Frankenmotor choices

[Tony_de_whitt]

Thanks

 

Yes s i did read about using the 251 pistons.

any ideas where they will sit in relation to the top of deck??

 

i thought using the .051 cometic head gaskets allowed for the 99 pistons to stick out of block and therefore give higher compression ratios. 

 

Which is is what makes the frankenmotor what it is.

 

thanks again

[idosubaru]

Oh yeah I don't know with the gasket thickness changes...wait for others.  there are online calculators for determining where you're compression sits based on what parts you're putting together.  i use those when i've done stuff like you're doing and don't memorize it all.  if you're trying to dial it in precisely you probably need to measure the thickness of your heads. 

Edited February 4, 2019 by idosubaru

[GeneralDisorder]

251 pistons sit at or below deck. You use the 642 factory gasket which is .021" IIRC. Don't need any calculations the comp is low 10's. They run fine. 

GD

[Tony_de_whitt]

On 2/5/2019 at 4:18 AM, GeneralDisorder said:

251 pistons sit at or below deck. You use the 642 factory gasket which is .021" IIRC. Don't need any calculations the comp is low 10's. They run fine. 

GD

Going well on all fronts apart from gaskets 

 

the ome 642 gaskets don’t have the same holes as the cometic and appears to block some of the passages 

 

any suggestions on altering etc??

 

cheers

[carfreak85]

3 hours ago, Tony_de_whitt said:

Going well on all fronts apart from gaskets 

 

the ome 642 gaskets don’t have the same holes as the cometic and appears to block some of the passages 

 

any suggestions on altering etc??

 

cheers

No need to alter the gasket, the engine will cool just fine, though I'm sure @GeneralDisorder will have more to say on the subject.

[GeneralDisorder]

1 hour ago, carfreak85 said:

No need to alter the gasket, the engine will cool just fine, though I'm sure @GeneralDisorder will have more to say on the subject.

Nope - you are absolutely correct. Many of the stock Subaru applications have partial port blockage right from the factory - and this may in fact be on purpose to slow down flow in certain areas, or promote additional flow through other passages to even out the cooling effect and prevent hot spots. In any case the porting makes no difference and any gasket can be used with any head so long as the bore diameters match. Do not attempt to modify the gasket in any way as you will most likely create a problem where one did not previously exist.

GD

[Tony_de_whitt]

Great

 

thanks very much for all your time and sharing you knowledge

 

much appreciated 

 

 

[Tony_de_whitt]

Ok

 

do we have advanced somewhat using the advice received in here.

 

The guy who I am working on this with was keen to do a few calculations before assembly.

this is the messsge he just sent me

 

Hi Anthony,
Compression ratio measured and calculated at 12,375 with standard thickness head gasket of 0.55 mm.
Check on line and see what feedback you get it seems too high to me.
Cheers Rob.

 

So is this measurement possible??

is it too high??

should we reduce with thicker gaskets??

 

thanks again

[GeneralDisorder]

That's too high. 

What pistons are you using? And what heads? There was many options discussed in this thread but you didn't specify what you actually are now using. 

GD

[Tony_de_whitt]

So in the end we didn’t have the choice to use  exactly what we wanted.

 

i will ask the engine man today.

 

im pretty sure he has used standard pistons and a late block

 

he had to take a fair bit off the heads is all I know 

and then did his calculations. Unsure if his method of calculating the ratio but he did mention using kerosene.

is there an easy method to measure the ratio??

 

i will try and get some

sizes of the parts he has used

 

 

[Tony_de_whitt]

What is the maximum compression ratio you could safely go with these engines??

 

thx

[Tony_de_whitt]

So I’m told

 

standard 2002 ej25

standard pistons

standard head gaskets

ej22 heads with 8 thou taken off.

 

thiughts on what compression ratio that should be

 

thanks

[Tony_de_whitt]

Ok 

 

engine guy re measured and realised he had made a mistake.

 

compression ratio has been recalculated at 10.2

 

using the components above.

all back on track and happy again.

 

one final question is...-

how can I tell if an engine block that was in the 99 outback hybrid model which has the new block old pistons.

is such an engine???

if it has been removed.

for example I have the chance to look through 26 short blocks. Is there a way I can tell which is the hybrid one. Piston makings??

 

block markings??

 

etc

etc

 

cheers ant

[GeneralDisorder]

The 99 block will say EJ25 on it, it will have a square shaped dish in the piston, and it will have an 8 bolt bell-housing. A 98 will have a 4 bolt bell-housing, and a 2000 will have flat top pistons. 99 is unique having D pistons and an 8 bolt. 

GD

[suprunner]

I've done the EJ25D block with EJ22 heads. Had a bunch of torque. I could drive around in 4th and 5th gear around town. BUT, trying to pass cars on the highway.... Really anything above 3500 rpm, and it felt as if it was choking. I now have a 251 block mated with 25D heads, STI headgaskets. I love this motor. I can be in 4th gear for a lot of town driving, and there's noticeable pull all the way to red line. I'm even running stock exhaust. This is the motor that should have been designed stock from the factory. Just my two cents. 

[el_freddo]

On 2/27/2019 at 1:47 AM, suprunner said:

 I now have a 251 block mated with 25D heads, STI headgaskets. I love this motor. I can be in 4th gear for a lot of town driving, and there's noticeable pull all the way to red line. I'm even running stock exhaust. This is the motor that should have been designed stock from the factory. Just my two cents. 

@suprunner - which engine management were you using to run the latest incarnation as mentioned above? 

Cheers 

Bennie

[GeneralDisorder]

1 hour ago, el_freddo said:

@suprunner - which engine management were you using to run the latest incarnation as mentioned above? 

Cheers 

Bennie

That combo runs fine using 25D management.

GD

[suprunner]

21 hours ago, el_freddo said:

@suprunner - which engine management were you using to run the latest incarnation as mentioned above? 

Cheers 

Bennie

 

20 hours ago, GeneralDisorder said:

That combo runs fine using 25D management.

GD

This motor is currently in a '96 Legacy L wagon, with the stock ECU. I'll be swapping it into a '98 outback, paired with a 5mt from an '05 GT wagon soon. I think the only problem with this setup is that it requires the intake of the DOHC, and might be a real headache to swap into anything that utilized the SOHC 2.5L... Correct me if I'm wrong? I'd love to move this into a newer platform if it won't be a problem. . .  I don't see what is so "exotic" about this build. I've seen that term used a few times. .  . STI gaskets are just gaskets... not made of Pixie dust, or Chicken Lips. Maybe because it's best to run 91 octane with it? But, aren't you supposed to do that with ANY of these high-compression frankenmotors? I think this motor would be awesome in a first gen lego, and a riot if it could fit in an EA82 platform paired with AWD. The 2nd Gen wagon's are not heavy, but they aren't featherweights, and this motor can push you into your seat a little bit. I think you could go crazy with cam work, and exhaust and it'd be even more peppy. Again, I'm running bare-bones stock with everything. 

[el_freddo]

It probably deemed exotic as it’s not the original SOHC EJ25D combination. But it definitely comes into the frankenmotor catergory. 

I was asking which engine management as I’m toying (in the back of my mind - so more like dreaming) with the idea of building one of these for my L series off-roader that’s already Gen1S2 EJ22E equipped.  But then I also think that if I break a cam belt in the frankenmotor then I’m up spoob creek without a paddle big time. 

So it’s in the air as to what happens, probably nothing, but it’s interesting to know the combinations and the engine management that runs them well. 

Cheers 

Bennie

[suprunner]

8 hours ago, el_freddo said:

It probably deemed exotic as it’s not the original SOHC EJ25D combination. But it definitely comes into the frankenmotor catergory. 

I was asking which engine management as I’m toying (in the back of my mind - so more like dreaming) with the idea of building one of these for my L series off-roader that’s already Gen1S2 EJ22E equipped.  But then I also think that if I break a cam belt in the frankenmotor then I’m up spoob creek without a paddle big time. 

So it’s in the air as to what happens, probably nothing, but it’s interesting to know the combinations and the engine management that runs them well. 

Cheers 

Bennie

How often do cam belts break? I've had only one bust, and that was an original at 182,000 miles in my old 1.8L EA82... Everyone talks of interference motors as if they've got contagious boils... I understand the risk of hurting components if the belt breaks, and the possible cost of fixing that (of course mine is going to snap the moment I turn it on this morning!) ... But why even bother with modifying a motor beyond its stock state? Is High Compression even that reliable in the long term? Wouldn't that add improper stresses that weren't necessarily designed into the system of these EJ motors? To me, if you're taking the risk of spending money and time on a motor build, you might as well make it work really well. Honestly, the 251 + 25D blows the 25D + 22 out of the water in use-ability... If you are making a strict rock-crawler, then the 25D + 22 heads will have a lot of low-end torque... but just fall on its face once on the highway. The 251 build has probably 90%-95% of the lowest-end-torque at worst... but you could enjoy the power all the way to 6k rpm if you wanted as well, making highway driving more enjoyable. I think the 25D + 22 head build would be phenomenal if you mated it with a Toyota W-series transmissions and transfer case setup... 4.56 or 4.88s....

 

My $.02

 

Greg

[suprunner]

In Case anyone is interested, this will help you create the 251/25D hybrid. @86BRATMAN helped me out with this information when I built my motor. I've done everything except that I'm using stock exhaust: 

"...run the 04-06 ej257 head gaskets, they are 3 layer steel unlike the ej251 single layer which is the most ridiculous thing I've ever seen. I use the sti gasket when redoing ej251 and ej253 head gaskets every time I do them and haven't had a repeat failure. Been using them for 6 or 7 years now. I wouldn't use the ej25d gaskets because of their thickness, they will leave you with a quench height that is much more than optimal for performance. Along with using the thinner gaskets you'll want to use an ej205/257 timing belt tensioner bracket, they have an extra idler pulley that will take up the extra slack that will be in the belt. The timing belt an all other timing components will be ej25d parts

For the clutch, I like the exedy stage 1 kit. Stockish pedal feel but gives a good bite. If you're looking to get the most performance from the engine equal length headers are the way to go, they take away the popular "boxer rumble" that unequal length headers give but they are better for power all through the rpm band.

 

You'll want to use the water pipe from the pump to the heater core from a 25d, the sohc pipe is different and will interfere with the inner timing cover."

 

Take care,

 

Greg