Honda / Acura K20a K24a Engine Forum banner

1 - 20 of 35 Posts

·
Registered
Joined
·
7 Posts
Discussion Starter #1
will an a2 head work on an a3 block? If not what can I do to the motor to gain more HP without doing a complete engine swap?
 

·
Registered
Joined
·
4,370 Posts
scratch that, in the K24 line, only the k24a2 and k24a1 will except the k20a2 head with out modification to internals, there are issues with valve clearance.

I had a brain fart there, ooops!
 

·
Registered
Joined
·
7 Posts
Discussion Starter #5
oh and where can a get a k20a2 head for a good price? and what other things would u recomend to do to a k20a3?
 

·
Premium Member
Joined
·
4,257 Posts
compression and ecu are 2 completely seperate issues... the cams in the a2 head are designed to work with the higher CR of the a2 block. Do a search. People have swapped the a2 head onto the a3 block. It works just fine and is definately a power bump, but many of those who have done it said that it wasn't all that they hoped for because they still have the low compression a3 block and are limited to 7k rpms.
 

·
Registered
Joined
·
7 Posts
Discussion Starter #9
Do u think i would be better off just doing a complete swap? If so is the k20a2 or the k24a2 better off in my 02 civic si? and how much do they cost? and where can i get them? Keep in mind that my civic si has airbag suspension on it. (if it really matters) where can i buy a new motor???????????
 

·
Registered
Joined
·
629 Posts
Do u think i would be better off just doing a complete swap?
It really depends on your goals. The K24A2 has more torque and is a very popular swap, and the co$t more too. K20A2 is a super motor too. If you are familiar with the B-series engines, its like comparing a B20vtec to a B18C5 engine. Both are great.
You can always spray 75 shots of NOS to your A3 motor and replace it when it blows.

And how much do they cost?
For the swap, be prepared to cough out $2800-6000

and where can i get them?
www.hmotorsonline.com
www.jhpusa.com
the Classified on this forum

Keep in mind that my civic si has airbag suspension on it. (if it really matters)
Both motors should weigh the same.

where can i buy a new motor???????????Honda
 

·
Registered
Joined
·
919 Posts
head swap... don;t do it... look at the pistons, you only have valve releifs on the a3 v-tec side (intake) not on the exhaust... then look at a2 pistons, reliefs on both sides... don;t play with fire
 

·
Premium Member
Joined
·
4,257 Posts
keep in mind that the a2 has bigger domes on the pistons which may be why the valve reliefs are there. of course no way to be 100% without claying the motor.

however since the blocks have the same stroke, same deck height, same rod length, and same compression height on the pistons. And a3 pistons don't have nearly as much dome, hard to imagine any valve/piston contact.
 

·
Registered
Joined
·
134 Posts
on ephatch.com there is a diy on how to put a a2 head on a a3 block, its not really that hard to do if u;ve worked on motors before
 

·
Registered
Joined
·
191 Posts
But by swapping an a2 head on an a3 and swapping out new aftermarket a2 pistons and rods what would keep the new motor from reving to 8k? since it does have the a2 ecu? is it a blance issue?
 

·
Registered
Joined
·
13 Posts
The guys that makes the Raz cams for the A3 said that the rods on the A3 will deteoriate quickly above 8k rpms.

Then there's another guy that put an A2 head on his A3 block and said for the money he spent, it's really not worth it, a couple hundred more and he could have had a complete A2 (seeing as how you have to have K-pro to make an A2/A3 run correctly, not to mention tuning it).
Both of the people mentioned above are on ephatch.com
 

·
Registered
Joined
·
14 Posts
I just saw that someone figured out how to make A2 cams(or really any K-series true-vtec cam) work in an A3 head. I' d say change the A3 head over to whatever cams you want and of course drop in a s2k valvetrain. Buy a CRV/TSX bottom end, put some high comp pistons and nice rods in it plus KPRO and for the price (maybe less since you already have the head) of an A2 swap you'll have a beast of a motor that you can beat the piss out of. The thing about just swaping an A2 is that after you've dumped the money on the swap, you are starting at square one with an engine again, you'll either want to turbo/supercharge/NA build-up on it since for the $3500 youre spending, you have a stock motor. Putting an A2 head on a A3 is pretty much a waste of time if you are really looking for serious power.
 

·
Registered
Joined
·
66 Posts
Schwebel said:
I just saw that someone figured out how to make A2 cams(or really any K-series true-vtec cam) work in an A3 head. I' d say change the A3 head over to whatever cams you want and of course drop in a s2k valvetrain. Buy a CRV/TSX bottom end, put some high comp pistons and nice rods in it plus KPRO and for the price (maybe less since you already have the head) of an A2 swap you'll have a beast of a motor that you can beat the piss out of. The thing about just swaping an A2 is that after you've dumped the money on the swap, you are starting at square one with an engine again, you'lal either want to turbo/supercharge/NA build-up on it since for the $3500 youre spending, you have a stock motor. Putting an A2 head on a A3 is pretty much a waste of time if you are really looking for serious power.
With the lower cpr of the a2/a3 wouldn't it be perfect for a turbo or sc?
 

·
Premium Member
Joined
·
4,257 Posts
mozze said:
With the lower cpr of the a2/a3 wouldn't it be perfect for a turbo or sc?
Correct, the CR is very boost friendly. However, the a3 rods are supposedly weaker than the a2 rods, so the bottom end could still be a limiting factor.
 

·
Registered
Joined
·
14 Posts
mozze said:
With the lower cpr of the a2/a3 wouldn't it be perfect for a turbo or sc?
Alot of peeps have turbo'd the A3 with great success, but realibilty is def an issue with daily driven boost levels greater than 7psi. A general rule of thumb is that a stock motor can accept about 7psi of boost and be reliable, not saying that you can't run more boost, but I like to keep my motors around awhile. With the mods I have suggested you can make the same amount of reliable power as a turbo'd A3 can and also for about the same price as a turbo kit, without the high maitenece. You also won't have the thought in the back of your head as you hit WOT of "Is my motor going to explode this run?". Also your motor would be lighter weight than a turbo'd A3. But yea you could just as well put low CR pistons in a frankenstein and turbo it. The problem I see with the A3 is that trying to build-up the bottom end is kinda pointless, I'm sure there are lots of threads on here to the differences in the A3 and A2 bottom ends so I won't go into that. I've built a crapload of frankenstein turbo'd VW engines (kinda new to hondas) and came to realize that reliability is 50% of the power equation.
 
1 - 20 of 35 Posts
Top