|
|
|
|
| Author |
|
|
Registered
Join Date: Jul 2008
Location: Spokane WA
Posts: 585
|
High Performance Valve Springs
In the process of rebuilding my 3.2 heads I'm contemplating going with upgraded valve springs and/or retainers. But I don't want to spend 6 to 8 hundred$ for unnecessary stuff. I do plan to use ARP rod bolts as a little RPM insurance and was considering valve springs for the same reason. My thinking is that with stock smog cams this motor will never see 7k rpm so springs may be overkill. So the question is what rpm will a stock cammed 3.2 rev to before the valves start to float? Are high perf springs worth the $$ for "money shift" overrev insurance? The downside, of course, is cost, hp lost to compressing the springs, and increased cam wear. Also, how durable are the stock springs? If the old stockers pass the compression test will they be reliable for the next 100k mi?
|
||
03-24-2012, 09:47 PM
|
|
|
Registered
Join Date: Jul 2001
Location: Portland Oregon
Posts: 7,007
|
If your stock springs still test good and don't require excessive shims, you are good to 6700 before float and that's well beyond the power peak for smog-type, OEM cams.
Race springs will simply accelerate wear on chains, sprockets, cams and rockers unless you need them.
__________________
Steve Weiner Rennsport Systems Portland Oregon (503) 244-0990 porsche@rennsportsystems.com www.rennsportsystems.com |
||
|
03-24-2012, 10:34 PM
|
|
|
Registered
Join Date: Jul 2008
Location: Spokane WA
Posts: 585
|
Thanks Steve, I appreciate your advice.
|
||
|
03-24-2012, 11:07 PM
|
|
|
Registered
Join Date: May 2003
Posts: 3,346
|
Consider buying titanium retainers instead. They will give you some increased RPM before valve float and don't increase wear.
-Andy
__________________
72 Carrera RS replica, Spec 911 racer |
||
|
03-26-2012, 11:04 AM
|
|
|
Registered
Join Date: Jul 2008
Location: Spokane WA
Posts: 585
|
That sounds like a good option Andy. Any idea how much of an extra margin the lighter retainers will provide with stock springs? It looks like around $200 for the retainers.
|
||
|
03-26-2012, 07:33 PM
|
|
|
Registered
Join Date: Jul 2005
Location: Atlanta
Posts: 1,241
|
By reducing the weight a few grams each valve you are indeed helping a bit and if you're not going to see beyond 6700-6800rpm you are in good shape with stock springs. Beefier springs are necessary only when the cam lobe starts getting radical with radical lift rates. Stock springs would cause the valve to 'loft' with a fairly radical cam profile so just be mindful of that if you are going to cam the motor.
|
||
|
03-27-2012, 11:55 AM
|
|
|
|
Registered
Join Date: May 2004
Location: Boulder, Colorado
Posts: 7,275
|
Stock springs are pretty good. The exact same springs were used from 1965 through 1989, if not into the 964 era also. They did the trick with the motors with rev limits up at or above 7,000 rpm.
I ran my 2.7 and 2.3 race motors at 8,000 rpm on the track with stock springs and pretty big cams (Elgin 315 and 310 respectively). I did have the titanium retainers to go with valves of those sizes. Didn't have any problems. But there was no margin for missed shifts there. Really little value added to a stock motor with bigger springs, or the Ti retainers, though the latter only hurt the pocketbook. |
||
|
03-27-2012, 12:28 PM
|
|
