408 milled heads, decked block, compression and pushrod length
Thread Starter
Staging Lane
Joined: Jun 2005
Posts: 67
Likes: 0
From: Australia victoria
408 milled heads, decked block, compression and pushrod length Hi the 408 is coming along great, my 6lt iron block was decked 0.022 from a stock deck hight of 9.230. I am going to mill the LQ4 71cc heads down 0.018 a new compression of 10.6:1 using a cometic gasket 0.051 compressed therefore 9.230-(0.022+0.018)= 9.190 new deck hight making a difference of 0.040 less.
1. am I safe going for 7.350 push rods.
2. should I go higher in compression driven 3 times a week drags 1 x month.
3. how much more head milling can I go before the port to port alignment is a problem. thanks
Iron block 4.030 6lt (decked 0.022)
4 inch crank
h beam scat forged rods
Wiseco forged pistons -8cc
Plasma rings
Heads LQ4 (not ready)
Comp Cam 244/248-609/615 @50 LSA 112
25% under drive pulley
baffeled sump
ported oil pump
dual chain
LSX fast manifold
90mm Fast TB
Injectors 42lb
Walbaro fuel pump
pushrods ????
Comp cam lifters
Stainless valves
Dual valve springs
Titanium retainers
Yella terra roller rockers 1.7
arp head studs
arp main studs
arp cam bolts
arp clutch bolts
arp fly wheel bolts
arp header studs
arp crank bolt
cometic head gasket 0.051
4.11 diff gears
6 speed manual
ceramic clutch
steel billet flywheel
1. am I safe going for 7.350 push rods.
2. should I go higher in compression driven 3 times a week drags 1 x month.
3. how much more head milling can I go before the port to port alignment is a problem. thanks
Iron block 4.030 6lt (decked 0.022)
4 inch crank
h beam scat forged rods
Wiseco forged pistons -8cc
Plasma rings
Heads LQ4 (not ready)
Comp Cam 244/248-609/615 @50 LSA 112
25% under drive pulley
baffeled sump
ported oil pump
dual chain
LSX fast manifold
90mm Fast TB
Injectors 42lb
Walbaro fuel pump
pushrods ????
Comp cam lifters
Stainless valves
Dual valve springs
Titanium retainers
Yella terra roller rockers 1.7
arp head studs
arp main studs
arp cam bolts
arp clutch bolts
arp fly wheel bolts
arp header studs
arp crank bolt
cometic head gasket 0.051
4.11 diff gears
6 speed manual
ceramic clutch
steel billet flywheel
LME just built my 408. I`m going 11.3.1 to get more power. i`m getting ET 245`s heads and all the bolt-ons with 90/90 set-up. Car in sig. The cam you have is about the same as mine. Mine is 244 248 620ish 114. I will be running a A4 with 3800 stall.
New GM 6.0L Iron Block, Eagle 4.000" Forged 4340 Steel Crankshaft, Callies Compstar 6.125" Forged 4340 Steel Connecting Rods, Wiseco -8cc Reverse Dome Pistons, Childs & Albert Dura-Moly Rings, Clevite77 Main, Rod, and Cam Bearings, ARP Main/Head Studs, and a Custom COMP Cam.
The heads are ET Performance 245CC 11* Heads. They have 2.080/1.600 Valves, REV Stainless Steel Valves, Manley Valvesprings, Locks, and Retainers, good to .650" lift. Combustion Chamber size is 64cc's. Compression will be exactly 11.3:1 using the stock GM 6.0L MLS Headgasket.
This is what the set-up looks like, with all the stuff I have in my sig to go with it. Will be bumping the shot to a 200!!!!!
I`m taking everything of my car in sig and putting it on my 408! she is going to FLY!
New GM 6.0L Iron Block, Eagle 4.000" Forged 4340 Steel Crankshaft, Callies Compstar 6.125" Forged 4340 Steel Connecting Rods, Wiseco -8cc Reverse Dome Pistons, Childs & Albert Dura-Moly Rings, Clevite77 Main, Rod, and Cam Bearings, ARP Main/Head Studs, and a Custom COMP Cam.
The heads are ET Performance 245CC 11* Heads. They have 2.080/1.600 Valves, REV Stainless Steel Valves, Manley Valvesprings, Locks, and Retainers, good to .650" lift. Combustion Chamber size is 64cc's. Compression will be exactly 11.3:1 using the stock GM 6.0L MLS Headgasket.
This is what the set-up looks like, with all the stuff I have in my sig to go with it. Will be bumping the shot to a 200!!!!!
I`m taking everything of my car in sig and putting it on my 408! she is going to FLY!
i say go with higher compression somewhere around 11:5 or little more.. I have LME motor with afr225's but with much bigger cam in lift 240/247 639/647 @114 for nitrous.. I made 519rwhp/487rwtq I think i could use more compression, even with the sucky gas we have over here in california Im going with more compression.. probably 11:5 wouldnt be bad to have..
There are a few question we need answered. After the block was decked, how far are the pistons out of the hole? Normal LSX pistons protrude roughly .007" out, plus the extra .022" would put you .029" out of the hole. If that is the case, you'll need at least a .064" head gasket to keep you quench in the right area. A .051" would leave you with only .022" quench, which is far to tight. Either way, you have now decked th eblock and the heads, so you will need a shorter pushrod. 7.350's would prolly be right on. As far as more compression, 11:1 would have been nice, but I believe your already on the verge of intake bolt alighnment problems, so I don't know if I'd mill any more off.
On another compression topic, if your builder was able to get the piston height back to nomal LSX standards,(.007"), I get your compression checking in at 10:75:1 with .051 gaskets. If the pistons are .029" out of the hole, then you'll be looking at 10:97:1 with .064 gaskets. Basically, we need to know how far your pistons are out, then we could make a much better determination.
On another compression topic, if your builder was able to get the piston height back to nomal LSX standards,(.007"), I get your compression checking in at 10:75:1 with .051 gaskets. If the pistons are .029" out of the hole, then you'll be looking at 10:97:1 with .064 gaskets. Basically, we need to know how far your pistons are out, then we could make a much better determination.
buy a pushrod length checker, nobody likes a noisy valvetrain because someone gets lazy at the end of a build. Ive also heard of guys shiming the rockers the amount removed from the heads. Dont forget about the difference of the base circle of the cam also factoring into pushrod length. I wish I had just got a pushrod length checker would of saved me alot of bullshit.
Originally Posted by GENIII
therefore 9.230-(0.022+0.018)= 9.190 new deck hight making a difference of 0.040 less.
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Thread Starter
Staging Lane
Joined: Jun 2005
Posts: 67
Likes: 0
From: Australia victoria
Thanks for the replys. I do have and will use a pushrod checker, I was worried that the length will be an unusual length after machined block and heads.
OK working out to exact calculations,
bore 4.030
stroke 4.000
rod length 6.098
piston comp hight 1.115
new deck hight 9.208
The pistons are at 0.0049 out of the hole.
gasket 0.051 compressed
stock LQ4 71cc chambers no milling yet.
thanks
OK working out to exact calculations,
bore 4.030
stroke 4.000
rod length 6.098
piston comp hight 1.115
new deck hight 9.208
The pistons are at 0.0049 out of the hole.
gasket 0.051 compressed
stock LQ4 71cc chambers no milling yet.
thanks
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I would mill them down to 64-66cc. This also depends on how efficient the heads are. We run 408ci's at 12-1 comp with AFR 225's and the 244/248 Cam. They ussually net 530rwhp on pump gas.
Originally Posted by Slowhawk
I would mill them down to 64-66cc. This also depends on how efficient the heads are. We run 408ci's at 12-1 comp with AFR 225's and the 244/248 Cam. They ussually net 530rwhp on pump gas.
Thread Starter
Staging Lane
Joined: Jun 2005
Posts: 67
Likes: 0
From: Australia victoria
Originally Posted by Beast96Z
I agree that this would be the best thing to do, but, in order to achieve that size combustion chamber, he would have to mill a substantial amount off the heads. With the block already being decked .022", I wouldn't want to remove no more than .030" off the heads for alighnment issues. Milling .030" from the heads would net you roughly 67cc's on the heads and about 10:9:1 compression. That's what I would shoot for anyway.
2. do aftermarket heads have any milling to lower there compression or do they just work on the chambers to achieve a 64cc so I dont end up with alignement problems.
3. I can sell off the heads and look at a set of bare ported 64cc from Patriot and use my valvetrain parts, get exactly what I need with less problems.
