Need help with valve spring selection

[mayhem]

I have a solid flat tappet cam, 241/251 dur @ 050, 515/520 lift. I have access to K-Motion 850 valve springs or Comp 924 springs. Which would you use & why? Any help would be greatly appreciated. Thanks.

 

[Chryco Psycho]

I would have to do some research on the K motion springs to compare as I have not used those before .
I tend to have an aversion to Comp as the source for everything cam related , their cam grinds are far from the best out there , especially for Mopar engines but no one seems to look anywhere else .

 

[moparleo]

You need to determine what RPM range you are going to see regularly as springs can lose a lot of tension right away with sustained high RPM's.
For a strip or cruiser ?
It makes a difference on what the rest of the engine/head specs are.

 

[mayhem]

'Psycho, I've also heard negative things about Comp cams. I don't know that I've heard anything bad about their springs. Do you know who makes the springs for Comp or do they make them in house?

'Leo, this will be a 'weekend run down to the ice cream store' build with rpms held to 6500 or less, 10.1 CR, aluminum heads - already have all this in the shop. No racing, no cross country touring.

Anyone got a better spring suggestion than the 2 above? Not trying to break the bank - just looking to keep the cam/lifters happy.

 

[mayhem]

More info: 73 Challenger, born as a 318, now 440, 727, 8 3/4 w/3.91 sure grip. Engine being pulled & sent to machine shop while body & interior get sorted.

 

[Chryco Psycho]

Sorry I don't know how supplies Comp springs , if the KMotion have similar specs I would probably use those .

 

[Challenger RTA]

Comp cam valve springs For the occasional run around or race. Valve Springs, Dual, 1.509 in. Outside Diameter, 347 lbs./in. Rate, 1.175 in. Coil Bind Height.
If I was on the track all the time and driving I go with the K-850 1.550 diameter double M-300 spring with damper good for flat tappet camshafts up to .630 lift. 135# @ 1.900, 419# @ 1.250, coil bind at 1.160. My thought is a lighter spring for street and a heavy for track. Nails bend screws tend to snap.

 

[mayhem]

'RTA, I agree the K-850s would make a great 'race' spring. How do you feel about a Comp 924 (95# on the seat, 285# at 1.40" open)?

 

[Challenger RTA]

As Moparleo said I would say it all depends what RPM range you are mostly running.
Understand the limits of you components. I don't know all what was done to block and head. for example. Where the guides cut down and Viton seals installed? Valve float would be my concern for the conditions that it would be driven. VSI can be installed to bring up seat pressure.
Stock 340 spring installed height about 1.650 @96 lbs
open pressure about 1.220 @238 lbs
coil bind at 1.100
This stocker was intended for about a .430 lift .There's other factors.

 

[gzig5]

Normally the cam manufacturer will have a recommended spring spec for each of the lobes they grind. Max intended rpm will go into the equation as well but some lobes are more aggressively ramped than others and need a stouter spring. I would suggest starting with a call to the cam grinder and ask them what they require for pressure on the nose (seated) and pressure at max lift. Then you can look at spring ratings and determine the one that will best achieve those numbers at the installed height that your valves allow. Comp has a similar cam to the spec you listed with a little more lift and they call for the 924 spring with it so that is probably a decent place to start.

Comp 924 spring spec
Max Lift: 0.665
Installed Height: 1.9
Coil Bind Height: 1.175
O.D. of Outer: 1.509
I.D. of Inner: 0.697
I.D. of Outer: 1.125
Spring Style: Dual
Spring Rate: 347
Seat Pressure: 112

The seat pressure seems a little low to me but I am far from an expert, but I used to sleep at Holiday Inns regularly.

 

[Chryco Psycho]

I agree , the 924 spring should work fine for you ,ramp speed is definately a factor but the cam you have has a slow ramp as it has a lot of duration for the lift .
I was getting solid cams custom ground with slightly less duration but in the .560-.575 range for example .

 

[mayhem]

Thanks guys! The Comp 924s seem right. I'll call the cam grinder just to be sure. I appreciate the help.

 

[mayhem]

Call to cam grinder & confirmed Comp 924 springs have the right specs for this engine.