the 5.3s are not even that "small" of a runner....i think the older design was around 220cc. the new ones are 215cc, but they are also a significant jump in price over the ported stock 5.3s.

by small runner i mean the AFR 205s or the Dart 205s....or possibly the Terminator 200s (they have bad rep though).

the push for the 5.3s on the board is because they perform and they don't cost alot. on top of that they have good flow without hogging the runners out (better low end) and they bump compression even on stock gaskets.

as for the deal with dynos starting at 3000rpm...i would still consider that "low end". >5000 would be upper rpm.

not many guys would start a race from 1500rpm. and casually driving around town at 1500-2500rpm you aren't too concerned with power since you're not likely going wot much.
but if i get in a street race, i'll downshift to get the rpms up into the mid range.

and if i'm throwing the car around some twisties...i'd aim for the mid range as well so i don't have to worry about shifting in the middle of the apex.

so showing power gains at 3000rpm is useful for me.

 

for this project, what r ur guys thoughts on a 5.3 head vs 5.7 ls6 head? both of course ported and milled. i got a pm about some ported 5.3s that were milled to 56cc, which seems really low to me. where would that put me cr wise? am i going to get a noticeable torque gain with the 5.3s over the ls6s and vice versa for hp with ls6s over 5.3s?

 

I would say the 5.3s are going to be your best bet. Mine flow just as well or better than most ported LS6 heads and you'll have the benefit of a bump in compression over the LS6 heads as well as better torque overall. For an all motor stock cubed car you wouldn't need a haed with any larger runner IMO.

 

Any idea where 56cc would put me CR wise?

Also, to keep on the same subject... what type of performance differences would I be looking at between a ls6 intake/ported TB and a FAST 90/90? Enough to make it worth the while and throw away from the stock looking engine?

 

you would see about 20rwhp more with the ported 9090.... i picked up 35rwhp over my ****ls1 intake****...

FWIW.. when i ran it with the ls1 intake i had 323s... then at the same time i did 410s and ported 90/90... so i could have picked up a few more hp if i kept my gears the same.. 4k stalled auto...

i have seen people sand the "FAST" and stuff off and paint it black and except for the little spot that is there for the fuel rails, but i have also seen people fill that in so it looks bone stock..

 

TSP... matt, jon.. whoever is doing this.. if he ends up not going through with you guys.. here in a few months when im ready to buy another ls1 for a DD.. i would love to work out a deal on a set of heads and see what the car picked up with just heads..

 

bah humbug

 

looking for some 5.7l ls6 heads vs 5.3l input..........

 

hmmm... with stock cam im not sure..

i know with something like an ms4,ms3 etc... i would want the PRCls6s hands down.. better flow..

with a more mid range cam, like a 228r, f13, etc... i would want the 5.3s probably.. those cams dont need a ton of air.. and are more mid range where the 5.3s would help out a little bit with throttle response and what not..

there is minimal difference between those two heads though... its not going to make or break a setup, i think its more of what you would rather have, me i would chose the PRCls6 heads.. some being a street car would chose the 5.3 heads.

 

car is a 100% street car.
From what I'm gathering, the 5.3's will give me snappier throttle response and more low end torque where as the ls6 heads might flow a bit better giving me more hp, but less low end torque compared to the 5.3's...

Yes, this would be a stock cam......

 

yea you are spot on.... i was torn when making a decision also... but i have a large cam... same principal though...

the difference between the two is going to be minimal.. your talking 3-5rwhp and tq. difference.. the 5.3s might give you a smudge of better throttle response, but again not enough to matter in a street race or something similar...

i say it truly is whatever you personally want.. i would go with ls6s.. along with im sure many others... and im sure theres just as many people that would go 5.3s..
have you asked TSP's advice yet?

 

Yea, I have sent them a few PMs, waiting to hear back

 

I say get a set of afr 205's and mill them to 59cc's to jack up the compression and be done. That way when you get great throttle response, good low end torque, great mid range, and also going to make a lot more hp up top then stock. Project will be a total sleeper.

 

minus the huge AFR logo on the heads I don't know much about heads honestly. I've always been a FI guy so I just bought some decent 6.0 L 72cc's for that last build to drop my CR. What are AFRs, a 5.3 or 5.7l head? Clearly they will outflow probably any 5.3l or ls6 head and milled to 59cc will pump up the CR pretty nice.

 

AFRs are going to dominate any 5.3l or ls6 head, not question about it.. they are an aftermarket casting..

but they also cost a pretty penny.. i wouldnt spend the money on those unless i was going for a full out build... your just looking for something out of the ordinary i think?

 

That's a small chamber size - especially if you run the stock cam. That would make the DCR pretty high.

 

Pretty interesting thoughts here. A friend of mine made 400rwhp/385rwtq with a crate ls6, fast 90/nw90, junk headers, m6 and 3.90s in the 9" spinning ZR1s with 315s. Sounds and drives like stock.

 

Pipe dreams.

This is about the most retarded thing I have heard for awhile. Put a cam in it idiot. You're just going to waste time and money and not gain **** for hp with "heads only"................

Some people shouldn't own cars.

 

I agree that I would cam first, but if you can bolt on heads in a C5 like nothing, then it may be worth a shot. You should see some nice gains with tuning, but you'll definitely need a cam to really optimize it. I definitely wouldn't do everything to optimize a "heads only" setup, like extensive milling, bigger rockers, etc that will give you PTV issues when you do cam it.

 

What makes you think you can come in here, bash a pretty intelligent idea, and call me an idiot? I have donated so much time and knowledge to this site that I feel it is completely unnecessary to bash me and call me an idiot. I shouldn't own a car? Maybe you should do some research and see some of the stuff I've already done. Plus there is already results and proof here that it does work. Enough said, stay outta here or be more considerate