Frankenmotor choices

[Tony_de_whitt]

Hello

 

can someone please point me in the direction of which ej25 engine block will work best for a frankenmotor??

 

ive read Ej25d which I’m pretty sure is from a dohc engine??

 

i read 1999 because of piston size and rod length. Do these have a different crank??

 

is there a specific year or model that would create the higher compression required with the frankenmotor.

 

any engine block years to avoid??

 

would a new ej25 2005 or older up be any better and why??

 

yup I’m a bit confused as to which is the best choice.

 

im running an old ej22  wiring system  from a 1992 legacy.

OBD1

 

twin port  ej22  heads 

 

thanks for your time

 

anthony

[GeneralDisorder]

The best NA combo we have found for 90's cars is a 257 bottom end, shaved 25D heads, 257 head gaskets, and eccentric timing idlers to correct the belt length. Slot the 25D intake to bolt it up if needed. About 10.6:1 compression. Probably very close to 200 HP and tons of torque. We have one in a lifted Forester with big tires and still gets 27 mpg. 

GD

[jonathan909]

Cool.  A couple of questions, svp?  How does one distinguish the various 25x blocks?  Casting, stamping, etc?  And when you "shave" a head, how much is typically removed?

[Tony_de_whitt]

Thanks for that info

 

what about using ej22 heads?

 

not sure how my current wiring and manifold etc would work with different heads

 

thanks

 

 

 

[GeneralDisorder]

EJ22 heads are worthless scrap metal. They can't flow any decent amount of power. Valves and ports are too small. Even with a turbocharger you can't hardly boost them past 250 HP. That's why Subaru didn't use that head design on a 2.5 block. They are pretty much a waste of time. 

You can build manifold adaptors and use a 20G ECU with an enduring solutions daughter board. 

GD

Edited January 30, 2019 by GeneralDisorder

[GeneralDisorder]

11 hours ago, jonathan909 said:

Cool.  A couple of questions, svp?  How does one distinguish the various 25x blocks?  Casting, stamping, etc?  And when you "shave" a head, how much is typically removed?

I think we took off like .040" on each head. 

Castings.... well if you are looking at bare short blocks then you can see the piston dome shape and you can see the semi-closed bridges on the 255/257. That would be all I need. They have a VIN on them also unless they are RDOT blocks not installed at the factory. 

GD

Edited January 30, 2019 by GeneralDisorder

[jonathan909]

1 hour ago, GeneralDisorder said:

I think we took off like .040" on each head. 

Castings.... well if you are looking at bare short blocks then you can see the piston dome shape and you can see the semi-closed bridges on the 255/257. That would be all I need. They have a VIN on them also unless they are RDOT blocks not installed at the factory. 

GD

I'm not keeping up.  I don't know what you mean by RDOT or "bridges", and "piston dome shape" suggests differences that aren't actually part of the block.  Please clarify?

[Tony_de_whitt]

General Disorder

 

i appreciate your knowledge and thanks for your reply.

 

i think the sort of power your talking about is way above why I’m after

 

its a frankenmotor I want and it’s the ej22 heads I’m going to use

 

whatvim after is someone’s knowledge on what bottom end is best used to create a powerful frankenmotor maybe 160-180 hp.

 

my old Vw engine was 90hp so effectively doubling it.

 

with anything above 200hp I guess

id rip my gearbox to shreds

 

thanks

 

[el_freddo]

From what I’ve read (not made a frankenmotor - yet) if you want to use the ej22 heads the 99 EJ25D is the bottom end to use. 

The reason for this has something to do with the block basically being the stronger EJ251 block but with the EJ25D pistons. The crank and rods are basically the same from what I can gather.

Bolt all that together and your EJ22 management should handle the job well. Just run the best octane rated fuel you can get your hands on  

Have fun!

@GeneralDisorder - what years is the EJ257 found in?

Cheers 

Bennie

[carfreak85]

6 hours ago, el_freddo said:

 

what years is the EJ257 found in?

USDM:  2004-current STI, 06-14 WRX, 04-13 forester, 05-14 Legacy turbo (not so sure on the legacy).  These all used one form or another of the USDM 2.5L EJ-T engine, but not all were EJ257 specifically (i.e. EJ255).

[FerGloyale]

10 hours ago, el_freddo said:

From what I’ve read (not made a frankenmotor - yet) if you want to use the ej22 heads the 99 EJ25D is the bottom end to use. 

The reason for this has something to do with the block basically being the stronger EJ251 block but with the EJ25D pistons. The crank and rods are basically the same from what I can gather.

 

The cranks and rods are not the same.  They are the largest major differences between.  Though the blocks are different too.  

 

 Early DOHC 2.5 blocks have Small 48mm rod journals, and a #3 thrust bearing location.  The water jackets extend all the way down the walls of the entire cylinders.  This leaves the cylinders left very tall and open all around, leading to resonance at the top and contributing to the head gasket failure rates.  The small rod journals are known to fail often too.  I'm not a fan of these blocks, although they do make GREAT power and rev QUICK (small journals, less crank mass) 

 

SOHC 2.5 blocks use larger 52mm rod journals (like all the rest of the EJs) and move the thrust to #5.  The water jackets at the top side of the block around the base of the cylinders is decreased.  This allows faster coolant flow, less stagnant pockets under the crossover.  It also gives more meat at the base of the cylinder to prevent  resonance.   These blocks had pistons that come right to zero at the block deck, later ones with AVLS, the pistons actually come way out of the block.

The 99's were a combo.  They are basically the old DOHC 2.5 pistons stuck into the new 2.5 block.  52mm journals, #5 thrust, sturdy cylinders.   

 

There were some changes in Oil pump rotor thickness too, though I am not clear on which are in what.....but they are all interchangeable, so find a 10mm pump if you don't have one.

[czny]

'99 EJ25D Lego OB block

EJ22 cyl head with Cometic gasket

'94 EJ22 cyl head, Delta 200 grind cams('97 mechanical rockers + cams), '99 EJ25D 

Cometic PN tag

[Tony_de_whitt]

Fergloyal 

Perfect

ive got those heads and gaskets 

 

so now I need to find a 99 block

just wondering what cars they were in in Australia

 

is there a certain engine code I can look for ??

do the heads need altering to increase compression??

 

thanks

[Tony_de_whitt]

Also read about some idling issues when changing cams. Is changing the cams vital??

thanks

[Crazyeights]

I tried a Delta Torque grind in my EA81 Hi-Po build and it was so noisy I couldn't stand it. The valve noise would not adjust out. Soon after two lobes failed and I had to pull the engine again. To their credit they did replace the cam and lifters and blamed the failure on the type of oil I was using. Has anyone ever heard any delta torque grind cam that wasn't excessively noisy? The extra torque was fun for a few hundred miles

Edited January 30, 2019 by Crazyeights

[GeneralDisorder]

Just use a complete 25D. Swap the pistons for 251's and use the 642 head gaskets. There's your 170 HP. No problem. 

You'll have a very hard time hitting anywhere near 160 with EJ22 heads. They just won't flow that much NA. 

The 25D manifold is compatible with the harness you are running. Just swap over the electronics. 

22 heads are a waste of time. That's why Subaru didn't use them on the 2.5. Duh. 

GD

Edited January 31, 2019 by GeneralDisorder

[czny]

1 hour ago, GeneralDisorder said:

Just use a complete 25D. Swap the pistons for 251's and use the 642 head gaskets. There's your 170 HP. No problem. 

You'll have a very hard time hitting anywhere near 160 with EJ22 heads. They just won't flow that much NA. 

The 25D manifold is compatible with the harness you are running. Just swap over the electronics. 

22 heads are a waste of time. That's why Subaru didn't use them on the 2.5. Duh. 

GD

Without changing pistons in a '99 EJ25D block, as in the above pic, would you say 2002-2003 EJ25D SOHC head would be a good choice & which cyl head gasket would you recommend?

EJ22 heads were chosen in yrs before these newer choices were readily available in self-serve yards in So Cal. Still want to run with Delta 200 grind cams if possible.

From Matt's Compression Ratio Calc, the combo would be about 10.04.

[Tony_de_whitt]

2 hours ago, GeneralDisorder said:

Just use a complete 25D. Swap the pistons for 251's and use the 642 head gaskets. There's your 170 HP. No problem. 

You'll have a very hard time hitting anywhere near 160 with EJ22 heads. They just won't flow that much NA. 

The 25D manifold is compatible with the harness you are running. Just swap over the electronics. 

22 heads are a waste of time. That's why Subaru didn't use them on the 2.5. Duh. 

GD

Ok

Pretty  new to all this so apologies if I need spoon feeding.

So I need the hybrid 99 model Ej25d or can it be any Ej25d??

swap out the pistons for 251,s 

what are 251 pistons out of??

 

642 head gaskets I’m unsure  what you mean?

 

and which heads are you saying to use?? Are you saying just use the same heads and keep it as a complete Ej25d engine heads and manifold??

 

then swap all my electrics from my current Ej22 set up and put them onto the complete Ej25D engine.

and my current wiring set up will run this engine fine??

 

also what sort or Hp would you get just using ej22 heads and a later Ej25 frankenmotor in comparison to the above set up??

 

appreciate your help on this

 

thanks

 

 

[GeneralDisorder]

Yes just use the complete 25D engine. 251 pistons are from 99 to 05 SOHC 2.5 engines. 642 is the last three of the OEM head gasket part number. Those are for a 2004 STI. That piston and gasket combo will be about 10.5 compression and the gaskets won't fail because they are less than half as thick as the D gasket. 

[Tony_de_whitt]

3 hours ago, GeneralDisorder said:

Yes just use the complete 25D engine. 251 pistons are from 99 to 05 SOHC 2.5 engines. 642 is the last three of the OEM head gasket part number. Those are for a 2004 STI. That piston and gasket combo will be about 10.5 compression and the gaskets won't fail because they are less than half as thick as the D gasket. 

Any 25D engine or the 99 hybrid that people are talking about with new case old  internals??

 

thx

[GeneralDisorder]

Doesn't really matter. You can also use the short block from a 251 without swapping pistons. 

GD

[el_freddo]

13 hours ago, GeneralDisorder said:

Doesn't really matter. You can also use the short block from a 251 without swapping pistons. 

GD

That’d be the easiest way to go. You’ll find these in the Gen3 Liberty RX and the Outback models.  There’s also the EJ253 engine in the mix there somewhere too. I don’t know if this complicated things or not.

Cheers 

Bennie

[Tony_de_whitt]

On 1/31/2019 at 3:49 AM, FerGloyale said:

The cranks and rods are not the same.  They are the largest major differences between.  Though the blocks are different too.  

 

 Early DOHC 2.5 blocks have Small 48mm rod journals, and a #3 thrust bearing location.  The water jackets extend all the way down the walls of the entire cylinders.  This leaves the cylinders left very tall and open all around, leading to resonance at the top and contributing to the head gasket failure rates.  The small rod journals are known to fail often too.  I'm not a fan of these blocks, although they do make GREAT power and rev QUICK (small journals, less crank mass) 

 

SOHC 2.5 blocks use larger 52mm rod journals (like all the rest of the EJs) and move the thrust to #5.  The water jackets at the top side of the block around the base of the cylinders is decreased.  This allows faster coolant flow, less stagnant pockets under the crossover.  It also gives more meat at the base of the cylinder to prevent  resonance.   These blocks had pistons that come right to zero at the block deck, later ones with AVLS, the pistons actually come way out of the block.

The 99's were a combo.  They are basically the old DOHC 2.5 pistons stuck into the new 2.5 block.  52mm journals, #5 thrust, sturdy cylinders.   

 

There were some changes in Oil pump rotor thickness too, though I am not clear on which are in what.....but they are all interchangeable, so find a 10mm pump if you don't have one.

Great info thx

 

so just to clarify 

 

what con rods are used in this combination for the frankenmotor??

Do you have a part number or year of engine or length etc??

 

and if I’m buying new pistons do I ask for pistons from a 97/98 dohc outback.

 

or do you have a piston part number.

 

thanks again

 

anthony

 

 

 

[Tony_de_whitt]

So can anyone help with this final issue??

 

ive sourced a late block. 52mm journals etc etc

 

we are using the cometic head gaskets .051 thickness

 

when searching for the early pistons there seems to be a few different sizes to choose from. 

 

Can someone possibly confirm what size piston will work best and give the most compression but not cause me issues??

I’ve been looking at 1998 outback pistons with a choice of 2.

and how far these pistons should sit in relation to the top of chamber??

 

 

Thanks again

[idosubaru]

98 are the old DOHC EJ25D pistons. If you’re hand picking the piston I don’t think you want those, you want 99+ EJ251 SOHC pistons.  

The 98s stick out way above the block surface  

Look up 2000 EJ25 pistons, those are the “251 pistons” or “99+ SOHC pistons”  those all refer to the same piston and are mentioned by GD in previous comments. 

look those 2000 year parts up when sourcing parts. 

99 is a goofy year to source parts because there’s a wild mix of old and new EJ engine parts across various platforms.

Edited February 4, 2019 by idosubaru