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Splitting HEAD'ache - 56K beware.


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68 replies to this topic

#26 Gloyale

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Posted 01 March 2007 - 02:32 PM

You are looking at "about" 1.2 cubic inches of material differance between the N/A pistons and the turbo piston, turbo pistons with the lesser of the two of course.


So if I use NA piston and remove about 0.6 cubic inches from head at each cylinder, I should end up around 8.5:1 like I want. Thanks

#27 Gravityman

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Posted 01 March 2007 - 09:50 PM

Make sure you read up on doing something like this. If you remove to much in a place that cant handle it you might destroy your head/engine. That being said, I dont see why it wouldnt work. :confused:

#28 Gravityman

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Posted 13 March 2007 - 02:35 PM

The Second part of this project is to see how much volume is in each of the intake ports. As far as I can tell there are really only 2 intake port designs on the ER27 head, the third looks exactly the same as the middle port. If that makes any sense.

I just got my head back from the machine shop yesterday and I am getting ready to port and polish them. Before I do that I want to find out how much volume is in each port. How I plan on doing this is by pouring molding rubber into each of the ports with the valves installed. Once the rubber has cured for 24 hrs I can remove the molding. Once removed, hopefully in one piece I can place it in a beaker of water and find its volume displacment. If I do this before and after the porting process I can compaire the original and post port displacment or how much material I removed.

Here is what I used.
Posted Image

This is the first 2 ports and the fuel boss filled with the latex rubber.
Posted Image

#29 Scott F

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Posted 14 March 2007 - 03:10 PM

Grav, have you looked into Extrude Hone? Consider these steps:

1) Hand port and cleanup, matching to gaskets
2) Flow bench
3) Extrude Hone
4) Flow bench to confirm balance

You know not to polish your intakes, right?

#30 Gravityman

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Posted 14 March 2007 - 08:33 PM

Yep I know not to polish the intakes. As far as the extrude hone goes its very cool but $$$$!!!. I have looked into it but prices start at $800 for 6 cylinder engines. A good Idea for a pure race car but not logical for a street/race car.

I should be starting the porting process this weekend depending on a few factors. I will keep an update.

#31 Scott F

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Posted 15 March 2007 - 08:44 AM

Your idea of measuring runner volume has merit, but flow is more important. Maybe you can find an affordable place to flowbench your heads before, during, and after porting.

#32 Gloyale

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Posted 16 March 2007 - 01:07 PM

I'd like to see another cut. Could you basically cut the bottom 1/3 off of the siamesed exhaust section. You could just cut the Cam side half you got after the 4th cut. There are 2 small freeze plugs on the cam side of head. I'd like the cut to go through those holes, parallel to the surface of the exhaust flange. I will try to get a picture with a line drawn on it, but I have never been able to get pics to upload. I always get a database error.

#33 Gravityman

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Posted 16 March 2007 - 04:21 PM

I'd like to see another cut. Could you basically cut the bottom 1/3 off of the siamesed exhaust section. You could just cut the Cam side half you got after the 4th cut. There are 2 small freeze plugs on the cam side of head. I'd like the cut to go through those holes, parallel to the surface of the exhaust flange. I will try to get a picture with a line drawn on it, but I have never been able to get pics to upload. I always get a database error.


Cool Its about time someone wanted me to cut something. :banana: First can I ask why you want me to make this cut? This is what I think you are saying that you want me to cut. Did you mean the yellow lines, left, right or both, or did you mean directly through both plugs along the green line. Let me know where you want it and I will try to post it tonight if I can get the cut off today.
Posted Image

You can upload pics when you update a thread but the pics have to be less then 50k. If you load a pic to your account in the photo upload option and then copy and paste it to the thread there is no maximum size photo and you almost never get an error.


Your idea of measuring runner volume has merit, but flow is more important. Maybe you can find an affordable place to flowbench your heads before, during, and after porting.


Yea, I know, The main reason I did the test with the rubber was to figure out the amount of material I removed and be able to compare the before and after. My machinist said that he would flow my heads for $50, I think he ment $50 for the preport but I asked him if that was for pre and post and he kinda went along with it and said that he would do both for $50. Not a bad price to find out the flow, consider that I dont think anyone on the forum has done this to their heads. I have to agree, If I dont get the flow test done that would leave this threat incomplete. Thanks for the pep-talk and good smacking around.

Oh I just got my carbide burrs to start the port job. I will first port the last section of this head that hasn't been cut and then disect it to verify that I didn't remove to much material and weaken the integrity of the head.

TO BE CONTINUED... :burnout:

#34 Gravityman

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Posted 16 March 2007 - 09:02 PM

Well... I finally got my carbide burr bits today and decided to start practicing and verifing cuts on the head. I started off with the Hydraulic Lash Adjuster bump in the intake port. It is one of the biggest restrictions in the port. Here is a before shot of the bump.
Posted Image

I went ahead and started porting the whole thing while I was at it. I want to cover every section of the port at a time ie, bump removal, deburring, smoothing and so on. Anyway here is what the bump looks like removed. It is actually a very smooth transisition, I cant even tell where it used to be after looking at the head for a little while.
Posted Image

More to come!

#35 Gloyale

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Posted 16 March 2007 - 09:53 PM

Cool Its about time someone wanted me to cut something. :banana: First can I ask why you want me to make this cut? This is what I think you are saying that you want me to cut. Did you mean the yellow lines, left, right or both, or did you mean directly through both plugs along the green line. Let me know where you want it and I will try to post it tonight if I can get the cut off today.
Posted Image


I want a cut along the left yellow line in photo. I just got my headsd back from the machine shop(cleaning, Vac test, milled .006 off of mating surface) These heads are in very good shape, with only one cylinder cracked between valves, very minor and it vac tested fine. Problem is, I look in the exhaust port and there is a crack through the wall seperating the 2 exhaust ports. It is in a parllel plane to the head, Cam side, going through that wall. Again, Vac test showed no leak there. I popped the freeze plug and looked through to the back side of that wall and can't see any crack. I took it to a local aluminum welder to zap it just to make sure. I want to know how the coolant passage looks where that V shaped wall diverges. I am tempted to sacrafice one of the heads I just pulled off the engine I am using for my bottom end build up. Now I am worried that the welder Is gonna F-up my freshly machined head so I want to wait just incase I need anopther head.
Damn, I wish I could get pics up. I swear I was trying with small files. I was doing it from work(dial up at home) and USMB seems to get bogged down with database errors during lunchtime.

#36 Gravityman

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Posted 16 March 2007 - 11:24 PM

Wow that $ucks!!!:eek: Ok let me try a different pic, mabe this will help. This is a pic of the inside of the head on the cam side you can see both freeze plugs. Tell me if any of these cuts might help a little better, or a combination of them, or if I am even on the correct path.

Posted Image

#37 Gloyale

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Posted 16 March 2007 - 11:46 PM

Wow that $ucks!!!:eek: Ok let me try a different pic, mabe this will help. This is a pic of the inside of the head on the cam side you can see both freeze plugs. Tell me if any of these cuts might help a little better, or a combination of them, or if I am even on the correct path.

Posted Image



The green line looks right. I like the position of the cut right below where the exhaust chambers split. If you cut there, and lifted the top part off, you'd look down into the coolant passage between the exhaust ports and the surface of the cam side of head. Hope you're following. I want to know if it's a flat wall in there, or if that passage follows the V. If it is a flat wall my crack is probably only between the two exhaust passages. No problem.
But if the coolant side of the exhaust passages follows the same contour, the crack will be crossing that V

#38 Gravityman

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Posted 17 March 2007 - 11:29 AM

The green line looks right. I like the position of the cut right below where the exhaust chambers split. If you cut there, and lifted the top part off, you'd look down into the coolant passage between the exhaust ports and the surface of the cam side of head. Hope you're following. I want to know if it's a flat wall in there, or if that passage follows the V. If it is a flat wall my crack is probably only between the two exhaust passages. No problem.
But if the coolant side of the exhaust passages follows the same contour, the crack will be crossing that V


Ok so just to verify I am going to cut on the green line. Do you want me to move it up toward the intake port inlet or down toward the exhaust port outlet. If so how much?:horse: Sorry, I want to make sure I get what you want.

#39 Gloyale

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Posted 17 March 2007 - 05:38 PM

Ok so just to verify I am going to cut on the green line. Do you want me to move it up toward the intake port inlet or down toward the exhaust port outlet. If so how much?:horse: Sorry, I want to make sure I get what you want.



Right where you've got it looks good, perhaps Slightly towards the "top" intake side. Slighlty more level as it relates to the picture. I really need to see how the wall that forms as the V tapers out is shaped. This is all assuming that you're 2.7 is same or similar to my EA82 heads. But you rock man either way.

#40 Gravityman

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Posted 17 March 2007 - 05:50 PM

OK buddy you got it. Make sure that you check back tonight, I should have it done no later then 2 hours.

#41 Gloyale

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Posted 17 March 2007 - 05:59 PM

Do you still have the NA pistons. Can you compare them to the turbo ones and see if there is the same thickness to the deck portion? I realise the Turbos are tubbed. But say if that tub was not there, are they otherwise identical. looking into them from the back side does the wrist pin yoke look the same? beefier? My machinist is willing to custom "tub" some 8.5:1 pistons from new .020 oversize NA ones. But not having any in hand to show him he wanted to know if there is enough meat. or if the NA pistons are substanstially lighty/wimpier than the turbos.

#42 Gravityman

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Posted 17 March 2007 - 07:34 PM

Here it is, the cut you wanted. It looks like the exhaust port floats in the coolant passage. Here is the exhaust outlet side of the cut which is the side I think you wanted to see. Please let me know if this is what you wanted to see or if you need me to take another picture.
Posted Image

Here is the intake inlet side of the cut.
Posted Image

FYI you are a very bad influance!

#43 Gloyale

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Posted 17 March 2007 - 07:43 PM

just as I though. The colant passage follows the contours of the exhaust ports. In the first pic, look at the top of the peak made by the exhaust ports coming toghether. move down about a half inch, and and that is where the crack in my head is. in the same plane as the mating surface of head, going right through that siamese wall. I have a feeling it was through or very close to through the V in coolant passge. I'm glad I'm having it welded up. Thanks.

#44 Gravityman

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Posted 17 March 2007 - 09:08 PM

Do you still have the NA pistons. Can you compare them to the turbo ones and see if there is the same thickness to the deck portion? I realise the Turbos are tubbed. But say if that tub was not there, are they otherwise identical. looking into them from the back side does the wrist pin yoke look the same? beefier? My machinist is willing to custom "tub" some 8.5:1 pistons from new .020 oversize NA ones. But not having any in hand to show him he wanted to know if there is enough meat. or if the NA pistons are substanstially lighty/wimpier than the turbos.


Just to let you know again you are a bad influance or I am just very easy. Here is another part of the deconstruction but not the head. I am kind of sad about this but I guess whatever, It is done. I CUT MY N/A PISTON IN HALF !!#*^#%. Call me crazy and make me stop this madness! I didn't think this would go beyond the cylinder heads. Anyway... here it is.
Posted Image

Here is the comparison of the Turbo piston (I WILL NOT CUT A TURBO PISTON, that is blasphemy!) I sketched this picture with near perfect accuracy .001+/- in. This shows the turbo piston material below the dish to be 25/64ths of an inch or .39in. The N/A piston only has a material thickness of .32in max. Basically, DONT dish the N/A pistons. There is not enough material there to remove and safely run a N/A let alone a turbocharged engine. SORRY!:-\
Posted Image

Here is another pic I thought was cool, just thought I would add it.
Posted Image

#45 Gloyale

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Posted 17 March 2007 - 10:50 PM

Wow. Damn. Well, I will have to figure something else out. My machinist suggested a thicker custom headgasket to lower the compression ratio. That will space the heads outward from eachother, making manifold fit uhhh.... awkward?

Hmm. I'm going to cut up one of my turbo pistons just to be sure you're turbo pistron are the samre as factory ones. I am also going to try to get some EA82 NA pistons to cut up. Maybe they tried to lighten the pistons on the 2.7 as compared to the 1.8? I can hope right? Maybe EA81 pistons? Guess I'll have to mill out the head.

#46 Gravityman

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Posted 18 March 2007 - 12:16 AM

Wow. Damn. Well, I will have to figure something else out. My machinist suggested a thicker custom headgasket to lower the compression ratio. That will space the heads outward from eachother, making manifold fit uhhh.... awkward?

Hmm. I'm going to cut up one of my turbo pistons just to be sure you're turbo pistron are the samre as factory ones. I am also going to try to get some EA82 NA pistons to cut up. Maybe they tried to lighten the pistons on the 2.7 as compared to the 1.8? I can hope right? Maybe EA81 pistons? Guess I'll have to mill out the head.


The turbo pistons I measured are EA82 turbo pistons. I have 2 sets, a used set in perfect condition and a brand new set I bought from subaru. DONT CUT THEM!!! The EA82 N/A pistons are the exact same as the ER27's N/A pistons. Truthfully I would suggest to just stick with the EA82 N/A pistons or convert to EA82 turbo pistons. If you are going to do anything to your head gasket or take your head off, it will only take about 2 hours more to swap the pistons.

You can turbo charge an N/A engine but you only need to add a little boost to get a good gain. N/A turbo'd engines have good low end response due to the higher compression and good high end with the boost. Just make sure you have a good intercooler on the engine and that you run 93 octane all the time to prevent knock.

afterthough. If you want you can have a company build a head gasket spacer like you said. I bought my copper head gasket from www.flatoutgaskets.com, I bet they can build you a custom spacer for well under $150. look at this, you can run even a 9.5-1 compression ratio on pump gas with great results.
Posted Image

#47 Gloyale

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Posted 19 March 2007 - 04:21 PM

I think I'm going to try to remove some material in the combustion chamber of heads:clap: :-\

#48 Gravityman

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Posted 20 March 2007 - 07:24 AM

Well this is just theory, If you keep the thickness of the combustion chamber wall thicker then .39 inches when you port it then you should have no problem. My reasoning is due to the thickness of the turbo piston, its thickness is .39". I still think the best way would be to just throw a Head Gasket spacer in or turbo pistons (didnt you say you have some?) and be done with it. Remove the guess work.

#49 Gloyale

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Posted 20 March 2007 - 09:41 AM

Well this is just theory, If you keep the thickness of the combustion chamber wall thicker then .39 inches when you port it then you should have no problem. My reasoning is due to the thickness of the turbo piston, its thickness is .39". I still think the best way would be to just throw a Head Gasket spacer in or turbo pistons (didnt you say you have some?) and be done with it. Remove the guess work.


I have Turbo pistons. The block I'm building up is from a turbo. However I cannot find a good source of NEW turbo pistons, oversized, for a reasonable amount. Where did you get yours? how Much?

I can however order NA pistons easy and cheap. And I like the idea of bumping the compression up a little. 8.5 seems a good number for a Turbo. It is what WRXs and other EJ turbos use.

I just like the idea of experimenting. I'll probably end up just building up the block I've got with the old pistons. They are in good shape. The cylinders aren't tappered. So I'll just rering and put new bearings in. I've got to get a solid motor into my car. I do plan to install my Spyder intake, Intercooler, with the new motor.

Once I do that though, I'll have another core to start fresh on. I'll be experimenting on that one. So I guess I'm really reseaching 2 seperate builds.

You're very first cut shows that the deck of the cylinder head is very thick. At least on the side opposite the spark plug. I wonder if a little material removedwould be enough. Wanna give me another cut on the first section you cut off. Right through the intake valve this time, parallel to the first cut. Then I can see what that shoulder has for meat end to end.

#50 Gloyale

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Posted 20 March 2007 - 10:01 AM

OK. so my Photoshop skills are not as good as yours obviously, but here is my idea
Attached File  headMod.jpg   36.79K   17 downloads


Red line shows where I would like a cut. Green is an idea of where I'd like to remove material from.




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