It seems like the general consensus in this forum is that 5.3L heads (in stock form) would be waste to put on an ls1, because even though they compression by about a full point, ls1 head 66.67cc = ~10.1CR, 5.3L head 61.15cc = ~11.0CR.But they are said to have horrible flow which would cancel out the increase in compression. But after a short search i find that stock for stock 5.3L heads flow only ~1-3 cfm less than a ls1 head. and that of course is done with the smaller 1.89" valve. That would lead me to believe that by simply installing the larger ls1 valves (2.00") into the 5.3L heads, that would make up atleast the 1-3cfm difference, and possibly flow better than the stock ls1 heads, with nothing more then a valve swap. I think the 5.3L heads deserve a little more credit than we give them, its already proven that ported 5.3L are just as good if not better then ported ls6 heads. I think stock 5.3L heads deserve a little more credit also. For the extremely budget minded Ls1 owner, who is in the market for some cheap, take-off heads.

I think the 5.3L heads wouldn't be a bad choice for NA applications, especially with upgraded valves. The increase in compression, would definitely bump up torque and make around town, and average driving more enjoyable with a little extra punch. and with a larger cam-only application, can help fix some of the horsepower loss down low, while still flowing the same if not better (again, as long as there upgraded with the ls1 valves).

And i don't think i even need to mention the added benefits of higher compression for a nitrous application. a jump from ~10.1CR to ~11.0CR would certainly be noticed.

Of course none of this applies to you FI guys, but then again if you can afford to go forced induction, you can probably atleast afford some 6.0L take-offs.

One thing that might be a concern however would be octane requirements. For those less fortunate out there, who can only get 91 octane, might have a problem. And i would imagine that with a ~11.0 CR that would force many nitrous applications passed the limits of 93 octane.

ok well unfortunately i ran out of time and i need to leave for work now, so i didn't get a chance to edit/proof-read, and really make a good case. But the basic point is that for an extremely tight budget, 5.3L take-off heads aren't as horrible of a choice as they are made out to be, as long as they are fitted with ls1 intake valves.

Flow numbers:
http://www.smokemup.com/tech/ls1.php
http://www.carcraft.com/techarticles...o_results.html

Any thoughts, insights? perhaps some sponsors have some benchmark/baseline tests of 5.3L heads laying around or burried deep in some filing drawer?

 

Just adding 2.00 valves to the heads will NOT increase flow. Why? Because the port below the valve is plunge cut by the factory for the smaller valve size and when you add the bigger valve, your machine shop will plunge cut it yet again and it will leave a significant ridge in the throat of the port. So it will still need a bowl port to gain significant flow over stock. Unless you can do that yourself, it kind of makes the whole budget idea go out the window.

 

im running fully ported stock valved 5.3 heads with a lil thinner than stock gasket 11.3 cr....trust me over a stock head its definatly a gain...the short runners and the raised cr turn the ls1 into a tq monster...

 

Good info!!!

 

Can I mill .020 to 5.3 head? Will that require even more octane gas? Planning to do this route with a 228R cam. I've a shop can get the head job done.

 

***** SAID HEAD JOB BAAHHAAHHAHA IM HIGH AS HELL REAL TALK

 

and

 

PERFECT!

Just what i was looking to hear. Ive got 706 Casting 5.3L heads off my 5.3L that i tore apart to use its just for an LS1 build (covers, valvetrain, crank & rods)

I notced that there were some sharp edges around the top of the valve seat where the cutter made some rough edges, so ive smoothed it all out and smoothed the entire ports out. Im hoping that will help me out in making it flow near an Ls1 head and make lots-o-torque. Which is exactly what im looking for.

Time will tell, im going to post some dyno info in the spring w/ the 706 heads, TR230 cam, LT's, Ls6 intake etc. See what the outcome is

Sheldon

 

Anymore info?

Im contemplating whether i should pick up some 243 casting heads.

 

lol! .. all these cheap ls1's are attracting all kinds of wierdo's

 

Great info guys! Im going to port my 706s, do a 2.00 valve and hope for the best. Going to see how fast a stock bottom N2O 5.3 can run. Nothing but rod bolts, cam, and the head work... Should be interesting

 

I'm asking some "local professional" to see if it's possible to run 11.5:1 with the 5.3 head. I won't go with a big cam those, maybe a 228R or 233/239.

 

i had the machine shop around here take my 5.7 stuff off my ls1 heads and put them in some 5.3 heads and cut the valve seats bigger for the new valves and what not and i kept my heads and only paid like 300 out the door i mean it was a hell of a deal and they went on and with only longtubes, a k&n intake, and those heads through an auto my lil 99 made 331rwhp and 340rwtq with the junk ls1 intake and everything. so im a for sure believer

 

stage 1.5 TEA 5.3 heads milled to 59cc and .040 cometic head gaskets for a 11.4 to 1 comp ratio..(flow 316 cf @.600 lift)..car is heads/cam and bolt ons making 452/418 ... stock 5.3 heads with 2 inch valves will not get eanywhere close to these numbers....