pay?

Ok so I've been searching and searching and I've found that people have thought of swapping dohc heads onto b20a3's. Has anyone successfully swapped a b21 head onto a b20a4? I believe they are similar. The b20a4 is carb sohc. I have the chance to get a full swap for cheap. It has a manual tranny so I'd be swapping to manual as well. I have a bunch of b21 parts laying around. It would be going into either a 90 or 91 si. If anyone has completed this swap what kind of power are you putting out? Is there a build thread that I'm just not seeing? I searched for over an hour.
umm i believe this isnt possible, mainly cause the head bolts dont line up...

i think... i thought the B20a anything was always a duel cam...
 

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I know the B20a3 and B20a5 are essentially the same block. Differences are the pistons, rods, water pump, rod bearing --> crank (maybe), timing belt gear (on crank).

The actual bareboned blocks are the same. You can put a B20a5 cylinder head on a B20a3 block if you swap the crank-side tbelt gear and water pump. The heads are interchangeable in regards to bore and bolt patterns.

I have a hunch that B20a3 pistons with a B20a5 head make for higher compression. The B20a3 head has more space in it and still 9.1:1. Hence the non-interference. I know the pistons in my B20a3 rose almost flush with the top of the block. My B20a5 had some space there.
 

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Discussion Starter · #7 ·
thanks i appreciate the info I might grab the block and tranny still but i'm leaning more towards rebuilding a b21 i have from the bottom up. b20 motors come in sohc and dohc and carb as well as fuel injected. i believe all the sohc versions are carb which is why i'd want to swap the head. thanks again
 
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