Home "machine" Subaru 2.5 heads

[TaperPin]

I plan on getting the head gaskets on my 04 outback replaced. The shop said the turn around time is going to depend on the time the machine shop can turn around the heads. Im thinking they plan to check the heads for flatness? If this is the case it seems like I can do this myself. First check them on a surface plate and mill flat if needed? I don't think a complete valve job is something I need.

I’m with you - it’s a 19 year old car that just needs to run again - no need to rebuild the head or pull the whole motor and rebuild it. There’s no rocket science to checking for warpage - most mechanics just use a straight edge and feeler gauges. Look it over real good for cracks and turn the head valve-side up and fill the combustion chambers with water to see how bad the valves leak - it‘s a quick easy ballpark test. I wouldn’t expect all the valves to seal completely - mainly looking for badly leaking burnt valves that might cause you to have to pull the head a short time down the road. Also look over the valve guides and seats for anything obviously different from the others like it moved one way or the other. The mechanics I know would reuse the head bolts on their own cars, but wouldn’t trust online head gaskets - too many counterfeit parts.

Head gasket is one of the best money saving jobs if you don’t mind doing it.

 

[DDoug]

I’m with you - it’s a 19 year old car that just needs to run again - no need to rebuild the head or pull the whole motor and rebuild it. There’s no rocket science to checking for warpage - most mechanics just use a straight edge and feeler gauges. Look it over real good for cracks and turn the head valve-side up and fill the combustion chambers with water to see how bad the valves leak - it‘s a quick easy ballpark test. I wouldn’t expect all the valves to seal completely - mainly looking for badly leaking burnt valves that might cause you to have to pull the head a short time down the road. Also look over the valve guides and seats for anything obviously different from the others like it moved one way or the other. The mechanics I know would reuse the head bolts on their own cars, but wouldn’t trust online head gaskets - too many counterfeit parts.

Head gasket is one of the best money saving jobs if you don’t mind doing it.

..and then advertise it as having a "completely rebuilt engine".....

 

[BT Fabrication]

I plan on getting the head gaskets on my 04 outback replaced. The shop said the turn around time is going to depend on the time the machine shop can turn around the heads. Im thinking they plan to check the heads for flatness? If this is the case it seems like I can do this myself. First check them on a surface plate and mill flat if needed? I don't think a complete valve job is something I need.

you can attempt it yourself,
but can you get better then 32RA and within a few tenths flatness? there is a reason there are specific machines that do this and not just a bridgeport....
DIY it and plan on pulling them again later to have it fixed a second time. they magnaflux them, check the valves, guides and flatness and min thickness.
have the engine shop at least check it first min. expect a couple weeks turnaround.

 

[TaperPin]

..and then advertise it as having a "completely rebuilt engine".....

Don’t forget to reset the odometer! Lol

 

[challenger]

I will get the heads done at a machine shop.
Thanks

 

[johansen]

you can attempt it yourself,
but can you get better then 32RA and within a few tenths flatness? there is a reason there are specific machines that do this and not just a bridgeport....

When i did my toyota head, sliding it around on the surface plate was enough to make it a mirror finish. Not everywhere of course, because its a bridgeport.

Why does it need to be within a few tenths for flatness?

 

[Garwood]

When i did my toyota head, sliding it around on the surface plate was enough to make it a mirror finish. Not everywhere of course, because its a bridgeport.

Why does it need to be within a few tenths for flatness?

It doesn't need to be within tenths at all, but it needs to be the correct finish for the type of gasket and clamping used. Most people fuck up their first time and give it too smooth a finish for modern engines.

Then you have lots of other things like the valve depths and cam journal straightness.

Most heads an engine rebuilder could surface 5 of them by the time a machinist figures out how to hold onto one.

 

[BT Fabrication]

When i did my toyota head, sliding it around on the surface plate was enough to make it a mirror finish. Not everywhere of course, because its a bridgeport.

Why does it need to be within a few tenths for flatness?

the headgasket ideally has half a thou deviation across the whole surface as any more then that changes the clamping load on it and you have a greater chance of head gasket failure by it blowing out.
thinking of it this way, there is just enough clamping pressure to hold the head down, and any deviation will cause gasket blowout.

 

[GregSY]

This all goes to what we can term 'good' and 'bad' engine design. When an Indy car engine is that finicky, we allow for it as the engine is an exotic racing engine which is operating at its limits and really isn't expected to last that long. When the engine Subaru sell to the public is that finicky, it's a bad design.

Any engine made by anyone that can't survive normal usage under normal conditions and be repaired on a basic level by the average - or even above average - mechanic is a bad design.

If an engine will lose a head gasket because it's been designed to live on the very edge of head bolt clamping...bad design.

 

[ezduzit]

...
If an engine will lose a head gasket because it's been designed to live on the very edge of head bolt clamping...bad design.

The average mechanic is not equipped to surface heads.

 

[GregSY]

I didn't say he was.

Another way to look at it is if the average machine shop - even a good one - can't meet the specs called for to refinish the head* surface then it's a shaky design, too.


*And the head would never have needed to be in a machine shop in the first place if it hadn't been designed in a marginal manner.

 

[ezduzit]

...And the head would never have needed to be in a machine shop in the first place if it hadn't been designed in a marginal manner.

Also not true. Overheating due to lack of maintenance, broken belt, ... can cause a head to require resurfacing.

 

[mjr6550]

I know quite a few Subaru owners. They all seem to have had engine problems at some point.

If you want to know why some people seem to think they are the best car on earth, look at some videos of European road rallies and watch a WRX drive like it was stolen. Of course, they get rebuild after every race.

 

[GregSY]

I suspect the multitudes of Subaru owners who have had head-related failures did in fact maintain their vehicles well enough. Let's face it...the modern vehicle can go 100K miles without overheating or needing much maintenance at all. A small 4 cylinder car with an aluminum engine (block or heads) is a hard vehicle to overheat....unless you are towing a 5th wheel in the mountains or something.

 

[EmGo]

Any engine made by anyone that can't survive normal usage under normal conditions and be repaired on a basic level by the average - or even above average - mechanic is a bad design.

Honda Civic - I forget what year. Was so bad about burnthough between three and four that I could do a head gasket complete in an hour and a half (instructions from an ace honda mechanic i knew, who made money by beating flat rate).

Does that make Honda a bad brand ?

(That car was the cause of another little episode, when the CHP drew on me ... but not relevant to its head gasket problems. I'm kinda glad it was just borrowed, I might not have survived actual ownership.)

 

[GregSY]

No, Honda is not a bad brand...one example of common failure doesn't qualify. I didn't say Subaru is a bad brand...just one that enjoys a far better reputation than it deserves. I think it's accurate to say the failure rate amongst Subaru engines is well above the norm as compared to most other brands, especially Japanese brands.

 

[jim rozen]

Some cars just have known bugs. My corollas are of a vintage that the intake manifold gaskets harden up over time, and develops enough air leak on cold days to throw an engine code. The fix is easy, a new silicone rubber intake manifold gasket. Good car, but with a well-known easy to fix bug.

 

[mhajicek]

Subaru's were great in the 80's. If I could get a brand new 1982 Subaru GL Wagon I'd jump at it.

 

[dalmatiangirl61]

look at some videos of European road rallies and watch a WRX drive like it was stolen.

Right here in Merica, if you have not gotten a ride in one, I highly recommend it!

 

[quadzilla87]

No, Honda is not a bad brand...one example of common failure doesn't qualify. I didn't say Subaru is a bad brand...just one that enjoys a far better reputation than it deserves. I think it's accurate to say the failure rate amongst Subaru engines is well above the norm as compared to most other brands, especially Japanese brands.

Subaru earned a bad reputation specifically because of that 2.5 engine. The design wasn’t bad the gasket material was. I’ve had a ‘93 Impreza with the NA 1.8 260,000 miles and I just got tired of replacing sensors, a ‘98 Impreza 200,000 miles no engine work done, it was too rusty to drive safely, 2004 forester NA 2.5, bought it with bad gaskets for song and replaced them myself, no head work and it was a long weekend job. If I remember from the Haynes manual the flatness spec was .0015”, could’ve been less. It had 220,000 on the original gaskets. The studs are torque to yield so if you don’t replace them you’ll be doing another gasket job in short order. 2003 WRX turbo 2.0 liter, 220,000 no engine work done, frame was rusted out and too dangerous to drive anymore. Another ‘03 WRX 180,000 no engine work done. The 2012 WRX I had was a 2.5 but they had the gasket material sorted out by then so no worries.