dual springs or single springs and shimming with vz14?

[CHR!S/DVK]

i am almost at the point where i can start building my engine but i'm still uncertain about the choice of valve springs.
specs of the engine are 85.5 p+c, 69mm counterweighted crank, 35/32 single port heads with an engle vz14 cam.
valvetrain upgrades are: lightened bugpack racing lifters, aircooled.net HD alu pushrods, swivel foot adjusters and some gene berg stuff;
-heavy duty outer springs(gb271)
-chrome-moly retainers(gb281a)
-hardened keepers(gb 344)
-valve shims .060" .030" .015"(gb285)

due to the fast ramps of the cam i am not sure if using these parts will make for a good working and long lasting valvetrain.
i heard that shimming the single springs can add some strength and prevent valve float.
or should i best be using dual springs? aren't they too tough for the valvetrain? wouldn't they ruin the idea of keeping the valvetrain as light as possible? (i was thinking of scat dual springs if i would choose dual springs)

p.s. just to make clear, the cam choice is not under discussion 

[Jim Ratto]

dual springs no question

[bluestar]

!! alu push rod ? be careful with dual springs , in my "offroad thing" , 1914cc with vz14 single Berg spring , never have any problem ... , sometimes , I stay long time full gaz ( Mud extration !!  ) and never have valve float .

[nicolas]

i would say singles would be fine with this cam, but it is rampy. the pushrods may suffer more from the springs like Bluestar suggests.

[Jim Ratto]

the single spring cannot quell the vibrations like a good interference spring will, and with the high lift, short duration profile of that cam, it isn't dectectable valve float (ie rpm related), it is what is going to happen to valvetrain as soon as those springs have enough of that cam. Keeper grooves going wide, retainers pulling through, valve ends mushrooming, seats moving. Been there, tried it years ago, ONCE. The only reason you might get  away with it is the limited rpm and acceleration a single port is going to achieve.
I run alum pushrods with dual springs, and have for 9 years, to 7500, no bending, no ends being driven in, nothing.

[SlingShot]

1600cc DP Sweep the floor motor. VZ-15, Rebuilt German Heads,HD (bugpack?)aluminum pushrods not sure what dia, HD Single Springs, stock 1:1s on solid shafts, swivel ball adjusters, Kadrons. This motor is in my single cab and I would say it has about 15,000 miles on it (no speedo) I take it up to 5,5K often without a problem yet. I worry more about the lifter bores more than anything, but so far so good.   

[Jim Ratto]

VZ = at least dual springs.

[CHR!S/DVK]

it is what is going to happen to valvetrain as soon as those springs have enough of that cam.

what do you mean by this?

Keeper grooves going wide, retainers pulling through, valve ends mushrooming, seats moving.

so you suggest there won't be valve float but long term effects like this?

the engine is a single port, so i don't think i will run that high rpms, about max 5k i guess?

what could some shimming do? could that add some steadiness to the retainers?




some other interesting information, the gene berg website tells the following about a cam similar to a vz14:
GB 295 
Short duration high lift for small class race engines with stock carb such as 1200cc. Designed for short course or off-road racing engines. Not recommended for street engines with stock carburetion. Delivers tremendous torque when larger engines up to 2000cc and/or carburetion is added. GB 273A springs mandatory. 276 duration, 0.418" lift at cam.

GB 295-E  Same cam as GB 295 in genuine Engle. VZ-14 

information about those springs:
GB 273A
Inner and outer springs. Set of 8. HD inner and outer. Gives about 150-160 lbs. at 1.500" and 280-290 lbs. at 1". SW 3#

but..:
GB 271
HD outer spring, set of 8. For mild street use. Can be used on a stock cam, our GB 295-296 cam with single 2-barrel carb or small dual carbs. Borderline for sedan engines with Kadrons and head work. About 125 lbs. at 1.500" and about 225 lbs. at 1". Use GB 281A retainers and GB 285 spring shims. SW 2#

[Jim Ratto]

it is what is going to happen to valvetrain as soon as those springs have enough of that cam.

what do you mean by this?

Keeper grooves going wide, retainers pulling through, valve ends mushrooming, seats moving.

so you suggest there won't be valve float but long term effects like this?

the engine is a single port, so i don't think i will run that high rpms, about max 5k i guess?

what could some shimming do? could that add some steadiness to the retainers?




some other interesting information, the gene berg website tells the following about a cam similar to a vz14:
GB 295 
Short duration high lift for small class race engines with stock carb such as 1200cc. Designed for short course or off-road racing engines. Not recommended for street engines with stock carburetion. Delivers tremendous torque when larger engines up to 2000cc and/or carburetion is added. GB 273A springs mandatory. 276 duration, 0.418" lift at cam.

GB 295-E  Same cam as GB 295 in genuine Engle. VZ-14 

information about those springs:
GB 273A
Inner and outer springs. Set of 8. HD inner and outer. Gives about 150-160 lbs. at 1.500" and 280-290 lbs. at 1". SW 3#

but..:
GB 271
HD outer spring, set of 8. For mild street use. Can be used on a stock cam, our GB 295-296 cam with single 2-barrel carb or small dual carbs. Borderline for sedan engines with Kadrons and head work. About 125 lbs. at 1.500" and about 225 lbs. at 1". Use GB 281A retainers and GB 285 spring shims. SW 2#

Think about what that VZ14 does. All the lift is at the cam (aside from what the VW rocker lifts 1.1 times lobe lift)... that cam has the same lift @ lobe that the FK47 has.. if that tells you something.
You're asking a lifter and rest of valvetrain up to adjuster/valve to lift the same amount as a drag cam, but in a shorter period of time (duration). Which means that all parts involved are going to accelerate at a frenetic pace. (things have to get from point a to b in 36 less crank degrees than FK47). A single valve spring is not going to be effective. Not only that, BUT the rocker ratio of 1.1 is not going to compress the spring (single or dual) to a lift of .560"+ like most "ratio rokcer cams", meaning less lb on vlavetrain to keep it under control. If you set your installed height up @ 1.600 let's say, and that VZ14 lifts to .470" (figure lash and flex) , your full open height is going to be around 1.15", so going by Berg's notes, not even 225lb over the nose. Not good.
I did try this many years ago, with a VZ25, which has less lift and a little more duration, which, all things being equal (we are not talking about unknowns like gear ratios, tire diam, car weight, carb CFM, head air flow, flywheel weight, oil temp) you would think would be a little more forgiving on springs. The geometry was set up by a professional engine builder (I had no clue how yet at 17 yr old), oil was 40wt Kendall "green". Within 8 months of regular driving (ie no track time), I found the following:
keeper grooves in valves were wallowed out and burred
keepers were burred up, as were ID of retainers
3 swivel adjusters were shot
seats pounded in brand new 041 heads
cracks between seats in all cylinders
obvious wear in floor of heads where springs danced
Motor was 87 x 69, 9.0:1, single 36DRLA, later updated to dual 36DRLA's, 12lb flywheel, 009, S & S header.
Just to show you how stubborn and stupid I was, I tried the same thing, a year later,  with W125.... with same results. After ruining so many parts, I finally listened to what others that were smarter and more experienced were trying to get through my skull.
years later I took a class on camshaft theory and valvetrain operation (taught by Dema Elgin), and it was clear as to why my "shortcuts" way back when turned out so badly.
Ever seen one of those movies of a valve spring at work under a strobe light?

[CHR!S/DVK]

thanks for you explanation, i'm becoming quite convinced of using dual springs.
i found two movie clips of valve springs on youtube, interesting to see how much springs are able to rotate and flex.

what would be a good estimation of amount lbs needed at the max valve light of my cam at 1.15"?

what kind of dual springs are good for my set up? i was thinking of scat ones.
how far will my heads need to be machined?

[Jim Ratto]

yeah I think it was Isky that did the movies of the valve springs in tremors.

Do you guys have access to a Rimac machine? I think the Bugpack springs I use were coming out @ just over 300# at full lift with FK10/86C, maybe 315 on first pull. This was at height of right around 1.050" if i remember correctly. Had to get rid of my Rimac when I moved years back. 

I would (this is Berg blue book way, and works for me) check actual lift @ every valve, and record it (write it on the head fin in red marker) with dial indicator. Then using a drill press or one of the bench valve spring tools, measure each springs "stacked height" (where coils touch, "coil bind"). You want the two measurements to be .100" apart, so shim the springs accordingly. It's tedious, but simple way to get the spring height dialed in. Don't just do one valve and set the rest like it... you'll have real problems doing that. I set up a few sets of ERCO triples this way, and the motors would sing to 7700 like clockwork, running a very serious .620" cam. While the motor was far from driveable in everyday world, it had a very "precision" feel to it, and was almost "too fast"... think the cam was 280' @ .050".... not your grandma's type of motor for sure.

[CHR!S/DVK]

so you mean that every spring needs to be 0.100" away from coil bind at full lift?
i thought that a springs needs to stay far away from coil bind.

some information about the scat dual springs i am thinking of:
20085 = Dual Springs 1.550" installed height = 175 LBS. seat pressure    – machine valve guide boss 
COIL BIND AT .900” = 340 LBS.
OVER ALL SPRING LENGTH (OUTER = 2.400") (INNER = 2.025")

unfortunately i don't have access to a Rimac machine.
i'm thinking of the scat springs because they are quite cheap en don't really need expensive hard springs for my engine.

the only thing is that my heads need to machine. there is a machining shop in the neighbourhood but what specification will i need to give them?
how much material need to be machined away and also from the ends of the valve guide?

[Jon]

A spring tension tester is just a few bucks at summit, if you get the type used with a wise.

[Diederick/DVK]

jon, do you mean a very light low tension spring only for testing? we have 2 of those. and we have the bench tool
the thing i'm wondering about is that when using a light spring you can't use a feeler gauge since the wire gauge is different etc. so, i suppose it then comes down to calculating like jim said?

[Jon]

I'm talking about one of these:


$65 for peace of mind

[Jim Ratto]

Jon, that's cool. I might have to pick one up. Been using a bathroom scale and my drill press.

I would use Bugpack 4046 springs over Scat.

[CHR!S/DVK]

Jon, that's cool. I might have to pick one up. Been using a bathroom scale and my drill press.

I would use Bugpack 4046 springs over Scat.

why would you pick bugpack over scat?
what is the difference between them? strenght?

[Jim Ratto]

look @ 88 x 74 post

[RFbuilt]

thanks jim for the clarity on those springs

rereading more about thim.. it seems theyre really good..  as vague as this sound.. its prolly not to stiff that it would slap the valve into the seat, but uniform integrity on them keeping the springs capability of doing its work well mid lift and full lift

me likey!!


also the interference fit u mention.. is the same that we call on inline 4 engines.. as "snap fit" retainers/springs

usually we prefer this on titanium retainers so the springs dont chirp or eat the contact portion of the retainer (tit.)

most excellent!