5.7 heads on a 6.4 short block?

[67Dart273]

I bought a 5.7 some time ago, bad crank, spun 2-3 rod bearings as I recall. A local guy has a warranty 6.4 short block "reasonable." Should I pick this up? What do I need to "meld" this short block into the 5.7 engine I have?

 

[67Dart273]

"Know.... body?"

 

[ghinmi]

What year is your 5.7? The 6.4 is a vvt motor so several things will not interchange if it is a 2008 or older 5.7

 

[Phreakish]

No idea for sure, but sounds like a maybe:
5.7, 6.1 And 6.4 Hemi Cylinder Head Comparison - Knowledge Base

Sounds like the only reason the 5.7 and 6.4 heads wouldn't swap is the 6.4 has wider guide spacing and only works with a larger bore, but 5.7 should/could/maybe/might fit a 6.4 lower end? Wouldn't flow as well, obviously. Would also probably take a custom tune or stand alone EFI - which I'd do anyway ;)

The VVT is another matter, but doesn't seem to have as much to do with the heads as it does the cam drive and phaser.

 

[67Dart273]

If I "can do anything" with this, the VVT will go away, and it will get something like Holley or Megasquirt. I have a 5.7 with crank problems but is mostly complete. The 6.4 is the block, crank, and pistons and rods.

 

[ghinmi]

Again, what year 5.7? Several parts changed over the years, you'll want to know what you're getting yourself into.

 

[67Dart273]

Again, what year 5.7? Several parts changed over the years, you'll want to know what you're getting yourself into.

Don't know. What do I look for?

The 6.4 is supposed to be a 2015

By the way, "on a hedge" I dragged this thing home. It's just "up the alley" from me

 

[Phreakish]

Block ID is stamped on the block just above the oil pan rail on the passenger's side, or is on a sticker on the valve cover for a 5.7 (According to the internet). Supposedly, the first number is the year followed by a letter that's the origin code.

The big pre/post '08 differences seem to be in the VVT - which if you're going to make it go away anyhow, shouldn't play in. I've found a few threads elsewhere on swapping 6.1 short blocks under 5.7 valvetrains of various vintages without much issue. The CR tends to be in the mid 10's depending on actual heads - thicker head gaskets seem to be the go-to for combo's that wind up on the high end.

Might be worthwhile to pop a head off the 5.7 and wander over to the 6.4 and do some mock up? Assuming that's even possible..

 

[67Dart273]

Thanks for your input. The 5.7 is torn down. I'll have to see if I can get a number. "Where it's at" not sure I can move it at this time, lol

LOL found the screenshot of the original CL ad. 5.7 is supposed to be a 2003

 

[Phreakish]

Read a few more threads on using other short blocks under 5.7 heads - seems some intakes may not fit without spacers, or using the later intakes. Of course that means matching port size/shape between various generation heads - so spacers are probably more prudent (And cheaper).

 

[ghinmi]

If it is in fact a 2003, there are a variety of small differences that you'll need to address. The cam, timing chain, gears, tensioner, etc won't work on the 6.4 shortblock. You'd need to check but the front cover probably won't work. The accessory pulley depth changed so all the 5.7 accessories won't be correct to work with a 6.4 damper. I'd suggest doing a lot of research. A vvt 5.7 would be a much better donor to finish out the 6.4 short block.

 

[Phreakish]

Here's a good guide:
5.7, 6.1, 6.4 Hemi interchange selection guide

Sounds like if you can find donor apache front cover and a VVT delete cam drive (is the original cam drive system there in the 6.4?), you could be in business. There seem to be a few on ebay for $85+
I'm assuming accessory drive would be a 'custom' affair anyway?

The older non MDS, non VVT lifters seem to be compatible with the 6.4L shortblock. Pushrods I haven't seen any info on but seem to be pretty easy to address.
The cam would have to be compatible with a VVT shortblock, but again assuming custom/aftermarket here anyway.

So it seems the oil pan, intake, heads (and covers, fuel rails, etc) and lifters will swap. The front cover, cam, cam drive, and many accessory parts probably won't. The compression will likely be down compared to a stock 6.4L, and choices for intakes will be a little limited and you may need to grind clearance in the block or use a spacer to raise some intake manifolds. It should still run like mad.

The rest is just a matter of getting the electronics to fire it off.

I'm no authority on the subject, but luckily there seems to be a lot of good info out there.

Looks like there's kits out there to use the early cams in late motors.

 

[67Dart273]

Electronics will likely be Holley HP or Megasquirt. That of course is assuming I live long enough, LOL. What you posted above actually sounds quite encouraging.