LQ4 w/140k miles--better to put LS2 rotating assembly or 243 heads?
03-08-2014, 01:42 AM
#1
LQ4 w/140k miles--better to put LS2 rotating assembly or 243 heads? I have an option on a 140k mile 2001 LQ4. Was thinking of either upgrading to 243 heads to raise the compression, or to buy a used 16k mile LS2 rotating assembly (w/24T reluctor). Thoughts on either approach? I'm trying to build a nice motor on a budget. Is there a used cam I ought to look for while I'm at it w/either option? One that will make lower end torque, not high rpm.
Thx
Thx
03-08-2014, 02:00 AM
#2
Even a set of 241's with a .040 gasket should get your compression with stock LQ4 pistons somewhere around 10.3 or 10.4:1 depending on exact chamber size and exactly how far out of the hole the pistons are (usually stock LQ4's are +.005 out of the hole). 243's would raise that to somewhere around 10.7ish IIRC.
If the cylinder walls look good and piston to wall clearance is good i would get a new set of rings & bearings and toss it back together with a mild cam and a set of budget heads. a cam that might seem a bit aggressive for a street 5.7 won't be as high strung in a 6.0+ liter so you'll be able to get a decent cam in there...
My combo is shaping up to look like this:
370cid LQ4
TEA CNC'd 241's with Lunati springs shimmed to spec for cam
Martin @ Tick Custom Cam
Pacesetter LT's & O/R Y to SLP Catback
LS6 Intake
85mm MAF & TB
Powerbond 25% UDP
and blah blah little stuff
I was hoping to be in the ballpark of ~450whp on a stock cube LS1. Martin seems to think the 370cid will bring the power about 100-200rpm lower with the possibility for just as much peak or maybe a hair more...with a nice line down low to boot...
On a stock cube LS1 you'll have spent about 3k to replicate my build. I paid $450 for my .030 over LQ4 as a starting point and i'm not sure what all the machine work will cost yet. i figure for 370cid i'll be under 4k still.
If the cylinder walls look good and piston to wall clearance is good i would get a new set of rings & bearings and toss it back together with a mild cam and a set of budget heads. a cam that might seem a bit aggressive for a street 5.7 won't be as high strung in a 6.0+ liter so you'll be able to get a decent cam in there...
My combo is shaping up to look like this:
370cid LQ4
TEA CNC'd 241's with Lunati springs shimmed to spec for cam
Martin @ Tick Custom Cam
Pacesetter LT's & O/R Y to SLP Catback
LS6 Intake
85mm MAF & TB
Powerbond 25% UDP
and blah blah little stuff
I was hoping to be in the ballpark of ~450whp on a stock cube LS1. Martin seems to think the 370cid will bring the power about 100-200rpm lower with the possibility for just as much peak or maybe a hair more...with a nice line down low to boot...
On a stock cube LS1 you'll have spent about 3k to replicate my build. I paid $450 for my .030 over LQ4 as a starting point and i'm not sure what all the machine work will cost yet. i figure for 370cid i'll be under 4k still.
03-08-2014, 12:10 PM
#4
no point if your current motor's specifications are within service limits. it's the same bore, same stroke. would you rather tear the motor down to toss in a STOCK rotating assembly from a LS2 just to bump compression or just toss on a set of heads and be done?
I know you're gonna be inside the motor anyways...but i'd rather put my money into the top end all things being equal...you will get much more of a return for that investment...
I know you're gonna be inside the motor anyways...but i'd rather put my money into the top end all things being equal...you will get much more of a return for that investment...
03-08-2014, 12:23 PM
#5
no point if your current motor's specifications are within service limits. it's the same bore, same stroke. would you rather tear the motor down to toss in a STOCK rotating assembly from a LS2 just to bump compression or just toss on a set of heads and be done?
I know you're gonna be inside the motor anyways...but i'd rather put my money into the top end all things being equal...you will get much more of a return for that investment...
I know you're gonna be inside the motor anyways...but i'd rather put my money into the top end all things being equal...you will get much more of a return for that investment...
I'm starting to lean to do both. I'm also thinking that maybe w/140k I wouldn't need a rebore, but a good honing and new rings, plus new bearings and LS2 timing chain I would be in pretty good shape. That would get me compression, better pistons/rods and better heads. Is the timing cover the same on LS2 cranks as w/LQ4?
