from stock spring( aluminium stock but ported heads L98).. what is the most general spring upgrade (part #"S)other than using comps or other performance type? it there machining involved? could LT4 stock springs be used? why is there a secondary spring inside the stocks?

1.6 RR & 981-16 for 89 up grade...not so sure about these....

thanks

 

Yes, LT4 springs can be used...that's what I did.

The second spring, from what others said in my thread I started, are used as dampers.

 

it there a part number and is there machining involved? what are the benefits using LT4? why? are stiffer? ok with 1.6 RR's?

i thought they were dampers in stocks but i think if these dampers would have not been there i would be looking at i mototr job ...i did break spring two days ago.. for now just repaired with stock..

tried doing a search but its not working still/agin

 

With a stock cam and 1.6:1 RRs the Comp Cams #981 spring works very well. It is a single spring with damper, fits the stock spring seat and will control the valves nicely.

The beehive spring (LT4 I believe) does not have a damper but rather uses the eliptical wire design to control resonance, which is the purpose of the damper in stock style springs.

 

Here a link to a page that will give you the P/N, seat pressure, etc. on the LT4 spring... http://www.sallee-chevrolet.com/Cam_...hotcamkit.html

They will support up to .525" lift, and are a single-coil design.

If you're going to go the LT4 route... http://web.camaross.com/forums/showthread.php?t=342998

The beehives are not the LT4 springs...they are a CompCams design. P/N #26915 & #26918. These springs support up to .600" lift, the variable diameter of the coils control resonance, and the tapered design results in less valvetrain mass since there is less material in the upper coils, and the retainer in smaller. (One forum member running these said the steel retainer weighed in 3grams lighter than the Ti retainers on his last springs.) Downside is that they are a bit pricy...$160 for the springs and $60 for steel retainers.

http://www.krcperformance.com/newcontent/beehive.html

Scott

 

i'm glad you chime in. i did take your advice and installed 981 on my 89 L98...would have the stock spring been enough? i am curious in the differences between 981 and stock

another question is running a 268R cam with 1.5RR On 87 L98 need 981 as well...??

does the lt4 spring fitment require machining head, retainers, spacers and new locks ?

 

If you were running higher than stock RPM the 981s were needed with 1.6:1 rockers.

My stock '88 springs only had 80lbs of seat force while I installed the 981s with 110lbs at the seat.

I can't find the 268R cam in the Comp Cams catalog; what is duration & lift?? I would use the spring recommended by the cam mfg, or an equivalent. In general, when you install a cam bigger than stock you need to increase spring pressure.

Clearly I had the wrong idea about the LT4 springs so don't have any specs on them. If they are a dual spring they will be too large for stock L98 seats, so the heads will need to be machined.

 

When i did my 1.6 rockers i switched to the LT4 springs. You will need the LT4 shim/seat and the cap to go with the springs. New locks are cheap also. No machining required to install LT4 springs . My 86 had exhaust rotators so i required alot more shims on the exhaust to get the correct installed height.
Dying valve seals led to this project

 

spec of 268r:

Camshaft Specification Table
Part Number 12-769-8
Engine 1955-1998 Chevrolet
262ci-400ci
8cyl.
Grind Number CS XR268 R-10
Description

--------------------------------------------------------------------------------

Intake Exhaust
Valve Adjustment 0.016 0.018
Gross Valve Lift 0.552 0.564
Duration At 0.015 Tappet Lift 268 274

--------------------------------------------------------------------------------

Valve Timing At 0.015
Open Close
Intake 28 60
Exhaust 71 23

--------------------------------------------------------------------------------

These Specs Are For The Cam Installed At 106 Intake CL
Intake Exhaust
Duration At 0.05 230 236
Lobe Lift 0.368 0.376
Lobe Separation 110

--------------------------------------------------------------------------------

Recommended Valve Springs 977-16


so installed hieght is 1.700" with 222 lbs seat pressure, requires machining as the spring is 1.400 od .700 id, new spacer and retainers required..


now with stock cam, i have no idea what that spec would be , but if you install 1.6 RR's. the lift will be more than the recommended .450 max lift before coil bind., so the 981 would be questionable at 105 seat pressure/max lift? ..from what i understand

 

That 12-769-8 is a pretty big cam so, as expected, the 977 springs are dual springs. Indeed these would require machining of the spring seat.

With gross Valve Lift 0.552/0.564, 1.6:1 rockers would take lift to .589/.602. Since the 977 spring will handle up to .600" lift with coil bind at .650", it would be touchy to use them with 1.6:1 RRs and that cam. Unless you can find a more suitable spring, I suggest you use the 1.52:1 ProMagnums for this application. Or you could split the ratios if you want to deal with selling the other half of the split ratio parts.

I think the stock '87 & '89 cam is the same (or very close) as that in my '88:
1.5:1 - Lift=.410/.423, Dur=211/219@.050” (int./exh.), LSA=117
1.6:1 - Lift=.437/.452, Dur=213/222@.050” (int./exh.), LSA=117

My 981 springs have a seat pressure of 110lbs at 1.700", an open load of 285lbs at 1.25" and coil bind at 1.130". So opening to 1.248" with 1.6:1 RRs is not a problem since I still have .118" before coil bind.

 

soo...
Part Number 08-302-8
Engine -9999 Chevrolet
305ci-350ci
8cyl.
Grind Number CS 264H-R12
Description

--------------------------------------------------------------------------------

Intake Exhaust
Valve Adjustment 0 0
Gross Valve Lift 0.48 0.48
Duration At 0.006 Tappet Lift 264 274

--------------------------------------------------------------------------------

Valve Timing At 0.05
Open Close
Intake -3 33
Exhaust 46 -6

--------------------------------------------------------------------------------

These Specs Are For The Cam Installed At 108 Intake CL
Intake Exhaust
Duration At 0.05 210 220
Lobe Lift 0.32 0.32
Lobe Separation 112

--------------------------------------------------------------------------------

Recommended Valve Springs 981-16

spec:
IS=1.700, max.rec.lift=.450, SPC=105, CB=1.150
now 264hr having a lift of .480 with 1.5RR's
from IS,1.700-.480= 1.222 tc of spring leaving 1.222-1.150(CB)=.072total clearance.. i would think that this leaves very little room...certainly would not work with 1.6RR's?

i can see where the 981's will work with stock cam as lift is .423 with 1.5RR..

the question is: using 1.6RR on stock cam(1.6:1 - Lift=.437/.452, Dur=213/222@.050” (int./exh.), LSA=117), why is it necessary to change stock springs?

 

First off my stock valve springs had over 100k miles on them and, more importantly they were engineered for stock lift and acceleration to run in a TPI engine that would not see much over 4,500rp. And I don't know the coil bind on the stock springs.

Since 1.6:1 rockers not only open the valve higher they also open it more quickly so more force is needed to assure that the valve follows the cam profile. Also I wanted to assure that the springs would control the valves to 6k RPM so I wanted new springs with a little more force.

You might get by with stock springs when going to 1.6:1 RRs but I wouldn't take the chance. With 1.52:1 RRs you could keep the stock springs.

If you want 1.6:1 RRs with that stock cam, try the TPIS 700-131 spring @$76:
1.270"-diameter (stock)
1.730"-110lbs
1.240"-minimum running height
1.140"-coil bind
These would handle 1.730-1.240=.490" of lift.