Reusing parts from 5.7 for lq4 build advice plz!
11-16-2016, 01:38 PM
#1
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Reusing parts from 5.7 for lq4 build advice plz! hey guys needing some insight into a potential build, so my 5.7 **** the bed I believe I spun a bearing I was beating on it pretty good one day then when I shut the car off and turned it back on I had no oil pressure and after 15 sec I could hear the top end valvetrain starting to knock. So I shut it off turned it back on and oil pressure came back and noise went away. Drove it a mile and shut it off and oil pressure once again non existent and valvetrain once again starting knocking hard so I left it off and didn't bother to turn it back on. Drained the oil and found silver metal shavings In the oil and opened the oil filter only to find more shavings in there.
so fast forward I just picked up an lq4 block with rotating assembly for $360, guy told me it was from a running 01 Silverado, it turns over by hand find there were no heads on it and it was very clean so I grabbed it. Well stupid me didn't even think to check the crank and come to find out it's the longer crank 😡 So my question is I'm going to be tearing apart both motors, I am just trying to get this car back on the road and trying to keep it in a budget I'm looking to see if I get the lq4 cleaned up if the crank from the 5.7 can be salvaged and just reuse the lq4 rods and pistons with it? Also the 5.7 had prc 2.5 ls6 heads and a tsp v3 cam that I would also want to reuse if they can be salvaged. Would the 5.7 crank be ok to use with the lq4 rods and pistons?
so fast forward I just picked up an lq4 block with rotating assembly for $360, guy told me it was from a running 01 Silverado, it turns over by hand find there were no heads on it and it was very clean so I grabbed it. Well stupid me didn't even think to check the crank and come to find out it's the longer crank 😡 So my question is I'm going to be tearing apart both motors, I am just trying to get this car back on the road and trying to keep it in a budget I'm looking to see if I get the lq4 cleaned up if the crank from the 5.7 can be salvaged and just reuse the lq4 rods and pistons with it? Also the 5.7 had prc 2.5 ls6 heads and a tsp v3 cam that I would also want to reuse if they can be salvaged. Would the 5.7 crank be ok to use with the lq4 rods and pistons?
11-16-2016, 01:56 PM
#2
It should bolt up.
To me, balance is the risk. What I've figured out is that GM very closely weight-matches their rods, pistons, etc. and balances the cranks to those weights. The rods are probably about the same weight but the larger pistons in the LQ4 most likely weigh more than the LS1 pistons. How much more? IDK. I do think that the different piston weight would necessitate different balancing of the crank. I would weigh them and see. If the weights are significantly different, I think it would run, but likely have some bad vibes.
Short answer is that it should bolt together but you probably need to have the assembly balanced.
To me, balance is the risk. What I've figured out is that GM very closely weight-matches their rods, pistons, etc. and balances the cranks to those weights. The rods are probably about the same weight but the larger pistons in the LQ4 most likely weigh more than the LS1 pistons. How much more? IDK. I do think that the different piston weight would necessitate different balancing of the crank. I would weigh them and see. If the weights are significantly different, I think it would run, but likely have some bad vibes.
Short answer is that it should bolt together but you probably need to have the assembly balanced.
11-16-2016, 02:10 PM
#3
Restricted User
There isn't exactly a major problem using the long crank. You would at the MOST just need to change the flexplate.
That's a lot easier than swapping to a crank that had spun a bearing.
That's a lot easier than swapping to a crank that had spun a bearing.
11-16-2016, 02:39 PM
#6
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I apologize I did forget to specify that this is an a4 car, so basically could I use the flex plate from the 5.7 and a spacer to mate it to my 4l60e? And if so what exactly would I need to make that happen?
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11-17-2016, 12:13 PM
#8
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11-17-2016, 12:53 PM
#10
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11-17-2016, 03:01 PM
#11
Did you check the part number on the crank? 01+ Lq4's don't have the longer crank. If you do in fact have the longer crank, the part number is 12552215 and is located on the crank.
Im in the same boat on whether or not to use the stock long crank in my build and a shorter crank that I picked up, I'm just worried about everything balancing properly with the short crank.
Im in the same boat on whether or not to use the stock long crank in my build and a shorter crank that I picked up, I'm just worried about everything balancing properly with the short crank.
11-17-2016, 04:38 PM
#12
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Did you check the part number on the crank? 01+ Lq4's don't have the longer crank. If you do in fact have the longer crank, the part number is 12552215 and is located on the crank.
Im in the same boat on whether or not to use the stock long crank in my build and a shorter crank that I picked up, I'm just worried about everything balancing properly with the short crank.
Im in the same boat on whether or not to use the stock long crank in my build and a shorter crank that I picked up, I'm just worried about everything balancing properly with the short crank.
yea its def the longer crank, and there is no way to mate it to my 4l60e even though they are both 2000. So I'm gonna talk to the machine shop and see what's going to be feasible if I can get away using my 5.7 crank
11-21-2016, 12:23 PM
#15
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08-01-2017, 03:04 PM
#18
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When I remove the cam what should I be looking for damage wise if there was low oil pressure issues? I'm getting close to having it out