From: Bruce White ([email protected])
Date: 16 Aug 2002
Time: 23:35:26
Remote Name: 129.96.230.51
Well I give up! I'm putting it together the way it is.....
What I found in heating the large camshaft bush to 100 degrees C was it got bigger by .001”….. Remember the old heating the washer trick in school? And did the hole get bigger or smaller?? Well I guess I should have realized what would happen. Anyway I then realized that containing the OD of the bearing might cause the ID to reduce so I moved on to plan B. I turned up a “heat sink” out of Ali and pressed the OD of the bush into that. Then I heated the centre of the bush (as best I could) to about the 90 to 100 degree point very quickly and took the measurement again as fast as I could before the Ali “heat sink” started to heat up. Well this time the ID did reduce by about .001”. I would think this would be a worst case example as you would never get this temperature difference between the OD and ID in an engine situation. So a clearance of .001” should most likely be minium on these.
I then went searching on the web regarding oil film thickness……
And after looking at a number of sites, I decided 5 microns sounded like the best oil thickness in a hot engine. One site if you are interested is at: http://www.swri.com/3pubs/brochure/d08/bearoil/bearoil.htm
I then checked a few other car sites with technical data and found…..
- Mercedes 220SB – Camshaft bush clearance max =.1mm (this is .00393”)
- And another engine spec that stated a Max of .004” and a Min of .001” (and suggested you should aim at .002” as the perfect value)
So the exercised proved a waste of time.
Re the fuel Barry,
In South Australia we have 3 solutions……. (This is MY view based on my personal checking with a refinery in Perth a few months ago – so others might like to state something different)
1 - Don’t worry about it as the engine is so low in Compression Ratio it might not mater
2 - Use LRP (lead replacement petrol) at the pumps – this is OK except it does have a shelf life of about 6 to 12 months depending how full your tank is, the temperature etc etc. This fuel is based on Super Unleaded which has more volatile additives then Standard Unleaded thus causing the shelf life problem.
3 - Use Standard Unleaded petrol and a product like Flashlube ever tank or two. This petrol will last for well over a year without causing major starting issues.
Bruce