Rebuilding head, missing camshaft caps

[420sxse]

I got a used head and cams (ka24de) from someone on these forums, and my machinist says they (the block and cams) look to be in good shape for a rebuild, but I didn't recieve the caps that hold the camshafts on (there are 12, correct?). Anyway, he said that is a problem, and because of the way the engine is made, I can't use some off a different head as there are variances in the size because of the way the engine was put together in the factory. He said he can't do the work necessary to use replacements and doesn't know how much it would cost. Is this correct for this engine? What would need to be done to replace them, and how difficult/expensive is it? Where would the differences be? In the journal that fits over the shaft? the overall height? Thanks.

TravisD

[DAEDALUS]

That is pretty much the case for all journal bearing caps. When manufactured, the caps are bolted on tight and then they drill a nice very precision hole down the center through all bearings for the cam to sit in. There is about .002" of clearance between the camshaft and the bearing caps at all locations, which is about 1/2 the thickness of a sheet of paper. (If there was no clearance, the cam wouldn't turn, and if the clearance is too big, the oil pressure would drop too low.) But when they drill the holes in the caps for the bolts, they're put in much looser, maybe to within a tolerance of .005 or .010". But it's OK since they're drilled first, before the camshaft hole is drilled. But once everything's done, it's locked in. There's no swapping caps because each cap uniquely matches the profile of the other 1/2 bearing at it's location. A machine shop could probably open everything up and put in graded journals, but I think this would cost more than finding another pair of used heads.

[420sxse]

Well, that was a pretty good and detailed explanation. I wanted to make sure it was absolutely necessary before I asked the guy to go on a hunt, but he's looking for them now. I just hope he can find them all.

Thanks,TravisD

[s13sr20chris]

let me just say that daedalus is absolutely right.

on the other(more ghetto) hand...i have seen cap swapped in every which-a-way. its bad, stupid, wrong, etcbut i have seen it done luckily with no PERCIEVABLE adverse effects. dont do it.

[DAEDALUS]

Yeah I've heard of it too. Probability says there's a really good chance you won't be that lucky. You maybe could sit down with a crate of bearings and find 6 that work, but 6 out of only 6 very unlikely. If you drag your fingernail across the seam of the 2 halves it should feel as smooth as glass. If you feel the ridge at all it's no good.There is a difference here though--if you take 6 bearings from the same engine then there is a better chance they'll work, because they were all drilled at roughly the same time, possibly with the exact same tooling. But variations in the machines and tools occur over time, and across assembly lines, so using 6 bearings from another engine is an entirely different situation statistically.