WhiteLegacyGuy

Hi
I have a aluminum 5.3 LM4 engine. I am planning on swapping it into my 93 Subaru legacy.

I dont know a lot about LS engines but i have reading a lot on these forums lately but have not seen any high power N/A builds for a 5.3.

I would like to know what it would take to make at least 400whp N/A on a M6 without spending a million bucks.

Im planning on forged pistons and callies compstar rods for extra reliability.
ls6 intake
big cam with appropriate valvetrain upgrades.

I was also thinking like 12to1 compression with E85. Is that to much?
Where is a good place to get custom pistons?

Are the stock 863 heads good enough? I know the intake valves are a little smaller. If I need to I will get some 799/243 heads but i would like to use what i have if i can.

Are the truck injectors big enough? The car already has a walbro 255 and a aeromotive fpr.

I will probably have to mod a set of ebay long tube headers.

please dont tell me to get a 6.0 or anything like that. I have 2 good 5.3's that i got for free.

Thanks
Derek

orangeapeel

iTrader: (18)

Most of the time you see people getting the FE 5.3 and going FI with them, or punching them out to an iron 5.7. I'm sure with heads/cam/intake you would be pretty close to 400rwhp, but can't honestly say you will hit it.

If you arent opposed to doing forced induction, you could get there with less work and the same amount of money probably.

Personally, I wouldn't suggest getting a big cam for this motor. You probably arent going to want much out of the 226-230 range. These days the proper lobes and custom grind can get you a long way.

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Can get you what you need. Give Texas Speed a shout. I know they probably get calls from builds like this frequently.

You are probably going to have to have a better set of heads, and all though it may not cost a million bucks, but a few grand may take you there. The 863 heads are going to be about as stock as you can get. Compression will probably help make the number as long as you are going to do a bottom end to support it.

WhiteLegacyGuy

Thanks for the info.
For now I want to stay away from turbo's and such. Just want to get the car running and have some fun with it this summer.

I do have a iron 5.3 also. I will look into boring that out. But I want to keep it light as possible.

I will probably get some ls6 heads.

What is the highest compression ratio I can safely run with E85?

Thanks

garygnu

are you going to use a carb ?you will need a high flowing fuel system with bigger injectors for E85..talk to TSP and see if some ls6 stage 1 heads will work.I think trick flow has a head for a 5.3.look at a LSr cam from comp or get a custom cam after you have your heads and intake and compression figured out.

orangeapeel

iTrader: (18)

I wish I knew more about E85, but I know it makes good power!

DONAIMIAN

iTrader: (18)

The bore of that motor is really gonna limit you as far as head selection goes. Without putting much thought into it 400w is going to be quite the task.

hammertime

iTrader: (1)

E85 should support a full point more compression than gasoline no problem, probably even more considering you are adding a cam which will reduce the DCR. You also need about 30% more fuel delivery than gasoline, so you should probably plan on 36lb or 42lb injectors to support that kind of power.

400rwhp from a 5.7L LS1 with an M6 usually requires a cam in the 224 - 230 range. With a little less displacement, you'll need more air flow to get the same power level. Plan on some good porting on those 5.3 heads, or better yet, go ahead and invest in 243/799 heads, and do some mild porting and milling to get the compression up as much as you can. 11.5 to 12.5:1 should be the sweet spot on E85. Run some thinner gaskets to keep the quench volume small as well.

All that should get you pretty darn close. It won't be cheap, but it sounds like you are starting out inexpensive any way.

WhiteLegacyGuy

Thanks guys for the info

I am gonna get some 799/243 heads.
I think im gonna shoot for that 12.5 to 1 comp ratio

Im gonna give it a go at making 400whp on a 5.3
now i just need to figure out what i need for pistons


thanks again

Hank Peabody

iTrader: (2)

Maybe look what it takes to make around 460whp in a 6.0 with the same heads and duplicate that setup on your 5.3 and you'll be close. Lots of 6.0 dyno results on here.