So now that the cylinder head is all lovely again, it's got to go back onto the block. First thing was to clean the block surface in readiness for the new head gasket, so I've used a razor blade and gasket stripper spray to clean the few spots where there was some residue from the old gasket. One theory that Tony Knight had for the gasket blow was that I had used coolant in the first fill of the radiator after the 2009 rebuild. Coolant has wetting agents to break down surface tension and improve heat transfer, but the wetting agent can also wick into the new gasket and soak it. That can create a leak path later. Makes sense to me, but it also means that we should make sure that everything is clean and dry before reassembly for the same reason.
I then cleaned out the head bolt holes with a tap, to get any crud out.
In readiness for these! ARP head stud kit.
Another possible theory for the gasket blow were that the old oem head bolts had gone soft. When you tension the head bolts down on a cylinder head, the thing that provides the clamping force is actually a slight, elastic stretching of the head bolt material. It's quite possible that after several decades, and at least one rebuild, that the bolts have lost their elasticity and so don't provide good clamping force anymore. Well anyway it seemed like good insurance to replace the oem head bolts with the ARP stud kit, which as you can see, is a stud and nut, rather than a bolt. First you install the studs, which screw in just by hand.
Then on goes a new OEM gasket, to suit the 89mm overbore that Hako has (I got it from
http://www.swmotorsport.com.au/ and suspect it might be a factory gasket for an LD diesel)
This actually means that refitting the head is a bit more tricky, since you have to carefully thread all those studs into the head. The holes in the head are 10.5mm, and the studs are 10mm, so it's a very snug fit, and some of my mates were kind enough to come and lend a hand. The cylinder head isn't that heavy, maybe 20kg or so, but it would have been a challenge to lift it over the fender and then work out how to slide it on over the ARP studs! So it really does make it a lot easier if you can snaffle a few guys (preferably with long arms and good upper body strength!) to help. But once the head is in place, it does slide into position very satisfyingly on those ARP studs.
ARP's instructions for torquing up the studs are pretty specific. You have to follow the factory pattern for torquing up the nuts (which is basically...start in the middle and work outwards) but ARP recommend torquing up in 3 steps of 20ft-lbs, working up to a final torque of 60ft-lbs.
And you have to use a special lube provided with the stud kit. The theory is that often, torquing up oem head bolts to 60ft-lbs doesn't actually give you 60ft-lbs of clamping force. Friction in the threads will account for some of it, as well as losses from the twisting of the head bolt against the block threads. So the ARP system of using studs eliminates most of that friction, and the supplied lube means that the friction experience between the threadsm nut and washer are consistent with the amount of friction that ARP has factored into their 60ft-lbs recommendation. Sounds good to me, and so the stud kit should in theory improve the head clamping, even if it's just from better/fresher materials. I don't want to do this again, so I was happy to try out every theory I heard of to make the engine better!
Once the head's all torqued up, the cam sprocket can be refitted, and the chain wedge pulled out. The sprocket went on easily, so thankfully the chain wedge did its job and the chain stayed put during the couple of weeks that the engine was all apart. You might also see the paint marks I made on the sprocket and chain to help in reassembly. Oh and yes for all you L-series guys out there, yes I did forget to refit the big washer onto the cam sprocket bolt, I fixed that after I took the photo
The next step is to refit the manifolds, and I've used a "bigport" gasket from Stewart Wilkins. He's got this process where he can stamp bigger holes into regular gaskets, to suit L-series heads which have enlarged ports.
The headers, which I painted in POR15 Black Velvet, have held up surprisingly well over the years, so all they needed was a wipedown.
The inlet and exhaust manifolds share a stud in a few spots, where you use a "bridge washer" to tighten down both manifolds. Because the exhaust flange is a little thicker, I made a step in the bridge washers.
The step allows the nut to sit flat on the bridge washer, which otherwise would have sat at an angle. The nuts are only torqued to 12ft-lbs, which isn't very much, but then again the 8mm studs aren't the strongest design.
Before the carbs go on, you have to fit these rubber softmounts, which insulate the carbs from engine vibration. By rights these shouldn't be recycled, but the rubber was still soft and pliant, so I figured they were good for another go.
The softmounts mean that you can't bolt down the carbs with conventional nuts, so you use these, which are a combination of rubber washer, metal cup washer, and nylock nut.
You tighten the nut so that the rubber washer squashes up a little bit, but not too much that the carb is deprived of movement.
Under the carbs go the heatshield, which might not look like much, but actually does a lot. The Webers sit directly above the headers, but I've never had any issues with fuel vaporisation or hot starting. Remove that heatshield and immediately you start to have problems.
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datsunfreak wrote:
No Kev, you are eating a duck fetus.
