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Guest Message by DevFuse

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Interference or not?

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38 replies to this topic

#1 Guest_97svx_*

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Posted 08 January 2003 - 11:32 AM

I am considering getting a 97 Outback with a 2.5 L engine. Is it an interference type or not?



#2 Guest_Scott109_*

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Posted 08 January 2003 - 01:03 PM

It is interference. All 2.5s are, regardless of model year. The 2.2s are not.


#3 Guest_WAWalker_*

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Posted 08 January 2003 - 01:23 PM

'96 2.5L had hydralic lifters and are not interferance engines.

#4 Guest_svxpert_*

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Posted 08 January 2003 - 02:47 PM

The 96' 2.5 is a DOHC engine and ALL DOHC engines (Subaru) are Interference.

#5 Guest_97svx_*

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Posted 08 January 2003 - 03:52 PM

The dealer is telling me that newer (98 and up) 2.5 L engines are non-interference. Are they also SOHC or is he pulling my leg?


#6 Guest_Legacy777_*

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Posted 08 January 2003 - 04:05 PM

<blockquote><strong><em>Quote:</em></strong><hr>It is interference. All 2.5s are, regardless of model year. The 2.2s are not[/quote]

This is not correct.

All 2.2's are non-interference.

All DOHC 2.5's are interference

All SOHC 2.5's are non-interferenece.

If you some how are not sure. All you have to do is look and see if you have two cams per head. All DOHC are interference & all SOHC are non-interference.

The valves hitting themself is what makes the engines interference or not, rather then the valves hitting the piston.

#7 Guest_97svx_*

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Posted 08 January 2003 - 04:10 PM

Thank you for the clarification. How can I see if there are one or two cams per head? Aren't the cams covered together with the timing belt?


#8 Guest_Commuter_*

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Posted 08 January 2003 - 04:50 PM

Just to muddy the waters...

My usually reliable Service Manager told me last year that all current North American engines are interference designs. This would include the 2.5L SOHC engine. Maybe he's wrong...


#9 Guest_Scott109_*

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Posted 08 January 2003 - 04:57 PM


You are correct - they are all interference. I personally e-mailed Subaru a few months back and asked them if the current SOHC 2.5 engine being used was an interference design and they said yes. They answered in 1 day - I was impressed with the speedy response from them.


#10 Guest_GlCraigGT_*

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Posted 08 January 2003 - 05:02 PM

ALL EJ series engines in the US are interference engines.

#11 Guest_ccrinc_*

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Posted 08 January 2003 - 06:40 PM

OK, we've been inside these things, up close and personal. Based on the damage (or lack of it) we've seen, here is THE Definitive Word:
EJ18 - NON-interferential
EJ22 - NON interferential, both turbo and N/A versions
EJ25 - DOHC, interferential, regardless of year
EJ25 - SOHC, also interferential
EJ30 - also interferential (and with a stupid timing chain to boot!):evil:
Word is still out on which, if any, of the EJ20 engines is or is not interferential. We've only rebuilt one Jspec which had not been damaged, so are not positive on that model.


#12 Guest_WAWalker_*

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Posted 08 January 2003 - 06:59 PM

I've been told that the 1996 2.5L was a prerun, (basicly, let the consumer test is for us) with hydrualic lifters, non-interferance and less likly to have head gasket problems.

'97-'99 2.5L came out with solid lifters, is an interferance engine, short skirt pistons that slap, headgasket problems, and they burn valves. Oops!

I've been told that the 2000 phase II 2.5L has hydralic lifters, '01on have solid lifters. Interferance or not I don't know.

When you are doing a timing belt on a DOHC engine if you go to turning the cams the vavles can be damaged from valve to valve contact.

In the event of timing belt failure the likelyhood of valve to valve damage is slim. The valve trian has little or no rotational weight and will stop turning rather quickly. On the other hand it will take a while for the crank shaft to stop. The valves that are open when the valve train stops turning is usually what stops the crank when the piston crashes with the valve.

#13 Guest_Commuter_*

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Posted 08 January 2003 - 10:07 PM


So you don't like the timing chains? :D

I was wondering aloud on another board why Subaru chose timing chains for the H6 engine. A person responded with an article from a Subaru engineer involved in the design of the engine. It essentially boiled down to one thing. <strong>Packaging.</strong> They wanted to keep the engine "package" as small as possible. A timing chain is not near as wide as a timing belt. The chain saved them the better part of an inch on the total length of the engine. :cool:

I don't want to turn this topic into a "belts vs chains" discussion. There are pros and cons to both.


#14 Guest_ccrinc_*

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Posted 09 January 2003 - 06:26 PM

Commuter...no, don't like chains. Baaaad. ;)
Walker...It's not whether an engine has solid or hydraulic lifters that makes it interferential. Some of the old EA81 engines had solid lifters and they were definitely non-interferential. We've done a few of the '96 EJ25 engines, and believe me, they are interferential.
Breaking timing belts in an EJ25 is a MAJOR cause of bent/broken valves and exploded pistons.
What makes an engine interferential is if something catastrophic occurs (like breaking a timing belt) when the piston is at TDC and the valves are open, and there hasn't been enough clearance designed into the engine (original manufacture) to allow the valves and pistons not touch.
This is mostly due to the longer stroke designed to get more power.
As mentioned above, the crank continues to turn thereby moving the pistons even though the valves have stopped moving.
Whatever valve happens to be open will be bent or broken depending on engine rpm at time of catastrophe.
Manual trannys cause even more damage because the weight of the flywheel adds even more centrifugal force to the crank.
(Damn, Rick knows this stuff inside-out. I know a lot of it, but he 'splained to me just exactly WHY an engine is interferential or not.) He's "da man!":cool:


#15 Guest_WAWalker_*

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Posted 09 January 2003 - 06:53 PM

Thats just what I had been told about the '96. <img src=http://www.ezboard.com/intl/aenglish/images/emoticons/ohwell.gif ALT=":\">

#16 Guest_Scott109_*

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Posted 10 January 2003 - 01:51 PM


Now that the facts are straight, you might want to archive this since it seems to come up a few times a year.


#17 Guest_Legacy777_*

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Posted 10 January 2003 - 02:53 PM

aight.....will do!

I'll stick it...and when things putter out, I'll dump it in the archives.

#18 Guest_Scott109_*

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Posted 10 January 2003 - 04:10 PM

Just to complete the "New Gen" engine list.....

1.8 used in Impreza - not interference
3.3 used in SVX - interference
3.0 6cyl in newer OB - interference
2.0 turbo in WRX - interference
all 2.5 DOHC and SOHC (96-present) - interference
all 2.2 - not interference

Did I miss any? Please correct me if I'm wrong on any of these.


#19 Guest_Skip_*

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Posted 11 January 2003 - 08:15 AM

at CCR Rick may be DaMan
but here's bettin'

Emily is DABOSS!!

She, as they say, ROCKS!!!!

#20 Guest_ccrinc_*

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Posted 11 January 2003 - 10:41 AM

Not bad for an old bat, eh? :smokin:
Actually, I forgot to mention the EJ33, which is, as far as I know, NON interferential. We haven't had the opportunity to build one yet, but since the design is an EJ22+2 it is logical that it is not interferential.

And I have been taken to task somewhat by "The BOSS, Rick" :) about the '96 EJ25...it is designed to somewhat "less" interferential because of heavier, so-called "non-interferential" pistons. They have valve-clearance dishes cut into the piston tops to, supposedly, allow the valves to not touch the pistons. Unfortunately, if there is any significant carbon buildup on pistons and valves (and there always is), they will hit.
It was so low powered though and inefficient, that that design was quickly given up in favor of the next model.
What gets me is, when someone is test driving a car, they want as much power and efficiency as possible, without much regard to the cost and pain of possible repairs later. And, of course, any "defects" aren't exactly pointed out by the manufacturer.
I guess the old saying still goes...caveat emptor.


#21 Guest_wrxsubaru_*

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Posted 12 January 2003 - 08:35 PM

I thought the EJ20t in the wrx was a non interfirence engine.

And the reason why most of subarus engines are interfering is because, the velvles hit each other and not the piston.

Whould the New EJ25t in the STI a interfering engine.

#22 Guest_synapse79_*

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Posted 13 January 2003 - 02:06 AM

what makes the DOHC interference is the valve angle from the use of the second cam.

So whats the conclusion, are the new 2.5 SOHC interference or not. Wouldnt the angle be the same as the 2.2 ???

#23 Guest_kickerz_*

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Posted 13 January 2003 - 11:20 AM

ironic subject!! My 2.5 DOHC just jumped time!!
Over the weekend I was traveling down the road at about 55 mph and not under acceration. The car just quit. I cranked it over while on the side of the road and not even a spudder. I had it flatbeded home and noticed a coolant leak from the upper hose where its clamp to the engine side. I also noticed that the leaking coolant ran down the front og the engine. I tore off the timing belt cover and notived that the belt had skipped at least two teeth. About 8K miles ago, I replaced the timing belt, thermostat, water pump, and the oil pump O-ring. After the repair everything ran great. Tonight I'll be doing a compression test. Should I expect to see low compression from bent or broken valves??? Or is there a remote chance that tyhe valves are OK???? The timing belt is still in great condition. If the valves are bent or broken, is there anyone on the board that has had there heads rebuilt with new valves?? How much$$$$????

Any info is much appreciated!!

#24 Guest_synapse79_*

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Posted 13 January 2003 - 11:40 AM

i dont know too much about how far it needs to go before damage is done, but it seems two teeth wouldnt hurt anything,ever had a car with adjustable cam gears.. but, maybe it does...

as for having the head rebuilt, if you take the heads off your self and take them to a machine shop, it wouldnt be too bad, 100 to 200dollar range. Two bad nobody like Crower makes TI retainers, shafts and dual valve springs for a reasonable price for subaru.. :mad: as now would be a good time to have that done. For like 600bux you can build a non-vtec honda head to run to 9,000RPMs and pull the whole way... anyways...

if you put a new belt on 8k miles ago, any idea why it skipped?
was it a subaru belt?
with the guide pullies on either side of the crank pully, it seems even if the belt tensioner went bad, which cant move much in the first place, the belt still would not be able to skip.

#25 Guest_kickerz_*

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Posted 13 January 2003 - 11:56 AM

The only reason I can come up with why the timing jumped is because of the coolant leak. That stuff is like snot! Slippery stuff!! My only guess as of now....

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