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Old 10-13-2019, 03:57 PM   #1
anthony_suby713
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Member#: 505885
Join Date: Sep 2019
Default Rebuilding EJ25 Cylinder Heads

Hello Everyone,

Hope everyone is doing well. I’m sure there are some machinist‘ on that mya have already posted this. Sorry if it’s a repeat but I thought I would share my end process on the rebuild, pertaining to setting that lash .

First step of the cylinder head rebuild is to degrease all the parts and disassemble. Make sure you stamp the head with a “1” in correspondence with the cam cradle. The easiest way for me is to lay down a paper towel and label the towel “1” and set all the parts from that head exactly how you took them off. Also the separate cam journals are stamped with arrows pointing towards the cam gears and the exhaust has a “e” in the code and intake has an “I” in the code. Like this. Also grind numbers on the bottom of the valves to ensure they go back into the same valve positions.






After they’re all degreased I sand blast the heads while cleaning the valve-train. Carefully inspect the valves on the valve grinder to see if anything was bent. (Not common unless there was some type of internal engine failure).

When finished blasting the heads make sure to blow with compressed air all the parts of the heads to ensure there is no sand anywhere especially in the cooling channels. Flush everything with warm water, blow out again, then flush with brake clean a few more times and continue to blow them out freeing the head of any sand.

When finished I put them on the machine to cut a fresh surface. (Almost every Subaru head I have cut has been warped at least .003-.006).



Ok so here’s the tough part. If the intake valves 45 is is good then don’t bother cutting them. They’ll most likely be within valve lash when reassembling them. However the exhaust valves take the most beating and mine were definitely pitted.

After inspection on the exhaust valves I saw that the lap line was nearing the inner edge also with pitting. So I cut 45 again to ensure I have a fresh surface to lap into the seats. (Also make sure the seats look good especially on the exhaust).

Now after you cut the 45, this means it will sink the valve deeper into the seat which in turn will throw off your valve lash. To fix this you have to cut the valve tips. THIS is the tricky part.



Unfortunately this process is not exact and there isn’t room for error. The way I have found to ensure I’m cutting the right amount to fix the valve lash.

So to do this, assemble the cylinder heads. Make sure you use the right torque settings on the cam caps. 200inlbs the larger bolts and 84inlbs on the for smaller ones up front.



Afte you do this rotate the cam on the exhaust to have the lobe poring up in the same angle as it sits on the bucket to ensure that you are on the flatest part of the cam lobe.



Now take the feeler gauges and measure your clearances.

Intake .005-.009
Exhaust .011-.015

I make the marks on the head and then get ready to adjust from there.



After you’ve got your measurements it’s time to cut the tips to get the right tolerances. Disassemble one valve at a time to cut. Measure the valve before you cut and then keep takeoff measurements on every thousandth the machine says it’s grinding off to ensure you’re getting the right results.




Reassemble and do the same for all of them.

Bolt back together and remeasure the clearances and there ya go!

Also make sure to use a light under the valves and look through the cylinder ports to see if any light is shining through to ensure you have a proper seal with the valves to the seats.


All done brand new rebuilt cylinder heads





Have a great day everyone !
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Last edited by anthony_suby713; 10-13-2019 at 09:53 PM.
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Old 10-13-2019, 05:59 PM   #2
motorbykemike
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please edit your cam cap tq specs for the noobs
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Old 10-13-2019, 09:47 PM   #3
anthony_suby713
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Member#: 505885
Join Date: Sep 2019
Default Rebuilding EJ25 Cylinder Heads

Quote:
Originally Posted by motorbykemike View Post
please edit your cam cap tq specs for the noobs


Did I get them wrong? **** idk off the top of my head. I thought they were 200in lbs for the large bolts and 84in lbs for the smaller bolts up front.

Last edited by anthony_suby713; 10-13-2019 at 09:53 PM.
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