5.7 Hemi -> Hellcat engine? What’s the difference

[speedbird1229]

Hey!

Hi everyone! I have a 70 Barracuda restomod project going and the car is already fitted with a 5.7 Hemi and 8HP70 which I was planning to supercharge with Vortech later. Now I have a chance to acquire a Hellcat crate engine which seems like a wise thing to do. Do you know - would the block fit on the same mounts that the 5.7 is currently on and is the back end of the block similar to the 5.7 in terms of swapping it in front of the 8HP70? Also, is the engine physical size different only on the height or are the heads also bigger?  P.S I do know the Hellcat uses the 90 version of the transmission but I have read the 70 should withstand the power on street use.

Thanks so much for any assistance.

[Dmod1974]

In your context, it's identical other than the blower sitting up top.  The heads are not physically bigger, but the intake mounting pattern is unique to the Hellcats and the heads are A356-T6 AL so they are stronger as well.  The engines weigh quite a bit more than a 5.7 too obviously.

[speedbird1229]

Thanks so much. Thats great to hear. I have a 2.75 exhaust already made. Do you think this would be sufficient?

In your context, it's identical other than the blower sitting up top.  The heads are not physically bigger, but the intake mounting pattern is unique to the Hellcats and the heads are A356-T6 AL so they are stronger as well.  The engines weigh quite a bit more than a 5.7 too obviously.

[Dmod1974]

For a Hellcat that's going to leave power on the table.  3" will still be restrictive and you'll see a measurable difference with cutouts.  717HP requires a lot of flow capacity! 

[speedbird1229]

I read somewhere that the Hellcat factory cars have 2.75 exhaust. Do you know what they actually have? I have an issue that the 3" might not fit all the way. I am also on Ridetech so sufficient clearance must be preserved.

For a Hellcat that's going to leave power on the table.  3" will still be restrictive and you'll see a measurable difference with cutouts.  717HP requires a lot of flow capacity! 

[Dmod1974]

I know the OE cat back piping is 2.75", but I don't know what it is precat.  If all you can fit is 2.75", you can still use cutouts when you need max power.  Like I said, even with 3" cutouts will show gains.

[speedbird1229]

Makes sense. Pre cat is 3" as far as I currently recall.

Do you have any experience on what is the best way to control this engine with? My builder was planning to make a custom map with Link ECU but I am just thinking there might be a better and easier way as these engines are retrofitted a lot in the US.

I know the OE cat back piping is 2.75", but I don't know what it is precat.  If all you can fit is 2.75", you can still use cutouts when you need max power.  Like I said, even with 3" cutouts will show gains.

[Dmod1974]

Lots of options out there now; all have their pros and cons.  I used the Mopar Performance control kit extensively modified and adapted to integrate seamlessly into my American Autowire harness.  I've never heard of Link before, but Holley, Hotwire, etc. are all common options.  The OEM kit has the benefit of OEM components and widespread tuning support, but full standalones are far more adjustable and support far more features.  Popular brands also benefit from widespread support too.  Pick your poison!

[speedbird1229]

Thanks I'll consult with my workshop guys and pick the right stuff.

Do you have any idea if the 8 3/4 axle would resist the torque on street use at all?

Lots of options out there now; all have their pros and cons.  I used the Mopar Performance control kit extensively modified and adapted to integrate seamlessly into my American Autowire harness.  I've never heard of Link before, but Holley, Hotwire, etc. are all common options.  The OEM kit has the benefit of OEM components and widespread tuning support, but full standalones are far more adjustable and support far more features.  Popular brands also benefit from widespread support too.  Pick your poison!

[Dmod1974]

You'll be on borrowed time if it hooks up for sure.  I know mine won't last long so I'll be swapping it for something else eventually.