I read somewhere that the GM 5.3L engine uses the same heads as the LS6. Why are more people using the 5.3L lately?

 

I believe they have smaller combustion chambers, allowing you more compression, without compromising PTV clearance.

 

I went with 5.3 liter heads on my head/cam swap. I went with them because they have smaller intake runners, which are supposed to increase the velocity of incoming air, and thus aid low-end torque. Also, for whatever reason, 5.3 Liter heads tend to be $100 or $200 cheaper than LS6 heads of the same porting. I went with Texas Speed's stage 2.5 5.3's, because they flow comparably (or a hair better) to their stage 1 LS6 heads. The LS6 heads with the dual springs would have cost me $125 more. I was originally going to go with a cam only, and I talked myself into going with some budget heads. I was looking for the best bang for the buck, and saving that $125 to get the same performance (and hopefully a bit better low end from the intake runners) was worth it. The Stage 3 LS6's were $650 more. If I were going to spend that much more, I would have just shelled out an extra $1000 and bought AFR's.

As far as piston to valve clearance, I thought the 5.3's are supposed to be pretty tight. I believe you have to flycut your pistons earlier with 5.3's (when going up in cam size) than with LS6 heads, but I'm no expert in PTV clearance, as I went with a small 224 cam.

P.S. The 5.3's do have smaller combustion chambers, and thus more compression, but you can take care of that issue with the LS6 heads by having them milled and/or using a Cometic gasket.

 

the 5.3 LS4 comes with the 243 casting heads on it, this motor is not to be confused with the Truck motor, its all alum and comes in the FWD wbodys

 

Smaller intake runners (higher velocity) and smaller 61cc chamber (more compression) are the primary reasons, also, they are cheap.

Bolting on stock ones won't do much though, but once ported, valves unshrouded, and loaded with larger valve(s), they are great budget performance head that offers a bit more compression and flow just as well as similar ported LS1 or LS6 head.

I'm running a set of TEA ported 5.3l heads that have been milled to an even smaller 59cc chamber size. Coupled with thinner .040" Cometic head gaskets, it got my comp ratio to 11.5.

Casting #'s for the 5.3 heads are either 862, or 706.

Also, stock 5.3 heads actually offer more p/v clearance due to the small 1.89" intake valve...but almost all ported versions out there will come with 2.00", 2.02", or 2.04" intake valves, and it's the larger valve size that reduces p/v clearance some. The intake valve on stock LS1/LS5 heads are 2.00"

I flycut mine, but I'm running a very large cam that just barely cleared with stock heads and gasket.

 

How much power over a stock LS6 head would a ported 5.3 make? I plan on using a 228/230 114 cam with it as well.

 

Alot of the flow you'll lose going to the 5.3 heads is the valve shrouding, the valve being so close to the combustion chamber wall. That and the LS6 heads have D-shaped exhaust ports that flow more.

 

They claim 40 or 50whp, but I think that's bogus. I picked up about 93whp when I added headers/LS6 intake/UD Pulley/cam/5.3 heads. Guys with my cam tend to hit 385 or 390whp on the conservative end (and I think my dyno is conservative). I hit 410, so I would guess the heads netted me 20 or 25whp over LS1 heads. Just a guess, though.