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L99 to ls3

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Old Dec 16, 2024 | 06:46 PM
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Default L99 to ls3

Long story short, my girlfriends ls3 broke a piston, ordered a low mile engine off eBay, when It gets here, it winds up being a l99. Seller offered a pretty significant refund to keep it. So I was wondering what all I would need to buy to delete the dod, afm, and vvt, keeping in mind I already have a ls3 donor engine. All I should need to buy are lifters and gaskets right? Just use the front cover, timing set, chain damper, valley cover, camshaft, etc from the ls3. Will probably go ahead and slide a small cam along with pushrods and valve springs in it since it will be apart
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Old Dec 16, 2024 | 08:26 PM
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Exchange the cam and entire valvetrain up to the rocker arms, plus valley cover.
You will lose a little compression, but this will regain a good chunk of the power difference.
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Old Dec 20, 2024 | 11:51 AM
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Are the LS3 heads still usable? Keep in mind that the L99 doesn't use the hollow stem valves. I'd swap those on as well. If you're keeping the stock cam, have the heads milled .010" and that will make up for most of the compression loss. Either that or install some .040" head gaskets.
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Old Dec 20, 2024 | 02:00 PM
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Originally Posted by LS1Formulation
......... install some .040" head gaskets.
This would be better as it will improve quench which gives more knock resistance.
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Old Jan 2, 2025 | 01:14 PM
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Originally Posted by LS1Formulation
Are the LS3 heads still usable? Keep in mind that the L99 doesn't use the hollow stem valves. I'd swap those on as well. If you're keeping the stock cam, have the heads milled .010" and that will make up for most of the compression loss. Either that or install some .040" head gaskets.
unfortunately one head is probably trashed, if it can be saved, it’s not in her budget at the moment. When one of the valves broke it must of put a lot of force on the guide because it cracked the head in the port on the side the valve bent towards, didn’t know the head gasket trick, will definitely do that. Thanks

wanted to slide a baby cam in it but decided to do some preventative maintenance type stuff instead. New oil pump, timing chain and damper, crank and cam sensors, gaskets, seals and o rings for everything
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Old Jan 4, 2025 | 10:38 PM
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Don’t want to start a new thread, do the holes in the lifter valley need to be plugged or is that just a gen v thing?
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Old Jan 5, 2025 | 03:40 AM
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Yes, they need plugged, or an LS3 valley cover installed. If reusing the LS3 cover, get new gaskets / o-rings.
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Old Jan 5, 2025 | 07:53 AM
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I didn't see lifter tray exchange on the list. This will be different for DOD versus non-DOD lifter setup.

If you don't use a stock LS3 camshaft, you'll need to re-tune for the upgrade.

A broke piston and valve could mean metallic debris circulated through the engine parts. Be sure to inspect any parts you reuse for damage or debris. You may want to buy new replacement lifters in case there's some inside the old ones.
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Old Jan 5, 2025 | 08:30 AM
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Originally Posted by 68Formula
I didn't see lifter tray exchange on the list. This will be different for DOD versus non-DOD lifter setup.
^ ^ ^ this is a good point. If the LS3 lifters and trays are still in good shape, you could just re-use them in the L99. The trays aren't expensive, so it would be a good idea to put fresh ones in there while you're at it. Just make sure you use a quality brand of lifter tray. Don't get the cheap, flimsy, Chinese crap from Amazon. Those will have you rebuilding the engine again.
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Old Jan 5, 2025 | 11:27 AM
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Only but genuine GM trays
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Old Jan 5, 2025 | 12:55 PM
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Ok so I am using all the engine covers off the blown up ls3, using its cam as it is in good shape still.

parts I’ve purchased are:

delphi lifters
btr lifter trays
btr valley cover gasket
btr head gaskets
btr head bolts
gm balancer bolt
btr flywheel bolts
btr exhaust manifold gaskets
btr intake manifold gaskets
btr water pump gaskets
btr steam vent gaskets
btr stock replacement pushrods (just for freshen up)
gm valve springs (freshen up)
rear cover gasket and rear main seal
front cover gasket and seal
oil pan seal
gm Oil pump
red oil pump o ring
New crank sensor
new cam sensor
btr timing chain
gm tensioner
getting the injectors rebuilt and cleaned

also cleaned all the **** off the valves, lapped the valves, broke all the sharp edges on the heads, cleaned all the gunk and carbon out of intake and exhaust ports, cleaned the tops of the pistons with a small dremel wire wheel and a shop vac and cleaned the hell out of everything

still need to track down an oil cooler gasket and gaskets for where the manifolds attach to the exhaust
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Old Jan 5, 2025 | 05:17 PM
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That's a pretty good list. I would add an oil galley barbell while you're at it. I have been using the BTR brand.
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