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Maybe I missed it in the above posts, but the most important spec for a rebuild, especially if boost is going to be used is ring gap.
Boosted engines need a lot more ring gap than NA engines to prevent ring gap closure under high heat and power.
The typical symptom of a top ring gap closing is a broken piston just like in the picture you posted. The gap closes under high heat from boost, then ring drag goes up exponentially, breaking the top piston land. Often the iron cylinder liner is also cracked from the radial pressure of the ring with a closed gap.The solution is at least 0.028", or more gap.
Hot rod Magazine a few years back took a junkyard well used 4.3 LS, disassembled it and reassembled it with all the original parts, then ran almost 100 dyno pulls under high boost, the last few runs at 1,000 horsepower. It held together.
The one and ONLY modification HRM made except adding boost? They increased ring gap to 0.028".
Maybe I missed it in the above posts, but the most important spec for a rebuild, especially if boost is going to be used is ring gap.
Boosted engines need a lot more ring gap than NA engines to prevent ring gap closure under high heat and power.
The typical symptom of a top ring gap closing is a broken piston just like in the picture you posted. The gap closes under high heat from boost, then ring drag goes up exponentially, breaking the top piston land. Often the iron cylinder liner is also cracked from the radial pressure of the ring with a closed gap.The solution is at least 0.028", or more gap.
Hot rod Magazine a few years back took a junkyard well used 4.3 LS, disassembled it and reassembled it with all the original parts, then ran almost 100 dyno pulls under high boost, the last few runs at 1,000 horsepower. It held together.
The one and ONLY modification HRM made except adding boost? They increased ring gap to 0.028".
Looking at .026 gap on the top and .24 on the bottom. Mostly because the forged pistons won't swell like the stock ones.
I don't think I'd want to trust the pan not to leak if I installed it from underneath with limited room anyway. One way or another, I'd be doing that pan install where it's out and easy to get to.
I was just wondering if the wings get in the way when removing the engine. Wasn't thinking about how far it has to go forward to clear the TT input shaft.
It's been a number of years since I was under there with the steering rack removed to do the cam etc,
At any rate, when the 6.2 goes in it will have the LS3 pan, no batwings to get in the way.
Looking at .026 gap on the top and .24 on the bottom. Mostly because the forged pistons won't swell like the stock ones.
It's the ring that swells.
The Wiseco pistons I use in my 5.3 suggest ,007" per inch of bore for turbo or supercharged use.
So in your case .028 for the top ring.
Second ring gap should be bigger to help relieve any trapped gasses.
I think if you do some research, you will find similar info.
I hate filing rings, it's very tedious!
Ron
Last edited by RonSSNova; Jan 16, 2020 at 06:08 PM.
For the steam kit I just bought two truck type front units, a brass "T" and some fittings and made my own.
The stock one wouldn't fit under my Fast intake manifold. I put it on my Nova.
From: Central PA. - - My AR15 identifies as a muzzleloader
I believe in the Beer Fairy
Originally Posted by RonSSNova
I was just wondering if the wings get in the way when removing the engine. Wasn't thinking about how far it has to go forward to clear the TT input shaft.
It's been a number of years since I was under there with the steering rack removed to do the cam etc,
At any rate, when the 6.2 goes in it will have the LS3 pan, no batwings to get in the way.
when I did mine I took everything out the bottom. I did my car at work where I have a shop crane for over top of the lathes. It's on Wheels so I was able to maneuver it over top of the car. It's largely similar to the ones available at Harbor Freight and if I didn't have it I would own one of those in a heartbeat. I was able to use a lifting strap down to a point on each side of the frame I'm simply lift the car while it pivoted on blocks that were underneath the rear jacking points. It works slick as could be. I had an electric hoist hanging from the trolley on the crane and could control it from underneath the car if I wanted to. They were of course jack stands and other things for safety.
I've done two out the bottom so far and I see people talk about them coming out the top but I really don't think I would even try it. Fact is I think you could lift the front of the car enough with a cherry picker to get the engine and cradle out from underneath. When I did my C5 I had the entire Driveline from engine to rear with both cradles assembled before I connected it. Only way to go in my opinion. I had the whole thing on one of those heavy duty Harbor Freight furniture movers and the engine was on a pallet jack. If I can find some pictures I'll post them here.
Looking at .026 gap on the top and .24 on the bottom. Mostly because the forged pistons won't swell like the stock ones.
I have forged pistons gapped at .30 up .28 down. No blow by .and im over 1k 26lbs boost. Just giving info. I have 60k on the engine.
. I have a 6.0 iron. I have stock crank, ls 7 lifters, and rockers arms.
Last edited by helga203; Jan 17, 2020 at 10:31 AM.
Going to a 4.0 crank will likely result in your pistons exiting the cylinder bore just a tad so you should consider a lsx tall block! With your ring gap yada yada ide be sticking with a 3.622 ! or start to brain storm shortening the bottom stroke. I would definitely mention this to your builder and make sure they rotate the engine and check for proper clearance at full drop! You’ll be happy this topic arose !
Last edited by Speedy007; Jan 17, 2020 at 03:25 PM.
A new lsx block build should be cheaper if your willing to take the weight of iron! A aluminum deck height of that same scal might be a 500 addition on !
As you can see the cylinder top have cracked why risk it at that point how long until it disintegrated?
Speedy,
I don't know that it is cracked. The builder said the block looked good and was not cracked. I will have the builder look at the cracks in the picture but I don't think they are cracks. I looked at the picture in detail and they look like the cracks are just on the head gasket material.
If the block is cracked I will not use. However an LSX block is not in the picture as they run about 3700 just for the block.
