BillK wrote: ↑Tue Jun 29, 2021 8:41 am
To be honest with looking at the specs in the GMPP catalog I would put it in just like it is. With the 3.73 gears it will probably be more than you will ever need. Save the money for your traditional build
Just my opinion,
Bar gets quiet - slight pause. Everyone starts laughing!
Seriously, I have thought about that, and youre probably right.
The spring pressure at stock seat installed height for that spring is only 90 psi @ 1.80". Open height spec is 295 @ 1.25". spring rate is 375 LBS per inch.
You want to shim the spring installed height to about 120 lbs @seat..
It is just right for both the Isky Z27 and the Isky hyd 201278. when installed correctly..
It is not a "roller spring"..
But it does work very well on mild to moderate hyd roller sbc cams too.
Install @ 1.72". seat pressure 120#. open pressure 304 #
net lift on the Isky (.507" lift gross) cam is only .491" with lash set..
It does not get any where near coil bind .which is 1.085" according to gmpp.
just right. gmpp #12499224
GM now uses these LS6 beehive springs on all their CT crate motors with vortec heads.
Its the oem stock vortec rocker arms that may need attention.
Check rocker stud to rocker slot clearance at full lift.
Needs .030" clear.. You can make the rocker slot a little longer by grinding it a bit.. (If needed)
Longer not wider. It ,if any ,will only need minor tweeking with the Isky Z/27 solid cam..
Not that hard. It will GLH. →→→
Remember with the guided style rockers use a round wire feeler guage to set valve lash (.016")
Elgin sells stock type sbc guided style rocker with a long slot also
Alternative.... This ct350 should be a factory oem " Roller block"
Which means it will accept all the OEM hyd roller valvetrain, lifters spyder + dog bones and a oem style sbc hyd roller cam.
Eg Melling cam #22280. 283/287 220/224@.050" .495/.502. 110 lsa 107/113
(I would install it at 104 in cl)
110 lsa (104/116)
Use the same gmpp LS6 springs + comp retainers.
Same 120# installed seat pressure.
Bolt in and go.. It will make very good power and torque.
Needs long slot guided rockers.
F-BIRD'88 wrote: ↑Tue Jun 29, 2021 1:54 pm
It does not get any where near coil bind .which is 1.085" according to gmpp.
Set I actually checked the coil bind was less, .480 lift and if I went 1.72 it would have been too close to coil bind. I was at 1.75 according to my notes and it was just a little over .080 from coil bind if I rem right. So -0.030 & -0.020 your 0.030 from coil bind on the springs I used.
Not the first time specs are wrong as many know from real world experience and why you should double check. I did because I found multiple diff coil bind specs for those springs at the time I was setting up the heads. When in doubt, pull your mic out!
Latest GMPP part number is now 19420455
Same spring design and purpose apparently new supplier.. Even if the coil bid height is 1.20"
You can then shim for a slightly higher 1.725 to 1.730" installed
height and get plenty seat and open pressure with all the cams I mentioned.
1.725 - .495 = 1.23 I used Camking's specs IF used with GM LS Blue springs
1.23 -1.20 = 0.030
What's you min from coil bind? I've read .080 to .050 min
FYI I haven't checked the new part number that aren't painted blue But there are still blue springs out there by the 12499224 part number mentioned in one of your earlier post. I'm not trying to be a jerk, I just don't want someone to have an issue from what I've noticed with the Blue springs IF they shim them down.