LS Break-in....
05-29-2007, 08:10 AM
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LS Break-in....
Last week I got my new LS (Q40) engine and yesterday decided I should get going on the break in.. The few neighbors I have were thrilled 
First I tore it down and checked the spacing on the engine. It was set at .190 @ .020.. I decided to raise the deck to .193 and the head to .023 to start with.. The prop is a 7.4X8 cut down to about 6.25" per the instructions on the Pspec website..
Anyway, the first run I left it pretty rich, about 22K and pinched it a few times.. I know everyone said that it should be around 27K with this prop but I thought I would leave it low on the first tank and the needle seemed to hold there pretty well.. So, on the second tank I brought it up to about 26.5 or so but I couldn't get it to hold the needle, it was either too rich or it would want to "run on" (28K +) and I would have to put my finger over the venturi to slow it back down.. As I got a few more tanks thru it things seemed to settle down a little but it is still really peaky.. I made some calls yesterday afternoon and the general thought was to raise the head a little more.. When the needle stays put for long enough to pinch it up to peak it's hitting in the low 29K range.. At this point it has about 50oz of fuel thru it..
I'm just wondering if anyone else is seeing/has seen something simular or should I start looking somewhere else other than the spacing, fuel tank, lines, etc..
First I tore it down and checked the spacing on the engine. It was set at .190 @ .020.. I decided to raise the deck to .193 and the head to .023 to start with.. The prop is a 7.4X8 cut down to about 6.25" per the instructions on the Pspec website..
Anyway, the first run I left it pretty rich, about 22K and pinched it a few times.. I know everyone said that it should be around 27K with this prop but I thought I would leave it low on the first tank and the needle seemed to hold there pretty well.. So, on the second tank I brought it up to about 26.5 or so but I couldn't get it to hold the needle, it was either too rich or it would want to "run on" (28K +) and I would have to put my finger over the venturi to slow it back down.. As I got a few more tanks thru it things seemed to settle down a little but it is still really peaky.. I made some calls yesterday afternoon and the general thought was to raise the head a little more.. When the needle stays put for long enough to pinch it up to peak it's hitting in the low 29K range.. At this point it has about 50oz of fuel thru it..
I'm just wondering if anyone else is seeing/has seen something simular or should I start looking somewhere else other than the spacing, fuel tank, lines, etc..
05-29-2007, 08:37 AM
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RE: LS Break-in....
It's got to get better than it is, doesn't it?? I think I'm going to push the head up to .025 and see how it goes.. If the needle's too soft I'll start bringing it back down..
06-08-2007, 01:24 PM
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RE: LS Break-in....
Just got back from lunch where I tested out my new head spacing.. It was 100% improvement on the needle.. Held a steady RPM, went up on the pinch and came down where it was on the release.. It did that thru 2, 8oz tanks of fuel.. Perfect!! Now I just have to get the plane done to put it in 
