[MacDaddy]

Lokidog wrote:

Actually I think MacBear may have a point with the oil grade. Most newer engines run on a lighter grade oil. A freshly rebuilt engine shouldn't need to run on 20w50. Especially if it has a later model head.

I use to run 20w50 before my rebuild. Post rebuild I have only used a 15w40.

I also wouldn't think 5-10mins of warming up an engine would glaze the bores. Not unless this was done while the engine was still bedding in, during it's first 1000k's.

Just back on the Oil thing...
Mineral Oil is recommended for older engines, that are not used in harsh conditions...

Semi-Synth Oil offers high performance engine protection, in newer and alloy engines, and is the best choice for hard driven cars, like a Zook !

Fully-Synth offers Ultimate protection for newer, and alloy engines, for use in High Performance Engines...

The Hayes Manual recommends using Semi-Synth, or a High Performance Oil...

I think you should really consider using a Semi-Synth 15W 40 in your engine after a rebuild, as i really dont think the 20W Mineral oil is giving your engine good lubrication and protection, especially as its a high revving Zook.... i wouldnt use a straight mineral oil in any of my Zooks now, Semi-Synth all the way !

[royce]

what do I put in a hard worked old engine then (better google before you answer too )

there is nothing high tech in a g series engine, other than my own observed habit of liking to burn really shit SG grade oil there is no need to use a synthetic oil in them, might keep stable for longer but no NEED

[alien]

yeah i think we can argue forever on which oil is best - but either way the difference in engine life running mineral or semi-synth might be 3 years over 30 years... not stuff rings 3 months =)

[royce]

incidentally will the mob that assembled it know what the bore and ring gap measurements were? would be easy to see where the problem was once its pulled apart.

[alien]

yeah ill leave that up to them - but i'll bring all these things up when i take it in just in case i get an "ohhhhhhh yeahhhhhh" response on one of them =) I doubt they wrote down measurements when they assembled it.

[alien]

OK... good news!!! You're all wrong... lol

The valve stem seals had hardened right up and have been replaced (must have been a dodgy batch) and 4 of the valve guides were outside of tolerances... so it wasnt rings at all.

Runs much better now!

[JrZook]

alien wrote:

OK... good news!!! You're all wrong... lol

The valve stem seals had hardened right up and have been replaced (must have been a dodgy batch) and 4 of the valve guides were outside of tolerances... so it wasnt rings at all.

Runs much better now!

So it was related to the jimny head the whole time (valve stems)? Thought it was only blowing smoke under load? Mmmmmmmmm weird. Still the rings lasting only 9000k's on your previous rebuild has me concerned Well lets hope its fixed once and for all now.

Dan

[alien]

Yeah it was... the previous time doing rings may infact have still been the head, it just had all the symptoms of rings.