Jump to content
Ultimate Subaru Message Board

High Compression OBS build


s'ko
 Share

Recommended Posts

Here are some info about a high compression motor I just put together for my OBS

Parts list:

Phase 1 EJ25 Shortblock w/stock pistons & rods (rebuilt)

Phase 2 EJ22 heads (120k)

Cometic head gasket w/100mm bore.

Phase 2 EJ22 Intake manifold

Phase 2 EJ22 engine harness and sensors

Assembly:

The engine pull was pretty standard.

picture.php?albumid=181&pictureid=1657

EJ22 came out and was beheaded.

Engine sat for a year w/minimal use & the coolant came out looking rust colored.

Heads were cleaned off and then assembled onto the freshly rebuilt EJ25 short block.

picture.php?albumid=181&pictureid=1659

picture.php?albumid=181&pictureid=1660

Heads were torqued down according to the FSM for non-turbo engines. (we’ll see how this holds up with the higher compression)

The crank timing gear had to be replaced with the phase 2 gear, b/c there were more tabs than the phase 1 gear. The gear slid right onto the crankshaft w/no issues. The woodruff key is in the same spot and lined up perfectly.

The sensors and the cam shaft timing pulleys from the EJ22 phase 2 heads were used. The knock sensor was taken from the EJ22 and put onto the EJ25 stock block. The temp sensor for the Phase 2 needs to be remove and put onto the Phase 1 water tube b/c it was 3 pins as opposed to the Phase 1’s 2 pins. The temp sensor on the Phase 1 can be removed and plugged. I left it in so in the future I can put in another temp gauge.

I used the power steering pump from the Phase 2 motor b/c there was a sensor on the wiring harness to determine if the power steering fluid was low.

All the other accessories bolted right up with no problems.

Timing was set according to the EJ22 specs.

The phase 1 short block is designed to fit onto the EJ tranny at 4 points. There are two bolts up top and the two studs at the bottom. The Phase 2 short block has 6 points. There are two bolts up top. One bolt at the bottom of the starter and a bolt near the set pin. Then there are the two studs at the bottom. In order to secure the starter, I took a bolt and cut the end off of it. Plan was to make the bolt into a stud at the bottom starter hole. I used JB Weld to secure the bolt into the hole and left a 1 inch of thread to secure the starter.

Impressions:

So far I have less than 100 miles on it. Once I get past the 500 mile mark, I plan to test the compression to see where it is at. Should have tested the compression before the rebuild to get a before and after.

Butt dyno tells me it’s faster, but then again, I have been driving a EJ22T RX before this.

Future plan:

EJ D/R box

2 inch lift.

Link to comment
Share on other sites

love the roundy headlights....curious to see how this goes .would like to build one soon.......cheers, brian

 

+1 on the roundy headlights, that looks really cool! I like the concept of your motor build, too. Would this EJ25/EJ22 hybrid animal still be interference?

Link to comment
Share on other sites

130 miles and counting on the motor

1st highway drive.

At 70 mph, the engine was purring at 3000 rpm.

80 mph, the engine was at 3500 rpm. I use to be over 4000 rpm at 80 mph.

No verdict yet on gas mileage, I have about 2/3 of a tank left.

Overall the impression is great. Now to somehow speed up the next 370 miles.

ECU is throwing P0420, but that’s to be expected b/c of the high flow exhaust.

Link to comment
Share on other sites

At 70 mph' date=' the engine was purring at 3000 rpm.[/color']

80 mph, the engine was at 3500 rpm. I use to be over 4000 rpm at 80 mph.

 

How did swapping motors affect the RPM to Speed ratio?

 

That should all be determined by the gear ratios?

 

Is it an Automatic trans? And now with more power it can hold the TC lockup at higher speed?

Link to comment
Share on other sites

What timing belt did you use? Im assuming the EJ22 Phase 2 belt...

 

I have been collecting parts and knowledge to build one of these myself, but Im going to be using Phase 1 EJ22 heads instead of Phase 2, and Ill but running Dual Weber IDF 40 carbs... The main thing I havent figured out yet is what timing belt to use, I figure the EJ22 belt, but I would like some clarification...

 

-Bill

Link to comment
Share on other sites

What timing belt did you use? Im assuming the EJ22 Phase 2 belt...

 

I have been collecting parts and knowledge to build one of these myself, but Im going to be using Phase 1 EJ22 heads instead of Phase 2, and Ill but running Dual Weber IDF 40 carbs... The main thing I havent figured out yet is what timing belt to use, I figure the EJ22 belt, but I would like some clarification...

 

-Bill

 

Catastrophic failure last monday. w/210 miles on the motor, the timing belt skipped and the motor is fubar.

suspect the idler pulley failing, but can't be sure. Driver's side cam is hard to turn so i am pretty sure that some valves on that side are bent. I don't know about the pistons.

 

pulling the heads sometime next month. Been really busy w/stuff.

 

one a good note, bank has accepted out offer for a house so I get a 2 car garage to play in. :banana:

 

bill, I used the Phase 2 stuff, but the phase 1 idler and other pulleys will bolt right up w/no problems.

 

BW

Link to comment
Share on other sites

this is exactly why i would use phase one stuffs for the entire build.to maintain a non interference motor.......or is that possible?am i thinking about that right?(scratches chin)..........cheerrs, brian

 

Idk, Ive heard different responses to that idea from several places, some say it would be non-interference becasue of the Phase 1 EJ22 heads, others say it would still be intereference becasue of the stroke on the 2.5 block... I honestly dont know...

 

-Bill

Link to comment
Share on other sites

Idk, Ive heard different responses to that idea from several places, some say it would be non-interference becasue of the Phase 1 EJ22 heads, others say it would still be intereference becasue of the stroke on the 2.5 block... I honestly dont know...

 

-Bill

 

It is all about Cam lift and timing. Of course if the heads or the deck have been machined too much this could change. But none of the EJ engines have pistons that protrude from the block.

 

 

 

Phase 1 or Phase II 2.5 block with pre-97 2.2 heads will be non interference.

 

Anything with post 97 2.2 or any phase II heads will be interference

Link to comment
Share on other sites

It is all about Cam lift and timing. Of course if the heads or the deck have been machined too much this could change. But none of the EJ engines have pistons that protrude from the block.

 

 

 

Phase 1 or Phase II 2.5 block with pre-97 2.2 heads will be non interference.

 

Anything with post 97 2.2 or any phase II heads will be interference

 

Phase 1 block w/phase 2 heads = interference. confirmed the hard way:rolleyes:

Link to comment
Share on other sites

Please sign in to comment

You will be able to leave a comment after signing in



Sign In Now
 Share

×
×
  • Create New...