I have two GMC motors I am working on, a 228 and 302. I have a few questions regarding valve springs. I do know that GMC used the same springs from their 228 all the way up to the 302, to include the 248 and 270 as well. I have read in several places that the springs are all the same for the Chevy inline sixes as well as the GMC's, they can be used interchangeably. So I purchased a new set of SBI springs, part number 160-1116, and the vendor told me "they should work for your GMC".
When I received the springs in the mail today, I noticed these springs are about an 8th of an inch taller then the original springs that came off of both the 228 and 302. I wanted to see if anyone on the forums had used these springs before without issue? I did contact both the vendor and SBI directly, and both claim they show no listings for ANY GMC inline six cylinder, only the Chevy motors.
Next I went onto EGGE's site to see the specs for the springs that they sell in their GMC kits. Their part number for their valve springs is 160-1126. The specs between SBI's and EGGE's springs are close to each other as shown below:
SBI 160-1116
Free Length: 2.250"
Outside Diameter: 1.341"
Inner Diameter: 0.969"
Wire Diameter: 0.182"
Solid Height: 1.390"
Closed Pressure: 78lbs @1.858"
Open Pressure: 192lbs @1.462"
Material: A877
EGGE 160-1126
Free Length 2.160"
Outside Diameter 1.344"
Inner Diameter 0.980"
Wire Diameter 0.182"
Solid Height 1.375"
Closed Pressure 65lbs @1.858"
Open Pressure 163lbs @1.530"
Material A877
As you can see the numbers are close. What makes me question it is the open/closed pressures. I would hate to wipe out a cam lobe. What are your thoughts?
As a side note, a reputable machine shop that completely rebuilt another 228 I have, used Sealed Power valve springs, part number VS424, a common spring. The only spec I could find for them online was the free length, which at 2.250" matched the SBI springs I just bought. I also found that VS424 interchanges with 160-1116. So as I sit here typing this, I just realized that I may have answered my own question, that yes in fact the SBI Springs 160-1116 will work, as they are currently being run on my other 228, and have been without issue since 2013. I guess now the question is, will my other 228 with the VS424 springs need a new cam shaft soon???
I'd still like to hear your thoughts. This post is also cross posted on the GMC tech site. Thank you in advance.
