V8ImpSS

I know mast makes a "small bore" rectangle port head. Is it worth running them over an aftermarket cathedral or CNCd 243 castings? What are the other benefits besides more intake options? Motor will be stock bottom end with a healthy cam that makes top end power with a sacrifice in the low end. Also thinking about upping the compression ratio and running pump 93 in conjunction with water meth. Also considering a small shot of nitrous for track use only.

Thoughts? Suggestions? Recommendations?

Jimbo1367

I would send your stock 243s to either AI or TEA & get them ported.

redtan

iTrader: (5)

Given the size of the bore and the size of the valves needed to fit, I would not bother with rectangle port heads.

Ger yours ported by AI and they'll be plenty for the little ol' 5.3.

V8ImpSS

Thanks guys, I was planning on just doing that with the 243's but I really want to do something different. the only intake option I have with the cathedral heads is a stock LS6, but with the rectangle ports their are a few aftermarket options that I believe would work, as well as the stock LS3 90mm TB setup.

Any other thoughts?

raven154

iTrader: (14)

Cant fit a fast intake on the 243's?

V8ImpSS

Nope the rear buldge on the FAST hits my power steering pump. Plus i havent heard the best things about the fast

redtan

iTrader: (5)

So is a square port FAST not have the same problem as the cathedral one?

Unless you have a pretty decent cam, I would not be worried about not being able to run a FAST intake.

V8ImpSS

I do plan on having a very healthy cam, as agresdive as i can go for a DD. but i do not plan to run a fast no matter which heads i choose. I have been told by many people that they arent worth the money, and cause problems when running with boost which might be in my future plans.

Im thinking about the modular holley intake, as well as a few others with rectangle port only.

redtan

iTrader: (5)

So if you don't plan on ever running an FAST intake, then why do you say that staying with cathedral port heads limits your choice of intakes? Do they not make carb style intakes for cathedral ports?

Have those style of intakes only been invented since the advent of the square port head in 2007 and did not exist before?

V8ImpSS

The aftermarket no longer makes most of the cathedral style intakes since the better rectangle port heads were released in 07. Im not going to use a carb style intake, the elbow required wouldnt fit.

Mez

iTrader: (1)

2nd the motion for CNC 243 heads. Big heads and cam will kill your low speed torque and make it a real pig.

bww3588

iTrader: (49)

Redtan, what he is saying is the fast intake will not fit. No matter what style heads. With cathedral port heads, the only stock style intake that is worth a **** that will fit under the hood is the ls6. With rectangle port heads, you have the ls3 or l76 that flows very well and fits.

With the large port of the ls3 style heads, even the small bore ones, will give you more problems than it's worth on a 5.3

You will be better off with cathedral heads, ls6 intake and a cam to match everything. It will still be a strong runner and more driver friendly.

BTW, I hope transmission upgrades are in the future as well.

V8ImpSS

Yes exactly thank you. This all is going to happen when my current trans blows which will be soon. It won't shift under WOT anymore...the replacement trans was designed for a 5000lb SUV like a GMC Acadia and it's also getting some beef thrown at it as well as a nice stall converter.

Some 5.3's can be bored out to LS1/6 spec giving me a 5.7. Are the cathedral heads worth it then? I want the most power possible the 1st time.

redtan

iTrader: (5)

Given the fact that you're going to have to run a small valved/small bore square port head, and the fact that the best aftermarket cathedral heads are far and above better than any current LS3 heads I would say you can make just as much if not more power with a good TFS/AFR cathedral port head.

And surely you can find a holley type intake for cathedral heads if you don't like the stock style intakes. Yeah they don't make them anymore, but it's not like all just dissapeared off the market...

gectek

iTrader: (2)

The only cathedral intake that is no longer made is the fast 78/90/92. They were replaced by the 102. That does not mean they are no longer avail. They go up for sale quite often but get snatched up quickly.

The other companies that made the other cathedral intakes still make them. BBK/Holley one is avail, and the Prof Products. You can also use an LS2 intake and have it ported and see good gains and still use the 90mm tb like you want from the LS3 intake. Or you can use a carb style mani with fuel injector bosses and a 4 bbl TB on it for an old school look.

The one that sees mixed reviews the most is the Edelbrock Pro Flow XT.

V8ImpSS

I wouldn't know where to look for the intake, nor what my options would be or part numbers...

V8ImpSS

The 4 bbl TB would look cool, but it would be a bitch to get it to work with my ram air hood. Are the BBK/HOLLEY/Prof Products stuff going to give me gains over an LS6 or ported LS2? Should I just get a 90mm ported LS6?

redtan

iTrader: (5)

They are, mostly in the upper RPM range with a hit on lower end torque.

Porting an LS6 is not really going to do anything, and getting a 90mm snout on there is expensive. A very well ported LS2 manifold with its 90mm opening performs just as well as a stock LS6 and I would venture is your best bet as far as a stock style intake is with a 90mm opening.

westtexasbuff

iTrader: (40)

There are small bore rectangular port heads. I think MAST makes them.

redtan

iTrader: (5)

True, but at 3k with 2.08/1.60 valves installed I would take an AFR 245 with 2.14/1.60 valves for $300 less.