Spring choice for BBC?
Thread Starter
Burning Brakes
Joined: May 1999
Posts: 865
Likes: 4
From: troy, mi
Spring choice for BBC?
Looking for thoughts on a set of springs for my 468 BBC in my '71. Last fall I put GMPP alum. ovals with 2.30 intake on with a Comp HE 284 hyd. cam. Broke the cam in with only the outer springs, everything went fine, and now I am ready to add the inner springs in and let her rip. But.... I've read some not so good things about the dual springs that come with the GMPP's. Is it worth installing another set of springs that are "better"?? If so, any suggestions or part numbers? Perhaps the single beehives with a Ti retainer? RPM range I'm looking at is 6200 max or so, car is 3.70 ratio with M-21, will have a 125 shot on it, DR's, etc. Thanks!!
Team Owner
Joined: Apr 1999
Posts: 21,953
Likes: 1,444
From: Reno Nevada
2024 C3 of the Year Finalist- Modified
The only way you can make an informed decision is: What are your spring specs for the GM and the Beehive. You have to know the spring rate and closed seat pressure at the installed height. Then you need to know your valve lift.
If you can get me those figures I could tell you what can get those heavy 2.300 vavles to not float under 6500 rpm
If you can get me those figures I could tell you what can get those heavy 2.300 vavles to not float under 6500 rpm
Thread Starter
Burning Brakes
Joined: May 1999
Posts: 865
Likes: 4
From: troy, mi
This is what i got off of the GM site:
The dual spring is 1.487" O.D. diameter and 1.10" solid height. The pressure at installed height is 116# @ 1.88" with 317# the average rate of pound per inch. Use with valve spring retainer P/N 3879613
The XE284 cam I'm using is 284/296 advertised duration with 240/246 @ 050. Lift is .574/.578 on a 110 LSA. I've heard this cam is prone to failure, ( of course after I installed it)so a big bad spring might not be the best. Thats why I was thinking a lighter spring like the BBC beehive with a Ti retainer might be the way to go, and keep float out of the pic until at least 6200 or so. Thanks!!
The dual spring is 1.487" O.D. diameter and 1.10" solid height. The pressure at installed height is 116# @ 1.88" with 317# the average rate of pound per inch. Use with valve spring retainer P/N 3879613
The XE284 cam I'm using is 284/296 advertised duration with 240/246 @ 050. Lift is .574/.578 on a 110 LSA. I've heard this cam is prone to failure, ( of course after I installed it)so a big bad spring might not be the best. Thats why I was thinking a lighter spring like the BBC beehive with a Ti retainer might be the way to go, and keep float out of the pic until at least 6200 or so. Thanks!!
Team Owner
Joined: Apr 1999
Posts: 21,953
Likes: 1,444
From: Reno Nevada
2024 C3 of the Year Finalist- Modified
http://www.compcams.com/Technical/Se...umber=11-250-3
This page talks about your cam and it recommends spring # 924-16 for your sub .600 lift cam.
This is the part number page for the behive spring that would work
http://www.powerandperformancenews.c...&Store_Code=CC
on this page go down to the 1.800 springs and look at beehive spring 26918 You can see that at the 1.800 installed height you would have .600 rec. max lift and 130# on the seat. If they are in stalled at 1.850 inches from the table the seat pressure drops to 114# and the max lift would be increased to .650. So your springs would run cooler.
IMO I would shim them for 1.825 or something close so the seat closed pressure would be nearer to 120# closed. I also can't get info on those recommended springs the 924-16.
http://www.compcams.com/Technical/Cu...ML/340-349.asp
This page talks about your cam and it recommends spring # 924-16 for your sub .600 lift cam.
This is the part number page for the behive spring that would work
http://www.powerandperformancenews.c...&Store_Code=CC
on this page go down to the 1.800 springs and look at beehive spring 26918 You can see that at the 1.800 installed height you would have .600 rec. max lift and 130# on the seat. If they are in stalled at 1.850 inches from the table the seat pressure drops to 114# and the max lift would be increased to .650. So your springs would run cooler.
IMO I would shim them for 1.825 or something close so the seat closed pressure would be nearer to 120# closed. I also can't get info on those recommended springs the 924-16.
http://www.compcams.com/Technical/Cu...ML/340-349.asp
Thread Starter
Burning Brakes
Joined: May 1999
Posts: 865
Likes: 4
From: troy, mi
Thanks for the info, I also found this in a valvespring article in Carcraft:Here is an excerpt
Comp then sent us a set of brand-new PN 29120 beehive springs designed specifically to address this valve-control problem on the Rat motor. As you can see by the accompanying spring-pressure chart, the beehive spring offers 30 pounds more load on the seat (part of this load is due to the shorter installed height), with open pressures within roughly 5 to 10 pounds. We installed these springs directly on the big-block heads with no prep work and with no other changes so we could do a direct comparative test.
Comp then sent us a set of brand-new PN 29120 beehive springs designed specifically to address this valve-control problem on the Rat motor. As you can see by the accompanying spring-pressure chart, the beehive spring offers 30 pounds more load on the seat (part of this load is due to the shorter installed height), with open pressures within roughly 5 to 10 pounds. We installed these springs directly on the big-block heads with no prep work and with no other changes so we could do a direct comparative test.
Team Owner
Joined: Apr 1999
Posts: 21,953
Likes: 1,444
From: Reno Nevada
2024 C3 of the Year Finalist- Modified
Originally Posted by DaveP
Thanks for the info, I also found this in a valvespring article in Carcraft:Here is an excerpt
Comp then sent us a set of brand-new PN 29120 beehive springs designed specifically to address this valve-control problem on the Rat motor. As you can see by the accompanying spring-pressure chart, the beehive spring offers 30 pounds more load on the seat (part of this load is due to the shorter installed height), with open pressures within roughly 5 to 10 pounds. We installed these springs directly on the big-block heads with no prep work and with no other changes so we could do a direct comparative test.
Comp then sent us a set of brand-new PN 29120 beehive springs designed specifically to address this valve-control problem on the Rat motor. As you can see by the accompanying spring-pressure chart, the beehive spring offers 30 pounds more load on the seat (part of this load is due to the shorter installed height), with open pressures within roughly 5 to 10 pounds. We installed these springs directly on the big-block heads with no prep work and with no other changes so we could do a direct comparative test.
Comp Cams doesn't even have that part number on their site. Car Rag mag's suck. You would think that they just might put out some good info and then they don't get it together with the Vendor.
You don't want more seat pressure to control valve float. Bounce on the seat from steep return ramps
You want more open pressure so the lifter follows the the cam lobe on a higher rpm motor
Thread Starter
Burning Brakes
Joined: May 1999
Posts: 865
Likes: 4
From: troy, mi
I priced out the beehive spring setup with summit with Ti retainers, it was about $470. I think I'm going to install the duals that came with the heads and see how they do, for that much $$ I'll wait a bit....
