Hemi build on 91 octane

[Jgress77]

Im wanting to 05 ecu swap and build my truck and after doing a few months if research I ran into an issue. I only have 87 and 91 octane fuel within 30 minutes of me. Would it be worth building a 5.7 on 91 octane? How much power could I realistically push out of one on 91? I was planning to do a built hemi and 8hp swap. But would I be better of throwing in a built 12 valve and 48re?

 

[MrBonez]

Depends on what you mean by "Built Hemi" since they can be built anywhere from mild to wild.

I understand you're wanting more power so I'm thinking you'll probrably be going with higher than stock compression with it, that may indeed make it need 91 to run without pinging itself to death.

For a milder build with stock compression 87 should be OK as long as you're not slapping a turbo or blower on it - Esp a blower. Turbo's are forgiving with pinging issues but blown engines are not forgiving at all, they just grenade and that's it, leaving you to collect the pieces when it blows AND blown engines more or less require all the octane you can give it anyway.

If just wondering about the sheer power difference between the two fuel choices, you'll be better off with 91 but unless you do some things with the build that raises power output you won't see much, if any real difference aside from helping/solving pinging issues and it will tend to run better too.

So..... Are you going for a standard street rod build or really going all in with it?

That's the real question ATM.

 

[Jgress77]

Depends on what you mean by "Built Hemi" since they can be built anywhere from mild to wild.

I understand you're wanting more power so I'm thinking you'll probrably be going with higher than stock compression with it, that may indeed make it need 91 to run without pinging itself to death.

For a milder build with stock compression 87 should be OK as long as you're not slapping a turbo or blower on it - Esp a blower. Turbo's are forgiving with pinging issues but blown engines are not forgiving at all, they just grenade and that's it, leaving you to collect the pieces when it blows AND blown engines more or less require all the octane you can give it anyway.

If just wondering about the sheer power difference between the two fuel choices, you'll be better off with 91 but unless you do some things with the build that raises power output you won't see much, if any real difference aside from helping/solving pinging issues and it will tend to run better too.

So..... Are you going for a standard street rod build or really going all in with it?

That's the real question ATM.

I want something fun that I can roast the tires as long as I hold into it. Im on 35s at the moment but want to drop the suspension and everything back down to a reverse level and srt10 wheels. Im nit looking for anything like 2000hp but I would like it to run fairly well and have enough power. Im not too sure on what I need to do honestly I've been told many different thing by many different people anywhere from itll only make 400hp to 6.4 swap would be best.

 

[MrBonez]

Decent street build is what you are describing and a 5.7 can get it done BUT....
It would be easier to get the power you want from a 6.4 because more cubes means more power in the basic sense of it.

Either way you go is fine but if not wanting to have to invest what could be a crap load of $$ into it for power, a 6.4 built right would be the ticket here for some good naturally aspirated power.
If you're going to be running a turbo then either engine would do, all you'd need then is to figure out cost, availability of parts and overall difficulty to do it based on which engine choice you make.
If you do go with a 5.7, make sure to run a good high volume (Hellcat?) oil pump in it - In fact I'd run one anyway regardless of engine chosen or how it's built.

The usual tricks with heads (Porting/smoothing the intake /exhaust passages and so on) or a set of aftermarket (Performance) heads will net some nice gains too along with any other basic street-rodding trickery you can come up with.

 

[Jgress77]

Decent street build is what you are describing and a 5.7 can get it done BUT....
It would be easier to get the power you want from a 6.4 because more cubes means more power in the basic sense of it.

Either way you go is fine but if not wanting to have to invest what could be a crap load of $$ into it for power, a 6.4 built right would be the ticket here for some good naturally aspirated power.
If you're going to be running a turbo then either engine would do, all you'd need then is to figure out cost, availability of parts and overall difficulty to do it based on which engine choice you make.
If you do go with a 5.7, make sure to run a good high volume (Hellcat?) oil pump in it - In fact I'd run one anyway regardless of engine chosen or how it's built.

The usual tricks with heads (Porting/smoothing the intake /exhaust passages and so on) or a set of aftermarket (Performance) heads will net some nice gains too along with any other basic street-rodding trickery you can come up with.

Would you happen to have an easier way for me to talk to you? Id like to ask you a few questions. Im a 2003 ram 1500 so I have a terrible ecu. How much can a built n/a 6.4 make on 91?

 

[HemiLonestar]

Only people in forums and YouTubers recommend running the hellcat oil pump in non-cat/boosted applications (or people trying to sell you one) lol....

Im wanting to 05 ecu swap and build my truck and after doing a few months if research I ran into an issue. I only have 87 and 91 octane fuel within 30 minutes of me. Would it be worth building a 5.7 on 91 octane? How much power could I realistically push out of one on 91? I was planning to do a built hemi and 8hp swap. But would I be better of throwing in a built 12 valve and 48re?

Sounds like a Costco station. If you're building for performance you're gonna be tied to 91 anyway. Pre-eagle with stock displacement and internals (cast crank) probably get away with 400-450 to the wheels (stock is 345 @ crank, usually about 270-280 to the wheels). For longevity & reliability sake upgrading the insides is never a bad idea, even if you just use a 6.1 crank and some better rods & pistons. 8HP swaps have been done in 3rd gens, it is fairly straightforward other than figuring out where to put the shifter. The front end of the 1500 isn't really made for the weight, you'd have to beef the front end to make it safe and it wouldn't be any faster. The power the diesel would need to make it significantly fast would likely start twisting the structure.

I want something fun that I can roast the tires as long as I hold into it. Im on 35s at the moment but want to drop the suspension and everything back down to a reverse level and srt10 wheels. Im nit looking for anything like 2000hp but I would like it to run fairly well and have enough power. Im not too sure on what I need to do honestly I've been told many different thing by many different people anywhere from itll only make 400hp to 6.4 swap would be best.

Most people who give outlandish advice don't know what they're talking about, including not realizing or knowing there are actual differences between the years and generations. "jUsT dRoP a 6.4 iN". A factory 6.4 is not a drop in for a 3rd gen. It will physically bolt to the mounts but that's where the fun ends. Whether you use a truck or car 6.4, the FEAD (accessory drive) is completely different, requiring hose and wiring reroute and extension. No PCM prior to 2009 will run a VVT engine and you can't swap one into a pre-CAN and have it work with the rest of the truck. You could change the tone ring and lock the VVT phaser but then you're just wasting the advantage it would give and may as well just go with a stroked 5.7 short block.

Honestly I wouldn't bother with the 03-05 swap because depending how far you want to take this, the factory ECM/PCM will always be the limiting factor. Beyond say 500hp you're better off getting a standalone. The Holley has been proven to work in 3rd gen electronic architecture and still allows use of your stock gauges (there is a 2004 with a stroked 6.1 & 8HP70 using a Holley running around Canadia).

 

[GeauxinUp]

You’re not getting 500 wheel out of a 5.7 without a power adder (nitrous/blower/turbo(s)). If you’re looking for n/a power, I’d look into a 6.4 with a standalone pcm setup. If you’re ok with boost, then build up the 5.7 to handle it. I’m not sure of the limitations on the factory pcm. Keep in mind, you’re already starting at a deficit with a pre-eagle engine. Sky is the limit, just depends on your pocketbook

 

[Jgress77]

Only people in forums and YouTubers recommend running the hellcat oil pump in non-cat/boosted applications (or people trying to sell you one) lol....


Sounds like a Costco station. If you're building for performance you're gonna be tied to 91 anyway. Pre-eagle with stock displacement and internals (cast crank) probably get away with 400-450 to the wheels (stock is 345 @ crank, usually about 270-280 to the wheels). For longevity & reliability sake upgrading the insides is never a bad idea, even if you just use a 6.1 crank and some better rods & pistons. 8HP swaps have been done in 3rd gens, it is fairly straightforward other than figuring out where to put the shifter. The front end of the 1500 isn't really made for the weight, you'd have to beef the front end to make it safe and it wouldn't be any faster. The power the diesel would need to make it significantly fast would likely start twisting the structure.


Most people who give outlandish advice don't know what they're talking about, including not realizing or knowing there are actual differences between the years and generations. "jUsT dRoP a 6.4 iN". A factory 6.4 is not a drop in for a 3rd gen. It will physically bolt to the mounts but that's where the fun ends. Whether you use a truck or car 6.4, the FEAD (accessory drive) is completely different, requiring hose and wiring reroute and extension. No PCM prior to 2009 will run a VVT engine and you can't swap one into a pre-CAN and have it work with the rest of the truck. You could change the tone ring and lock the VVT phaser but then you're just wasting the advantage it would give and may as well just go with a stroked 5.7 short block.

Honestly I wouldn't bother with the 03-05 swap because depending how far you want to take this, the factory ECM/PCM will always be the limiting factor. Beyond say 500hp you're better off getting a standalone. The Holley has been proven to work in 3rd gen electronic architecture and still allows use of your stock gauges (there is a 2004 with a stroked 6.1 & 8HP70 using a Holley running around Canadia).

Do you have anyway I can messege you direct to ask a few questions? Maybe Facebook or anything?

 

[GeauxinUp]

Only people in forums and YouTubers recommend running the hellcat oil pump in non-cat/boosted applications (or people trying to sell you one) lol....

Not sure I necessarily agree with that. If you’re talking about yanking one out and replacing just for the hell of it, then yes. If you’ve already got the engine tore down for a cam/lifter replacement, chances are you’ve got higher mileage, and replacing the oil pump is generally a good idea. From what I remember, the “hellcat” pump is minimal cost vs stock or melling, so might as well get a little more volume.
Just my $.02

 

[HemiLonestar]

You are of course welcome to your opinion, especially as it directly supports what I said.

Only people in forums and YouTubers recommend running the hellcat oil pump in non-cat/boosted applications (or people trying to sell you one) lol....