Milling heads (5.7 or 5.3), and ability to run on 91?
04-23-2003, 08:19 PM
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Milling heads (5.7 or 5.3), and ability to run on 91? I am going with a less radical cam, and making my set-up a bit more streetable/legal. I want to raise the compression a bit if i can without many problems.
First my question is will 5.3 heads with no porting flow as well as 5.7 heads? If not then i'll just mill my stock heads.
I am in CA so i can only run 91, is 10.8:1 (.030?) as high as i can go reliably, or could i get to 11.1:1 (i think thats .040, right?) without problems? Will i get much KR with either compression? What will it do for my streetability/reliability? Is the cost worth it if i'm not going to port my heads or anything?
Will this affect emissions much?
First my question is will 5.3 heads with no porting flow as well as 5.7 heads? If not then i'll just mill my stock heads.
I am in CA so i can only run 91, is 10.8:1 (.030?) as high as i can go reliably, or could i get to 11.1:1 (i think thats .040, right?) without problems? Will i get much KR with either compression? What will it do for my streetability/reliability? Is the cost worth it if i'm not going to port my heads or anything?
Will this affect emissions much?
04-24-2003, 04:48 AM
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Re: Milling heads (5.7 or 5.3), and ability to run on 91? i am interested in this too, ttt for ya. <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />
04-24-2003, 09:19 AM
#3
Re: Milling heads (5.7 or 5.3), and ability to run on 91? My daily driver has 11:1 compression and on warm days I get some KR with our crap gas (91 octane). My timing map is very conservative and I still get occasional KR. IMO you sould go easy on compression and make up for it with ignition timing. Other factors like headers and gears will also have some effect on KR. High compression ratios will increase NOX output, but shouldn't cause you to fail a smog test. Cam selection will have more effect on smog results. Longer duration lobes and tighter LSA will make passing smog tests here in CA tougher. LT headers and deleted CATS will cause problems unless you can find a sympathetic smog station. <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />
Decisions about compression, cams, exhaust etc. should be aimed at achieving your overall combination. Hope this helps.
Good luck,
Richard <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />
Decisions about compression, cams, exhaust etc. should be aimed at achieving your overall combination. Hope this helps.
Good luck,
Richard <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />
04-25-2003, 02:09 AM
#4
Re: Milling heads (5.7 or 5.3), and ability to run on 91? </font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by cy:
<strong>
First my question is will 5.3 heads with no porting flow as well as 5.7 heads? If not then i'll just mill my stock heads.</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">No. The 5.3's don't flow as well. The biggest factor being they have smaller intake valves. And even if you installed the larger 2.00 valve of a stock 5.7 they won't flow as well.
<strong>
First my question is will 5.3 heads with no porting flow as well as 5.7 heads? If not then i'll just mill my stock heads.</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">No. The 5.3's don't flow as well. The biggest factor being they have smaller intake valves. And even if you installed the larger 2.00 valve of a stock 5.7 they won't flow as well.
