Milling heads for more compression?
05-27-2010, 01:17 AM
#1
Former Vendor
Thread Starter
Member Since: Nov 2005
Location: Spring Texas
Posts: 8,995
Likes: 0
Received 2 Likes
on
2 Posts
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?
05-27-2010, 06:22 AM
#2
Team Owner
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.
05-27-2010, 06:58 AM
#3
Drifting
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; 05-27-2010 at 07:01 AM.
The following users liked this post:
jbbowtie (04-25-2023)
05-27-2010, 07:45 AM
#4
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.
05-27-2010, 08:49 AM
#5
Melting Slicks
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!
05-27-2010, 10:06 AM
#6
Former Vendor
Thread Starter
Member Since: Nov 2005
Location: Spring Texas
Posts: 8,995
Likes: 0
Received 2 Likes
on
2 Posts
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
05-27-2010, 04:42 PM
#7
Race Director
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.
05-27-2010, 08:02 PM
#12
Melting Slicks
05-27-2010, 11:19 PM
#14
Melting Slicks
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.
05-27-2010, 11:23 PM
#15
Former Vendor
Thread Starter
Member Since: Nov 2005
Location: Spring Texas
Posts: 8,995
Likes: 0
Received 2 Likes
on
2 Posts
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.
05-28-2010, 02:14 PM
#17
Melting Slicks
05-28-2010, 03:53 PM
#18
Former Vendor
Thread Starter
Member Since: Nov 2005
Location: Spring Texas
Posts: 8,995
Likes: 0
Received 2 Likes
on
2 Posts
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.
The following 2 users liked this post by Johnny Hardcore:
Dads2kconvertible (04-18-2023),
vette4fl (04-16-2023)
