A repost about the LS1:
Not related to lower end knock of the LS1 but some reasons for oil burning and piston slap
The LS1 uses a 3.66620 stroke and a 3.8796 bore with a 6.100 rod that makes for a very aceptable 1.6841 rod ratio. But it came at a cost. They stacked the piston rings and reduced the tension of the rings over a LT1 by 30 percent. Why the reduction in ring tension? I am clueless.Did they not test these motors prior to putting them in between the fenders of a car?Certainly they did but supect it was a money/time issue. Just my opinion.
When they moved that ring set up 1.5 mm they knew they were going to have some piston rock with the use of the slipper skirt style piston generally known for poor oil control.The piston weighs 434 grams which is pretty light for a street motor,it came at a cost though.
They have also used a thinner ring set than the normal 5/64 used on the small Chevy and others. I cannot find out the actual width of the ring but think it to be probably a 1/16 top and second ring which is usually reserved for race motors. That there and the combinations of the 30 percent less spring tension plus a little piston rock is going to burn some oil.I have found the static compression of these engines but do not know the nominal compression which might help in knowing why they reduced the ring tension
The piston speed is not a factor on the LS1 motor. At 6000 RPM it is moving a mere 3662 feet per second.
The fix? Spread the rings back to normal and use the KB method of running the oil control ring through the piston pin hole with a pin in the piston to stop rotation plus a different skirt for less rock, clearanced for the rod and to get the ring tension back up to the norm and a more streetable width for oil control.A 5/64 ring with proper tension will not flutter at 6500 rpm if all else is correct.
Other ways to fix would to be to use a shorter rod and custom piston except that would decrease the dwell time at or near TDC and effect computer/injector timing,,too much to tackle imo for a warranty fix given emmissions
It is not exactly a "shaker motor". The rod ratio proves that but if rounded off a bit it is 3.700 stroke-3.900 bore which is getting close to being a square 345.69 ci motor as opposed to the 350 Chevy which is 3.480 stroke-4.00 bore and used a 5.700 long rod which is a stroked 327 motor.
They were relying on relative good cylinder head flow to off set this and gearing to offset the affects of that long rod and the power band a rod of that length in a motor of this size is usually operated in. In my opinion they would have been much better off to use a 5.700 Powdered Metal rod and a bit larger bore with a better piston design.
I understand GM has offered a "fix" for this in a new piston and or ring set. Can someone tell me what this consists of? Hopefully it did not include the new style tapered face ring?
These are just some thoughts I have without digging into it all too much as I doubt I will ever own one of these motors so no more digging for info and of course,opinions will as usual, vary
Is this a terrible engine? I don't think so but in my opinion they could have bettered it.)
When I said I am clueless on the ring tension I meant they should have known what would happen imo ,,I understand now the "fix" does not incorporate any type of ring pinning to stop rotation.
Every early small Chevy I have tore down with high miles and burning oil had the rings aligned on 4 or so of the 8 pistons. Something to think about when trying a cleaner to fix a consumption problem
When you see a 383 using oil, much the same is happening and alot of them do use oil
[ October 10, 2002, 10:56 AM: Message edited by: dragboat ]