5.7 vs 6.4 SRT build and swap

[gumper]

For my 70 Duster, and this is what I want. A 600 horsepower, Holley EFI tuned on methanol drag race engine that can also run on pump gas if I want. The decision needs to be made on how to get there.

If I were to buy a running SRT 6.4, swap the cam, add some headers and tune it on alcohol I think it would be close to the 600 number I want. The factory compression is pretty high, and they are build pretty stout. The 5.7 would require an entire engine rebuild with rotating assembly, head work, etc... Cost wise the 6.4 would be less expensive to get the same power numbers I believe? That of course depends on scoring a good deal on the engine to begin with. Both engines would require the same manifold, headers and basic swap items.

What are some thoughts? 600 is the number I picked in order to get the car to run 10.20s at sea level. It weighs 3300 with me in it, 727 and 4.10 gears. Right now it runs 10.70s with the LA stroker that has disappointed me.

 

[318willrun]

The 6.4 has a NET rating of 485 hp. What would that be Gross ? You wouldn't have far to go to get your 600.

 

[Hellcat Cuda]

6.4 block is beefier than the 5.7. The 5.7 has a cast crank; the 6.4 crank is forged. 6.4 is a much better platform to start with. Add some "drop in" forged rods / pistons and you have a real nice short block.

 

[Cuda416]

6.4 block is beefier than the 5.7. The 5.7 has a cast crank; the 6.4 crank is forged. 6.4 is a much better platform to start with. Add some "drop in" forged rods / pistons and you have a real nice short block.

Agreed, with flow numbers in the 340 range, no porting is really required either. 600 would be easy to attain.

 

[loganscuda]

Just drop the cash and get a helephant crate 1000hp. But as stated above the 6.4 would be better option. If you went with the 5.7 you could do a 6.1 crank and heads and cam.

 

[gumper]

Sounds like the 6.4 is the ticket.

I can imagine the headers will be a ****. Have either a choice of 1 7/8 shorties, or 2” long tubes from TTi.

 

[Rolling_Thunder]

6.4 block is beefier than the 5.7. The 5.7 has a cast crank; the 6.4 crank is forged. 6.4 is a much better platform to start with. Add some "drop in" forged rods / pistons and you have a real nice short block.

My opinion is if you're going to swap pistons and probably rods then you're not far behind a drop in stroker kit --- could get a forged rotating assembly and drop it into a 5.7L block and have a 6.4L... You also know the exact components within the engine. Gen III heads are out there and super cheap... I find 6.1L heads for like $400 a pair rebuilt. Can get random cores for like $150 a pair. I've been thinking about doing something similar to get a forged short block to swap under my 6.1L top end for boost later on.

Anyway - you could go with a factory 6.4L but by most accounts they are made of glass when it comes to power adders... the weak points are the mentioned rods and pistons... why drop more coin for a 6.4L when you can build a better short block for around the same money

 

[gumper]

Well my 410 is f**ked, so I’m eying the hemi much sooner than expected.

Is there anyone out there that builds G3 Hemi crate motors? I want 600 horse on methanol. No local guys have any experience with Hemi motors, and I don’t want them experimenting with my dollars.

 

[loganscuda]

Well my 410 is f**ked, so I’m eying the hemi much sooner than expected.

Is there anyone out there that builds G3 Hemi crate motors? I want 600 horse on methanol. No local guys have any experience with Hemi motors, and I don’t want them experimenting with my dollars.

Modern Muscle Extreme in Virginia, Inertia Motorsports in Texas. I’m sure there’s some on the West Coast.

 

[Rolling_Thunder]

Arrington Performance Sells crate engines...

 

[408 swinger]

I would keep an eye out for a 6.4 truck engine. Cost is way less to start than an SRT 6.4. Truck heads are same alloy as Hellcat heads. So, boost or high compression ready. You'll be swapping cams anyway, so you'll want to talk to a pro about cam selection. Methanol wants/needs a high compression ratio to be efficient. Pump gas engines can have as high as 13 to 1. Which, is a good ratio for methanol. But, it's all in the cam to make that work. I see you're in Butte, what is your track elevation? That will have an effect on your compression and cam selection as well. I also wonder if the same injectors can be used for both fuels. Would the meth set up have to use a larger/lbs. per hour injector? All in the tune? Also q's for a pro.