340 Valve Springs

[Dean N]

My ("new") engine has been sitting for ~30 years, so I pulled a couple springs (singles with dampeners) and tested them, one that had been compressed all this time and one that had not. Installed height measured at ~1.687, and the uncompressed spring tested out to ~290# at 1.180 (0.507 lift). I don't know what the cam is, but it has ~0.468I/0.507E total lift. Durations could not be checked at this time, but that wouldn't matter on the springs anyhow.

It appears the springs that were in it were Mopar P5249847s, which now seems to be unobtanium and quite potentially discontinued. The popular Comp 901s bind at 1.160, so I can't use those. Now what?

EDIT: I am seeing differing data on the 901 bind height. Still looking...

 

[Dean N]

Possibly Comp 942, but I'll need different retainers.

 

[Dartfreak75]

Iirc luniti has some 1.1 bind springs. Also make sure to check and double check your installed height mine where not where they were "supposed" to be. Even after the valve job they came up short of the install height needed. At the installed height you measured the 1.1 spring will give you a .587 lift max alway add .015 for tolerances but that's still a .572 max lift

 

[Chryco Psycho]

Funny how everyone looks to Comp like there is no other companies out there .
Have you looked into Behive springs , they are far better anyway .
Try Crower Crane Engle Lunati etc , I bet there are 100 different companies making valve springs out there .

 

[Dean N]

Iirc luniti has some 1.1 bind springs.<snipped>

I looked at Lunati and the 73126 just might do, though they state an installed height of 1.8. Not sure what the result would be on mine at 1.687. I don't think that would be much of a problem, but I will try to verify. Open pressures are a bit higher, but not by much, plus I am not 100% sure of what I currently have. All I know is what I measured, and since the springs have been installed for ~30 years, surely the pressure readings will be lower than they were originally.

 

[Dean N]

Funny how everyone looks to Comp like there is no other companies out there .
Have you looked into Behive springs , they are far better anyway .
Try Crower Crane Engle Lunati etc , I bet there are 100 different companies making valve springs out there .

I looked at Crane 99839, but was unable to find more complete specifications. Couldn't find a listing of Engle springs. Crower, after looking through pages and pages of springs, mostly doubles and others that wouldn't work, so I gave up. I also looked at PAS & PSI, but didn't see anything even close. I tried to look into beehives and conicals, but didn't get very far. I couldn't find enough data on them.

 

[Dartfreak75]

I looked at Lunati and the 73126 just might do, though they state an installed height of 1.8. Not sure what the result would be on mine at 1.687. I don't think that would be much of a problem, but I will try to verify. Open pressures are a bit higher, but not by much, plus I am not 100% sure of what I currently have. All I know is what I measured, and since the springs have been installed for ~30 years, surely the pressure readings will be lower than they were originally.

You will have to subtract the difference between the 1.8 and the 1.687 and subtract that from your coil bind because you will have compressed the spring that much. I think it's like .113. As long as you use the 1.687 number to figure your height and not the 1.8 it should be ok. What is the coil bind on those? Also the diameter is important because you can run into retainer clearance issues with the rockers

 

[Dean N]

Bind is listed at 1.100. By my math there is still 0.080 until bind, but I still don't know if it is all going to be too stiff. Extrapolating the pressure of the Lunati per thousandth of compression (which I know is only ballparking it) is ~0.364 PSI 0.001. Squeezing down on it 0.113 more than suggested installed height adds ~41 psi to the installed PSI, so:

My Existing: ~100 installed,~290 open
Lunati 73126: ~144 installed, ~329 open

I don't know if that 44% increase of seat pressure is anything to be concerned about.

 

[Dartfreak75]

Is this a street car that is gonna be driven just for fun? Here is my suggestion not knowing the rest of the engine combo but a pretty safe option. Since you don't really know the cam specs or the recommended spring etc. I'd spend 200 bucks and get a luniti voodoo 701 or 702 cam and a set of luniti microtrol lifters and just use your comp 901 springs. It will be cheaper in the long run. To use those springs your gonna have to use new retainers keepers etc with the 901s you can use your factory retainers and keepers and you will know the cam specs and can degree it in. That's what I'd do.

 

[Chryco Psycho]

44% increase is a lot , when I get a few minutes I will try to get some research done , Or Call Lunati tech .
Beehives are a far better spring for a number of reasons the harmonics are far more stable & increasing the clearance to the rockers really helps also .

 

[Chryco Psycho]

This may help you out

this video is also good about the frequency problems

 

[Chryco Psycho]

The speed is mind blowing , at 600 rpm the pistons are at TDC 10 x / second & the valves are opening 5 x / second
Take that to 6000 RPM & the pistons are at TDC 100 x/ second & the valves are opening 50x / second !!
Take a coat hanger & bend it between your fingers it gets hot fast , imagine a steel spring moving 50x/ second & the heat the oil has to remove to keep the springs alive !!

 

[Steve340]

Assuming your calculations and measurements are correct you would want to stay at 290 lbs of open pressure or you are going to lose lobes on the cam when you fire it up.
If the engine has been turned over a lot while sitting you may want to reconsider using that cam.

 

[Dean N]

Dartfreak75, just a driver. I was hoping to be able to simply get the car together to enjoy a little bit, but simple seems to be unrealistic. The springs I currently have are unknown, and 901s would be lighter than my 29 year old springs.

Chryco Psycho, I'll try to make some calls early next week. Visitors in town now cuts all my time. I did order one Lunati 73126 to check on my spring tester to see it my calculations were correct.

Dteve340, I agree I should stay with what was in there, but that 290 is off a spring that has been on a mounted on a head for 29 years. What it was when it was new I don't know. 300? 310? More?? FWIW, I also tested an old fully compressed spring, and it was ~260# at open height.

 

[Dartfreak75]

Imo i would swap the unknown cam. 507 is pretty aggressive cam for the street. I understand where you are ive been there myself. Heck I still am lol. If your on a budget and just want get it running buy a summit cam. They make them in a couple different grinds. The 6900 is pretty mild and a safe bet. It's more of a stock cam and best part they are cheap. Like 89 bucks and you can get a set of lifters for 50. Then you can slap it together break it in and run it. And you won't have to worry about clearances and making stuff work with that unknown cam

 

[Rod Crain]

I have a new set of Comp 901-16 Mopar small block spring and work in a machine shop I can check the bind height tomorrow if that would help you. Rod

 

[Dean N]

Thanks for the offer. I saw more data posted that it is 1.100, but even if that is so, it appears Comp 901s would be lighter than my existing 30 year old springs.