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Ls3 / L92 / L94 Intake Valves

 
Old 06-19-2019, 01:45 PM
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Default Ls3 / L92 / L94 Intake Valves

So whatís the deal with all the different 6.2 intake valves?

These are the GM part numbers for each:
Ls3 - 12569427
L92 - 12617533
L94 - 12627970

The L92 valves are by far the cheapest, with the L94 valves being more expensive, and the Ls3 valves being the most expensive at upwards of $25 per valve.

Now, the L92 valve appears to have a single angle, while the L94 and Ls3 appear to have two angles, judging by pictures on RockAuto and eBay. If that is true, are those angles on the valves and valve seats identical between the L94 and Ls3? If so, there shouldnít be anything stopping someone from running the lighter Ls3 intake valve in a pair of bone stock L94 heads, correct?

I have a L94 going in an Fbody, solid roller planning to spin to 7k with spray, possibly up to 7500 off spray. Iím not sure if that necessitates ditching the L94 intake valves and/or exhaust valves for lighter ones, but Iím trying to avoid having any machine work done to this engine if at all possible. Can I just stick with my factory valves? I know itís a rather loaded question, but in general, what can you spin an engine to with these heavier valves? (not going to for sustained periods of time). Iíd rather save my $200 and put it towards a more premium solid lifter or rocker setup if I can avoid valve upgrades, because eventually Iíll end up going with an aftermarket head anyway.

TIA for any info..

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Old 06-19-2019, 02:32 PM
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Real deal ls3 valves are hollow stem, thus the price, but also extremely lightweight for their size.

L92, l9h, l94 valves should all be the same 3 angle profile solid stem stainless valve. There might be some minor changes like manufacturer, but none that Iím aware of.

Last edited by bthomas; 06-19-2019 at 02:41 PM.
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Old 06-20-2019, 01:18 AM
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Originally Posted by bthomas View Post
Real deal ls3 valves are hollow stem, thus the price, but also extremely lightweight for their size.

L92, l9h, l94 valves should all be the same 3 angle profile solid stem stainless valve. There might be some minor changes like manufacturer, but none that Iím aware of.
Yes, thatís what Iím finding now, too.

According to this thread, I should be alright spinning it high as long as the rest of the valvetrain is up to the task..

If I find the valves to be leaky I suppose itíll make more sense to go ahead and upgrade while the machine work needs to be done anyway.
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Old 06-20-2019, 10:09 AM
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Mainly stouter springs to handle the added weight, but better pushrods won't hurt either.
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Old 06-20-2019, 01:44 PM
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While the stock L92 solid valves make great power they eat up spring life pretty quickly. The LS3 hollow stem ( Ferarra made ) weighs exactly the same as the LS3 exh valve and will allow your springs to live much, much longer. On mild lobes 6500 RPM max the L92 valve is fine imo but the LS3 valve is better all the way round the block and up the corner. Theres some places with good prices on them, I think I paid 14ea on my last set price matched through Summit
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Old 06-20-2019, 04:04 PM
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Originally Posted by cam View Post
While the stock L92 solid valves make great power they eat up spring life pretty quickly. The LS3 hollow stem ( Ferarra made ) weighs exactly the same as the LS3 exh valve and will allow your springs to live much, much longer. On mild lobes 6500 RPM max the L92 valve is fine imo but the LS3 valve is better all the way round the block and up the corner. Theres some places with good prices on them, I think I paid 14ea on my last set price matched through Summit
Appears the exhaust valves are the same in the trucks, the part numbers on GMPartsDirect match. Are you just dropping in the Ls3 intake valves in truck heads without machine work? Works just fine?

I'm just trying to stay out of the machine shop. Having a valve job done will lead to me getting new exhaust valves as well. Then might as well have the heads decked. Now have the block deck checked. Oh and might as well have the crank polished and a line hone on the mains since I have a set of ARP main studs kicking around. Now we need new main and rod bearings with the crank journals polished. Hot tank the block and heads, sure, why not...

Thatís how I see that going. 😂

I just want to re-ring this thing, throw in my ARP rod bolts I have sitting around, convert all the valvetrain and throw an Ls3 intake and ATI balancer on it and be done. So I can put together the engine Iíve always wanted while the car is up and running.
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Old 06-20-2019, 04:11 PM
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Plenty of dudes drop em in and go. I do a blue test and lap em in lightly with fine grit compound. I'm talking maybe 10-20 spins by hand on a wood suction cup type lapping tool then I do approx 40-50 laps using clear coat polishing compound. All lightly done it doesnt take much and you dont want to over do the lapping. Then I assemble and test with gasoline poured into the ports and let sit for 4 hours or so and check for any bleed down. if there is some I lap a bit more but with new valves I have yet to see bleeders. On the exhaust side I do the same but the exh valves take a **** kicking so sometimes I reface the exh valves and do the same procedure. The seats in LS3/L92 heads always seem to be near perfect, its the valves that take the abuse. I also give a little port clean up with sanding wheels along with a light bowl blend where the seat meets the port especially needs attention.

New seals and I do a wiggle test on the guides before any of the above to make sure they are not worn out. Even high mile heads with stock cams always seem to have good guides. On higher lift cams the guides get sloppy faster than i would like. Using Psi M1511ml springs now, have used PAC before all good with the beehvies in my experience.
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Old 06-21-2019, 09:51 PM
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Originally Posted by cam View Post
While the stock L92 solid valves make great power they eat up spring life pretty quickly. The LS3 hollow stem ( Ferarra made ) weighs exactly the same as the LS3 exh valve and will allow your springs to live much, much longer. On mild lobes 6500 RPM max the L92 valve is fine imo but the LS3 valve is better all the way round the block and up the corner. Theres some places with good prices on them, I think I paid 14ea on my last set price matched through Summit
I thought stock LS motors are validated for hundreds of thousands of miles?

Some truck exhaust valves are inconel. Iím building heads with stainless LSA intake and LY6 inconel exhaust valves from a 2500 truck, for long term durability if I ever squeeze it later. Auto trans, so 6k rpm limit.
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Old 06-22-2019, 04:11 PM
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The L92 intake valves are inconnel i believe. They are excellent quality valves I have pulled some from very high mile engines now that were still like new. The exhaust valves seem to take all the beating on the contact face mostly. Guide wear has been very little to none on both ports even with high miles. Adding higher lift cams has been eating them up though, 30-50k miles and done.

The only downside to the stock L92 intake valves is weight. They will expire the valve spring life a lot faster than the hollow LS3 valves will. Other than the weight? I believe the L92 intake valves are better quality because inconnel is tough expensive material.
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Old 06-22-2019, 09:40 PM
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Thanks for all the info, cam! Great thread.
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Old 06-22-2019, 11:05 PM
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Inconel is typically used on exhaust valves due to the temperature. Intake valves run significantly cooler as they have fresh air charge flowing across them.
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Old 06-23-2019, 11:28 AM
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Originally Posted by LS7Bird View Post
Thanks for all the info, cam! Great thread.
Happy to help

Originally Posted by FormulaBoat View Post
Inconel is typically used on exhaust valves due to the temperature. Intake valves run significantly cooler as they have fresh air charge flowing across them.
I'm not certain what they are made of but they are stainlessy/nickely in feel, look, and weight. My science fingers told me this
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