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Old Jan 29, 2007 | 06:15 PM
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Question 383 or 408?
I'm trying to decide on what i should do. I just put a set of PRC CNC 243's on my Trex LS1 and ended up with the bottom end knocking a month later. I want to upgrade the engine so I'm thinking of either a 383 or a 408. I would like to get the 408 but are my heads too small? I don't wanna put my practially brand new heads to waste. If i'm looking to hold on to the heads should i get the 383 instead of the 408?
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Old Jan 29, 2007 | 06:19 PM
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Get the 408 and have the chambers on your heads opened up to 4.030". The heads will perform just fine on the 408. Opening the chambers is cheap and easy for a skilled shop.
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Old Jan 29, 2007 | 06:31 PM
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Originally Posted by TheCarKid
I'm trying to decide on what i should do. I just put a set of PRC CNC 243's on my Trex LS1 and ended up with the bottom end knocking a month later. I want to upgrade the engine so I'm thinking of either a 383 or a 408. I would like to get the 408 but are my heads too small? I don't wanna put my practially brand new heads to waste. If i'm looking to hold on to the heads should i get the 383 instead of the 408?
Your set of heads are much better suited for the 383 rather than the 408. Also,unless money is no object,the 383 is far less expensive to build on a LS1.
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Old Jan 29, 2007 | 08:30 PM
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both will be an upgrade over the 346 but i vote for the 408. a 408 shortblock compared to a 383 isn't that much higher if you buy them both as a shortblock.and as beast has said just have the chambers opened up for a 4.030 bore which will unshroud the valves and add some cfm of flow.
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Old Jan 29, 2007 | 09:06 PM
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Originally Posted by slow trap
both will be an upgrade over the 346 but i vote for the 408. a 408 shortblock compared to a 383 isn't that much higher if you buy them both as a shortblock.and as beast has said just have the chambers opened up for a 4.030 bore which will unshroud the valves and add some cfm of flow.
If you intend to build a good quality motor,starting with the short block. Then there is a considerable difference in the pricing of a 383 vs 408. If you don't beleive me - check out the CARTEK web sight.
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Old Jan 29, 2007 | 09:33 PM
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Originally Posted by david vericker
If you intend to build a good quality motor,starting with the short block. Then there is a considerable difference in the pricing of a 383 vs 408. If you don't beleive me - check out the CARTEK web sight.
You should look into the parts that are going into each motor. There are diffrent packages, as Cartek is listing. The diffrence in price between a 383 and a 408 is next to nothing. The stroker kits cost the same. The only thing he will have to buy is a 6.0 block, thus that is the only price diffrence. Assuming you can't find one at the local junk yard for next to nothing, a new 6.0 block can be had for about $600 I believe. Also, ported LS6 heads are fine on a 408. As long as he gets the chamber to match the bore he is going to run, they will be equaly suited on either motor.
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Old Jan 30, 2007 | 12:27 PM
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thanks a lot guys for all your input. hopefully i'll get all this done before the weather turns nice again. i think i'm prolly gonna go with the 408, but we'll see. thanks again to all who responded.
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Old Jan 30, 2007 | 03:36 PM
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Originally Posted by TheCarKid
thanks a lot guys for all your input. hopefully i'll get all this done before the weather turns nice again. i think i'm prolly gonna go with the 408, but we'll see. thanks again to all who responded.
Give LME a call. They quoted me the same price on a 383, 402 or 408 shortblock. Now you will have to go iron block on the 408 but for the same price as a 383 you can have a 408!

They are a sponsor so you can find LME -------------->
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Old Jan 30, 2007 | 03:36 PM
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no replacement for displacement, go 408
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Old Jan 30, 2007 | 05:23 PM
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Dont waste your time with a 383. My old 383 with GTP stage 2 heads and 232/232 cam mad 420/400. Then built a 402 with Patroit stage 3 heads a 244/248 cam car made 515/497.
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