I have tried many searches but I can't find a direct answer for my questions.

What is the short version of LS1 heads vs the 5.3L heads that many companies are offering? Is it just a different casting? Is one structurally better than the other? Any downsides to going the 5.3 route?

I am looking for a nice set of street heads to run with a 224 or 228 cam on a stock displacement LS1 to make 400+rwhp. I am considering AFR 205s, MTI, PRC, etc but the choices are numerous and I haven't found a clear winner

 

I recently searched this. The 5.3s flow the same as the LS1s, but the 5.3s have a 59cc chamber and the LS1 has a 64cc or 66cc. Also the 5.3s are cheaper. These are not for FI cars. You either go N/A or spray with these, since your compression will be above 11:1. For the price of "as cast" 205s(which are actually 200s) you can have fully assembled stage 2 5.3s which will flow pretty much the same and have more compression.

 

ported w/ bigger valves they will flow well, stock 5.3's will not flow as well compared to a stock 5.7 head.

 

I purchased a set of 5.3 liter heads yesterday, and i'm going to be running a TSP228R, .588 lift, at 112 lsa. What size intake and exhaust valves should i use? I was plannin on going pretty big and using 2.055 and 1.60 valves because i plan on running a wet 100shot of nitrious. Are those valves going to be to big, or will it be better to run much larger valves?

 

just to add in a 4.8 and a 5.3 head is also the same

 

I have seen flow bench numbers that compared.

 

Off of Patriot's site.

STAGE II - 4.8L - 5.3L


Valve Size Intake 2.02 Exhaust 1.57


*Super Flow 1020 Flow Bench Ratings

Chamber_cc 61:.15 .100 .200 .300 .400 .500 .550 .600
Int_cc 213- 67 - 133 -194 -242 -274 -290-296
Exh_cc 78 -61 -108 - 147 -183 -205 -213 -220


STAGE II 1997+ LS1


Valve Size Intake 2.02 Exhaust 1.57


STAGE II

*Super Flow 1020 Flow Bench Ratings

Chamber_cc 66.:67 -.100 -.200- .300 -.400 -.500 -.550 -.600
Int_cc :213 - 67 - 133- 194 - 242 - 274 - 290 - 296
Exh_cc : 78 - 61 - 108 - 147 - 183 - 205 - 213 - 220

 

I have been contemplating slapping my stock 4.8 heads on the LS1 because of the compression increase, but was leery of running the smaller stock 4.8 valves. Is the swap only worth it on a set of worked heads?

I might need to change lifters soon, and since I already have the heads, it would be a super easy swap. I'm running a TR224 cam if that makes any difference.

 

You will be spending a ton of time for very little gain. Have the heads done corectly and a nice cam and you will see a hell of a difference.

 

Thanks for the reply, this is exactly the info I was looking for! So really the 5.3L heads are a great way to go for an N/A motor without spending a huge amount of money. I wonder if 11:1 is too much for 91 octane?

I guess I'll take the AFR 205cc heads off my list since these 5.3L heads should do everything I need for less money!

 

read my post again.

you said, "The 5.3s flow the same as the LS1s, but the 5.3s have a 59cc chamber and the LS1 has a 64cc or 66cc."

the stock 5.3's do not flow the same as the stock 5.7's .

with porting and bigger valves, the 5.3's will flow very well...which is what you posted.

 

OK maybe they don't flow the "same" but they compare. Nobody in there right mind would swap heads that are unported especialy from LS1-5.3. These are both stage 2 heads so my guess would be that untouched heads would compare too.

Whatever man. The point is budget minded guys should go 5.3 and you seem to agree. I'm not on here to start arguments (even though it can be entertaining at times), just state facts and opinions, offer help when I can, and seek it as well.

 

stock 5.3 heads have a 61cc chamber, you need to unshroud the valves in order to fit bigger valves in. this increase the CC to ~62cc. an unmilled 5.3 head with a .054 gasket on a stock shortblock will put you @ 10.8 CR. stock 5.7's have a 66cc chamber and ls6 heads have a 64cc chamber. Jamie is correct; stock for stock 5.7's outflow the 5.3's due to the bigger intake valves (2.00 vs 1.89 respectively). once ported the difference is inconsequential.

as far as the AFR's you get what you pay for; great flow thats been independently verified with high velocity.

 

I should have originally stated ported to ported, with same size valves. I bet unported to unported with same valves, they would flow the same. Oh sorry "similar".

Yes, AFRs are the best money can buy. I believe we are talking cheep power hear, other wise he would have mentioned a LS6 or AFR head instead of LS1 and 5.3. I'm not a walking encylopedia, and I don't have time to look up exact details for every cenario. I generalize unless precise info is requested. Thank you for filling the holes though. As mentioned earlier I too am searching this topic and appreciate the info.

I think I made my point in answering the guys question correctly without tons of specs.

 

After more searching I think the 5.3 heads are the ones for me! They will go nicely with a stock bottom end and a TR224 with other bolt ons and the extra compression is a nice bonus. Now I need weed out the lesser products and end up with the best bang for the buck pair. No point in spending huge dollars on the 5.3s or I'd just buy some hand ported AFR 205s!

The top of the list seem to be Absolute Speed, TEA and MTI unless I am missing someone? Obviously there will be may opinions on this topic but is there any reason to think there might be a best 5.3L head out there? Please help me before the cash leaves my pocket!

Thanks