LT1 head question
Thread Starter
Team Owner
Joined: Apr 2001
Posts: 22,267
Likes: 3
From: Dallas TX
LT1 head question
Are LT1 heads 64 or 68cc stock? and how much should I have the heads milled to obtain 10.8-11:1 compression? 3.75 stroke 4.03 bore flat top pistons.
[Modified by Glock'94, 12:00 AM 12/13/2001]
[Modified by Glock'94, 12:00 AM 12/13/2001]
Safety Car
Joined: Mar 2000
Posts: 3,620
Likes: 2
From: Hillsboro OR
Re: LT1 head question (Glock'94)
Neither, 58 cc. If you have flat tops your going to have high compression.
Head Chamber HC = 58 cc
.040 gasket G = 8 cc
Swept Volume SV = 784 cc
Piston Valve Rel PR = 5 cc
CR = (HC + G + SV + PR)/(HC + G + PR)
So you will have: (58 + 8 + 784 + 5)/(58 + 8 + 5) = 12.4 :eek:
Maybe the ones you got have some dish in them.
Head Chamber HC = 58 cc
.040 gasket G = 8 cc
Swept Volume SV = 784 cc
Piston Valve Rel PR = 5 cc
CR = (HC + G + SV + PR)/(HC + G + PR)
So you will have: (58 + 8 + 784 + 5)/(58 + 8 + 5) = 12.4 :eek:
Maybe the ones you got have some dish in them.
Thread Starter
Team Owner
Joined: Apr 2001
Posts: 22,267
Likes: 3
From: Dallas TX
Re: LT1 head question (AquaMetallic94LT1)
Thanks for the info. The only "dish" the pistons have to them are the valve cut outs.... hhmmmm..... as long as the block is in good shape, i'm not having it 0 decked.. so maybe that'll keep it down a bit.. I definitely don't want to be having to run anything over 93 octane to keep from getting detonation!
[Modified by Glock'94, 12:50 AM 12/13/2001]
[Modified by Glock'94, 12:50 AM 12/13/2001]
Melting Slicks
Joined: Jun 1999
Posts: 2,872
Likes: 3
From: Wilmington NC
Re: LT1 head question (Glock'94)
Glock,
just saw some interesting posts from the lt1tech board.... if you raise the size of the balance coolant tubes on the back of your heads to a -6 line it will substantially drop the temps of the heads with the reverse cooling.. also, to raise your combustion chamber cc volume be sure to completely polish the chamber.. do not remove material unequally, but smooth all the surfaces and be sure their are NO SHARP point! including the edge of the chamber, chamfer it slightly or better yet a small radius.. this will fight detonation well.. and with proper tuning you should be fine on pump gas!! good luck! just figured i would through you some ideas!
chris
PS i decked my heads .020" and used the IMpala Head Gasket anyone wanna do the math on thatone! :lol: :lol: :lol: :lol: compression begets power!
Chris :cheers:
[Modified by lcvette, 10:22 AM 12/13/2001]
just saw some interesting posts from the lt1tech board.... if you raise the size of the balance coolant tubes on the back of your heads to a -6 line it will substantially drop the temps of the heads with the reverse cooling.. also, to raise your combustion chamber cc volume be sure to completely polish the chamber.. do not remove material unequally, but smooth all the surfaces and be sure their are NO SHARP point! including the edge of the chamber, chamfer it slightly or better yet a small radius.. this will fight detonation well.. and with proper tuning you should be fine on pump gas!! good luck! just figured i would through you some ideas!
chris
PS i decked my heads .020" and used the IMpala Head Gasket anyone wanna do the math on thatone! :lol: :lol: :lol: :lol: compression begets power!
Chris :cheers:
[Modified by lcvette, 10:22 AM 12/13/2001]
Race Director
Joined: May 2001
Posts: 14,165
Likes: 9
Re: LT1 head question (lcvette)
Huh, did I mention the compression on my friend's Z-28? He had that the block zero decked, TDC is right at the top, pretty nice actually. His pistons are DISHED and supposed to make around 11.5:1 compression. Oh and he's had the heads milled 20. He's thinking it makes around 12.5 As for now it's ok on 93, but when he gets it dyno'd next month we'll know for sure how much retard he's getting.
Thread Starter
Team Owner
Joined: Apr 2001
Posts: 22,267
Likes: 3
From: Dallas TX
Re: LT1 head question (AquaMetallic94LT1)
Neither, 58 cc. If you have flat tops your going to have high compression.
Head Chamber HC = 58 cc
.040 gasket G = 8 cc
Swept Volume SV = 784 cc
Piston Valve Rel PR = 5 cc
CR = (HC + G + SV + PR)/(HC + G + PR)
So you will have: (58 + 8 + 784 + 5)/(58 + 8 + 5) = 12.4 :eek:
Maybe the ones you got have some dish in them.
Head Chamber HC = 58 cc
.040 gasket G = 8 cc
Swept Volume SV = 784 cc
Piston Valve Rel PR = 5 cc
CR = (HC + G + SV + PR)/(HC + G + PR)
So you will have: (58 + 8 + 784 + 5)/(58 + 8 + 5) = 12.4 :eek:
Maybe the ones you got have some dish in them.
Safety Car
Joined: Mar 2000
Posts: 3,620
Likes: 2
From: Hillsboro OR
Re: LT1 head question (Glock'94)
Correction, it's 12.04 actually (double check your calculations)... that's a little better. But I would still like to have it closer to 11:1
Now with new facts we try this again (.030 deck) :
(58 + 8 + 6 + 784 + 5)/(58 + 8 + 5 +6) = 11.2
Live with it. 2FST4U says he's got guys running 12 on pump gas. The best situation is to have zero deck because the engine runs better with a tight quench area. You still have to maintain .040 clearance for piston rock but the head gasket takes care of that. You could enlarge the combustion chambers to reduce the compression. The trick is to do it evenly between cylinders and unshroud the intake valve without ruining the chamber design.
I thought I read that the LT1 heads are 58 cc and LT4 heads are 54.5 ccs which is where the compression change came from. Damn two mistakes in one post. :bb
Take a picture of your intake port bowls after the heads are cleaned. It would be interesting to see what that area looks like before an porting is performed.
[Modified by AquaMetallic94LT1, 10:22 PM 12/15/2001]
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Thread Starter
Team Owner
Joined: Apr 2001
Posts: 22,267
Likes: 3
From: Dallas TX
Re: LT1 head question (Glock'94)
Ok, found the final judgement... here it is... * Combustion chambers are almost identical (there was a negligible .4cc difference) Volume for LT4 Combustion chambers are 54.4cc's.
source : http://home.tir.com/~steveher/lt4.html
source : http://home.tir.com/~steveher/lt4.html
