Compression SBE??? How much is too much milling?
12-21-2009, 09:43 PM
#1
Compression SBE??? How much is too much milling? What is the compression people have ran on the stock bottom end, i have some TFS 215 heads right now at 60cc, with a .040 cometic gasket, and flycut what is needed (.100 is the max correct?)...
i dont mind running two tunes; one for the street on 93 pump and one for the track with 100 or a 93/100 mix, my question is how much is too much milling?
i thought i read somewhere that the more you mill the more you hurt the flow through the heads? is this true? What would the absolute min cc size you would recommend where it does more harm then good? or is there no such thing?
right now i should be around 11.5:1 with no relieves 60cc size chambers, 0.040...
Lastly does anyone have a table of a rough guess to how much cc the relieves will add to the chamber, say by depth, (so a .050 cut will add 1.1cc) or there abouts)I know it depends on the valve size, but a rough guess will work (the intake is 2.04)...
i dont mind running two tunes; one for the street on 93 pump and one for the track with 100 or a 93/100 mix, my question is how much is too much milling?
i thought i read somewhere that the more you mill the more you hurt the flow through the heads? is this true? What would the absolute min cc size you would recommend where it does more harm then good? or is there no such thing?
right now i should be around 11.5:1 with no relieves 60cc size chambers, 0.040...
Lastly does anyone have a table of a rough guess to how much cc the relieves will add to the chamber, say by depth, (so a .050 cut will add 1.1cc) or there abouts)I know it depends on the valve size, but a rough guess will work (the intake is 2.04)...
12-22-2009, 11:10 PM
#6
On The Tree
what matters with milling is deck height. trickflow has a thicker deck than stock heads, so they are stonger. i have pistons that have -4 cc valve relieves and compression went down 10.5 to 10.4.
12-23-2009, 11:14 PM
#7
Your current chamber volume and compression is very ideal, if not a tad conservative, for 93 octane.
The reliefs you will end up grinding in the heads would be lucky to displace 2 cc's of volume.....probably slightly less.
That still puts the final figure at 11.4 ish with a piston to head distance (quench) of .035 or so. You could have milled another cc or so and gotten to 59 cc with the fact you have 93 octane available, but I wouldn't lose sleep over that slight extra increase unless you wanted to maximize every singe facet of the build (which you might....Im not sure).
Anyway....crickets.....LOL
Hope this helps!
-Tony
The reliefs you will end up grinding in the heads would be lucky to displace 2 cc's of volume.....probably slightly less.
That still puts the final figure at 11.4 ish with a piston to head distance (quench) of .035 or so. You could have milled another cc or so and gotten to 59 cc with the fact you have 93 octane available, but I wouldn't lose sleep over that slight extra increase unless you wanted to maximize every singe facet of the build (which you might....Im not sure).
Anyway....crickets.....LOL
Hope this helps!
-Tony
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12-24-2009, 09:36 AM
#8
Your current chamber volume and compression is very ideal, if not a tad conservative, for 93 octane.
The reliefs you will end up grinding in the heads would be lucky to displace 2 cc's of volume.....probably slightly less.
That still puts the final figure at 11.4 ish with a piston to head distance (quench) of .035 or so. You could have milled another cc or so and gotten to 59 cc with the fact you have 93 octane available, but I wouldn't lose sleep over that slight extra increase unless you wanted to maximize every singe facet of the build (which you might....Im not sure).
Anyway....crickets.....LOL
Hope this helps!
-Tony
The reliefs you will end up grinding in the heads would be lucky to displace 2 cc's of volume.....probably slightly less.
That still puts the final figure at 11.4 ish with a piston to head distance (quench) of .035 or so. You could have milled another cc or so and gotten to 59 cc with the fact you have 93 octane available, but I wouldn't lose sleep over that slight extra increase unless you wanted to maximize every singe facet of the build (which you might....Im not sure).
Anyway....crickets.....LOL
Hope this helps!
-Tony
and what would you guess the gain be if say i wen to like 54cc and brought the compression to around 12.1:1 (3cc reliefs, if possible) and ran two tunes with a dual pcm... one tune very conserative for street 93 and then another for 100oct track...
now i am not sure if i would run out of relief room with flycutting the pistons, and the deeper the cut the more i go in the other direction for compression...also is there a cc size where flow is drastically affected for the worse...
I am just looking at all paths to take and was trying to think outside the box some over the standard 11.5:1...
12-24-2009, 10:04 AM
#9
Staging Lane
Join Date: Nov 2007
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i am definately not a compitent LS1 guy to answer your question but you can take this for what its worth
on my BBC 615ci race engine my brodix maneater heads have only 70cc combustion chambers with a 4.60" bore and it makes over 1300hp on motor, the small shallow combustion chamber has a better flame travel when combined with a shallow dome piston (15.4 to 1 comp) so i would assume that your shallow combustion chambers once milled combined with your flat top pistons would yeild similar results, and i dont think fly cutting your pistons would hurt the compression, you should still gain compression with milling the heads.
i admire your thinking out of the box, mostly how i think too, thats the way to find more power than the next guy......
on my BBC 615ci race engine my brodix maneater heads have only 70cc combustion chambers with a 4.60" bore and it makes over 1300hp on motor, the small shallow combustion chamber has a better flame travel when combined with a shallow dome piston (15.4 to 1 comp) so i would assume that your shallow combustion chambers once milled combined with your flat top pistons would yeild similar results, and i dont think fly cutting your pistons would hurt the compression, you should still gain compression with milling the heads.
i admire your thinking out of the box, mostly how i think too, thats the way to find more power than the next guy......
12-25-2009, 08:34 AM
#10
Chris Im running 5.3 truck heads milled to 54 cc chambers and -4cc mahle flat tops with 11.63/1 compression on pump gas with 239/243 .612.612 LIFT 112 LSA +2 ADV. i have to pull my motor to rering it and will most likely either adv. the cam 2 deg advanced more or get a custom cam to match my intake. My truck intake held on all the way to 6800 before its started becoming a real restriction but my cam in a 347 wants to go way more rpm then that. My heads seem to do pretty well even milled that much.
12-25-2009, 12:08 PM
#11
Chris Im running 5.3 truck heads milled to 54 cc chambers and -4cc mahle flat tops with 11.63/1 compression on pump gas with 239/243 .612.612 LIFT 112 LSA +2 ADV. i have to pull my motor to rering it and will most likely either adv. the cam 2 deg advanced more or get a custom cam to match my intake. My truck intake held on all the way to 6800 before its started becoming a real restriction but my cam in a 347 wants to go way more rpm then that. My heads seem to do pretty well even milled that much.
i dont wanna have to much milled off when i get domed pistons...who knows maybe i will go more, i can never make up my mind...haha
i am going to go with a very similar cam i think 239/243 .624/.624 111+3...
12-25-2009, 01:26 PM
#12
Staging Lane
Join Date: Jan 2009
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i dont mean to jump in on the post but i also have a question on this. I am buying the trick flow 215s very shortly and was going to get them milled to 59cc from the stock 64cc they come with. is it a must to get the pistons flycut? my cam has a .598 lift and i am running stock bottom end.
12-26-2009, 11:51 AM
#15
I have a set of old stock flycut pistons on my bench from my SBE motor 3 years ago, I think I flycut .080 but i'll try to meaure it for you. I'll pack some clay in them so it's flush to the piston face and then peel it out and drop it in a graduated cylinder full of water, that should give you a ballpark on how much they displace but I cant image it being more than 1.5-2cc's.
