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 $$$ does this job cost? c) how does compression affect throttle response? Is is similar to that of a stroked engine? |
Compression is definitely a plus. What cam are you running? You need to also make sure the shop that does the milling can hit the flatness and surface roughness required for the gaskets you will be running. My compression is 11.3 but I am also running a thinner gasket to help with detonation. There are calculators you can use to figure it out.
|
Originally Posted by TheRadioFlyer
(Post 1574200169)
A few guys on LS1 tech have suggested I mill the 243 heads i'm getting about .020" from the deck which should bring compression to 11:1.
a) has anyone tried this? b) about how much $$$ does this job cost? c) how does compression affect throttle response? Is is similar to that of a stroked engine? 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. |
Originally Posted by vettenuts
(Post 1574200710)
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. |
Originally Posted by TheRadioFlyer
(Post 1574200169)
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? The biggest improvement I notice when I bump compression is the throttle response. BIG difference! :thumbs: |
Originally Posted by vettenuts
(Post 1574200710)
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 |
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.
|
I'm interested in this too. What gains can you expect from just milling the heads and a retune?
|
The experts would tell you to check valve to piston clearance.
|
Originally Posted by Paul 75 L82
(Post 1574206893)
The experts would tell you to check valve to piston clearance.
|
Originally Posted by ctusser
(Post 1574207064)
He'll be fine with the 221/226 cam he's running.
221/226 .565/.560 114 I'm repalcing both lifters and pushrods as well so I can get custom lengths if requried. |
Originally Posted by TheRadioFlyer
(Post 1574207281)
Well i plan to run 1.8 rockers with this cam:
221/226 .565/.560 114 I'm repalcing both lifters and pushrods as well so I can get custom lengths if requried. |
Originally Posted by ctusser
(Post 1574208333)
Its the duration and lsa more than the lift. By the time full lift is achieved the piston is inches down.
|
Originally Posted by TheRadioFlyer
(Post 1574210200)
Are you saying my setup should clear? I'm not familier with the total valve lift formula.
|
Originally Posted by ctusser
(Post 1574210405)
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.
|
Originally Posted by TheRadioFlyer
(Post 1574207281)
Well i plan to run 1.8 rockers with this cam:
221/226 .565/.560 114 I'm repalcing both lifters and pushrods as well so I can get custom lengths if requried. |
Originally Posted by TheRadioFlyer
(Post 1574207281)
Well i plan to run 1.8 rockers with this cam:
221/226 .565/.560 114 I'm repalcing both lifters and pushrods as well so I can get custom lengths if requried. |
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.
|
Originally Posted by TheRadioFlyer97
(Post 1574216763)
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.
|
Originally Posted by 427troy
(Post 1606517389)
My grandma must be your mechanic?
Maybe your grandma also got a hold of your laptop? |
All times are GMT -4. The time now is 04:21 AM. |
© 2024 MH Sub I, LLC dba Internet Brands