silent running

Good news! With the aid of my bench vice and a file, I filed some flats into the threads of a couple of the old head bolts and after a lot of careful winding in and out, lubing with 3-in-1 oil, cleaning out and then recutting again, finally I got the thread in the block clear! I ended up making a 1st and 2nd tap with slightly different lead-in profiles to do the job and I'm well pleased to say the least...

The last ARP stud is fitted, now I need to complete the short block by fitting the water pump, oil pump, crossover pipe and oil cooler. I will also be cracking on with building the heads up now that the chambers seem the right volume.

Matt578

Congrats nick, Glad you got that thread clear! Now you can get on with the rest of the build

stoneface

iTrader: (6)

Good news indeed. Well done

silent running

Moral of the tale: check your head bolt threads BEFORE sending your block off for expensive machining!

j16jrf

iTrader: (3)

this is a cracking read, well done mate getting there nicely.

will prob be doing this myself next year

Matt578

Your more than welcome mate

Atari Boy

I must say that I really impressed with the effort that everyone is going to help each other out.
I doubt other forums have such an attitude.

Good work Nick btw, I will give your handy work the once over tomorrow.

silent running

I've now hit upon a problem getting the heads shimmed - after having the seats recut, the effect has been that the valves have recessed further into the heads. Meaning the tappets are now closer to the cam lobes at the other end. So close in fact that without a shim in place the tappet-to-cam clearance is only 1.25mm, and the smallest shim I have is 2.29mm...

So I'm now trying to figure out whether I can have a mm or two taken off the end of each stem, or get the shims 'thinned' somewhere, or get a new set of much thinner shims made. The idea of shortening the stems sounds reasonable, but I'm not sure that this would actually provide any extra clearance, because the retainer would not get lower at all, and the shims sit in the retainer.

Matt578

You can rub the shims down yourself i believe nick, but its hard work lol

silent running

Yeah I'll say. I'm gonna try and grind down the stems shorter rather than thin out the shims too much. I wouldn't trust the strength of them if they were down to 1mm.

ZEN Performance

you're fooked.

silent running

Care to expand on that Paul? I've done all the measurements and worked out exactly how much to take off each individual valve stem, it comes to 1-1.4mm. As long as I get it taken off nice and square I can't see a problem. Certainly Scholar Engines did mention it might be necessary to take a little off the stems following the valve job and it's a service they offer. I didn't take them up on it at the time because I didn't know how much I'd need yet. I can only assume that after 40 years of building race engines they know what they're doing...

If there's some compelling reason for writing off the heads, then let me know - perhaps there's a limit of how much you can take off? But seeing as the mm or so I'm planning on will not end up forcing the shims to ride on the retainer base, I can't see a problem.

The Stitcher

iTrader: (12)

im sure he will sort things out captain sarcazmo remined me not to ask you for any help

exvaux

iTrader: (1)

yeah i thought it wasnt the best of posts for someone of zen's standing,talking down to the mere mortals like us when all that was needed was a bit of advice,or maybe thats just me

Tim W

iTrader: (1)

Paul may have been a bit abrupt there, but he was a busy bee yesterday!

I hate to say it but your head castings are screwed, too much material has been taken out of the seats and they need replacing, the cost of replacing 16 seats will out weigh the cost of a set of head castings.

Grinding back the valves is a bad idea you go through the hardening and they will wear, quite apart from the resultant collet issues.

Your best bet will be to source another set of castings unfortunately

banny sti

iTrader: (68)

Tim on hand on heart that is no excuse to talk to someone like that, would you do that to someone face to face?

I doubt it very much as you get an appropriate verbal or possibly even a physical response, it is easy to be rude over the internet as there are no repercussion to the actions.

However in Paul's case it does not show him in the best of lights and could affect his business reputation.

Silent running the head castings are same for all models regardless of uk, wrx or sti, so should be cheap enough to pick up some 97/98 head castings.

Banny

silent running

So the only problem then is that the valve stem tips will need hardening again? Not that much trouble surely? I wouldn't mind too much dumping the head castings and getting another set - they were standard UK v4 heads anyway - apart from that my money and time have been spent on these ones. Skimming, hand porting and polishing, recutting seats to spec, equalising chamber volumes etc. That's too much of an investment to throw it away for want of taking a max of 1.4 mm off the end of the stems then hardening them again...

Thanks to those who gave helpful replies; hope you can see where I'm coming from here, I'm weighing up what's best to do and scrapping these heads that have had a lot of work just because of what seems a minor issue, doesn't seem an efficient way to go about things.

The Stitcher

iTrader: (12)

if you do go for new castings i have one but broke the other trying to get pulley off but one is perfect just pay postage and its yours let me know fella

silent running

That is very kind of you, much appreciated. If I need it, I'll let you know!

Welloilbeefhooked

iTrader: (3)

Can't the shims be machined down Nick? Has your local Motorsports place advised on this yet?

Wayne.

silent running

Possibly. If they can be, then that might be worth doing. I was really just wondering whether they would still be strong enough to work, even if rehardened. And there might be an issue with them being a bit loose in the retainers once they were so thin that there wouldn't be much edge on them if you get what I mean, i.e. becoming more of a disc than a cylinder.

Basically I have a few places that can do the work I think. This old local boy who does a lot of engine building and machining in the area, near where I work so I'm seeing him tomorrow. He's happy to shorten and re-harden the tips. Then there's Scholar which is where the valve job and skimming was done, but I used them mainly because they were convenient at the time as a one-stop-shop to get everything done in one go, but they're a bit far away. My local motorsport garage use Scholar for all their machining work anyway so they're just a middle man really. Plus I have another SNetter who has very kindly offered to have a crack at them if I can't get anything sorted out locally.

ZEN Performance

Excuse me?

I didn't have time to post a lengthy explanation of what to do, ESPECIALLY as I had already given specific warnings about what to look out for to prevent such problems, or be aware of them beforehand.

Shims at 1.2mm thick will not work AT ALL in the standard format. You need to machine the retainers and it will not leave enough engagement and leave you running the risk of spitting a shim out.

But fear not. There is a solution, cheaper and less hassle than machining he valves, although you will need to machine the retainers to give clearance on the valve followers. DO NOT GRIND THE VALVE TIPS.

StickyMicky

dam i thought he was winding him up

silent running

OK well that's good to know there is another way. But what is it exactly that I need to do to the retainers? Machine out some of the thickness from the underside face that sits on top of the spring?

My machinist has the valves and is ready to start work on the valves tomorrow unless I tell him to hang on.

ZEN Performance

If your shims targets are in the 1.2 mm range that's a significant amount of material that has come off somewhere. Either someone was too keen machining the seats, or the refacing the valves or both. If we have to machine the seats on a head we normally use new valves and we usually end up with shims in the 2.2-2.3 mm range (note that they are typically 2.4 from the factory).

If you get down to needing shims in the 1.2 mm band you will on some heads need to machine top surface of the retainer so the button on the cam follower does't sit on the retainer itself. You could machine the tips of the valves, and the core material is hard enough to allow this. Depending on the type of retainer used you could fit v5-> valves as they already have a shortet stem (head to collet groove is the same) but I am guessing that's not an option here. However you can't get around the fact that a 1.2mm shim isn't going to want to stay in the retainer for very long, especially with factory springs.

The answer? Top hat shims.

Similar to those used on the v1-2 solid follower heads you can use shims that locate around the tip of the stem. The recess wants to allow for at least 0.25mm collet to shim clearance, and the recess doesn't want to be too tight otherwise you can have the shim jack itself up the valve stem and cause problems. You will end up with about 3mm of engagement of the shim on the valve and you can get away with the thickness in the centre that you need to make it work.

You can buy such shims from Piper cams, but I tend to make my own from ground silver steel stock and harden them afterwards (the steel is made to be easily hardenable with a single quench).

This story is a good example why it's a good idea to do a dummy build of heads so you know what you might have to do before committing to a paticular valve/spring/retainer/shim combination.

bren@apex

iTrader: (20)

Mm, yeah, youd think so. Tell that to my Skylines head where they failed to seat the valve suides properly so the retainers kissed the stem seals on each cam rotation leading to a serious oil consumption problem. Theyd used the measurements for a GTR, not a GTST.

After being told we were talking rubbish we had a drift made up to reseat the guides to the correct position but Scholar had taken so much meat out of the ports that the head actually split when we tried seating the guides. Oil was dripping straight through a hairline crack in the roof of an intake port and turned the Skyline into a serious disco smoke machine! The head was bin fodder.

They then they bucked, weaved, argued and pointed the finger of accusation at us to try to get out of any type of responsibility for the screw up. Absolutely appauling service and attitude towards their customers, disgusting. I dont normally get into this stuff online but that really pissed me off.

Matt578

Top post Paul, your more cleaver than you look

silent running

Not knowing the history of the heads, I suspect now the seats may have been recut once before. To be fair, I did specifically ask for the seats to be cut right back to spec and do whatever needed doing. At least I've got perfect width contact faces!

Shame I didn't do a trial build beforehand, for some reason I built the valvetrain up bar the cams thinking shimming was a hassle I'd leave until later.

Anyway, that's a good point about the button in the tappet, I'd not figured that in my workings out so even if I did shorten the stems I might still need to machine a little off the retainers as well - I'll check how that measures up. Fitting v5 valves isn't something I'd thought of, but yes the numbers check out and it would give me an extra 1.4mm clearance on the inlet and 1.5 on the exhaust putting me right in the zone to use the thicker shims I have pretty much as they are. But that's an expensive option unless there's anyone wants to do a straight swap of a set of STi3/4 valves for a set of STi5/6 - unlikely!

I've already completely ruled out sub-2mm shims. The 1.xmm thicknesses referred to are really only theoretical target thicknesses to help visualise the problem.

Now I've had a look at 'top hat' shims they do seem to be the right solution as I'd like to avoid further machining of my valves or my tappets if I can, but the thing is whether I can figure out what I need from my current measurements...

Taking the Piper shims listed as an example, for £4 a throw, as I don't know what you can offer just yet... 6mm ID are available and anywhere from 3 to 6mm thickness. No idea how close to the collets they'd come down. My collets sit around 4.5mm down in the retainer and as long as the shims were shorter than this there'd be no issues with clearance to the retainer edges; they'll be in clear air so to speak.

However, the thickness of the Piper shims would be way too much. Can you do the same sort of thing then, but to my target thicknesses? I need a single 0.95mm, 2x 1.05mm, 4x 1.10mm, 6x 1.15mm and 3x 1.25mm. Please let me know soon as you can as I need to get these valves back from the workshop assuming I needn't go ahead with the machining!

silent running

That's not good. Problem is, out this way in the wilderness of the East coast, engine building machine shops are almost non-existent and they were the only practical option at the time I needed to get all the work done. Still, looks like we're on the right track now, which is the main thing. I'm hoping to actually be starting her up by the end of October - one more pay day to go which will pay for my new modine oil cooler and a Hybrid FMIC and it'll be ready to install, assuming no further head problems.

ZEN Performance

You can use the piper shims but you need to machine both sides to get the right clearance and sufficient collet clearance, and they are supplied on the basis that they are machine/grind to fit.