Well, I haven't posted in a while since I guess everyone else is as fed up as me. But damnit I'm going to get to the bottom of this.
July, as I said, I took off the pan. Pan seal wasn't great so I resealed it but no bits in the bottom. Tidied up a few things and threw it together with high hopes. I put in an all new set of head bolts at the same time since I didn't like how many cycles I'd done on the others. ARP again of course. All plugs were oil free now (yes, even #6) apart from the one that had always been worst, #7. The bugger. Oily as ever. I was still heading out to the races and I could confirm that it had to be from the heads not the bottom because the car looks clean on a run. But if, for example, I'm on the road and overtake someone I'll get the blue smoke as I coast back down. Or if I leave it running in the garage it will start to do a thin blue haze up in the roof.
September I did a compression test all round which showed that compression in holes hadn't changed. #6 was a little down as it always has been (it's the sleeved one and the one I found that groove in) but, significantly, #7 had as good compression as ever and maybe a teensy bit more. So that really made me think I'm still looking for the problem up top. I checked the valve seal again to make sure it was well seated (remember, I've replaced all the seals twice). Then I took out #7 rocker stud again and gooped it up well to try to seal it. It has been bugging me that I always have to clean up the threads. The stud comes out with a shiny glaze on them. I run a tap on it and the hole and it screws in tight but it felt to me like maybe the threads gaul a little..
Another race weekend, another oily #7. Good thing I have a big bag of spark plugs.. This is really pissing me off now.
I decided to review. Looked over my notes and pictures. One thing I can tell is that my two heads came from slightly different batches I guess. Or went to different machining stations. Both heads have valve cover holes that don't go through to the intake. But passenger head has rocker stud holes that are mostly blind. One or two have a slight crack into the intake runner but for the most part they are practically blind holes. On #2 I even had to slightly shorten the stud threads to stop it bottoming out. Driver's side head the rocker stud holes all clearly poke through into intake runners but #7 is definitely the worst having more than 50% of its area, maybe 60%, open to intake vacuum. I reasoned that it probably is slightly harder to seal since it gets more suction. But still hard to see how it pulls so much oil through either the new well-seated valve seal, the now fully sleeved headbolt hole, or the rocker stud which I put sealer on.
Anyway, I got my caliper out and sure enough the rocker stud hole is pretty deep. There's a good quarter inch of space at the bottom of the stud when it is fully installed. I decided to really go for it and found a rubber plug about the right diameter. I put RTV around it and put it in the bottom of the hole. Sealed up the stud in the normal way and installed. Figured maybe that would do it at last.
It was a while until I could drive again. Headed out to a car meet at the OK Diner on the A19 near me
Anyway, I was chatting there to Daz, who is a cool guy who has a shop in Middlesbrough called DC's Rod and Custom (and is the owner of "Carolina Blue" in the picture) about my struggles and he asked me if the rocker stud hole threads are bare or have inserts. I wasn't sure, now that I thought about it. I'd noticed the exhaust bolt holes had wire-type thread inserts but never paid attention to the rocker stud holes. Since I kept getting silvering on the thread of the stud I assumed maybe they were bare aluminium. He was telling me that they normally don't have much trouble sealing up threads but if I were doing inserts I should get these Wurth Time-sert ones that are solid.
Well, I got back from that meet OK. Took the car out again a few days later and passed a guy. As I coasted back down I saw the unmistakable blue in the rear mirror. Pulled #7 and sure enough...
Well, of course I wanted to burn the car down, really. Only I didn't. What I wanted was the non oil-burning car I had before I took a grinder to my heads...
Anyway. As desperate as all of this felt I'm not much of a quitter. I was thinking that really the one thing I could do -- pain in the arse and cost me a set of gaskets -- is to swap the heads left to right. I'd have to move the water plugs, of course. But I would know once and for all if the oil followed the head or stayed with the hole.
But then I just got kinda depressed because even with all I've done I think it's pretty clear it's head. I started looking at my old pics from the various tear downs I've done this year and I saw pretty clearly that the rocker stud holes do have wire type inserts. Then I did some googling around and looking at these Wurth thread inserts. An idea started to form.
So, here's what I'm thinking:
Valve seals: I'm not buying it. Replaced twice. Seals are seated. Valve stem not damaged. Guides not loose...
Headbolt holes: Clearly were an issue for #2 and #6, both of which stopped taking oil when I got them properly sleeved. I guess the sleeve for #7 could look good and still seep but given the amount of fouling on a short drive... I'm not buying it.
Rocker stud: As many times as I've sealed that bugger it remains my prime suspect..
What if those wire thread inserts are moving and wallering out the aluminium on the back side of the wire inserts when I tighten the stud and they get pulled. Since they are like a spring I figure they can move a fair amount and even stretch and change thread pitch. I guess I could be in a situation where I seal the bolt threads to the insert pretty well and oil can just migrate around behind the thread insert "threads" where I guess it is just getting looser each time I take out the stud and put it back.
So I'm thinking of ordering a Wurth 7/16-14 "Big Sert" kit (it's a "second time" kit which I guess I need because the hole already has a heli-coil type insert) and see if the solid insert seals nicely to the head. Then just thread seal the stud and cross fingers. It's not a cheap option but what do you think? What can I be missing here?
Sam