Gen 4 5.3 vs 4.8
12-26-2012, 11:20 AM
#1
Piss Pumps for Sale
Thread Starter
iTrader: (5)
Join Date: Nov 2006
Location: Moncton, New Brunswick, Canada, The True North Strong and Free!
Posts: 2,685
Likes: 0
Received 1 Like
on
1 Post
Gen 4 5.3 vs 4.8
Looking to take the ol 5.3 as far as I can before I do an ls7 swap. So I have a few questions Id like to confirm first. I know in gen 3 motors the 5.3 had a dished piston and the 4.8 had flat tops, is this still the case in the gen 4?
12-26-2012, 11:34 AM
#2
No. Your Gen IV 5.3 has flat top pistons in it and is 9.9:1 compression with either the 243/799 64 cc heads it has on it. GM did this in the Gen 3's of course with the L33. The 4.8 actually has the exact same top end as your 5.3 which coupled to it's shorter stroke nets only 8.8:1 compression( GM powertrain lists all these specs).
The LR4 and LM7 used to share the same heads as well but with the 61 cc chambers the difference from having dished pistons in the 5.3 and flat tops in the 4.8 kept their static compression ratio about the same.
That is no longer the case with the Gen IV's.
The LR4 and LM7 used to share the same heads as well but with the 61 cc chambers the difference from having dished pistons in the 5.3 and flat tops in the 4.8 kept their static compression ratio about the same.
That is no longer the case with the Gen IV's.
12-26-2012, 11:56 PM
#3
Piss Pumps for Sale
Thread Starter
iTrader: (5)
Join Date: Nov 2006
Location: Moncton, New Brunswick, Canada, The True North Strong and Free!
Posts: 2,685
Likes: 0
Received 1 Like
on
1 Post
No. Your Gen IV 5.3 has flat top pistons in it and is 9.9:1 compression with either the 243/799 64 cc heads it has on it. GM did this in the Gen 3's of course with the L33. The 4.8 actually has the exact same top end as your 5.3 which coupled to it's shorter stroke nets only 8.8:1 compression( GM powertrain lists all these specs).
The LR4 and LM7 used to share the same heads as well but with the 61 cc chambers the difference from having dished pistons in the 5.3 and flat tops in the 4.8 kept their static compression ratio about the same.
That is no longer the case with the Gen IV's.
The LR4 and LM7 used to share the same heads as well but with the 61 cc chambers the difference from having dished pistons in the 5.3 and flat tops in the 4.8 kept their static compression ratio about the same.
That is no longer the case with the Gen IV's.
Anyone know how much I need to mill my stock 243's to get my compression ratio up around 11:1? Im thinking somewhere around .035? I know I shouldnt have any pvc issues with this setup or problems getting my intake to seal to the heads, also Ill obviously be getting a D.O.D. delete aswell as the vvt.
I also recently bought a 3200 stall for the 6L80e, plan on going with a tr224 224 112 lsa cam, but I am open to suggestions
12-30-2012, 10:52 AM
#6
TECH Addict
iTrader: (21)
Join Date: Apr 2008
Location: Fort Worth, Texas
Posts: 2,625
Likes: 0
Received 0 Likes
on
0 Posts
I would talk to one of the guys that knows cams before you go milling and upping the comp before you know what cam you want. Static compression isnt as important as Dynamic compression and you need to know what that is using a calculator and intake valve events with a certain cam/head combo
Thread
Thread Starter
Forum
Replies
Last Post
