Pistons are the way to go for changing compression since you need to replace them anyway but I would still have block and crank checked and honed, cheap insurance. No experience with 6.4 cam but when reading before I bought my cam people were saying it will run with 6.4 cam but needed tune to get full potential, same as any aftermarket 5.7 cam that is aggressive.
Rebuilding a 2005 5.7L Hemi
Hi,
I just bought a 2005 5.7L Hemi as a rebuild project. Plan for now is to put it in my 2008 Wrangler to replace the one I swapped in it about a year ago.
The engine has 250K miles and was run hot with a bad water pump, both heads have dropped seats and the heads are toast. Lower end looks really good, except a couple of the pistons, but the cylinder walls are good, or good enough.
My plan is to get some used heads later on, I assume heads from 2005 to 2008 will work.
I want to build the lower end first.
1: I'd like to put in 6.4L cam and lifters, what does this gain me? I don't need or want high RPM gains, I'd like more power in the low to mid RPM range.
2: I want to increase the compression ratio to about 10.5 to 1, maybe a little higher, but under 11:1. Can I get new pistons to do this, or is machining the best way to go?
3: I want to reuse the stock crankshaft and the rods, but new pistons.
Any thoughts are appreciated.
Thanks
I just bought a 2005 5.7L Hemi as a rebuild project. Plan for now is to put it in my 2008 Wrangler to replace the one I swapped in it about a year ago.
The engine has 250K miles and was run hot with a bad water pump, both heads have dropped seats and the heads are toast. Lower end looks really good, except a couple of the pistons, but the cylinder walls are good, or good enough.
My plan is to get some used heads later on, I assume heads from 2005 to 2008 will work.
I want to build the lower end first.
1: I'd like to put in 6.4L cam and lifters, what does this gain me? I don't need or want high RPM gains, I'd like more power in the low to mid RPM range.
2: I want to increase the compression ratio to about 10.5 to 1, maybe a little higher, but under 11:1. Can I get new pistons to do this, or is machining the best way to go?
3: I want to reuse the stock crankshaft and the rods, but new pistons.
Any thoughts are appreciated.
Thanks
1 - 4 of 4 Posts
6.4 cam may not be ideal for the Wrangler set up, if it is meant for the Charger/Challenger/300, but if there is one for the truck 6.4's, then go for it!
Like stated, you will need new pistons anyways, and to get the compression ratio you want, you have to get them spec'ed that way, as machining the block deck lower for better compression is a big no-no, especially the 3rd Gen HEMI blocks.
I would not reuse the factory rods if you are getting new pistons anyways, as they are going to be a weak point now, and I don't remember if the 5.7 HEMI's used powdered metal rods or old-school cast rods. If powdered metal, then no, you can't reuse the rods anyways.
Like stated, you will need new pistons anyways, and to get the compression ratio you want, you have to get them spec'ed that way, as machining the block deck lower for better compression is a big no-no, especially the 3rd Gen HEMI blocks.
I would not reuse the factory rods if you are getting new pistons anyways, as they are going to be a weak point now, and I don't remember if the 5.7 HEMI's used powdered metal rods or old-school cast rods. If powdered metal, then no, you can't reuse the rods anyways.
Hemis use powdered rods and they are pretty strong but i wouldn't use them on a high rpm motor. You can reuse them as long as they don't need to be machined and the caps are marked and reinstalled the exact same way because they are fractured caps. Hot rod or one of those magazines has been toying with a hemi with a stock bottom end for a while and it's holding some pretty good power.
1 - 4 of 4 Posts
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