cstchevy

wondering about swapping the 6.0 aluminum heads on to a 5.3. Would this help with horsepower? Engine will run a radix supercharger. What kind of power will I be looking at.

Texas Terminator

if you are going to leave them stock, it will flow a bit better and lower your compression a bit (good for the blower). how much of an increase is hard to tell, maybe 20hp or so.

Hit Man X

Don't those have a 2" intake valve too? I don't think it's going to help as much as you think...only upside is reduced compression. That 2" valve is going to shroud the combustion chamber and reduce velocity...thus losing power. But that may be okay w/ a Radix as it's forced induction.

I say keep the 5.3 heads and use the money to be spent on the 6.0 heads for a good dual pattern blower cam or save for the inevitable trans build.

Texas Terminator

no doubt. your tranny will DEFINATELY go pretty soon if you drive it like you stole it.

cstchevy

So when I upgrade to a blower cam what will be my next step in the power range. Tranny is taken care of. I was thinking the heads would help the flow. Maybe just get the 5.3 ported and polished. then go do internals(forged on the 5.3) is it worth it. Or just build up a 6.0 and through the radix on top. any ideas would be appreciated. New to the LS1 engine base.

Flyer

iTrader: (1)

I think heads and a cam would be a nice touch.

Hit Man X

I'd get a street cam like a 214/220 .520/.540 114LSA. Slight chop at idle, power from bottom to top. My choice for mild-med street daily driver. I think Comp or Crane has one similar. The larger exhaust dur will pull the crap from the comb chamber more efficiently.

If you go w/ a 6.0 motor, then I'd do the 6.0 heads. They are made for that motor. It's got a 4" bore...the 5.3 is a 3.78" bore. If you stick w/ a 4.8/5.3 block keep the 5.3 heads and massage them a bit....clean up valve throats, short turns by the valves, slightly widen the ports, etc.

Stock cranks are stout, stock rods are pretty damn good too. If you go w/ a 6.0 motor, you could run stock crank, stock rods, and some good forged pistons...just use ARP hardware.

BUT...soon there are going to be some budget priced stroker cranks. $1000 for a 4" stroke that in a 6.0 motor w/ a .030" overbore will give a a 408....you'll certainly have to get longer rods like 6" or 6.2" (the longer the better, as always! hahaha) Matched with some heads and cam you will have AT LEAST 420rwhp. That'd be able to do cheaper than the cost of the Radix alone...

Then I'd consider a used Procharger setup to feed that 408. I am unsure if the Radix can support the airflow to do it. Well you could adapt a Kenne Bell compressor to it or have it torn down, ported, balanced, etc.

What are you realistically looking for and how much to spend?

Flyer

iTrader: (1)

I've thought about the 408 .. I've put LOTS of thought into it in fact. I priced everything out and shopping from one place using the listed prices on the web (usually lower if contacted on a personal basis) I came up with 6k to build a fully forged 402 with nice heads and a cam.

As for a cam ... Hit Man is pretty close to what I'd run. I've had a 218/224 .524/.534 on a 114 recommended to me by CompCams. After knowing what I do now ... that still looks like a damn nice blower cam. It will definantly have a notable idle and will need to be tuned.

cstchevy

the radix is already on the truck, that is a expesive piece to get rid of. would like the 408 but would want to run my blower on it. 6k sounds about right. I have a guy here who builds these engines and sales the parts for it on ebay. I am looking to make around 550hp. My truck that I have coming is putting 410 a the crank and should be running around 13.5 in the quarter with 4.10 gears. I am just looking to the future, never can keep one thing the same on my trucks. thnx for all your help.

Hit Man X

I wouldn't do a forged crank on the street unless I planned ALOT of boost or heavy nitrous...costs too much. Nodular Iron is plenty strong for my needs N/A under 6200rpms and maybe a 100hp shot. RPMs kill internals first usually, then deflection. Forgings are less likely to stress fracture due to flex as their tolerances are different.

That cam I mentioned is a mild street cam for a small block. I am going to build a 408 or 427 for my F-150 (cubes will be determined by the block I run, production or FMS) and a 218/224 cam is TINY for that motor. I need something like a 234/240 .535/.555 114LSA to feed it right to 6000rpms on a 408. Hell I could go a tad larger like a 238/246 Adv it 4* too...I will be running either the AFR 205 or 225cc SBF heads too once again that goes back to what block I choose.

Either way I choose I will make easily 400rwhp through a built tranny and 4.10:1 gears.

$6K for a 402 WITH heads and cam I'd say would outperform a Radix on a 5.3. Don't forget, with the introduction of the AFR heads that means already ported castings will get cheap. So you could cut some corners being frugal too...