FA20 vs FA24
 

Backstory -- skip to next Dash line to get to point

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Shit happened, hydro-locked and seized engine courtesy of a SUV that plowed through very deep puddle that I was trying to drive around. I now am looking at getting a new short block put in the car and the old block to do whatever with. Initially, I was planning on rebuilding/upgrading the pulled sb as a learning experience and put back into or into another car. I've always wanted to play around with an engine like this but never had one that wasn't in a perfectly good functioning vehicle..that I used on a daily basis.



So after pulling the engine and seeing where the starting point is. Hopefully it's just the rods that are shot but was told to possibly expect crank and cylinder damage also. I only really only care about the crank since I want to bore it to 2.4L (maybe sleeve) and going forged rods anyway. Pricing things out I saw that getting a FA24 sb is outright cheaper than boring out and sleeving a FA20. ofc down the rabbit hole I go and currently stuck with a couple questions that I am finding exceedingly hard to answer with google searches. Probably because they are dumb but without any further ado.
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First question. (probably already guessed if the intro was read)


1. What's the difference between the FA20 and the FA24? I mean is the FA24 just a bored out FA20 or are there physical differences between the FA20F or FA20DIT that it is derived from?


2. Cylinder heads? Do I have to do anything with them if I go the bigger bore route? Are they like one size fits all or do they need to get work done to match?


There are more questions but they're the when you 'cross the bridge first' sort.

The FA24F is probably based on the FA20F, but just bored out. The FA20F is the FA20DIT. You could check product numbers to see if they share the same head.

https://dsportmag.com/the-tech/educa...s-of-the-fa20/

https://dsportmag.com/wp-content/upl...k-1024x768.jpg
https://dsportmag.com/wp-content/upl...3-BRZBlock.jpg

It may seem cheaper to buy a FA24F block instead of boring out the FA20D block, but it might make for less headaches. I would really reach out to a builder.

FA20F
https://i.ebayimg.com/images/g/Sc0AA...57/s-l1600.jpg

FA24F
https://i.ebayimg.com/images/g/tzUAA...mS/s-l1600.jpg

FA20D
https://i.ebayimg.com/images/g/KhYAA...aK/s-l1600.jpg

They don't look the same to me.

Think most people looked at this and decided if you’re going to do a swap might as well do a k24, LS, or JZ.
But
I’d love to see someone do a built FA24 would be a cool swap. Keep us updated if you go down this path.

I don’t think he is doing a swap. He wants to bore out/resleeve the FA20D block to 2.4L, but he realized the cost of sleeves and tooling is more expensive than sourcing a used, or buying a new, FA24F block. I think he wants to use the FA24F block with FA20D heads, intake manifold, etc, like doing a 1.5JZ, which is a 1JZ top on a 2JZ block—same idea—FA20D top on a FA24F block.

I don't think anyone has attempted to assemble a FA24 bottom end with FA20 heads yet. It was an idea until the rumor of a 2.4l twin in a little over a year killed that bother.

I would just buy a built fa20 block and go FI. FA24 is waste of time.

Why do you say that? Depending on his goals, if it works, it could be much cheaper. If he just uses an used FA24 shortblock fully dressed, he probably wouldn’t need to build the motor for modest goals, and he would be getting the additional torque and spool from the extra 400cc.

https://oppositelock.kinja.com/a-bit...rod-1844008143

I have not even seen an FA20F shortblock swap from WRX. I don't think FA24F will be easier. With a built FA20D shortblock, FI is trivial compared to those swaps. That is what I would do.

I think PulsarBeeerz is right that this idea lost traction with news of a FA24D possibly in the works for the next 86, but, if that doesn't happen, a stock short block could be a cheaper option. There is more displacement with larger rods.

I agree that if it isn't a straight drop in then a built FA20D is the way to go. Unless someone has big power goals or certain performance goals then it makes no sense to spend the money to sleeve and bore out a FA20D or try to massage a FA24F shortblock into a FA20D.

I suspect fitting a FA20F or FA24F shortblock will be much more work than a straight drop in.

I ever go higher power than 300 whp in the future, I will get a built FA20 shortblock with low compression and increase the boost. Below 300 whp, I would stay with stock compression.

I don't really know. The blocks don't look terribly different. The main difference seems to be the rear and some bolt down points. Specifically, the FAxxF series engines have the starter on the opposite side of the motor than the FA20D, which would likely make the swap not possible, yet there was some people who did a FA20DIT swap, but I don't know what transmission they used or how they made it work.

OP, keep us informed how you go. This has been in the back of my mind for a while as something to try.