Jump to content
Ultimate Subaru Message Board
GeneralDisorder

DIY Head Resurfacing... or "Post-apocalyptic machine shop techniques!"

Recommended Posts

I know I've mentioned it before, but..... yes you CAN resurface your own heads. And it's not even that hard. Especially with Subaru heads because they are aluminium and very small. This time I took some pictures of the end result, the rig that does the job, and some pictures durring the process that show the progression from warped/pitted to smooth and flat.

 

First of all - the first one I finished next to an untouched unit:

 

headcompare1.jpg

 

A good cleaning in the parts washer, some scraping of the gasket material residue, and a spritz of bra-kleen:

 

headcompare2.jpg

 

About 30 seconds of surfaceing. You can see where the low spots and high spots are and you can see the clear (and rather deep) groove that was created by the original HG fire ring. That groove is not acceptable. It needs to be removed so the new gasket is firmly held. The more of this groove we remove - the higher the clamp force will be on the new fire ring.

 

resurfacing1.jpg

 

Clean the paper and another 1 minute or so of circular motions on the "resurfacer". You can really see how the head is "cupped" and the center is not even touching our paper yet:

 

resurfacing2.jpg

 

Another few minutes of work:

 

resurfacing3.jpg

 

And the final result:

 

resurfacing4.jpg

 

Now they match. I will be going over both of these with a finer grit paper to finish up the surface. You don't want them too smooth though as the gasket needs some imperfection to "bite" into it. Too smooth is a bad thing - about a 320 grit is the finest finish you need on a Subaru head:

 

headcompare3.jpg

 

Here's the simple rig used for this job. Solid workbench with a laminate top that's been scraped smooth of any imperfections and checked for general level-ness and flatness. Doesn't have to be totally perfect - that's the job of the glass. I then backed the 5/16" thick glass with a 1/2" thick section of plywood - also checked for basic flatness. The paper (wet-dry 220 for initial stock removal, and 320 for finish) is glued down with contact cement (the glass is cleaned with mineral spirits between paper changes) and the lubrication is WD-40. You have to use a lot of WD-40. You MUST use it to clean the paper as well as lubricate the sanding operation - other chemicals will break down the paper and the glue.

 

surfacegrinder.jpg

 

This little rig has saved me time, money and waiting on several projects. It seems that often I am assembling engines on the weekend and the machine shop isn't open. They also want money for their services and while I don't begrudge them some business from me here and there - I prefer to trade a few minutes of my time that I would otherwise have spent driving to and fro to drop them off and pick them up simply doing this job myself. It takes about 30 minutes per head with paper cleaning, paper changes, etc.

 

GD

  • Like 7

Share this post


Link to post
Share on other sites

That is a very worth the effort you have spent to document this.

 

Cheaper route than sending off the heads. Just as good of a result if not better, due to less shaving this way.

 

Always use a high quality feeler guage and a high quality straight edge ( I am talking Snap-On or MAC) to check the levelness/warpage, before, during, and after. Not all straight edges are actually straight believe it or not. But snap-ons are as close you can get to perfect.

Share this post


Link to post
Share on other sites

This is actually a very valid method for older engines and has been used as long as there have been headgaskets. Now if you have a serious warp issue it has to go to a shop or a more modern engine.

Share this post


Link to post
Share on other sites

I've done this on VW carbs and manifolds, using a level instead of the glass plate. It worked great, and was definitely worth the time! It's easy to just keep tightening the bolts and blaming the gaskets when things don't seal well... but once you start taking the material off, you can see just how "un-flat" the surfaces really are! :eek:

Share this post


Link to post
Share on other sites

Yes - as Nipper pointed out there are some "modern" engines that require a very specific surface finish. Though I don't beleive that any of Subaru's engines to date are that particular. I have had plenty of them resurfaced at the machine shop and they have never asked me what specific engine it came from - and all of them come back with the same characteristic swirl pattern of a blanchard grind. Actually pretty rough compared to my 320 grit wet-dry.

 

A straight-edge is also not just a reasonably straight bit of metal or wood. As bheinen74 points out - to make the check you really ought to have a proper machinists straight-edge. You can get them from ebay for very little. A metal ruler will NOT be straight enough.

 

It's important to take note of the DEEP ridges that are formed by the head gasket fire rings - especially on the older EA engines. It's as important that these be removed as it is for the head to be flat. To some extent a bit of warpage is actually not a problem - the bolts will pull it flat. But the imperfections near the fire ring can lead to premature failure regardless of how flat the head may be. This is why I question any shop (including the dealerships) that doesn't resurface at least the heads.

 

Also - it's very interesting/educational to see the progression from warped to flat. You don't get to see this if you take them to a shop. You just take them a head and you really have no idea how flat or warped it was unless they call you and tell you it's so bad they can't save it :dead:

 

GD

Edited by GeneralDisorder

Share this post


Link to post
Share on other sites
You should add this to the USRM.

 

I will probably end up doing this for my headgaskets.

 

I got the work bench and the glass, I do that with all the outboard boat motors I've rebuilt, there's nothing worse then blowng a head gasket while on the middle of the lake on a good fishing day!

Share this post


Link to post
Share on other sites

One thing I'll add..... To my knowledge I have never had an engine blow a head gasket after I've replaced it. I've been doing this Subaru thing for a few years now and I have done a ton of engines both ways - machine shop and home resurfacing. Neither has failed me yet. Part of this I attribute to attention to detail and cleanliness.

 

If a job is worth doing - it's worth doing right and to the best of my ability.... something my grandfather passed on to me and it is THE most important concept that permeates my shop. Anyone that has worked in the shop with me knows that I will hold them to it as well while they work under my supervision. No half-assery on my watch!

 

GD

  • Like 1

Share this post


Link to post
Share on other sites
One thing I'll add..... To my knowledge I have never had an engine blow a head gasket after I've replaced it.

 

If a job is worth doing - it's worth doing right. Anyone that has worked in the shop with me knows. No half-assery on my watch!

 

GD

 

And that's why my car is out your house, I have complete confidence in what you do and look forward to the finished product and very much appreciate the time and effort you have put in to this. You have gone way above and beyond on this one, and I thank you for that.

 

Those heads look awesome by the way,

 

The next time I pass a broke down Loyale on the side of the road with steam rolling out from under the hood, and realize, it’s not me this time, I’ll have General Disorder to thank.

 

You have no idea how much I appreciate the time you’re putting into that car.

 

With out you and Rugby Subie helping me out with this, I know I’d be in a world of hurt.

Share this post


Link to post
Share on other sites

Small note to add- wet/dry is better overall, but WD-40 works quite well on 'dry' sandpaper too- it does not attack the adhesive.

 

Now, just doing this on a concrete floor, no sandpaper- that's old-school.

 

 

Dave

Share this post


Link to post
Share on other sites

I currently work for an independent Subaru shop in the area is this is basically what we do on EJ22s and EJ25s to clean the head surface, both on the heads and the block. I use a scraper to clean most of the old gasket material off (the coating from the headgasket), then a piece of red scotch brite with brake clean to scrub the surface and then some 220 wet/dry with brake clean, followed by 400 to get the final result. Now after I clean it with scotch brite but before the sanding paper, I check it with a straight edge and a .002 feeler gauge to check the flatness of the heads.

 

Great write-up GD, especially for a DIYer!

Share this post


Link to post
Share on other sites
Small note to add- wet/dry is better overall, but WD-40 works quite well on 'dry' sandpaper too- it does not attack the adhesive.

 

Now, just doing this on a concrete floor, no sandpaper- that's old-school.

 

 

Dave

 

 

Really old school is a flat rock :P

 

And newer subarus do have a finish requirement, but that's only if the head was warped and had to be machined.

Share this post


Link to post
Share on other sites

Hmm... I have an old countertop sitting in the garage that could work, I would just need to find some glass.

 

GD, would you say this is doable on an EJ251 engine if all it needs is a little lapping of the valves? I guess if we can get the heads done outside for $100ish each, it may not be worth it the time and trouble.

 

Is that a standard size sheet of paper? Also, did you just move the head back and forth, in circles or a "proper" figure 8 like you would lapping Detroit injectors parts?

Share this post


Link to post
Share on other sites

A peice of steel that's in the range of flatness of ordinary window glass (A lapping plate for example) is quite expensive by comparison to the glass.

 

Glass is cheap and it's the most common thing in our daily lives that is almost perfectly flat - due to how it's produced as a molten sheet product. It is also not subject to being bent and staying that way..... steel warps even as it cools from production and thus has to be ground flat - an additional step not needed for glass - making things like lapping plates fairly expensive. Also HEAVY. They are usually in the 3/4" to 1.5" range.

 

We had a lapping plate at my last job - no one used it - we all had peices of glass hanging around our bench instead since it was lighter :-p.

 

GD

Share this post


Link to post
Share on other sites
GD, would you say this is doable on an EJ251 engine if all it needs is a little lapping of the valves? I guess if we can get the heads done outside for $100ish each, it may not be worth it the time and trouble.

 

Is that a standard size sheet of paper? Also, did you just move the head back and forth, in circles or a "proper" figure 8 like you would lapping Detroit injectors parts?

 

Yes - EJ251 heads can be done the same way. Though if some serious valve work is needed such as a seat replaced, etc due to being burnt....probably not worth the effort since you are making the trip and waiting on the shop anyway.

 

That is a standard sheet of paper - I keep the head moving in circles. I would do figure 8's but my sheet of glass isn't quite large enough and I've found that you need multiple sheets glued down tight to each other and then you still end up with edges being torn..... it's more work than is neccesary in this case as circles do the job well enough.

 

Someday I may "upgrade" to a granite surface plate and larger sheets of paper (does anyone make such animals or will I have to cut up sanding belts?):

 

http://www.ebay.com/itm/18-x-24-BLACK-GRANITE-GRADE-B-SURFACE-PLATE-STAND-/230290100102?pt=LH_DefaultDomain_0&hash=item359e5c0f86

 

GD

Share this post


Link to post
Share on other sites

Yeah, the boss and I discussed it and we will just send them out. I like the idea though. Have you ever lapped with baking powder or toothpaste? That would be for an extra fine finish.

Share this post


Link to post
Share on other sites

I have used toothpaste to polish plastic. Works pretty good for watch faces, etc.

 

I've never needed a baking powder finish on any metal parts - I have gone as far as 1200 grit wet-dry on compressor disc valve seats. I would fill them with solvent in my parts cleaner and make sure they had a solvent-tight seal before installing them...... I'll give the baking powder a try sometime though - sounds cool.

 

GD

Share this post


Link to post
Share on other sites
I have used toothpaste to polish plastic. Works pretty good for watch faces, etc.

 

I've never needed a baking powder finish on any metal parts - I have gone as far as 1200 grit wet-dry on compressor disc valve seats. I would fill them with solvent in my parts cleaner and make sure they had a solvent-tight seal before installing them...... I'll give the baking powder a try sometime though - sounds cool.

 

GD

 

I have never tried either, only heard of toothpaste, then I wondered about the 1,000,001 uses for baking soda.

Share this post


Link to post
Share on other sites
Yeah, the boss and I discussed it and we will just send them out. I like the idea though. Have you ever lapped with baking powder or toothpaste? That would be for an extra fine finish.

 

I have for that extra minty intake air taste :) It works well.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×