Spring pressure

Hi , i'm about to order a set of springs for my Hemi , it's a 526 with a 14-71, 12-1 comp, 2" installed height , '96 Dart heads, Ti and Stainless Manley valves ,Manton Pushrods, and i'm going to rev it to about 8K ish but want it to live if it goes over, I'm probably going with Pac springs, My Question is what pressure springs should i get ?
Thankyou for any help/advice
Wayne

 

If you go with the PAC springs (that's what we use) make sure you get the latest mods from Manton, drilled rockers & adjusters, so you get lots of oil to the push rods. Also a good idea to have the thick walled push rods if you run lots of spring pressure. We run about 600 lbs on the seat, but we have a screw blower. 450 or 500 lbs should be good with a roots.

 

but ken you are running fat heads and he is running a fuel head..I think he can use 375 to 400 on the intake,,what do you think?..dave

 

i have been running 320 on my fuel heads with a roots. you guys got me wondering if i need more spring.

 

I don't think it matters what kind of head you run. I think the main things to consider are the weight of the valve, the diameter of the valve head (area) and the boost. If you are not sure what it takes to open the intake valve, set up with your normal spring pressure and make up a jig to put regulated air inside the port. If the valve tries to pop open at 50 psi, and your blower puts out close to 50 psi, then you need more spring.

 

i never ran under 340lb with the fuel heads 385lbs to 400lbs @2.100 with a roots but you need to keep an eye on the valves get good locks and just watch for wear over time

 

We never run more then 350# pressure, get rid of them at 310#..big springs are hard on valve train...50 + years racing ,you don't need big pressure for roots and 8,000 rpm.. More spring pressure when you get big,big boost numbers (48/50lbs +)...at 8000 rpm i would'nt think you will have 40 lbs...we run 350/360 lbs on our aj 96 hemi fuel heads with a littlefield 14:71 hh, 46 lbs of boost..
Santo
330 332-1752

 

how many valves are on the seat at any particular time

how many valves are on the seat at any particular time

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Can one of you rocket scientist tell me how many valves are on the seat at any particular time and how many valves are open or on the over lap in a V8 ?
When you figure this out, think about how much boost is trying to open a intake valve.

 

I agree with Mr. Sitko and I also believe 475-600 #s is where you need to be and PAC is the right choice in my opinion . The harmonics and heat produced with a "weak" (under 400 #) spring will increase and compound other valve train issues . You will also have seat, valve facing and guide maintenance that often is overlooked when the valve is chattering in many differing size orbits around the guide center. You will notice the difference in maintenance , power and valve train life !

NOTE: I also believe you may have too much compression in your set up .... but that doesn't mean it can't work for what you are doing. You must do it for a reason ?

 

Now i maybe wrong but how many valves are open at once doesnt have an impact on the total boost number you see on the racepak. If the racepak says 50 lbs. than 50lbs. is waht is tryin to open any closed intake valve no matter how many intakes are open!!!

 

So, what your saying is that the blower is putting out a lot more than 50 lb's of boost yes?

 

Wow thanks for the replies ! there's a few different opinions here, I was thinking somewhere around the 450 mark myself but wanted to see what you guys think,
my engine has too much compression? what would you recommend ?
the boost will be around 35-40 llbs from it's previous figures.
My Valves are, 2.375 " Titanium inlet and 2" stainless on the exhaust .
Just had to tig up the 'o' ring grooves in the inlet as the 'o' ring was hanging into the inlet port (Not good) going to match port it next week then re cut the grooves further out,
if it was easy everyone would do it !

 

When I was building and tuneing the motors for my brothers TA/FC 511 ci in brad 5 back in 2003, we ran 5.66 255 i had the springs at 375 lb's now he has them at 425 not running any better and is snaping the tips off the ex valves or pushing the valve tip tru the retainer, so what changed since 2003 beside his bank book balance? again californised

 

Ha ha, i like my bank balance the way it is which is why i'm asking you guys !
(actually the bank could do with a top up !)

 

Your 450 mark sounds really good. Depending on how hard you run it, you might start getting valve float on the exhaust. A 2" stainless valve is heavy and will pull down on a weak spring. You might consider a lighter valve if the price doesn't bother you too much.

 

Thanks for all the replys everyone, I'm not planning on running it really hard (yes it's going in the bus on my Avatar) I want it to last rather than run it really hard and damage it all the time
Thanks again
Wayne

 

hey Wayne..this has been a great thread..lots of info..Dave

 

600 lbs! For real?

What kind of spring compressor do you use? Does Mr. T run your compressor

 

I was thinking the comp was a little high , how much effect would .020" added to the gasket thickness have on the compression ? is there a formula for thou to comp points is what i'm trying to get at ?
6.80's @ 200 Nice !

 

Here you go, http://www.csgnetwork.com/compcalc.html