DIY: Head Gasket Replacement - Subaru Impreza GC8 & RS Forum & Community: RS25.com
 
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DIY: Head Gasket Replacement
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Old 04-21-2008, 02:10 AM   #1
Brydon
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Default DIY: Head Gasket Replacement

So I made a quick guide. Anything else you guys want added?















Once the motor is out and the manifold has been removed or you can just take the bolts out of the manifold and let it dangle. Which is how I've done it. Get the timing belt off and you should be looking at basically this.



On the right is a small bolt that will need to be taken off so the head can come off in a few minutes.



Now that that is all taken care of you can move on to taking the heads off. Since this is SOHC you do not need to remove the cams or cam pulleys. This is much easier then the DOHC heads that require some impacting of a 10mm hex bolt off. Or in a lot of cases cutting them off because they are seized on to the pulleys.



So start by removing all the valve cover bolts from the valve covers. As soon as the head is off I reinstall the valve covers to keep dust, dirt, or anything else from getting in the heads. It also makes the heads easier to store and you never loose the valve cover bolts.



Once the valve cover is off you will see the heads of the head bolts. They look weird because most people have never seen 12 point bolts before. This requires a 14mm 12 point socket. Please don't cheap out on this because you don't want to strip one out because you are using tool bought from the local auto parts store that were made in tiawan and cost $10 for a set of socket. I spent hundreds on my Snap-on impact full set from 10-24mm but that is not nessasary also. But they have never failed me and I've done alot of motors.



This is what I use and it works great. The bolts are tight on there because they are stretch bolts. So this is a good time to call up that body building friend of yours and finally put him to use.... Or just man up and do it. There are 6 bolts to take out so start with the outside four bolts and then the center ones. It doesn't actual tell you to do this on deinstall but that is how I do it.



After the bolts are all off your head will come right off. Put the valve cover back on and store the head to the side out of your way.



This coolant pipe now needs to come off because it is bolted the the left head. Three 10mm bolts and it will be free.



Now it is time for the valve cover. After doing the first head you should be well on your way to understanding what needs to be done. So take off the valve cover and place it somewhere safe with the bolts left in it.



Sometimes the bolts are really on there and they require a little extra leverage. Never try impacting these off as you will probably destroy the bolts. So just like the last head, take off all six head bolts and the head will come right off.



Now that both or at least of your heads are off you can start to reassemble. You now have two choices. If you have not overheated the heads and don't think they need to be planed then you can go right into the assembly. If not you will need to take the heads to a machine shop.

If you are ready to continue than make sure that the block matting surface is clean and free of old gasket material.



Place your new fresh gasket on your block making sure that everything aligns and the oil passage is on the correct side. They are reversible so don't screw this up! Also the gaskets are the same from left to right head.



Now turn your attention to the head. make sure this is free of gasket and oil/water. A razor blade might help you smooth this out but make sure not to nick the head or the block while cleaning.



Place the head back on the block and start the head bolts (Make sure to apply some oil to the threads and washers). Make them snug but don't tighten them yet. I know the picture is crappy but notice the colors on top of the head bolts? The are different. Out of your six there should be two that are different colors. They go in the center. If you are ordering new ones (I generally don't) Subaru will know the two different part numbers.



1) Tighten all bolts to 29 N-m (3.0 kgf-m, 22 ft-lbs) in alphabetical sequence.
2) Then tighten all bolts to 69 N.m (7.0 kgf-m, 51 ft-lbs) in alphabetical sequence.
3) Back off all bolts by 180" first; back them off by 180" again.
4) Tighten the bolts (a) and (b) to 34 N-m (3.5kgf-m, 25 ft-lb).
5) Tighten the bolts (c), (d), (e) and (f) to 15 N.m (1.5 kgf-m, 11 ft-lb).
6) Tighten all bolts by 80 to 90" in alphabetical sequence.
CAUTION: Do not tighten the bolts more than 90".
7) Further tighten all bolts by 80 to 90" in alphabetical sequence.
CAUTION: Ensure the total "re-tightening angle" [in the former two steps], do not exceed 180".



For those that need the real thing. This is A



This is B



This is C



This is D



This is E



This is F



Now do the other head the exact same way and you will have a complete long block again.



All you have to do now is re-install the valve covers and retighten the Intake manifold. Then re-install the motor and you are ready to go driving.

Remeber to not over tighten the valve cover bolts. They are easily broken.

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Old 04-21-2008, 02:15 AM   #2
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wow awesome DIY...thanks!

i hope i won't have to bother with this for a long while...

i really need to spend some money on some quality tool sets.
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Old 04-21-2008, 04:03 AM   #3
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sweet...is that a bellaire?
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Old 04-21-2008, 04:18 AM   #4
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sweet...is that a bellaire?
Yes 56 chevy! The Other is a 41 Ford coupe all rodded out.
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Old 04-21-2008, 04:27 AM   #5
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Yes 56 chevy! The Other is a 41 Ford coupe all rodded out.

Ill send you pics of my roomates rebuilt 57. OMG best exhaust note ever! black and chrome all original..fuel injected motor so sexy..thanks for the nice writeup
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Old 04-21-2008, 07:24 AM   #6
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Dang dude! You a mind reader too? I'm just about to do the HGs in my car. Every little bit o-help is gonna help! Cheers!
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Old 04-21-2008, 08:26 AM   #7
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Yeah, I've done one set of headgaskets on my old motor... and just found out that I have to do them on my new motor

I should have all of the parts sitting on my door step by 5pm today...

The only addition I have to this is that you may want to mark your bolts for the two 90 deg bits of the torque sequence. This will help you make sure that you don't exceed 180deg overall:



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Old 04-21-2008, 10:16 AM   #8
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Quote:
Originally Posted by AcquaCow View Post
Yeah, I've done one set of headgaskets on my old motor... and just found out that I have to do them on my new motor

I should have all of the parts sitting on my door step by 5pm today...

The only addition I have to this is that you may want to mark your bolts for the two 90 deg bits of the torque sequence. This will help you make sure that you don't exceed 180deg overall:



-- Dave

this is a good idea..when i did mind..since i didnt took out the engine.in the small speac.they are hard to make sure how many deg that i am doing..good idea
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Old 04-22-2008, 07:37 PM   #9
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Hey Brydon.. I know your still working on this thread, and perhaps the answer to this is comming. But... have you heard of a break in period for a new HG? I've read the odd post about easy driving the car for 1k. Can't say I've ever heard of that for an HG before. Sure, for a new engine, or a new clutch.. but HG?
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Old 04-22-2008, 07:41 PM   #10
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Hey Brydon.. I know your still working on this thread, and perhaps the answer to this is comming. But... have you heard of a break in period for a new HG? I've read the odd post about easy driving the car for 1k. Can't say I've ever heard of that for an HG before. Sure, for a new engine, or a new clutch.. but HG?
There is no need to "break in" head gaskets. Motor break in is to 1) flush the system of assembly lube and contaminants 2) seat the rings to increase compression and decrease oil consumption.

If you only replace the head gasket then I would say give it a good heat cycle and go to town!
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