Valve spring upgrade for stock cammed 300

C

Cbolton78

I am looking for a valve spring recommendation for my turbo 300. I am building a similar build to the turbo Maverick found in carcraft magizine.. My 300 won't see the high rpms and boost levels that that 300 sees. So maybe a spring upgrade isn't needed. I actually am tempted to run it as is. What do you think?

Thanks for your help

Colter
 
well if you don't plan on upping the revs or changing the cam, you shouldn't need stiffer valve springs.

someone with more experience will chime in, but your two biggest concerns with valve springs are float (more lift or higher rpm) needs a stiffer spring or a spring with a different resonance point (beehive)

and spring crash, which comes from having too much lift and not enough spring travel.

neither of these should be concerns using a stock cam at stock rpm.

that maverick has been discussed on here before and most of us think there is more to that engine than meets the eye. Head porting, bigger valves, cam, shoot one guy on here blew a hole in the cylinder wall at about 400 hp, so don't expect to bolt on a big turbo and run 10 second passes.

Good luck and keep us posted!
 
Thanks for the reply

well if you don't plan on upping the revs or changing the cam, you shouldn't need stiffer valve springs.

someone with more experience will chime in, but your two biggest concerns with valve springs are float (more lift or higher rpm) needs a stiffer spring or a spring with a different resonance point (beehive)

and spring crash, which comes from having too much lift and not enough spring travel.

neither of these should be concerns using a stock cam at stock rpm.

that maverick has been discussed on here before and most of us think there is more to that engine than meets the eye. Head porting, bigger valves, cam, shoot one guy on here blew a hole in the cylinder wall at about 400 hp, so don't expect to bolt on a big turbo and run 10 second passes.

Good luck and keep us posted!
Click to expand...

I have always felt the Maverick has had more going on then readers are led to believe. It's a great story though.

Back to the valves springs. If I do plan to get more revs out of the stock cam (is it worth it) any recommendations?

Also I don't plan on big boost. Just plan on something semi reliable and for the occational burnout :D
 
I ordered a set of 903-12 comp springs for my stock cammed engine $50.00 cdn or soo, pulled the p/n from one of comps larger cams. Noticed with the turbo that the engine easily breaths in the higher rpm's (feels like a v8) cheap insurance to floating some valves. Im sure there is better springs out there but for something that will bolt on with an extra set of intake retainers figued they will be more than ok for a starting point.

Comp 903-12 (box label)
seat load: 80lbs @ 1.700"
Open: 212 @ 1.250"
Spring rate: 293 lbs/in
coil bind 1.125
 
Applying boost pressure to the back of the valve has the same effect as lowering your spring rate.

Example:
If you have a valve with a surface area of 2 sq inches and apply 7psi boost to the engine, you will effectively reduce spring pressure by 14lbs.

I have always upgraded springs on a turbo car, and have never worried the springs after assembly!
 
Link to the thread with a block failure at 400hp please?? That makes me worry about my build. I've seen that maverick in person, Lebanon valley is my home track, even though its in another state lol it's the closest one. The guy makes a pretty convincing story of it being mostly stock. One thing to consider. His boost level is around 20psi and he's running race gas. Most turbo builds on this forum have never been dyno'd but the stock fuel pump has been maxed out on many trucks, which is good to roughly 300 hp. This is done on pump gas with boost under 12 psi on engines with no exotic work. A big part of what makes that maverick so fast is the car itself is set up very well, I think it's pretty light, it hooks hard, goes straight, and shifts fast. I wish turbob or jonl would dyno their trucks.
 
after doing some reading and such i found that the 903-12's are basically a stock replacement spring for this truck. a new spring is still better than a 20 year old one.
however, i decided to change things up. found these guys after some searching and measuring, they are a single ovate spring, and require new retainers and the spring seats to be cut in to 0.834" about, as they are quite a bit narrower. also if i remember they were relatively cheap so i decided to throw in 10 degree keepers and retainers. :beer:
http://www.compcams.com/Products/CC-%27 ... %27-0.aspx
 
Have you already changed to a all metal timing gear set??

you stock cam gear (Fiber) will not last long with stiffer valve springs than stock.
 
You betcha, had to change them out after i re rung the engine. The truck back fired and stripped a couple of the fiber gear teeth, made such a racket sounded like a couple rod bearings went, when it was running. Went to a cloyes gear set, both gears are steel vs a steel/aluminum set. Definately a difference in the noise/ harmonics changing out the fibers.
 
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