Anyone had experience running 948 springs, in tighter than the recommended 2.100? The best I can do if I go to a 948 is installed at 2.050. That yields 366 on the seat. I do have good parts, Manton 1/2 inch pushrods, jesel valve gear, lobe is a comp 1625b, .501 lobe lift. I was told their is good power to be had with my heads by going to a higher lift, as they keep increasing flow all the way to .900.
The jesel rocker I want to run is a 1.700, which will give a gross lift of .8500. Comments?

I RUN MANLEY NEX-TEK SPRINGS TIGHT .JUST CHECK FOR COIL BIND . CALL COMP THEY WILL TELL YOU RIGHT OVER THE PHONE

How tight are you running them? Seat pressure? Any problems with breakage? The 948 spring will work OK up to the lift I have planned at 2.050

From what I've seen they have a good track record. An engine I just went threw last winter had '948's with the inner-most spring removed. 325lbs. @ 2.05 800@ 1.3" C/B @ < 1.14" Against my saying he never backed down the rockers (until I got the motor 4 months after last run). It had run about 50 passes in a the prior year in an easy environmet Ti valves, .745" lift gentle profile, <7800RPM, 7/16" double-taperd Mantons. etc...The rates I gave you were 'used, as-received' and all within 2% of one another. I would almost rather utilize the correct spring before I shimmed to .060" before C/B if that's what your thinking. There is a thorough post on YB about valvetrain dynamics (In C.U.'s section) you might consider referencing. I also have a program here but, you'd have to PM me pertinent data.

Thanks for the response, HCB. My dilemma is not being able to get a correct spring to fit with a 2.050 max installed height, yet still allow .850 net lift. The 947 springs I have now are supposed to be in at 2.000 which only allows .810 max net lift if everything is perfect. My head porter set me up with +.050 locks and +.100 retainers(?) to get me as much room as he could.
There are guys running faster than me with 440-1 heads, and I feel the need to catch up, maybe pass em
After reading a bit of the YB thread, I think I will go out to the shop and do a little measuring.!!

How much can be cut from the spring seat to gain install height? I ran into a problem using the +0.100" retainers and +0.050" locks, it caused the rocker to hit the retainer before the valve stem.
This was with my Victor heads, T&D 1.6 rockers and PAC 1325 springs installed at 2.00". I ended up just using standard locks 1.950" install height, and having a bit more spring pressure, but my lift is only 0.715". I though about cutting the spring seat some more, but I'm not sure how thick the aluminum is between the spring seat and the port roof?

This deal is maxed out. I have the max + retainers made, same for locks, can't cut the seats any more. Spring cups are as thin as they make. The retainers are TI, and I really don't want to change them. If the 948 would be stable without the inner third spring, that is definitely something to look into.

CV makes spring cup that are .40 thou, most cups are .60-.80 thou.Maybe this will help????

Greg have you looked at any of the springs from PAC yet? How big of a diameter can you go to? Maybe they have a spring that would be a good fit. FWIW I have Nexteks at 2.100 and 1.677 diameter.

Al, hoping to keep this somewhat low budget. The little bulb just came on, and maybe due to the fact I only run up to 7500 rpm, I could put my 947 springs in a touch high, say 2.020 if I need it. After reading the post on YB, I need to get my butt out there in the shop and start measuring true coilbind, true net lift, and do the math the right way. Then maybe I will have some more possibility's. Right now, it looks like mathematically a gross lift of .850, minus .026 lash, minus .010 deflection gives a true net lift of .814 . At .814 + .060 + 1.130 coil bind, I come up with a needed installed height of 2.004? Might just work. I can shim it from 2.050 to get back to 2.010, which would make me happier about the true seat pressure.

OK, so maybe this thread will somewhat morph into your valvetrain archeive. I would tighten up the lash some JMO.

OK, got some relevant numbers!
Installed height, retainer to head--- 2.112
spring cup--- .037
True installed height of 947 with +.050 locks, +.100 retainers-- 2.075
Spring coil bind, measured with retainer 1.100
Max lift with checking spring, an inner from triple, .000 lash--.781
Max lift, with 947, .000 lash, .758 (edit ,in at 2.025)
Lobe, .501 lift
Rocker, 1.55 jesel
Pushrod, 1/2 inch manton
Loss due to compression, flex etc .023
Looks like I now have options I did not know of.
True net lift, as is, -.024 lash, .734 lots of room.
Theoretical numbers
1.7 jesel rocker
.025 lift loss (flex, etc)
lash .024
Gross lift, .852
Net lift at the valve, .803
Needed installed height to keep it all happy-1.130(comp cams spec CB) +.060 + .803 = 1.993
Seems a bit short, but those are the numbers I came up with.

The 948 is 0.015 less CB height than the 947 Higher seat pressures are better for RPM and lifter life.

I like the Comp pacaloy springs because they go soft but don't work harden/shatter when they fatigue life out like other manufacturer's springs.

0.02

Bump!

You may assume some error in Jesel's 1.7 ratio as well. From what I have seen .02-.03(+). How much room do you have between the retainer bottom and valve seal? Also are you sure the rocker change will use the same pushrod length? What about a camshaft change with the same base circle height?

Good points all. Pushrod length combined with base circle and rocker configuration will have to be checked. Thanks for the great input. Will get this put in my VT post!
I don't run valve seals, alky motor. Lots of lift room there.
If I go with a 948 in at 2.075, and getting the spring within .060 of CB is not needed, that would seem to be my best option? I here there is a PAC-1347(?) spring that fits also?