How much CR gain from .050 mill on heads?
Thread Starter
Joined: Nov 2001
Posts: 10,060
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From: Canton, GA
How much CR gain from .050 mill on heads? I think the stock heads are 67cc? How much CR will I gain, or how many cc's will I lose from the chambers?
Just trying to figure out what my CR will be with zero deck height and 15cc dish pistons.
And yea, I did get shorter pushrods <img src="gr_tounge.gif" border="0">
Just trying to figure out what my CR will be with zero deck height and 15cc dish pistons.
And yea, I did get shorter pushrods <img src="gr_tounge.gif" border="0">
Re: How much CR gain from .050 mill on heads? According to Lingenfelter, for every .005 milled you drop 1cc. This applies to all LS1 family heads. The heads are also good to .050 milled so theoretically you could lose 10cc's. On a stock displacement LS1 this equates to ~.13 pt of compression per cc. So if you went all the way you could get about 11.6 : 1
Hope this helps...
[ March 09, 2002: Message edited by: XtraCajunSS ]</p>
Hope this helps...
[ March 09, 2002: Message edited by: XtraCajunSS ]</p>
Thread Starter
Joined: Nov 2001
Posts: 10,060
Likes: 33
From: Canton, GA
Re: How much CR gain from .050 mill on heads? Well, since I have 15cc dished pistons, that should bring me back to about 9.5:1?
This is how I figured it:
15cc dish - 10cc for milling .050 = net 5cc loss from stock
so, 5cc x .13 = net .65 loss in CR from stock
Stock is 10.1:1, so I will be at about 9.5:1? This doesn't sound right. Supposedly I am at 9:1 now with 15cc dishes, so with 5cc net loss why would I be at 9.5:1? Those numbers seem a little conservative IMO.
Using the numbers provided, I am currently at 8.4:1. Seems a little low.
15cc dishes x .13 = 1.96 loss to CR
Heads are milled .010 now, so add back .26 to CR = net 1.7 loss in CR from stock, or 8.4:1
[ March 10, 2002: Message edited by: Reckless ]</p>
This is how I figured it:
15cc dish - 10cc for milling .050 = net 5cc loss from stock
so, 5cc x .13 = net .65 loss in CR from stock
Stock is 10.1:1, so I will be at about 9.5:1? This doesn't sound right. Supposedly I am at 9:1 now with 15cc dishes, so with 5cc net loss why would I be at 9.5:1? Those numbers seem a little conservative IMO.
Using the numbers provided, I am currently at 8.4:1. Seems a little low.
15cc dishes x .13 = 1.96 loss to CR
Heads are milled .010 now, so add back .26 to CR = net 1.7 loss in CR from stock, or 8.4:1
[ March 10, 2002: Message edited by: Reckless ]</p>
Thread Starter
Joined: Nov 2001
Posts: 10,060
Likes: 33
From: Canton, GA
Re: How much CR gain from .050 mill on heads? VMoore...you should be at about 11.2:1 according to the above formula. Here you go:
.042 milled/.005 = 8.4cc loss = net 51.6cc chambers
.13 per cc x 8.4 = 1.092 gain in CR
According to the numbers, you'd be at 11.2:1 from a stock CR of 10.1:1 (LS1 stock CR is 10.1, not 11.1).
Todd
.042 milled/.005 = 8.4cc loss = net 51.6cc chambers
.13 per cc x 8.4 = 1.092 gain in CR
According to the numbers, you'd be at 11.2:1 from a stock CR of 10.1:1 (LS1 stock CR is 10.1, not 11.1).
Todd
I can shift faster than you.
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From: Baton Rouge, LA
Re: How much CR gain from .050 mill on heads? [quote]Originally posted by vmoore:
<strong>Where does that put me..? 5.3L heads with .42 milled off...? Stock CC is 60 and stock compression is suppose to be 11.1:1..</strong><hr></blockquote>
Vince, you already know what you compression ratio is. You told me the head porter CC'd the heads and it came out to 57cc. Since you are using the factory gasket, bore/stroke, etc., this comes out to 11.6:1.
You really need to port the heads and do the necessary chamber work before applying the formula XtraCajunSS posted. Since your heads have 2.08/1.60 valves, the porter had to open the chamber up quite a bit to unshroud the huge valves (stock intake valve size on a 5.3l head is ~1.94). This will add volume to the chamber, thus decreasing compression ratio.
<strong>Where does that put me..? 5.3L heads with .42 milled off...? Stock CC is 60 and stock compression is suppose to be 11.1:1..</strong><hr></blockquote>
Vince, you already know what you compression ratio is. You told me the head porter CC'd the heads and it came out to 57cc. Since you are using the factory gasket, bore/stroke, etc., this comes out to 11.6:1.
You really need to port the heads and do the necessary chamber work before applying the formula XtraCajunSS posted. Since your heads have 2.08/1.60 valves, the porter had to open the chamber up quite a bit to unshroud the huge valves (stock intake valve size on a 5.3l head is ~1.94). This will add volume to the chamber, thus decreasing compression ratio.
Re: How much CR gain from .050 mill on heads? My heads have been cut .050" and the cc of the chamber is 61cc. This gives me a compression ratio of 10.90 with stock pistons and head gasket. Hope this helps. Use the 61cc number...it will get you close.
__________________
2013 Corvette Grand Sport A6 LME forged 416, Greg Good ported TFS 255 LS3 heads, 222/242 .629"/.604" 121LSA Pat G blower cam, ARH 1 7/8" headers, ESC Novi 1500 Supercharger w/8 rib direct drive conversion, 747rwhp/709rwtq on 93 octane, 801rwhp/735rwtq on race fuel, 10.1 @ 147.25mph 1/4 mile, 174.7mph Half Mile.
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2009.5 Pontiac G8 GT 6.0L, A6, AFR 230v2 heads. 506rwhp/442rwtq. 11.413 @ 121.29mph 1/4 mile, 168.7mph TX Mile
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2022 Cadillac Escalade 6.2L A10 S&B CAI, Corsa catback.
2023 Corvette 3LT Z51 soon to be modified.
Custom LSX tuning in person or via email press here.
2013 Corvette Grand Sport A6 LME forged 416, Greg Good ported TFS 255 LS3 heads, 222/242 .629"/.604" 121LSA Pat G blower cam, ARH 1 7/8" headers, ESC Novi 1500 Supercharger w/8 rib direct drive conversion, 747rwhp/709rwtq on 93 octane, 801rwhp/735rwtq on race fuel, 10.1 @ 147.25mph 1/4 mile, 174.7mph Half Mile.
2016 Corvette Z51 M7 Magnuson Heartbeat 2300 supercharger, TSP LT headers, Pat G tuned, 667rwhp, 662rwtq, 191mph TX Mile.
2009.5 Pontiac G8 GT 6.0L, A6, AFR 230v2 heads. 506rwhp/442rwtq. 11.413 @ 121.29mph 1/4 mile, 168.7mph TX Mile
2000 Pewter Ram Air Trans Am M6 heads/cam 508 rwhp/445 rwtq SAE, 183.092 TX Mile
2022 Cadillac Escalade 6.2L A10 S&B CAI, Corsa catback.
2023 Corvette 3LT Z51 soon to be modified.
Custom LSX tuning in person or via email press here.
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Verdad Gallardo Thread Starter
Joined: Nov 2001
Posts: 10,060
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From: Canton, GA
Re: How much CR gain from .050 mill on heads? vmoore...my bad man, forgot about the 5.3 heads on your car. Oooops <img src="gr_emb.gif" border="0">
Anyhow, I'm not sure the duration of the cam is as important as the lift. The lift determines how high the valve is pushed open. I have .561/.569 lift cam. If the heads are milled more than .030, a shorter pushrod is needed to bring the valvetrain geometry back into better agreement. Thus, I will be using 7.350" instead of stock 7.400".
Valve clearance isn't a big deal for me because I have dished pistons, so I have built in clearance.
Todd
Anyhow, I'm not sure the duration of the cam is as important as the lift. The lift determines how high the valve is pushed open. I have .561/.569 lift cam. If the heads are milled more than .030, a shorter pushrod is needed to bring the valvetrain geometry back into better agreement. Thus, I will be using 7.350" instead of stock 7.400".
Valve clearance isn't a big deal for me because I have dished pistons, so I have built in clearance.
Todd
TECH Regular
Joined: Jan 2002
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From: Orlando, FL
Re: How much CR gain from .050 mill on heads? Max lift isn't really the deciding variable in P/V clearance. The exhaust closing and intake opening timing events along with ramp rates will determine if you are going to run into trouble. The ARE 226/234 0.554 0.575 grind has no issue with P/V clearances with the heads milled 0.030". Vince I don't understand why anyone would try to get you to go to a very large cam unless you had the intention of shifting in the 7200-7600 range (large = 230+ on the intake duration).
TECH Apprentice
Joined: Jan 2002
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From: Texas
Re: How much CR gain from .050 mill on heads? I thought anything more than .035" milled and you have alignment problems with the intake. The air "stumbling" in the intake would negate the minor increase in compression. Or, try to find LS6 heads.
Todd
Todd
Thread Starter
Joined: Nov 2001
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From: Canton, GA
Re: How much CR gain from .050 mill on heads? This was Nick's suggestion to get back lost CR from my boost motor buildup (without pulling the bottom end). He said I should be able to regain a whole number in CR by using .050 milling.
I emailed Nick to get him to add some input here. I know there is noe perfect answer, but just looking for a ballpark number before I start tuning this thing next week.
Todd
I emailed Nick to get him to add some input here. I know there is noe perfect answer, but just looking for a ballpark number before I start tuning this thing next week.
Todd
Launching!
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From: Houston, Texas F-Body Heaven!!!
Re: How much CR gain from .050 mill on heads? Whenever you're not sure about a combination, as Jon. He's done 'em all. <img src="gr_grin.gif" border="0">
<img src="graemlins/camaro.gif" border="0" alt="[Chevrolet]" />
<img src="graemlins/camaro.gif" border="0" alt="[Chevrolet]" />
