A18 Replacement For A20a3

[1987AccordLx-i]

alright..i need emergency help.. i want to know if i can use an A18 block and use my A20A3 head so that i could use my fuel injection system still.. will it work?? please respond quick.. i kinda need this info before i complete the sale

[A18A]

A18A block yes, not sure about a A18A1 though.

[1987AccordLx-i]

A18A block yes, not sure about a A18A1 though.

damn.. i have the A18A1 sitting at the shop and there waiting for me to respond to them as to wether the head will work on it..

[cygnus x-1]

Assuming it's an A20A1 and not an ET2 then yes, it's compatible.
I started with an A18A1 ('87 Prelude) and put an A20A1 head on it. The A18 block was bored out to 2.0L specs and now it's essentially an A20 block.
A20A1 and A20A3 heads are essentially the same.

The only thing with the A18 is that you will lose a little compression unless it's bored to 2.0L specs. I would have to work out the numbers to know how much.

EDIT: You'll lose approximately 0.3 compression points. So if you started at 9.3:1 you would get about 9.0:1 with an A18 bore (81mm).

C|

[1987AccordLx-i]

Assuming it's an A20A1 and not an ET2 then yes, it's compatible.
I started with an A18A1 ('87 Prelude) and put an A20A1 head on it. The A18 block was bored out to 2.0L specs and now it's essentially an A20 block.
A20A1 and A20A3 heads are essentially the same.

The only thing with the A18 is that you will lose a little compression unless it's bored to 2.0L specs. I would have to work out the numbers to know how much.

EDIT: You'll lose approximately 0.3 compression points. So if you started at 9.3:1 you would get about 9.0:1 with an A18 bore (81mm).

C|

ok so i get the compression part.. but i have the A20A3 head.. so if its compatible then im gunna go ahead and seal the deal with the shop and get this A18A1 and slap the a3's head on it

[1987AccordLx-i]

so far the swap is a success.. A20A3 head on an A18A1

[A18A]

oh so you're 4x4explorer on youtube?

[1987AccordLx-i]

oh so you're 4x4explorer on youtube?

thats me

[Ichiban]

Assuming it's an A20A1 and not an ET2 then yes, it's compatible.
I started with an A18A1 ('87 Prelude) and put an A20A1 head on it. The A18 block was bored out to 2.0L specs and now it's essentially an A20 block.
A20A1 and A20A3 heads are essentially the same.

The only thing with the A18 is that you will lose a little compression unless it's bored to 2.0L specs. I would have to work out the numbers to know how much.

EDIT: You'll lose approximately 0.3 compression points. So if you started at 9.3:1 you would get about 9.0:1 with an A18 bore (81mm).

C|


What prevents the ET2 block/head from interchanging with the A20, other than port layout on the ET2 head, of course?

[2ndGenGuy]

There are baiscally two types of the "A" motors. What I've been calling the early A motors and the late A motors. The early A motors are like the ES, EZ. They have a small oil channel on the back of the block and the head. The later A motors, like the A18, and A20 have a bigger oil channel.

Early A Motors:
http://i66.photobucket.com/albums/h256/jgturk/9289PT.jpg

Late A Motors:
http://i66.photobucket.com/albums/h256/jgturk/9440PT.jpg

Where the ET2 fits in, I'm not sure. The auto parts sites list the same headgasket for A18 and ET2. I've also heard that there have been some ET2s that use one gasket, and some that use the other.

[cygnus x-1]

What prevents the ET2 block/head from interchanging with the A20, other than port layout on the ET2 head, of course?

EDIT: What he said.^^^^^^

There is an oil passage on the back of the block that the ET2 doesn't have. Look in the upper right corner of this picture:
http://bluegreenlabs.com/Prelude/Engine-build/Engine-cylinders-close.jpg

That part is supposedly different on the ET2. I've never actually seen one but I think Rich may have some pictures. And yeah, it seems to be somewhat of a question mark where the ET2 fits in. The local yard has a 2g right now with an ET2 and I was trying to figure out which one it was. But it's so buried that I couldn't see it or even get a hand in there.

C|

[Ichiban]

Good info. Pictures too, makes it easy for stupid people like me to grasp.

I actually have a complete ET2 sitting at my parents house. I wonder if this whole issue was the cause of Mustardcats "ET2 head on ES2 block smoking problem"?

http://www.3geez.com/forum/showthread.php?goto=newpost&t=54064

[1987AccordLx-i]

did the swap already gentlemen... sorry i havent posted.. ive been busy.. well it seems to be accepting the a20a3 head.. its not as responsive as my original a20a3 block but its still got plenty of top end.. kinda boggs off the line at full throttle but its a good setup if you have the a18a1 sitting around.. i plan on rebuilding my a20a3 block and slapping it back in so i can have more power and response.. and i just dont like this a18a1.. it was messed up to begin with

[AccordB20A]

Sounds like what my a18a engine running on the b20a fuel injection did. I think its cause its running a 2 liter fuel map on a 1800 motor lol

[1987AccordLx-i]

Sounds like what my a18a engine running on the b20a fuel injection did. I think its cause its running a 2 liter fuel map on a 1800 motor lol

good theory.. it might be that or just that the compression is off if your running the a18a1 block with the b20a/a20a3 heads... someone said that it makes a difference because we loose about .3 compression.. ill look into it


EDIT: heres what Cygnus x-1 said

Assuming it's an A20A1 and not an ET2 then yes, it's compatible.
I started with an A18A1 ('87 Prelude) and put an A20A1 head on it. The A18 block was bored out to 2.0L specs and now it's essentially an A20 block.
A20A1 and A20A3 heads are essentially the same.

The only thing with the A18 is that you will lose a little compression unless it's bored to 2.0L specs. I would have to work out the numbers to know how much.

EDIT: You'll lose approximately 0.3 compression points. So if you started at 9.3:1 you would get about 9.0:1 with an A18 bore (81mm).

C|

[2ndGenGuy]

Good info. Pictures too, makes it easy for stupid people like me to grasp.

I actually have a complete ET2 sitting at my parents house. I wonder if this whole issue was the cause of Mustardcats "ET2 head on ES2 block smoking problem"?

http://www.3geez.com/forum/showthread.php?goto=newpost&t=54064

Oh man, I bet you're right!!!

[1987AccordLx-i]

Oh man, I bet you're right!!!

so your the one talking about the ET2 head on ES2 block?.. sad to say i dont have much experience with those engines (dont really like carbs) but my setup it was more trial and error type thing.. thank god it worked tho or id be out of a car right now

[cygnus x-1]

good theory.. it might be that or just that the compression is off if your running the a18a1 block with the b20a/a20a3 heads... someone said that it makes a difference because we loose about .3 compression.. ill look into it


Mmm... Probably you won't notice the change in compression. More likely it's just the change in displacement. The 1.8L and 2.0L will have different fueling requirements. And of course the 1.8L will have a little less torque for the same reason.

C|

[1987AccordLx-i]

Mmm... Probably you won't notice the change in compression. More likely it's just the change in displacement. The 1.8L and 2.0L will have different fueling requirements. And of course the 1.8L will have a little less torque for the same reason.

C|

well i heard that the 2.0's fuel mapping is different then the 1.8L.. not sure if that makes a difference but i know that the 1.8 is definately less powerfull then my original 2.0

[cygnus x-1]

The difference in displacement is 10%. So the required fuel should be 10% less.

C|

[1987AccordLx-i]

The difference in displacement is 10%. So the required fuel should be 10% less.

C|

so pretty much whats happening is the 1.8 is getting more fuel then what is required?

[cygnus x-1]

so pretty much whats happening is the 1.8 is getting more fuel then what is required?

Probably, although it should be able to compensate for it somewhat because of the O2 sensor. I don't know, it's kinda hard to say. Engine responsiveness is subjective. It will have less torque though anyway.

C|

[1987AccordLx-i]

Probably, although it should be able to compensate for it somewhat because of the O2 sensor. I don't know, it's kinda hard to say. Engine responsiveness is subjective. It will have less torque though anyway.

C|

yeah torque was compensated.. has poor exceleration pre 3k revs.. after that it gets a little kick..

but i might have a problem with my o2.. been having it for a while.. it might be sending the wrong info to the ecu.. twice its thrown the o2 code but i never fixed it.. just cleared the codes.. but now it doesnt show the code.. :rant: idk whats going on

[cygnus x-1]

yeah torque was compensated.. has poor exceleration pre 3k revs.. after that it gets a little kick..

but i might have a problem with my o2.. been having it for a while.. it might be sending the wrong info to the ecu.. twice its thrown the o2 code but i never fixed it.. just cleared the codes.. but now it doesnt show the code.. :rant: idk whats going on


Was that with the A18 block or the A20 block? I wondered if the computer might complain about the A18 since it should theoretically run too rich compared to the A20. That may have tripped the O2 sensor code. Are the older ECUs self learning?(I don't know) If they are that might explain why it stopped showing the code. Or you just have a dodgy sensor.

C|

[1987AccordLx-i]

Was that with the A18 block or the A20 block? I wondered if the computer might complain about the A18 since it should theoretically run too rich compared to the A20. That may have tripped the O2 sensor code. Are the older ECUs self learning?(I don't know) If they are that might explain why it stopped showing the code. Or you just have a dodgy sensor.

C|

it was throwing it with the a18a1.. which is the one i have now.. it threw it once or twice then just stopped.. but the signs of a bad o2 are there.. wierd idle at running temp.. bad response.. i changed my ECT sensor so thats out of the question.. but im going to check it again in a while.. ill check all the sensors on the manifolds.. but theres this green sensor on the intake manifold (right side) on the last runner.. whats that one for?

[cygnus x-1]

it was throwing it with the a18a1.. which is the one i have now.. it threw it once or twice then just stopped.. but the signs of a bad o2 are there.. wierd idle at running temp.. bad response.. i changed my ECT sensor so thats out of the question.. but im going to check it again in a while.. ill check all the sensors on the manifolds.. but theres this green sensor on the intake manifold (right side) on the last runner.. whats that one for?


That green sensor I believe is for intake air temperature.

C|

[1987AccordLx-i]

That green sensor I believe is for intake air temperature.

C|

ok good to know.. i really want my initial torque back!! it sucks when i run my car and it boggs on take off! haha

any ideas to stop the bogging?

[MessyHonda]

ok good to know.. i really want my initial torque back!! it sucks when i run my car and it boggs on take off! haha

any ideas to stop the bogging?


buy an adjustable cam gear

[1987AccordLx-i]

buy an adjustable cam gear

sounds expensive..


think the timing could be off?

after i run the hell out of it, at idle it starts missing for like 10 min then it gets better