Head Porting tips???
07-05-2005, 04:36 PM
#1
Head Porting tips???
I'm about to start cleaning up the heads for my lq9 and would like any advice I can get. I already have a good idea of what I'm gonna do. No hogging out, just smoothing the casting on the intake and exhaust ports and blending in the valve guides. When my work is done, I'll bring them get a 3-angle v-job. Unless a competition 5-angle would be better but I heard that's for serious race applications...???? Also gonna mill them a bit, I'm guessing .025-.030. I'm not sure. Anyone know how much I can take off safely???
07-06-2005, 10:03 AM
#2
Along with what you mentioned, blend in the valve seats to the bowls and polish the combustion chambers. As for how much to safely mill, it depends on what cam you are goinging to run. I was told not to mill more than .060 off any LSx type head regardless of cam. The bigger the cam, the less you can safely mill due to piston to valve clearance. What compression are you planning on running?
07-06-2005, 10:07 AM
#3
Like BigKid said, I wouldnt go more than .060. I only went .030 with mine. On the intake runners, dont polish them to a perfect mirror like shine. You want a little bit of turbulence in the runners. Just smooth out the casting flaws and Id call it good.
07-06-2005, 10:25 AM
#4
BigKID- I wanted to stay away from the combustion chambers b/c I don't want to lose any compression.....unless cleaning the chambers makes up for it.??? The lq9 is already 10.1 so I figured it wouldn't hurt to step it up a bit more. What kind of compression would .030 off give me? I guess I want to get it as high as possible for pump gas and still be reliable.
07-06-2005, 10:27 AM
#5
Originally Posted by 99Silver5.3
On the intake runners, dont polish them to a perfect mirror like shine. You want a little bit of turbulence in the runners.
Guess it's time for research.
07-06-2005, 11:32 AM
#6
Definately polish the cc but dont remove any material or reshape them. This will get rid of any hotspots to ward off detonation. 
As for the polishing the intake runners, yes you can. Since we have a dry intake charge, turbulance in the intake runner is not needed to keep the fuel suspended in the air like on a wet intake. However, I did not polish any of mine to a mirror finish. Just got them nice and smooth.
As for the polishing the intake runners, yes you can. Since we have a dry intake charge, turbulance in the intake runner is not needed to keep the fuel suspended in the air like on a wet intake. However, I did not polish any of mine to a mirror finish. Just got them nice and smooth.
07-06-2005, 01:00 PM
#7
Originally Posted by BigKID
Definately polish the cc but dont remove any material or reshape them. This will get rid of any hotspots to ward off detonation. As for the polishing the intake runners, yes you can. Since we have a dry intake charge, turbulance in the intake runner is not needed to keep the fuel suspended in the air like on a wet intake. However, I did not polish any of mine to a mirror finish. Just got them nice and smooth.
As for the polishing the intake runners, yes you can. Since we have a dry intake charge, turbulance in the intake runner is not needed to keep the fuel suspended in the air like on a wet intake. However, I did not polish any of mine to a mirror finish. Just got them nice and smooth.Trending Topics
07-06-2005, 01:14 PM
#8
According to the little CR calculator I made in excel when I was doing my heads, this is what I get for milling 71cc 317 heads on a 4.0" bore using a .060 mls gasket.
"milled CompRatio
0.000 10.12
0.010 10.25
0.015 10.32
0.020 10.38
0.025 10.45
0.030 10.52
0.035 10.58
0.040 10.65
Take into account that these are estimates as I am not exactly sure of the amount milled per cc that would come off a 317 head. These numbers are more than likely lower than what the actual compression would be since I used the .009"/cc I calculated for my 5.3 heads.
"milled CompRatio
0.000 10.12
0.010 10.25
0.015 10.32
0.020 10.38
0.025 10.45
0.030 10.52
0.035 10.58
0.040 10.65
Take into account that these are estimates as I am not exactly sure of the amount milled per cc that would come off a 317 head. These numbers are more than likely lower than what the actual compression would be since I used the .009"/cc I calculated for my 5.3 heads.
