UkLegacyT

as title, to eliminate noisy tappets

any other parts needed, apart from two complete heads. they are wrx, 1995 ish?

thanks

ian

ustolemyname??stevieturbo

iTrader: (1)

Hi, As mentioned before, get complete heads, with rocker covers and preferably coils. The legacy coils can be made to fit, but it is messy. Impreza uses single bolt coils M8 thread. Legacy is two M6 bolts. The plastic timing belt cover section that is bolted to the engine is different also ( just remembered ) The casting bosses around the camshafts is larger on the impreza and fouls the legacy cover, and one of the bolt holes is in a diffrent place, so it is a a good idea to get these also. I think it is mainly the drivers side that is different. Front sections are as legacy. The oil filler cap sits at a slightly differnet angle too I think, but you will have your legacy one anyway. I did read before about stripping the oil gallery plugs from the legacy heads, and giving them a good flushing out, which helps restore oil flow and sorting the noisy lifters out, but if your gonna remove the heads, the impreza is a better idea. Definately quieter running.

UkLegacyT

nice one steve,
ill get the coils and timing covers aswell then

get that tdo5 next week too, so gonna do the manifold aswell

ian

UkLegacyT

steve,
was it you that was saying about getting a lot of detonation?

if so, is the compression different when fitting the heads?

cheers

ustolemyname??stevieturbo

iTrader: (1)

I am not sure about the CR. I never checked. I just needed a bottom end as the wrx engine had melted a piston, and my old legacy motor was lying around after having shredded the belt ( although in good health ) so i just decided to use it as it was free. I am getting det. above 6500 rpm at around 14psi. So it might be worth a look at the pistons. I think the heads are the same cc, but again, I never checked.

dfullerton

Urgent i tried this myself. went as far as buying 98 heads from midland impreza.coil packs, but when my mechanic when to fit them it turns out that you need pistons as well. maybe 94 wrx heads are different but 98 heads will not fit without pistons.

UkLegacyT

thanks for the replies guys.

steve, is it 14.5 psi peak? if so then it would have dropped lower by 6500rpm, seems strange to get det

dave, will find out exactly what the year is, then find if the pistons are different....

cheers, ian

UkLegacyT

impreza and legacy both listed as 8.0 : 1 compression

ustolemyname??stevieturbo

iTrader: (1)

14 psi steady throughout the rev range. The heads I used were off a 94wrx. Out of curiosity, What explanation did your mechanic give to say why he needed the pistons also? as from a quick visual there appears to be very little difference ( difference that would actually prevent fitting )on most engines I have seen, from 90 legacy turbo, through to 98 sti4. I have built a few combinations, prefering to use the early blocks with the later heads. The pistons, although differing in appearance slightly ie, cutouts etc, all look to be quite similar. Whether they be crappy cast pistons as in Uk cars, or forged sti types.
Maybe someone else out there has more specific details??

duczz

I looked into this option with quite a bit of detail and everywhere I asked including Possum Bourne Motorsport and a few other performance places all said I would have to change the heads and the pistons together , I havnt actually found out why this is the case but yeah thats what all the so called experts reccomend.

Pavlo

It might have something to do with the change in compression ration that happened in about 96is (can't remember when exactly) but they did go from 8.0:1 up to 9.0:1.

Paul

UkLegacyT

the heads i can get are from a 95 wrx. i always thought the bottom ends were the same as uk models, with only sti's having lighter forged pistons for the extra revs.....

not heard about it jumping from 9.0:1 seems quite high for a turbo car really

Pavlo

Well, vauxhall 2.0 turbo engine runs 9.75:1

So 9.0 is not that high at lowish boost.

Paul

dfullerton

Reson is because the legacy heads are dished and the pistons are flat. with the impreza the pistons are dished and the heads are flat.. so if you put the impreza heads on legacy pistons the valves will hit the pistons, get it

UkLegacyT

bugger! that aint gonna work then

his wrx engine is in bits, so will ask him to look at the pistons on his engine just encase there are any variations with different MY imprezas.
cheers dave

dfullerton

I wish i had done the whole job , but settled for a head rebuild at Risbough 4 wheel drive. £900 but they do fantastic job. But you cant beat impreza lifters. make sure you get the wright pistons they are marked A B or C

UkLegacyT

no if the pistons are dished on the impreza, i wont bother getting the impreza heads, too much arsing about.
ill just take the legacy ones off, and port them instead.
have they fitted impreza lifters in the legacy heads then?

DGRALLYING

Reading with Interest...


As i am in the next couple of weeks going to take my car off the road to change the followers (anyone know where you can get them cheap?????) but i think i may have to look into porting the heads at the same time.

I did speak with Howard at HDC Subaru who has put impreza heads on his Lego, but unless you have got all the right bits it is a bit of a pain to do, therefore standard option for me.

Dean

ustolemyname??stevieturbo

iTrader: (1)

Legacy pistons are not flat and impreza heads will not cause the valves to hit the pistons. I AM running 94 wrx heads on my UK 92 legacy turbo short motor. Legacy pistons do have a dish, just slightly different in design to the impreza dish. The heads are interchangeable, and it will def not raise the compression to 9:1
A few low power/boost modern cars do run quite high compression ratios, Subarus do not. For tuning purposes you dont really want a high CR. While the heads are interchangeable, the design of them is totally different. A legacy runs ballstud hydraulic tappets, with a cam follower ( like a 2.0 ford pinto ). ie the camshaft acts on the follower opening the valve with perhaps a 1:1.5: ratios or similar. Imprezas also have smaller diam. valve stems, the legacy ones bigh quite big ( and probably more restrictive ) An impreza whether it be late model bucket and shim, or earlier hydraulic, acts directly over the head of the valve via the hydraulic follower. A much better design. It would be impossible to convert legacy heads to this design.
If there is a change in CR, It would only be by a very small amount, certainly not as much as raising to 8.5:1
The only mods i had to do where as mentioned at the start of this thread regarding coils and timing belt covers ( the back plate, not the actual front cover )

ustolemyname??stevieturbo

iTrader: (1)

If you like, I will be removing the engine in the next month or so to fix the big ends, and I can take a few pictures to let you see the pistons side by side with wrx type. Although I will be changing the pistons when rebuilding to sti forged pistons. I can also take a few pics of the 2 heads. It will probably be a month or so as I am working on another project which I want to finish before strippng more engines, as my garage is a in a bit of a mess at the minute..

dfullerton

When my heads were rebuilt they used new hydrolic lifters £26 each. ouch. in my post i meant impreza lifters are a better design
By the way look forward to the pics

[Edited by dfullerton - 5/18/2002 11:47:46 PM]