Street 318 valve springs

[MopaR&D]

Now that I have some money I've started to put together all the parts I need to buy. I plan to get a Lunati Voodoo 256/262 cam and lifter kit, but I forgot that I probably need new valve springs. The ones that Lunati recommends with the kit seem pretty beefy; in fact, a little too beefy. They are rated at 365 lbs. open and come with spiral dampers. Do I need springs this stiff, or can I use softer ones without the dampers? Also, can I use the old retainers and other hardware from the heads that I have (pair of #302's, and my old original open-chamber heads)? Mind you I doubt I'll rev this engine much over 5500 RPM (maybe 6000 max) as I also plan to use a regular Performer intake, stock or mildly ported #302's most likely with stock valve sizes (depending on how much money I have), and stock exhaust manifolds.

 

[furz4]

I would think that standard 340 HP factory springs would be fine. They have a dampener too but are a more street friendly pressure. A lot of newer cam profiles have a very high rate of lift on the ramp and do take a little more pressure. I know there are guys here that run that cam so you should be able to get good information from what people are using. Be sure to check any spring when installed with a high lift cam for coil bind at full valve lift. and make sure the retainer does not contact the top of the valve quide at full lift.

 

[fishy68]

Wow are you sure on that spring pressure? I have a much larger Lunati Voodoo (276-284) and it doesn't even take a spring that heavy. Are you possibly mixing up spring pressure with spring rate? I could see a single spring rated at 365 lbs. per inch. That just means when opened at .500 lift the pressure will increase approx. 183 lbs. more than the seat pressure rating. I'm sure those are single springs too. My dual springs are only 340 lbs. open. With a cam as small as you have I wouldn't expect it to make any power above 5500 much less 6000 even in a small cube 318. I agree with FURZ4 that the Lunati is ground pretty aggressive. You might be able to get away with stock high perf. 340 springs but the Lunati springs might be cheaper and I bet better. Mopar Perf. stuff isn't cheap (in price).

 

[rumblefish360]

Not going with the recomended springs would void any possible warranty and could shorten cam life span. Lunati did the homework on what works, why would you not believe them or use what they say works with there own cam?

Go with the recomended spring by the cam manufacturer.

 

[moper]

What Rumble said. You do not have the background to correct the manufacturer. Those springs may have a 365lbs open pressure at a certain max lift, but my guess is at the lift for you cam choice, they are much lower. I dont have lot of expreience with Lunati stuff... But all modern cams like the XE Comps, Hughes, and the Voo Doo series all require much more spring than the earlier type grinds of similar size. If you go too light, the valves will bounce when closing because of the fast closing ramps. That is why the 268 versions of those cams say a single spring with dampner is acceptable, but a true dual assembly is preferred. A single spring with dampner is the entry level performance spring. They are not really heavy.

 

[MopaR&D]

I checked on them and fishy68 was right, the open pressure is only 265 lbs. @ 1.250" with a rate of 363 lbs. I was just surprised when I clicked on the "suggested parts" link and saw that set of springs for $115. Guess I'll have to warm up to that quickly.

 

[66dartgt]

Compare the spring rates for the stock 340 and what lunati is suggesting. I'll bet there's little difference. But if in doubt, buy the matched set as your cam warrantee is based off using matched parts. The problem with warrantees is that they only will pay for what failed, not your whole engine if it gets damaged, so how I doubt how useful these warrantees really are.

You should be able to use the stock spring retainers with a single spring and damper, just make sure you aren't using a set that has rotaters.