View Full Version : LS3 heads...Blue springs?


Chevyratracer
08-03-2011, 11:39 PM
Bought a set of ls3 heads parts # 12629063. Just got them opened the box and was suprised to see blue spings on them. Are these also good for a .570 lift cam or are they diferent. GMPP catalog says they come with ls6 springs, is this a replacement for the "yellow" springs?

crainholio
08-04-2011, 07:18 AM
Yup, GM switched from yellow to blue.

Jim85IROC
08-04-2011, 07:26 AM
Are you guys sure that the "yellow" springs will do .570 lift on an LS3 head? I remember on the LS6 heads they were rated for that, but all the literature for the LS3 heads that I've seen specifies .525 lift... I assume due to the larger, heavier valve compared to the LS6 heads.

crainholio
08-04-2011, 11:15 AM
Several factors come into play during spring selection, beyond the cam's lift value. The ramp rate, valve weight, intended RPM range, etc...all are critical in picking the right spring.

crainholio
08-04-2011, 11:20 AM
...but all the literature for the LS3 heads that I've seen specifies .525 lift... I assume due to the larger, heavier valve compared to the LS6 heads.

The factory LS3 cam is 0.551" lift.

Chevyratracer
08-04-2011, 11:43 AM
So if I use the blue springs from the ls3 heads on my 5.3 with a ls6 cam it'll work

allblowdup
08-04-2011, 02:01 PM
The factory LS3 cam is 0.551" lift.

Only the 430hp ls3 is .551 lift. The crate ct 525and 376/515 is .525, the lsa is .492 the gm hot cam is .525. ls3376/480 is .525

The springs are rated for .570 lift but only use the .525/.492/.551 in those particular engines. Kind of a one spring fits all deal.

65SSZO6
08-09-2011, 10:30 PM
I think you can only use LS3 heads on 4" or larger bore? 5.3l is 3.89" bore? Check your bore before installing.

MattSapp95_T/A
08-09-2011, 10:58 PM
Yes the heads will not fit on a 5.3... The bore has to be 4.000 or bigger

yonerhottlt1
08-10-2011, 01:50 AM
Yes the heads will not fit on a 5.3... The bore has to be 4.000 or bigger

THIS! :nod:

DietCoke
08-10-2011, 05:06 AM
The blues are the same IH and coil bind as the yellows, with a little more seat and open pressure GM switched to them mid 2011 MY