22 replies to this topic

[Nev]

Once every 6 month oil change isn't so much in the grand scheme of things, I change mine every 1000 miles or so as my engine is more highly strung. After circa 30 oil changes I can do a change in about 15 minutes now. I expect you'll be a pro changer too soon :)

Edited by Nev, 05 June 2015 - 07:01 AM.

[siztenboots]

it would be worth getting an analysis of your oil Nev, just to see if oil scraper rings are doing their job and check the bores and see what the rings are like. you put uprated main bearings in the build so it would nice to know how they are doing

[Nev]

it would be worth getting an analysis of your oil Nev, just to see if oil scraper rings are doing their job and check the bores and see what the rings are like. you put uprated main bearings in the build so it would nice to know how they are doing

 

I would like to, but finding somewhere is the problem. When I rang round I got crazy quotes or simple dis-interest from large scale commercial places.

 

Overall the engine is making reasonable vacuum on coasting (18 inch/Hg at 3000 rpm coasting down a hill), this has improved from the initial build. I still get a good deal of blowby (compared to a factory engine) but for a highly strung race engine that has to cope with huge temperature variation on the pistons I think it's quite acceptable. The piston to bore gap is something like 80% more than OEM from memory, so if the engine is just being used to potter along the pistons + rings don't get to swell enough - this is when there is more blowby and occasionally after cruising at 70 say I can get a puff of smoke out of the back. Once you start booting it for 30+ seconds the pistons + rings get to swell to the intended operating size get hot enough to fill the bore, and vacuum/compression increases on my gauges.

 

I use super cheapo 20w50 old skool mineral oil and just change it very often. It still smells of fuel and dilutes, but with 1000 mile intervals, the fur on the magnetic sump plug is pretty minimal. I adopted this policy when I found fully synth oil was glazing the bores and stopping the rings from bedding in.

 

Overall the engine prefers being properly hammered at high loads and high RPM, sitting in traffic and coasting around at low RPM simply doesn't do it any favours in my experience.

 

My AFR at start up is about 12, which strikes me as a bit rich, I think this is main reason for the petrol getting into the oil.

 

The bearings are fine, there is no glitter/gold/bronzy residue in the sump.

Edited by Nev, 05 June 2015 - 08:28 AM.