silent running

Having never done this before, some advice would be very much appreciated. I have a pair of version 4 heads to work on and I want to remove the valves/springs to have a look at their condition. I've never used a valve spring compressor before, so before I go down to the motor factors and buy one, is there anything special that I need for a Subaru head? There seem to be a few different styles of compressor out there.

Not having a dismantled head in front of me it's a bit tricky to work out what goes where. Presumably the compressor will have one end bearing on the face of the valve and the other end reaching round so you can wind it down onto the spring, so you can then pluck out whatever there is in there to hold things in place, once the spring force is off it?

Some people say rebuilding a head is easy, others say let a professional do it. I'd rather do it myself if it's a straightforward job, but I just need a walkthrough! Stuff like lapping in valves etc is probably easy if you've done it before, but I've never done it before...

ticky

YouTube - Subaru Cylinder Head Disassembly

I used something very similar to the one in the video to remove the valves (valve spring compressor) was not specifc for subaru but done the job ok.

Getting the collets back on is a different story very tricky but I used a dab of oil to keep them in place. The magnetic tool is very useful & worthwhile to get.

Just make sure to everthing is labelled & goes back where it came from ie valves, buckets, shims springs etc.

Lapping the valves is simple I just used the fine paste. Keeping the suction cup on the valves alway seemed to slip off.

I removed the oil gallery hex bolt plugs & used plenty of de-greasing cans, brake disc cleaning spray cans & wd40 along with water hose pipe & air to clean the heads.

The last job was measuring & reshimming the valves to spec.
inlet 0.008" +/- 0.001"
exhaust 0.010" -/- 0.001"

Ticky

silent running

Nice one Ticky. I think that's answered everything I need. Just to be sure, 'lapping' the valves is just the process of grinding the seat to match the back of the valve head for a perfect airtight seal? Presumably it doesn't need much actual material removing?

DJ_Jon

iTrader: (7)

IIRC, when you lap a valve in, if you keep checking the valve edge, when you can see an unbroken 'line' all the way round then you have lapped it in.

very little material is removed.

stoneface

iTrader: (6)

As above really and i have this one which is perfect for subaru heads Link

bandit1216red

Hi Silent
All whats been said is true ok
but ya might as well get the valve seats recut and the valves refaced properly while there out
to wide a seat gives the wrong sealing pressure and 2 narrow will just burn em out again
seat angles are 45 degrees and want 2 be 1.5mm wide on all contact areas

silent running

Good stuff, I think I have all the info I need now - still getting over the cost of a compressor LOL

So Bandit, I could just take a bare head with the valves along to a specialist and tell them 45 degrees and 1.5mm wide contact and that's all there is to it?

gaz-cole

just make sure that don't get any valve lapping paste on the valve stem, if you do you do make sure that is cleaned off very carefully.

silent running

good point!

eggy

hi guys, im in the middle of a rebuild, and just at the stage of refitting the skimed heads,, i sent a mate to the machine shop with the heads complete(my fault ) he came back with all the buckets /shims/ect in a bag mixed up ,,,,,

how do i go about sorting them all agian

172sport

iTrader: (6)

figure in new shims £8 ea

silent running

So the clearance you're shimming for is against the base circle of the cam lobe as it turns, then as the ramp of the lobe comes round the slight clearance is taken up, valve opens, reaches maximum lift on the nose of the lobe, then as the valve comes back down off the lobe, you get the slight clearance again once back on the base circle? Someone correct me if I'm wrong!

And presumably on the earlier hydraulic valvetrain, there is no clearance at all as the tappets are pressurised to stay tight to the cam lobe all the time?

So shimming my v4 heads will be just a case of seeing what fits and gives me the clearance I want, and buying whatever extra ones I need.

172sport

iTrader: (6)

yup, 0.25mm ex and 0.2 in from memory

stoneface

iTrader: (6)

You can adjust thickness off your shims by rubbing on a carbide sharpening block and checking with a mic until correct.

silent running

OK update time; valves and springs are out, but I've still got the guides, spring seats and stem seals in there - am I right in thinking the guides are just a press-in fit so I can knock them out from the combustion chamber side? They're not screwed in or anything are they?

Is it normal to replace stem seals as a matter of course when rebuilding a head?

ZEN Performance

leave the guides alone! they are part of the head, and unless significantly worn, DO NOT TOUCH! If they are worn they can be changed, but the relavent valve seat will need cutting too, to true it up to the new guide (a pain I know but very necessary).

You will want to change the stem seals, and if you're buying them from your stealer, you might want to check our prices first! I use angled hose pliers to remove stem seals, but your mileage may vary with the tools you have available.

Clean all the valve seats with solvent and a rag to get rid of surface carbon, check the exhaust seats in paticular for pitting, then check the valves for worn valve heads. We've replaced exhaust valves on most of the builds we've done on engines that have had a hard time. If the pitting is bad, you may want to get the valve seats ground/cut by a local machine shop. Then lap valves in to the new seats all round. Inlets will probably be fine as is BTW.

When it comes to shimming, do a search, it's a PITA at times, especially if you get valve seats cut as you're likely to need totally different thickness shims for those valves/seats that have been machined or changed.

silent running

Excellent, thanks Paul, I was just about to knock them out to have a look at them so you stopped me just in time. Hopefully I won't need to do much more than clean everything up and replace the seals, I'll worry about shimming when I come to it.

Is it worth tidying up all the casting marks in the ports? There seems to be quite a hefty lip where the valve seats start that could easily be ground out while I've got everything apart. Apart from that I'd leave the rest of the inlet ports fairly rough and smooth out the exhaust ports.

silent running

So this is my plan for working on the head and unless I hear that it's a very bad idea, I'll go ahead and do it.

I'll leave the valve seats themselves well alone at this stage; in the end I'll just lap the valves in before reassembling. I'm going to lightly polish the combustion chambers, then grind out casting imperfections along the ports especially the rough step in the throat where it meets the back of the seat. I'll be careful not to change the shape of the throat and bowl area, just clean it up. The exhaust ports will end up with a light polish if I can do it, the inlets I'll leave fairly rough, although a lot smoother than they are now. The only place I'll be actually reshaping will be when I do some port matching.

ZEN Performance

inspect before making decisions that could see you stripping the engine a second time.

silent running

Yes I won't be very happy to do the same job twice. I'll go easy on the heads. The only question left is regarding the valves themselves - they seem to be a good fit in the guides, measure up to spec, the exhaust valves are a little looser than the inlets which is how they should be. They all spin up perfectly straight in a drill so that's good. The line on the backs of the valve heads where they touch the seats look a little uneven on some of the valves - i.e. varying slightly in width. Is this something that means they need throwing out, or just correcting by lapping in? Any other reason to replace valves that I've not thought of. As far as I can see they seem OK.

ZEN Performance

look for black spots on the ex valve seats, this will pits in the sealing face filled with carbon, bad news. The sealing face of the valve should have a straight edge with a 45º angle to match the seat. It should NOT BE CONCAVED! It's possible to reface valves to take out any (very ) minor runout and to clean up the shape, but beware when cutting seats and valves that the shims don't end up being very (too) thin.

paul

silent running

OK I didn't even think of look at the profile of the sealing face on the valve to check it was a straight 45 degree angle. Some exhaust valves look fine, some look very slightly concave and some are noticeably concave. My inlets seem all pretty good.

So just to confirm; even the slightest concave on the sealing face of the valve means replacing it?

ZEN Performance

I can't make that judgement for you, we would replace any suspect valves.

silent running

OK well concave of any kind means not a perfect seal I suppose, which would be a shame when rebuilding an engine from scratch.

Do any aftermarket firms make valves for the EJ20? I found Supertech and Crower do, but only for the later models that need a 104.7mm long valve. My v3/4 ones are 106.2.

bandit1216red

why not take em n get em refaced at 45 degrees they might not need much of a grind 2 get em true???
and while ya at it get ya seats recut in the heads
worse case for you might be inlet valves refaced and new exhaust valves
though u was on a tight budget lol

silent running

Well that's what I'm thinking about Bandit. Just I want to keep as much work 'in house' (i.e. in my garage!) as possible. Soon as I start taking jobs out to people to do, the bills start mounting up!

The valves sealing faces don't look too concave although it is quite noticeable on some. But let's say I did get them refaced at 45 degrees, and get the seats recut to match. Surely that'll move the valve back into the head a little bit once it's all assembled? How much does it generally cost to get this kind of work done? I'm wondering whether it might be more economical to get new valves at £8 or £9 a throw rather than recut them...

ZEN Performance

You didn't look very far for valves! we stock supertech valves for the V3/4 heads, £22.95+vat each for inconel ex valves. Personally, if you don't have to cut the ex valve seats, then you might get away with refacing the valves, if you have to do both then you will possibly run into complications when coming to shim the heads. If your current ex shims are in the 2.5-2.6mm range, then you have a good chance ofsuccess, but if they are 2.3mm or so, you are going to really struggle without new valves.

It's going to cost you about £160inc vat extra to replace all the exhaust valves compared to refacing them. And you might save money when it comes to shimming them too.

silent running

What you're saying Paul, re: cutting valves vs. seats vs. shimming problems, is pretty much what I was thinking although this being my first head build, I couldn't put it as succinctly. My shims are mostly 2.45-2.65, but there are a few in the 2.3 range.

However, I'm not sure what valves I should have been looking at...just to be sure what I've got, my current v3/4 exhaust valves measure up at 106.2 x 5.9(x) x 32.

This exact size was only listed in the Supertech catalogue as for the EJ25 non-turbo, in black nitrited finish rather than Inconel so I wasn't sure if they were suitable. Are these the ones you mean?

ZEN Performance

I stock V3/4 valves, inconel exhaust and stainless inlet, for your application. I requested that Supertech add them to their range. They are on the shelf, ready to go (along with Supertech stem seals, which are cheaper than the OE item.)

Phildodd06

How much would a set of valve stem seals & valve guids cost for V5 Type-R heads? (thats if you sell them)
Cars running 310bhp, not really going to mod it anymore.