Anyone swap out their 243s for 5.3 heads?

 

I've heard of people swapping 241's or 243's for 5.3 truck heads. The only thing I don't understand is why. What exactly is attempting to be accomplished here?

 

I thought the 5.3's flowed very similar to the 243's but raised the compression ratio a bit. I remember that was a popular swap for LS1 guys 10 years or so ago.

 

Yea I've heard of people swapping 241 ls1 heads for 5.3 heads, but not a lot about swapping 243s for 5.3 heads.

 

Did a search on comparisons between the two. 243's have better top end, 5.3's better low end. 5.3 has smaller combustion chambers which increases compression a few tenths. 243's are the better choice between the two. If all you want to do is increase your compression just go with a thinner head gasket or have then milled.

 

If you decide to go with the 5.3's anyway, I suggest also "upgrading" your air intake system and exhaust manifolds to the ones found on the '97-'00 Coupe.

 

Previous owner had texas speed install 5.3 heads and cam package on my 01z. Coupled with long tubes and borla, it dynoed at 426hp

 

I called tsp today. He said stock for stock the 243s are much better, but a worked over set of 5.3 heads are good upgrade.

 

Worked 243's will still give you more average power and peak power than worked 5.3's. Here are a few options, in case you're interested:

www.totalengineairflow.com/cnc-ported-cylinder-heads/gm/ls1ls2

www.advancedinduction.com/LSX/AiLSxCylinderHeads.php#243

http://rpm-motors-inc.com/shop-tour/

http://www.proheads.com/pricing.html


The advantage to the 5.3's is that you can sell your stock 243's, thereby recouping some of the cost.

 

I believe I can offer some real world experience on this subject as I've built many many engines with the different combinations listed above.

The 5.3L casting is an extremely potent casting in the right hands. The smaller chambers for added compression and the shape of the exhaust valve can make some really spectacular numbers. I've done stock bottom heads/cam cars that pull 450-470rwhp with a 5.3L casting all while running a stock LS6 intake.

The shape of the exhaust valve on the 5.3 (706) casting can flow a TON of exhaust cfm with the right CNC program and with opened up runners the intake can easily exceed 300+ cfm. Of course mid lift cfm is where it matters and I believe that's were the 706 casting really shines.

I think we could go on forever with a 243 vs. 706 casting debate but I can say this. In the right hands, a 5.3L casting will make a car just as fast as a 243 casting will. The capability of the car does not always boil down to which cylinder head made more power down on the dyno.

I'll also take this opportunity to reminisce a little (and cry for selling this car). Many many moons ago my mint condition 1998 SS Camaro with Total Engine Airflow worked 5.3L castings, a Cam Motion 230/232 camshaft, stock LS6 intake, and all the other necessary bolt ons made 474hp/420tq on a stock bottom end. I consistantly ran 11.0's-11.20's @ 123-125mph in that car. It weighed 3550lbs with me in it.

 

My buddy Ben has PRC 5.3 heads on his 02 Z and a 233/239 cam and has stock LS6 intake manifold and hes making 453/406. I believe there is still room for him to improve on those heads if he send them to a good porter and gets a FAST 92 with ported LS2 90mm TB and some proper Longtubes.

 

Don't underestimate the 5.3 heads. 243s may be slighty better in most applications, but the 5.3s can really shine with the right work.

I had a set of TEA 5.3s on my 2000 Z28 engine combos and they were excellent.

 

I agree, my results in sig below are with 5.3 heads...

Now if I already had 243s then I would get them ported and run a thinner head gasket to bump compression.

 

My reply above was comparing stock unported heads. If thats the case I would stick with 243's. If youre having porting done then yes 5.3's may be a good option.