[nikwho]

Hello all,
I'm trying to finish my BBC swap on my '68 GMC. It's got a '69 427 of of a '69 Camaro.* It's got a new forged 3.76" stroke crank and has been bored to 4.280; +0.030".* It has forged rods and pistons, 10:1 compression with 291 heads, 2.19"/1.88" valves, 1.75" primary Heddman headers, Edelbrock RPM Air-Gap intake, Quick Fuel Q-Series 850cfm carb, MSD Pro-Billet distributor & MSD Digital-6 Plus ignition box.* I'm running a Comp Cams XE-274 hydraulic flat tappet cam.

Comp reccomends 624 or 630 valve springs, though I've heard of lots of issues @ or above 5000 RPM with the 624 springs.* I've also read about guys using Isky 8005-A valve springs and being very happy with their performance.*

I've got a set of Edelbrock #5745 valve springs that came in a set of Victor Jr. 24° heads.* I'm wondering if they'll be a good fit for my application.* If they wont, I'd probably lean towards running the Isky springs.

Here's what I've got on ea h set of springs:

Comp 924:
seat pressure- 112 lbs. @ 1.88"
Open pressure - 355 lbs. @ 1.200"
Installed height - 1.88"
OD- 1.509"
Coil bind - 1.175"
Open height - 1.28"
Spring rate - 347#

Comp 930:
seat pressure- 153 lbs. @ 1.900"
Open pressure - 383 lbs. @ 1.250"
Installed height - 1.9"
OD- 1.550"
Coil bind - 1.160"
Open height - 1.25"
Spring rate - about 354#

Isky 8005:
seat pressure - 135 @ 1.875"
Open pressure - 395 @ 1.225"
installed height - 1.875"
OD - 1.530"
Coil bind - 1.160"
Open height - 1.225"
Spring rate - 400 lbs./in.

Edelbrock #5745:
Seat pressure: 125 @ 1.975"
Open pressure: 330 lbs @ 1.425”
Installed height: 1.975"
OD - 1.550"
Coil bind - 1.150"
Open height -
Spring rate - 372lbs./in (1/0.550"=1.8181 x 205 = 372))
*
The springs look fairly comparable to me. The Edelbrock springs have a taller installed height, by about 1/10th of an inch, but lower seat pressure. So, by my math, these springs installed at 1.875" would be approx 125 lbs + 10%, or 37.2 lbs, which would equal 162lbs. But, I read a spec somewhere about these springs having a seat pressure of 135 lbs, but didn't specify the in taller height.

Any help would be greatly appreciated.

Nik