L92 Power Handling
06-01-2009, 10:56 AM
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L92 Power Handling What can the stock L92 parts handle as far as power? I picked up an L92 that had the somewhat common valve problem which took out a piston/rod and head. The crank looks great but I will have it polished just in case and the cylinder only needs a hone. My question is, I am at the point where I do one of the following:
1) Buy 1 stock piston/rod set-up and do a stock rebuild, maybe some upgraded rod bolts
2) Buy 8 new rods/pistons, aftermarket and keep the stock crank
3) Buy a complete rotating assembly and rebuild aftermarket
I would like to keep this somewhat on a budget and I really don't care one way or another about stroking it. Since one head was trashed, I was going to pick up a set of CNC heads and run the VVT with wither Comps new phaser cam kit, or Mast. Down the road, I *might* have some fun with it and throw a small power adder on it, but nothing crazy.
So what are the safe power limits on the stock parts? I think I have read a couple times that the LS cranks are good to pretty high HP levels and some people have kept the crank and just done rods/pistons. Any input or thoughts on which route to go?
1) Buy 1 stock piston/rod set-up and do a stock rebuild, maybe some upgraded rod bolts
2) Buy 8 new rods/pistons, aftermarket and keep the stock crank
3) Buy a complete rotating assembly and rebuild aftermarket
I would like to keep this somewhat on a budget and I really don't care one way or another about stroking it. Since one head was trashed, I was going to pick up a set of CNC heads and run the VVT with wither Comps new phaser cam kit, or Mast. Down the road, I *might* have some fun with it and throw a small power adder on it, but nothing crazy.
So what are the safe power limits on the stock parts? I think I have read a couple times that the LS cranks are good to pretty high HP levels and some people have kept the crank and just done rods/pistons. Any input or thoughts on which route to go?
06-01-2009, 10:39 PM
#3
Budget? Forged pistons,stock rods, arp rod bolts, and have it balanced. If you got another 4-500 bucks then do a set of rods. The strength of stock L92 heads are about the same as stock LS1/2/6 heads. Get a nicer set of valves (hollow stem) for the l92's
06-02-2009, 12:34 AM
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Well I was going to run a set of CNC'd L92's from either TSP or SD since the dropped valve trashed one of the heads.
Since I have one destroyed piston,
and one bent rod,
At a bare minimum I need to buy 1 stock rod and piston. Or do I buy 1 stock rod and all new forged pistons? Or forged pistons and rods using the stock crank? Or a complete forged rotating assembly?
I would like to stick to one of the first two and save the $1000 on the crank because I feel that if I am realistic with myself, an all forged rotating assembly might be way overkill for my power levels. With my current LT4 build, I made the mistake of going WAY overboard on the engine, and never even came close to the power levels that it was built to handle...Oliver rods, Oliver billit mains, Cola crank, JE custom forged nitrous pistons, and the list goes on...
But what are the stock pistons/rods good for? What is the stock crank good for?
Since I have one destroyed piston,
and one bent rod,
At a bare minimum I need to buy 1 stock rod and piston. Or do I buy 1 stock rod and all new forged pistons? Or forged pistons and rods using the stock crank? Or a complete forged rotating assembly?
I would like to stick to one of the first two and save the $1000 on the crank because I feel that if I am realistic with myself, an all forged rotating assembly might be way overkill for my power levels. With my current LT4 build, I made the mistake of going WAY overboard on the engine, and never even came close to the power levels that it was built to handle...Oliver rods, Oliver billit mains, Cola crank, JE custom forged nitrous pistons, and the list goes on...
But what are the stock pistons/rods good for? What is the stock crank good for?
06-02-2009, 04:45 AM
#6
This all comes down to how much money and power you want to make. Buying a cheap set of forged rods for around $350 and put in a set of pistons at the same time is the best budget and longevity option. A 4 inch crank will make more power.
The stock crank is good for more power than you sound like you will be throwing at it. they tend to flex around 1000 horsepower, but I've seen others push more through them.
The stock crank is good for more power than you sound like you will be throwing at it. they tend to flex around 1000 horsepower, but I've seen others push more through them.
06-02-2009, 10:06 AM
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The guy I got the motor from works at a local dealership and he said that there was a run of the heads that had an issue with either the retainer or locks breaking, causing the valve to drop into the cylinder. This motor was the 3rd Escalade they had done at that dealership. Maybe common isn't a great word to use, but apparently it isn't just a fluke.
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06-02-2009, 10:37 AM
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This all comes down to how much money and power you want to make. Buying a cheap set of forged rods for around $350 and put in a set of pistons at the same time is the best budget and longevity option. A 4 inch crank will make more power.
The stock crank is good for more power than you sound like you will be throwing at it. they tend to flex around 1000 horsepower, but I've seen others push more through them.
The stock crank is good for more power than you sound like you will be throwing at it. they tend to flex around 1000 horsepower, but I've seen others push more through them.
What is a good set of rods to run? I have not seen much for less than $600 or so...I was looking at the Compstar rods, or eagle H-beams with Diamond pistons.
06-02-2009, 10:54 AM
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The guy I got the motor from works at a local dealership and he said that there was a run of the heads that had an issue with either the retainer or locks breaking, causing the valve to drop into the cylinder. This motor was the 3rd Escalade they had done at that dealership. Maybe common isn't a great word to use, but apparently it isn't just a fluke.
06-02-2009, 02:00 PM
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I think it is the locks that were letting go. Must have gotten a bad group of locks because I guess it is only an issue in a certain run of the engines. I am not sure if that bleeds over into some of the complete heads available from GM or not...
06-02-2009, 02:44 PM
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I was about to say bad locks myself.
As far as max power the heads can handle - multiply the cfm per intake port * 2.05, which will give you a max HP reading without a power booster. L92 heads flow well over 300cfm stock - have seen a lot of 6.2L builds in the 550 to 575hp range with stock rotating assembly. No idea of durability besides the dyno pulls though.
As far as max power the heads can handle - multiply the cfm per intake port * 2.05, which will give you a max HP reading without a power booster. L92 heads flow well over 300cfm stock - have seen a lot of 6.2L builds in the 550 to 575hp range with stock rotating assembly. No idea of durability besides the dyno pulls though.
06-02-2009, 05:53 PM
#14
Anyone else have any information on this " L92 valve drop" problem? I wonder if it might be valve float dislodging the locks. Are the retainers snapped or cracked on any of the examples so far? The retainers aren't really L92 specific and have had years of reliable use. The only thing L92 specific would be the larger valve that might lend to valve float.
06-02-2009, 08:15 PM
#15
That is the kind of information I am looking for. I figured that the crank was the strong part of the system and would be fine for my plans, if I am realistic with myself.
What is a good set of rods to run? I have not seen much for less than $600 or so...I was looking at the Compstar rods, or eagle H-beams with Diamond pistons.
What is a good set of rods to run? I have not seen much for less than $600 or so...I was looking at the Compstar rods, or eagle H-beams with Diamond pistons.
The crank is not an issue of strength, but rather power. You obviously aren't trying to set any crazy records so a stock crank would be fine with the power you are going to be making. The thing is do you want to spend the money on the added power of a 4 inch crank? That is up to you to decide.
06-02-2009, 08:40 PM
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If you are trying to do this on a budget buy a set of SCAT I beams for $300 and put a set of forged pistons in the car. SCAT sells them in stock length for either a .945 or .927 pin. They'll be more than adequate for the amount of power you'll be putting down.
The crank is not an issue of strength, but rather power. You obviously aren't trying to set any crazy records so a stock crank would be fine with the power you are going to be making. The thing is do you want to spend the money on the added power of a 4 inch crank? That is up to you to decide.
The crank is not an issue of strength, but rather power. You obviously aren't trying to set any crazy records so a stock crank would be fine with the power you are going to be making. The thing is do you want to spend the money on the added power of a 4 inch crank? That is up to you to decide.
06-02-2009, 08:44 PM
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Anyone else have any information on this " L92 valve drop" problem? I wonder if it might be valve float dislodging the locks. Are the retainers snapped or cracked on any of the examples so far? The retainers aren't really L92 specific and have had years of reliable use. The only thing L92 specific would be the larger valve that might lend to valve float.
06-02-2009, 08:57 PM
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I got one the same way. My L92 broke the valves for #7 and sent debri into #3 also, but rods were still good. I put in two new GM pistons @ $26 each and a new head (complete) for $500. I just need a harness and a few more things to put it into a G-Body.
06-02-2009, 11:13 PM
#19
That is the closest comparison you are going to find. There was also an increase in the bore size, but everything, but the bottom end is the same.
06-03-2009, 10:45 AM
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https://ls1tech.com/forums/dynamomet...mm-tb-mix.html
That is the closest comparison you are going to find. There was also an increase in the bore size, but everything, but the bottom end is the same.
That is the closest comparison you are going to find. There was also an increase in the bore size, but everything, but the bottom end is the same.
