jonbill

Rebuilt engines need the zddp protection more if anything. Older engines I think may have a degree protection from work hardening.

Ah, interesting. Is that with that middle carb disconnected from the linkage? If so, I'd suggest something in that carb is binding as it heats up and the metal expands. Could be the throttle plates themselves (need recentering) or possibly the shaft or bearings.

When its hot and acting up, can you still close the throttle plates with your fingers?

That makes sense.

Sounds like a simple case of the map not supplying enough fuel as you start to put it under load. Increasing fuel pressure will make it richer everywhere - doesn't it offer more precise tuning?

That is a fantastic job.

Clearly the internal return spring on that middle carb isn't doing its job. Either the spring is weak or the throttle shaft or plates are binding. If you disconnect the internal spring, you'll be able to feel whether there's any binding. Even without fixing the problems on the individual carbs, the linkage with a strong spring should be able to pull all throttles closed. If it can't, and it's not a throttle stop on the linkage limiting it, then I would think the carbs aren't balanced perfectly and one of the other carbs has reached its stop earlier and is preventing further movement of the linkage.

Sounds like you just need stronger/more return springs.

I imagine Haltech are expecting it to run with paired injectors so it doesn't need to know the cam's position. AIUI there's not much advantage to sequential. A little better on economy I think. I'll be converting mine to EFI with Speeduino this winter with paired injectors.

You can get custom made springs Ali for not too much. Less than those Eibachs I expect. Springcoil.co.uk made mine. They even let me send them back a couple of times for just carriage cost (because I mis-specced them)

That sounds a good candidate to me. I've had a couple of toyota engines with stuck oil control rings that used a lot of oil, but didn't smoke. The one I had that smoked had knackered valve stem seals. Does the engine have a modified cam and big lift?

Perhaps: There was an incident in the engine that blocked something that drove oil pressure up. That caused something else to deliver oil into the combustion Chambers, even after the original high pressure incident is resolved. I can't imagine how high oil pressure could damage valve stem seals or oil control rings. I can imagine high oil pressure might damaging the head gasket and leak oil into a couple of Chambers, but hard to think how that might make all cylinders equally sooty.

I read it as: Oil pressure was observed to be "high", relief valve was removed or Modified and then it started smoking.

Does it smoke at idle or only at higher revs? What colour smoke? The idle relief should do its job before 80 psi.

Those pics don't really look like an oil burner to me, unless its only just started. It just looks like it's been running too rich.

I think that's better. The Webers will be happier with more static advance. You could go even further and take out a few mm of range in the centrifugal advance limiter.

I used to use a pertronix igniter and it had similar misfire problems over 6k. I'd try a 280zx distributor if you can borrow one from somebody near.

Thanks, very nice.

Is that the AZC kit? Looks good.

Running different jets in different venturi is only masking the real problems, if it helps at all. I think you have a couple of different problems. I bet they're not balanced properly which will cause the idle problems, and secondly the main circuit isn't starting right at the limit of the progression holes so goes lean before the main circuit starts. The bigger idle jets fill the gap there but it'll be rich during the progression phase. Smaller chokes or perhaps changing the emulsion tube will get the main circuit to start earlier. Which emulsion tubes do you have?

This can take up a lot of slack: https://www.rhdjapan.com/kameari-l-type-twin-idler-gear-earl-s-blue-l6.html

None of it sounds like the diff to me - diff clunks and bangs are a deeper note. This is more like something hitting the exhaust. Maybe.

Is the sound constant? Does it change depending whether you're going straight ahead or turning? Is it speed related or does change when you change gear? Can you post a recording? I'd describe a diff with the pinion shaft moving in the housing as sounding like a wheel of fortune. But that won't be constant, and would imply that you've got two dead diffs.

I meant skimming [emoji4] yeah, I wasn't 100% sure whether it retarded or advanced. Having thought again I agree with you, it'll retard it.

Any amount you change the cam height affects the timing. Slimming the head a small amount I think advances the timing a small amount. This can be adjusted for with the 3 dowel jokes on the sprocket, or an adjustable sprocket. The limit of this is the amount of chain Slack the tensioner can take up which may be somewhere around. 75mm for the standard tensioner. Cam tower shims aren't the only remedy for it though - there are alternate tensioners you can get (from Kameari for example) which can handle more Slack in the chain.