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6.4 rotating assembly into 5.7 builds

Posted By: mshred

6.4 rotating assembly into 5.7 builds - 03/17/24 08:39 PM

Wondering if anyone has built a combo out of a 5.7 block (early or late) with the crank and rods from a 6.4? I know the pistons wont work since they are over .170" larger, so wondering if there is an off the shelf piston for this that works? What heads and compression? Power numbers? Wondering what some have done since I know the 6.4 crank is supposed to be quite strong.

Any experience or combos you're willing to share are appreciated.
Posted By: HotRodDave

Re: 6.4 rotating assembly into 5.7 builds - 03/22/24 04:02 PM

Ive contemplated the possibilities and decided it is just best to buy a good used 6.4 block and used pistons before boring a 5.7 block unless you had a brand new block that didn't need bored but you would still need custom pistons that cost as much as a good used 6.4 block. The 6.4 blocks have gotten a lot cheaper lately.
Posted By: mshred

Re: 6.4 rotating assembly into 5.7 builds - 03/25/24 01:30 PM

Originally Posted by HotRodDave
Ive contemplated the possibilities and decided it is just best to buy a good used 6.4 block and used pistons before boring a 5.7 block unless you had a brand new block that didn't need bored but you would still need custom pistons that cost as much as a good used 6.4 block. The 6.4 blocks have gotten a lot cheaper lately.


Thanks for the input Dave. Everything G3 hemi around here is still crazy expensive, guys still want 2k for early 5.7 cores although some pop up for $500-$800 from time to time. Anything 6.1 or 6.4 is crazy money still, but someone local was selling a 6.4 rotating assembly and I thought maybe the crank and rods could work with a custom or off the shelf piston. Just wasn't sure who was doing it. I figured the 6.4 pistons would be a no go just on the bore size alone.
Posted By: Doright

Re: 6.4 rotating assembly into 5.7 builds - 03/25/24 02:32 PM

I put 6.1 pistons in a 5.7 with Eagle heads and big cam makes great power @ 10.5 to 1 with a mild tune.
Posted By: mshred

Re: 6.4 rotating assembly into 5.7 builds - 03/27/24 06:48 PM

Originally Posted by Doright
I put 6.1 pistons in a 5.7 with Eagle heads and big cam makes great power @ 10.5 to 1 with a mild tune.


Can you share any more details on it? Stock 6.1 pistons and 5.7 crank? What are the cam specs and power numbers?
Posted By: Dart 500

Re: 6.4 rotating assembly into 5.7 builds - 04/15/24 04:08 AM

Originally Posted by mshred
Originally Posted by HotRodDave
Ive contemplated the possibilities and decided it is just best to buy a good used 6.4 block and used pistons before boring a 5.7 block unless you had a brand new block that didn't need bored but you would still need custom pistons that cost as much as a good used 6.4 block. The 6.4 blocks have gotten a lot cheaper lately.


Thanks for the input Dave. Everything G3 hemi around here is still crazy expensive, guys still want 2k for early 5.7 cores although some pop up for $500-$800 from time to time. Anything 6.1 or 6.4 is crazy money still, but someone local was selling a 6.4 rotating assembly and I thought maybe the crank and rods could work with a custom or off the shelf piston. Just wasn't sure who was doing it. I figured the 6.4 pistons would be a no go just on the bore size alone.


I would buy the rotating assembly and then keep your eyes out for a block and everything else needed, even if it requires a trip over the border. Piece it together over time
Posted By: HotRodDave

Re: 6.4 rotating assembly into 5.7 builds - 04/18/24 04:00 PM

I just had a thought this morning, I'll try mocking it up today and let you know if it looks like it will work.

03 to 08 5.7 blocks are slightly taller and the later eagle pistons are slightly shorter, I am gonna try a 6.4 crank in an early 5.7 block with the later pistons and see how far out the deck they are and if not too much then maybe double up the head gaskets as long as the top ring don't go out of the chamfer in the cylinder and skirts don't collide with counterweights...
Posted By: HotRodDave

Re: 6.4 rotating assembly into 5.7 builds - 04/18/24 04:03 PM

should be a 359 or 5.9 litre plus a decent compresison bump but it won't allow for a big cam as there is no valve relief...
Posted By: RAMM

Re: 6.4 rotating assembly into 5.7 builds - 04/24/24 12:50 PM

I did this with Icon pistons and a 6.125" rod length. The pin bosses did interfere with the counterweights. J.Rob
Posted By: RAMM

Re: 6.4 rotating assembly into 5.7 builds - 04/24/24 12:53 PM

Originally Posted by mshred
Originally Posted by HotRodDave
Ive contemplated the possibilities and decided it is just best to buy a good used 6.4 block and used pistons before boring a 5.7 block unless you had a brand new block that didn't need bored but you would still need custom pistons that cost as much as a good used 6.4 block. The 6.4 blocks have gotten a lot cheaper lately.


Thanks for the input Dave. Everything G3 hemi around here is still crazy expensive, guys still want 2k for early 5.7 cores although some pop up for $500-$800 from time to time. Anything 6.1 or 6.4 is crazy money still, but someone local was selling a 6.4 rotating assembly and I thought maybe the crank and rods could work with a custom or off the shelf piston. Just wasn't sure who was doing it. I figured the 6.4 pistons would be a no go just on the bore size alone.


I have a 6.4 longblock for sale Mshred. The heads are ported Eagles and they were ported by member SixPackGut. J.Rob
Posted By: RAMM

Re: 6.4 rotating assembly into 5.7 builds - 04/24/24 12:59 PM

Originally Posted by mshred
Originally Posted by HotRodDave
Ive contemplated the possibilities and decided it is just best to buy a good used 6.4 block and used pistons before boring a 5.7 block unless you had a brand new block that didn't need bored but you would still need custom pistons that cost as much as a good used 6.4 block. The 6.4 blocks have gotten a lot cheaper lately.


Thanks for the input Dave. Everything G3 hemi around here is still crazy expensive, guys still want 2k for early 5.7 cores although some pop up for $500-$800 from time to time. Anything 6.1 or 6.4 is crazy money still, but someone local was selling a 6.4 rotating assembly and I thought maybe the crank and rods could work with a custom or off the shelf piston. Just wasn't sure who was doing it. I figured the 6.4 pistons would be a no go just on the bore size alone.


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