Milling heads for more compression?
Thread Starter
Former Vendor
Joined: Nov 2005
Posts: 8,995
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From: Spring Texas
St. Jude Donor '08
Milling heads for more compression?
A few guys on LS1 tech have suggested I mill the 243 heads i'm getting about .020" from the deck which should bring compression to 11:1.
a) has anyone tried this?
b) about how much $$$ does this job cost?
c) how does compression affect throttle response? Is is similar to that of a stroked engine?
a) has anyone tried this?
b) about how much $$$ does this job cost?
c) how does compression affect throttle response? Is is similar to that of a stroked engine?
Team Owner
Joined: Mar 1999
Posts: 22,025
Likes: 192
From: At the beach in little Rhody
Compression is definitely a plus. What cam are you running? You need to also make sure the shop that does the milling can hit the flatness and surface roughness required for the gaskets you will be running. My compression is 11.3 but I am also running a thinner gasket to help with detonation. There are calculators you can use to figure it out.
Drifting
Joined: Jan 2008
Posts: 1,722
Likes: 138
From: Florida
St. Jude Donor '09
A few guys on LS1 tech have suggested I mill the 243 heads i'm getting about .020" from the deck which should bring compression to 11:1.
a) has anyone tried this?
b) about how much $$$ does this job cost?
c) how does compression affect throttle response? Is is similar to that of a stroked engine?
a) has anyone tried this?
b) about how much $$$ does this job cost?
c) how does compression affect throttle response? Is is similar to that of a stroked engine?
I replaced my cam during the same tear down, so I cannot say how much of the added power was strictly due to the increased compression ratio.
Last edited by ipuig; May 27, 2010 at 07:01 AM.
Pro
Joined: Mar 2007
Posts: 507
Likes: 5
From: Macungie Pa
Compression is definitely a plus. What cam are you running? You need to also make sure the shop that does the milling can hit the flatness and surface roughness required for the gaskets you will be running. My compression is 11.3 but I am also running a thinner gasket to help with detonation. There are calculators you can use to figure it out.
Also, Vettenuts, can you explain how running a thinner gasket would help with detonation ??
Sorry to the OP if this looks like a hi-jack.
Melting Slicks
Joined: Nov 2003
Posts: 3,011
Likes: 9
From: Dublin GA
A few guys on LS1 tech have suggested I mill the 243 heads i'm getting about .020" from the deck which should bring compression to 11:1.
a) has anyone tried this?
b) about how much $$$ does this job cost?
c) how does compression affect throttle response? Is is similar to that of a stroked engine?
a) has anyone tried this?
b) about how much $$$ does this job cost?
c) how does compression affect throttle response? Is is similar to that of a stroked engine?
The biggest improvement I notice when I bump compression is the throttle response. BIG difference!
Thread Starter
Former Vendor
Joined: Nov 2005
Posts: 8,995
Likes: 2
From: Spring Texas
St. Jude Donor '08
Compression is definitely a plus. What cam are you running? You need to also make sure the shop that does the milling can hit the flatness and surface roughness required for the gaskets you will be running. My compression is 11.3 but I am also running a thinner gasket to help with detonation. There are calculators you can use to figure it out.
so far this is the cam i'm shooting for: 221/226 .565/.560 114
http://sdparts.com/details/scoggin-d...-center/sd0067
Race Director
Joined: Sep 2005
Posts: 11,060
Likes: 291
From: Pasco WA
I recommend calling TEA, and explain your setup/goals, and see how much they'd charge to do your 243s. I think you'd be happier with the results of a integrated design, than just milling the heads to bump CR. About the thinner gaskets to help reduce detonation..... thinner gaskets reduce "quench"; the gap remaining at the top of the cylinder/head interface can produce hot spots, which can induce detonation. It's not a problem unless your pushing the limits of timing/gas quality/CR. I went to 10.95 CR, with 8.55 DCR, and with the factory MLS gaskets, which I believe are about .055 compressed, got absolutely no knock retard with 92 octane gas. I don't know my timing numbers, though.
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Thread Starter
Former Vendor
Joined: Nov 2005
Posts: 8,995
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From: Spring Texas
St. Jude Donor '08
Melting Slicks
Joined: Dec 2006
Posts: 2,186
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From: Woodinville WA
Thread Starter
Former Vendor
Joined: Nov 2005
Posts: 8,995
Likes: 2
From: Spring Texas
St. Jude Donor '08
Melting Slicks
Joined: Dec 2006
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From: Woodinville WA
It's not the total lift that gives you problems with piston to valve contact, because when the valve is all the way open the piston is near the bottom of its stroke and at the bottom of the cylinder. The large duration cams which keep the valves open longer when the piston is comming up is what causes the PTV issues. That is a small cam and you wont have problems with contact even if milling .020 to bump compression.
Thread Starter
Former Vendor
Joined: Nov 2005
Posts: 8,995
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From: Spring Texas
St. Jude Donor '08
It's not the total lift that gives you problems with piston to valve contact, because when the valve is all the way open the piston is near the bottom of its stroke and at the bottom of the cylinder. The large duration cams which keep the valves open longer when the piston is comming up is what causes the PTV issues. That is a small cam and you wont have problems with contact even if milling .020 to bump compression.
Team Owner
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From: Raleigh / Rolesville NC
Melting Slicks
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From: Dublin GA
Thread Starter
Former Vendor
Joined: Nov 2005
Posts: 8,995
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From: Spring Texas
St. Jude Donor '08
On suggestion from my mechanic, i will not be milling my heads. My block has 130K miles on it and I'd prefer not to overstress it much. I think 10.5 compression will be just fine.
Heel & Toe
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From: Oregon, USA
Melting Slicks
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From: Sleepy Hollow- NJ
