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Frankenmotor


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25 replies to this topic

#1 Twitch de la Brat

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Posted 21 September 2012 - 12:17 AM

Figured we could use a frankenmotor thread in the NA performance forum :brow:

Now, for general information to those who don't know what a frankenmotor is, its (typically) an EJ25D (96-99 Legacy/OB 2.5L) short block with EJ22E (90-97 Legacy 2.2L) heads and EJ22E intake and exhaust.
There are variations upon this basic setup (reversal of the block and heads for example) but this is generally what people refer to when they say "frankenmotor" in the EJ section.

Now, here comes the why. Why would somebody take the time to do this?
Well, most of the time its because somebody either needs to rebuild an EJ22E and they want more power or because they simply want more power without a turbo.
Because its a high compression motor and builds more power (typically) than a standard EJ22E and is less complicated than swapping in the rare (but impressive) EJ22T or the EJ25D (which is headgasket prone).
Some estimates put it at 170hp and 180ft lbs of torque, making it one of the most potent NA 4 cylinder engines you can put into a Subaru, not to mention there have been (unofficial) reports of improvement in fuel economy (as long as you can keep your foot out of the throttle ;) :burnout: ).

Let the discussion begin!

Twitch

#2 Twitch de la Brat

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Posted 21 September 2012 - 12:29 AM

Now that I have this thread up, I'm going to post my question.

I have a block with 140k on it (unknown history but still in good shape visually, no known specs on the tolerances yet) and recently rebuilt heads (15k or so) for my frankenmotor.
Now, it was recommended to me to replace the rings, rod bearings and main bearings before I do the swap, because he claims that there is a good likelihood that I'll be replacing them in a year or so anyway because of the upped compression.
It was running when pulled, although it may have been overheated once.
The cylinders do need to be honed, but I may be able to do that without cracking the case on the engine.
So, would you say to pull it apart and rebuild it? Even for a backyard mechanic like myself or should I just hone it and throw it together?

Twitch

#3 Gloyale

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Posted 21 September 2012 - 03:32 PM

If you are gonna Hone it, then might as well split it and do the bearings too.


Otherwise I'd leave it alone and just see what it does.

Get another 2.5 shortblock to rebuild at leisure.


The only reason I'd hone and re-ring it, without doing bearings would be if you KNEW that the shortblock smoked/burned oil. Otherwise it's just gonna bump up the compression and strain the bearings more.

Rod bearings in the 25D are small, weak, and known for issues.

In my opinion these motors, and all 25Ds should be kept under 5500 rpm.

#4 Fairtax4me

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Posted 21 September 2012 - 06:41 PM

How do you hone a block without a full disassembly?
Agree with Gloyale, do it right or don't do it at all. If it needs to be honed at 140k, how hard was it ragged on by its previous owner(s)? The home in the 2.2 in from my wagon was nearly perfect at 175k. The same for the 2.2 out of my 96 sedan.

If it really NEEDS to be honed, it NEEDS bearings as well.

#5 Twitch de la Brat

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Posted 21 September 2012 - 09:08 PM

The only reason why I was thinking a hone was because of some crud that has found its way into the cylinders (open block, no heads, not the best storage conditions) so a basic hone would be more than enough to clean the crud out and take any surface rust off.
But I guess Brillo pads will do the same with less work ;)
Anyway, it didn't need bearings when I received the block and sitting around probably didn't kill them, so I think I'll just clean up the block and put it together.
Any recommended cleaners for oil passages and coolant passages?

Twitch

#6 DOHCEJ22E

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Posted 21 September 2012 - 09:09 PM

I have done this.
My hybrid build is a 22E block with 25D heads bolted onto it.
I estimate the power at something like 150bhp although it might actually be closer to 145-140bhp.
The engine's cylinder still had an unbelievably nice hone at 100K & there is now 1500 extra miles on that block in hybrid form.
I chose the 22E block despite it's lower compression because it's really much tougher than the 25D has been proven to be.
Power isn't completely unlivable & it's actually VERY fuel efficient (my scan tool picks up 33mpg overall & 25mpg when I'm traveling around 75mph without cruise control).
The 25D would probably be as tough if it were generally maintained right but even so, it does not have forged rods (big minus) & it's cylinder walls are thinner.
I had a 25D block.
I don't miss it a single bit.

#7 Twitch de la Brat

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Posted 21 September 2012 - 09:16 PM

I have done this.
My hybrid build is a 22E block with 25D heads bolted onto it.
I estimate the power at something like 150bhp although it might actually be closer to 145-140bhp.
The engine's cylinder still had an unbelievably nice hone at 100K & there is now 1500 extra miles on that block in hybrid form.
I chose the 22E block despite it's lower compression because it's really much tougher than the 25D has been proven to be.
Power isn't completely unlivable & it's actually VERY fuel efficient (my scan tool picks up 33mpg overall & 25mpg when I'm traveling around 75mph without cruise control).
The 25D would probably be as tough if it were generally maintained right but even so, it does not have forged rods (big minus) & it's cylinder walls are thinner.
I had a 25D block.
I don't miss it a single bit.


I read your build thread and was most impressed by it. Very valuable info and I may link to it for another variety of a frankenmotor.
The reason I'm not going the route you did is because I have an EJ22E in my car from the factory, not an EJ25D. Swapping out the heads and the intake and the exhaust would be more hassle than to just swap the block, plus the lower hp number.
And in my case with fresh heads and a shot block, I'm not going to keep the crap and toss the good, if you know what I mean ;)

Thank you for replying and you may see your info pop up in this thread.

Twitch

#8 DOHCEJ22E

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Posted 22 September 2012 - 08:52 AM

And in my case with fresh heads and a shot block, I'm not going to keep the crap and toss the good, if you know what I mean ;)

Thank you for replying and you may see your info pop up in this thread.

Twitch


I know full well what you mean :D But if you're going to go with the 22E heads on the 25D block, make sure that the head & intake manifold ports are opened a little & matched so you can get maximum airflow. An intake spacer will definitely help (Grimmspeed makes them for the EJ22). Low end TQ FTW!!!

#9 cal_look_zero

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Posted 22 September 2012 - 02:07 PM

I have a Frankenmotor. EJ25D block, single port 22E heads, Delta cams, Grimmspeed phenolic spacers, 300cc DW injectors, port matched heads, Cometic "hybrid" head gaskets shaved .010 under, 10mm oil pump with 2 shims, 2" header, and some other stuff. Another build similar to mine put down about 175 WHP, and he was a little lower compression than me.

Basically a brand new engine. Ended up with all new internals, new valves/springs/retainers, etc. About 7000 miles in now and I average 22mpg on the hilly freeway/in town, 26mpg on flat freeway, and have yet to have anything with less than 8 cylinders or a turbo beat me.

#1 rule: Don't screw with your intake.

#10 wounded brat

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Posted 22 September 2012 - 03:10 PM

does puttin 2.2 heads on a 2.5 block make it an interference motor.

#11 Gloyale

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Posted 22 September 2012 - 04:16 PM

#1 rule: Don't screw with your intake.


Do you mean the Filter and snorkus? Or are you talking about the intake manifold and valve ports?

Sounds like you matched your intake to the heads?

I ported my heads very lightly, basically just de-burred the inside of the cast passages, and I'm very happy?

Elaborate?

#12 ivans imports

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Posted 23 September 2012 - 10:22 AM

I do thiss because i have 60 ej subaru engines laying around all a little bitt diferent is a good way to see what you can get away with 2.2 with 2.5d heads or 2.5 with 2.2 heads or 2.5 with 2.2 crank and 2.51 heads or 1.8 with 2.2 heads or 2.2 with 2.51 heads or eas with wrx pistons or any motor you can think of have done about all of them my daily driver is a 09 sti short block with 99 twin cam heads wrx turbo western star intercooler in a 79 wagon with 5 speed high low it works good

#13 Fairtax4me

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Posted 24 September 2012 - 09:55 AM

does puttin 2.2 heads on a 2.5 block make it an interference motor.


Yes it does. The 2.5 piston crowns are different, and the ej25d stroke is so long the pistons actually stick out past the deck surface of the block at the top of the stroke. If you use the wrong head gasket with the 25D block the pistons will hit the cylinder head.

#14 DOHCEJ22E

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Posted 24 September 2012 - 10:09 AM

Yes, the piston tops are different & come up over the deck of the block.
Whether it's a DOHC EJ22E (EJ22D) or a SOHC EJ25D (EJ25E), they will both become interference engines because of their head/piston combinations (& I think strokes.)

#15 ivans imports

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Posted 24 September 2012 - 10:29 AM

i can plane the heads and block height adjust the comp by useing different thickness of headgasket if you use a 2.2 crank in 2.5 d engine will lower the piston in bore then can deck the block down makes a 2.35 engine big pistons short stroke low comp big berrings and reliablity have made 4 now all work very good

#16 cal_look_zero

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Posted 24 September 2012 - 02:20 PM

Do you mean the Filter and snorkus? Or are you talking about the intake manifold and valve ports?

Sounds like you matched your intake to the heads?

I ported my heads very lightly, basically just de-burred the inside of the cast passages, and I'm very happy?

Elaborate?


Yeah, the snorkus is a crucial part of the MAF system. MAP cars can get away with an aftermarket intake, but without a tune, MAF based cars run like crap without the snorkus.

My car came without one, and fell on it's face after I built my frankenmotor. Slapped a snorkus on and it pulls hard through every gear above 2k rpm.

#17 Mugs

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Posted 25 September 2012 - 08:10 PM

By snorkus do you mean aftermarket air intake system...ya know the "cold air" ones we see on all the car that are riced out?

I seem to remember having this problem with a freiken build I did. We just put the stock air intake system on, but then highly modified it.

#18 cal_look_zero

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Posted 25 September 2012 - 08:26 PM

http://t0.gstatic.co...pww4ouUh_G0LPkQ

Snorkus

#19 DOHCEJ22E

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Posted 26 September 2012 - 09:51 AM

That snorkus ^ is a resonator that supposedly keeps air vibration down or something along those lines. It is located inside the fender near the front of the wheel well. I don't touch those at all.

#20 Gloyale

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Posted 26 September 2012 - 10:13 AM

http://t0.gstatic.co...pww4ouUh_G0LPkQ

Snorkus


I was reffering to the piece between the MAF and Throttle body.

That in the pic there is a Water seperator.

Highly effective too. I watched a bone stock 97-ish Legacy cross though a 3 feet deep channel of water. It was a short, but deep crossing........the guy punched it into the water, submarined the front end, then popped back up and blasted through. I can only assume that water seperator held enough water for that short crossing. not recommended, but it worked.

#21 muddblood

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Posted 11 October 2012 - 08:00 AM

Sorry, new to this forum and newish to Subie's as an owner. I read some of the posts here syaing the 2.5 engines are junk, but I need more power out of my 2.2l legacy for all these mountain passes in CO. So I stumbled on this frankenmotor thread and I have questions relating to frankenmotors.

1) Which is better: 22 block and 25 heads, or 25 block and 22 heads. Better meaning yeilding the most power but more importantly, the most reliable (as far as head gasket failures).

2) I kind of like the idea of the 2.3l stroker (25 block, 22 crank, STI pistions, ect)...how reliable is that? For every day driving? I'd LOVE to get 175 hp into my little wagon but I also need it to be very reliable as it is my dailey driver.

3) I am also considering a turbo on my 2.2. How would that compare in power, cost and ease of modification to building a frankenmotor. I can get a motor (ANY motor in their yard) from pull and pay for $200 ($250 with tax and crap).

The 22 in my legacy has somewhere around 170k miles and runs like a champ, but it desperately needs more power, especially at altitudes over like 6,000', which is not that hard to do here in Colorado. Honestly, I'd like nothing more than to throw the 3.3 (around 250k miles) out of my SVX into it, but I am not sure what I am doing with the SVX just yet (tranny went out, replacement tranny has no 2nd gear).

The legacy is my dailey driver so any mods would have to be fairly easy and quick, say a weekend or so.

#22 Rally_Blue

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Posted 11 October 2012 - 08:54 AM

Lots of information on NASIOC regarding your questions. Some threads can get a little off track at times but there is a good amount of information there if you spend the time to filter though it

http://forums.nasioc...isplay.php?f=31

#23 cal_look_zero

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Posted 29 October 2012 - 04:53 PM

I'm looking into either a PerfectPower6 or MegaSquirt so I can actually tune my engine. I think it's modified too heavily for the stock ECU to be able to fuel it properly.

The car pulls hardest right at 4k rpm; like a turbo kicking in. Definitely something I want to mitigate and get a more fluid powerband.

#24 presslab

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Posted 29 October 2012 - 10:11 PM

I'm looking into either a PerfectPower6 or MegaSquirt so I can actually tune my engine. I think it's modified too heavily for the stock ECU to be able to fuel it properly.


You could hack the stock ECU.
http://www.ultimates...ad.php?t=134517

#25 cal_look_zero

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Posted 30 October 2012 - 04:52 PM

You could hack the stock ECU.
http://www.ultimates...ad.php?t=134517


I could, but running a PP6 will allow me to have Pre run it on the dyno and tune it perfectly as opposed to the "hotdog into the air" method of mapping by butt dyno/engine load/feel.

It's a ways down the line for me.




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