Which engine? Subaru 2.5 STI/Subaru 3.0/Honda j35/ Honda k24, Building a weekend/track car, help me pick the engine Options

[rupert14]

I am trying to decide which engine to swap into my 914. In the past I put a honda J35 in a baja bug and it would roast 33" tires all day long. It was a great engine for a baja bug. I have a local shop that is pushing me toward a subaru 2.5L STI turbo motor. I have also read about very happy owners of 3.0 flat six suby engines in the 914. A buddy of mine that runs NASA has a k24 in his car that puts almost 250hp to the ground with just cams. The good part about the k24 is that it is light.

I plan to just use it as a fun weekend car and once a month or so on track here in AZ for HPDE4. I am currently running a 2001 BMW 330ci at the track but I also have a speck e30 and a few street e30's. I want to be around 300hp (stock J35 is 300hp/300tq) and I am ok swapping the trans if necessary. My trans was recently gone through at a Mr. Evil gathering and is a strong side shift.

I realize many of you have more experience than me with these engines so what is your vote? I will be adding a wide body and the fattest tires I can stuff in there.

1. Subaru 2.5 turbo STI motor
2. Subaru EZ30R 3.0 six
3. Honda j35 V6
4. Honda k24 inline 4

[bahnzai]

You should talk Mike, @fasthonda
He put a f20c in his 914

[Chris914n6]

Things to consider...

The stock 914 trans is maxed out at 300hp/300tq and you can't be hard/reckless with it.
The Subaru trans is stronger and more modern, so that is a benefit with the Subaru motors.

That FastHonda K24 car is for sale in the classifieds. There is also a build thread here.

The Honda J35 is compact but still kinda big, same as my vq35de. Had to trim sheetmetal to fit.

So back to the Subaru 2.5L. Fits pretty well. Usually better to start with a WRX and build up as the STI is pricey. It's also a popular conversion with many build threads and suppliers to use.

[rupert14]

So it sounds like the best bet for occasional track days is also a subaru trans?

I also have a lead on a boxster 2.5 engine and trans. Is it worth trying to keep it all porsche?

[tazz9924]

If you go subaru make sure you get your oil right; new pickup, better pan and such. They tend to starve easily.

[BENBRO02]

The K24 is a fantastic engine. I just sold my 2005 Acura TSX 6 spd in August with 372,000 miles on it. Some of those were on the track and it never broke. I was at track day bouncing off the rev limiter all day and then would drive it home afterwards. New Mobil 1 every 5,000 miles.

[emerygt350]

for the money spent I wonder how close a pmb/raby crate motor might get (or even your own build)? Even if you got only 150 hp out of the crate motor, if it means 300 lbs of weight savings it might be a wash. If prices are close, it might be worth looking at the hp per lb for each. low and light with good power might be a better track car than a possibly higher center, more weight with high HP.

[mlindner]

I'd go either Boxster or a air cooled 3 or 3.2. Can't get much more fun than that. Your investment and appreciation will make it worth it. I only have a 2.2, mod solex cams and PMO's and it just rips.

[76-914]

If you go subaru make sure you get your oil right; new pickup, better pan and such. They tend to starve easily.

(IMG:style_emoticons/default/agree.gif) That goes double for the Ford Eco Boost. (IMG:style_emoticons/default/beerchug.gif)

[fasthonda]

I vote K24. Perfect motor for sale on BringaTrailer.

https://bringatrailer.com/listing/honda-k24z7-engine/

I recommend you build it as a street car. Would be a much better investment. You can still track it, but also enjoy it anytime. With the K24 you are probably maxed out at 220 hp, but that's plenty for a 914.

[ClayPerrine]

A Boxster engine won't fit in a 914 chassis. The valve covers hit the inboard ears for the suspension pivots.

Lots of the Boxster guys are putting Subaru motors in. They are cheaper than a replacement Boxster motor, they make more horsepower, and they are easier to service.

And because it is a flat six, they work with the factory Porsche ECU. You just have to change the sensors and the throttle body in the Subi motor for the Porsche ones.

[Chris914n6]

A Boxster engine won't fit in a 914 chassis. The valve covers hit the inboard ears for the suspension pivots.

I thought the issue was narrowed down to just the coil on plug, which could be replaced with a chevy LS coil?

[technicalninja]

I vote K24 as well.
That motor is possibly the best 4 cylinder ever built by ANYONE!
They can go 500 NA and above 1K blown.
Nothing else comes close to IMO.

That motor that fasthonda listed should have 300+.

Something about it is not optimal.

Most K24 with K20 headed mixes go 300+

Maybe it had to meet certain criteria for its class of racing.

Overall, besides the wimpy dyno sheet that looks like the BEST K20 swapped K24 I've seen yet.
I wonder what that will go for?
I'd guess 5-6K...

I am trying to buy a used K24-A2 from a friend. I don't really have a home for it yet. It's a "maybe" for either a 914 or a NB Miata. Doner car is a 05 TSX and I believe it's the highest HP variant to start with. It has individual exhaust ports and requires a dedicated header.

Those "Z" variants (like the auction) have a single rectangular exhaust port which makes installing into other vehicles EASY. It also makes adding a turbo easy as well.


Now, it's not the "optimal" motor as it was not designed by "German rocket scientists".

If I had unlimited funds, I might buy a late model (or NEW!) 4 cyl 718 Boxster/Cayman and just "back half" it, swapping everything past the firewall over to 718 junk.

If the non-S is used the 2.0 badging would still be correct!

Can you imagine the conversations with others?

Yep, it's just a 4 cyl 2 liter...


I'm with Chris916n6 regarding the 986/987 Boxster/Cayman stuff.
I'm under the impression that it will fit with ignition modifications.
It's supposed to be super tight and require engine manipulation to do any work on it all.
Now, I haven't actually tried yet and I'm betting the fit is tight enough that some cars won't clear.

Clay was the first person to put the "Just back half it" into my thoughts...

[nimblemotorsports]

Most of the time the right answer is to use the engine you have, and that doesn't mean the flat 4 Porsche, I mean whatever donor is available. If you have to go out and buy something do what is most popular and thus has lots of tech support and parts available,
So probably the 2.5 subaru. I hear they have head gasket issues..
I have a EZ30 and have thought of putting it in my 914, but I never do what is popular and have a W8 that needs a home. Audi has a 2.7T V6 that bolts right up to a boxster transaxle..



(IMG:https://cimg2.ibsrv.net/cimg/www.rennlist.com/1600x900_85-1/654/2-684654.jpg)

[fasthonda]

The Turbo charged EJ Subaru powered car currently on BringaTrailer doesn't appear to be very fast from watching the video. I know it's hard to tell it a video, buts that's my impression. and that Subaru boxer engine noise sounds awful to me. No thanks.

https://bringatrailer.com/listing/1973-porsche-914-118-2/

[Chris914n6]

The Turbo charged EJ Subaru powered car currently on BringaTrailer doesn't appear to be very fast from watching the video. I know it's hard to tell it a video, buts that's my impression. and that Subaru boxer engine noise sounds awful to me. No thanks.

https://bringatrailer.com/listing/1973-porsche-914-118-2/

Poor choice in muffler. Ricer (IMG:style_emoticons/default/stromberg.gif)

And you're right, it is slow, specially for a turbo. Too much rear tire?

[fasthonda]

https://bringatrailer.com/listing/1973-porsche-914-118-2/
[/quote]
Poor choice in muffler. Ricer (IMG:style_emoticons/default/stromberg.gif)

And you're right, it is slow, specially for a turbo. Too much rear tire?
[/quote]


Sold for $44k not including fees. Slow, raspy loud and w/ 916 bumpers molded into the sheet metal. It does have a nice interior. Wow.