5.7 VS. 5.3L heads
10-22-2002, 03:55 AM
#1
5.7 VS. 5.3L heads 5.3L heads have higher compression than 5.7L heads resulting in more power. If this is the case, then why doesn't everyone get 5.3 L heads? What would hold you back from changing to these..price, supercharging, nitrous applications?
What is the compression ratio for these combinations? I'm conmpletely ignorent on this topic but this is what I faintly remember?
5.7L = 69cc?
5.3L = 63cc?
5.7L = 10.5:1?
5.3L = 10.8:1?
5.7L milles .0030 over = 10.8:1?
5.3L milled .0030 over = 11.1:1?
Can you safely mill 5.3L heads and does that effect piston to valve clearance? Would you be better off going to a 5.7L head milled over or to a 5.3L head as is? Please explain, i'm trying to learn. Thanks in advance- Mike.
BTW: If the 5.3L heads makes more power, why didn't GM just use those from the factory? They could have saved $$ on mass producing the 5.3's.
<small>[ October 22, 2002, 03:57 AM: Message edited by: SStolen ]</small>
What is the compression ratio for these combinations? I'm conmpletely ignorent on this topic but this is what I faintly remember?
5.7L = 69cc?
5.3L = 63cc?
5.7L = 10.5:1?
5.3L = 10.8:1?
5.7L milles .0030 over = 10.8:1?
5.3L milled .0030 over = 11.1:1?
Can you safely mill 5.3L heads and does that effect piston to valve clearance? Would you be better off going to a 5.7L head milled over or to a 5.3L head as is? Please explain, i'm trying to learn. Thanks in advance- Mike.
BTW: If the 5.3L heads makes more power, why didn't GM just use those from the factory? They could have saved $$ on mass producing the 5.3's.
<small>[ October 22, 2002, 03:57 AM: Message edited by: SStolen ]</small>
10-22-2002, 04:16 AM
#2
TECH Fanatic
Re: 5.7 VS. 5.3L heads I am no expert, but from what has been posted here; If you are comparing the 5.3 vs 5.7 heads, a stock set of 5.3s have smaller valves and flow less than a stock set of 5.7s
So, why would anyone want a set of 5.3s? Well they will give a higher CR than the 5.7s due to there smaller chambers. And [when ported and larger valves installed], they will then flow about the same as the ported 5.7s
Same flow, but more CR (for those who want it).
As far as the 6.0 heads, they flow every bit as good as stock 5.7s. In fact, I understand they flow slightly better. May have a flow profile closer resembling a set of stock LS6 heads. So, why the use the 6.0s? There bigger chambers yield lower CR for those folks running boosted engines.
Personally, I think for a non-boosted engine running 91-93 octane pump gas, a set of properly ported 5.7 LS1 heads milled .035" will work well. That will still give a CR between 10.6-10.7 to 1
Want even more flow? Get a set of ported LS6 heads. Mill them .035" and you still get the 10.7 to 1 CR, but with slightly greater flow than the ported 5.7 LS1 heads.
TOO MANY CHOICES ! <img border="0" title="" alt="[Eek!]" src="gr_eek2.gif" />
Just my opinion,
Ron,
______________________________________________
<small>[ October 22, 2002, 04:43 AM: Message edited by: Kimchee and Rice ]</small>
So, why would anyone want a set of 5.3s? Well they will give a higher CR than the 5.7s due to there smaller chambers. And [when ported and larger valves installed], they will then flow about the same as the ported 5.7s
Same flow, but more CR (for those who want it).
As far as the 6.0 heads, they flow every bit as good as stock 5.7s. In fact, I understand they flow slightly better. May have a flow profile closer resembling a set of stock LS6 heads. So, why the use the 6.0s? There bigger chambers yield lower CR for those folks running boosted engines.
Personally, I think for a non-boosted engine running 91-93 octane pump gas, a set of properly ported 5.7 LS1 heads milled .035" will work well. That will still give a CR between 10.6-10.7 to 1
Want even more flow? Get a set of ported LS6 heads. Mill them .035" and you still get the 10.7 to 1 CR, but with slightly greater flow than the ported 5.7 LS1 heads.
TOO MANY CHOICES ! <img border="0" title="" alt="[Eek!]" src="gr_eek2.gif" />
Just my opinion,
Ron,
______________________________________________
<small>[ October 22, 2002, 04:43 AM: Message edited by: Kimchee and Rice ]</small>
