Proper Valve Spring setup

[sattydaddy]

Hello I am currently in the process of putting back together a Mopar 408 stroker I recently purchased that had to be taken back apart due to use of improper head gaskets (did not use an mls gasket and the fire rings in the gaskets exploded from compression).

During the process of discovering this head gasket issue and doing some research on the Speedmaster heads that were put on the engine by the previous owner it was discovered that the owner had ordered the wrong style of head from speedmaster79.com based on the cam he decided to use in the build (Mopar performance P4452761AE FLAT TAPPET).

Speedmaster offers two fully loaded small block Mopar heads the difference between the two is called out below.

PCE281.2149- for use with hydraulic roller cam. (THIS IS THE SET I HAVE)

PCE281.2146 - for use with flat tappet cam. (THIS IS THE SET THE PREVIOUS OWNER SHOULDVE PURCHASED ACCORDING TO THE CAM HE PURCHASED)

After speaking with the folks at Speedmaster I was told that the only difference is between these two loaded head assemblies were the spring height and the closed in open seat pressures with the flat tappet( 2146)having greater closed and open Seat pressure then the set of heads I was provided( 2149). I.E. they use the same exact valve springs between the 2 heads p/n pce272.1007 but a different spacer is used to achieve a different spring height and pressure.

QUESTION: how can I calculate the proper spring setup for the Mopar performance cam P4452761AE currently installed in this engine.

Note: I am hoping that I am able to use the springs that I was provided in the loaded Speedmaster heads spring part number pce272.1007 I just need help on how to calculate the proper seat pressures / shims that I would need to get the correct spring height to achieve these pressures.


This is my first time ever trying to fit valve springs to a camshaft so please bear with me if I didn't explain something correctly.

 

[sattydaddy]

Full list of build specs and all parts included in above paragraph.

CAM
Mopar performance ( purple shaft) cam - P4452761AE
Cam style: hydraulic flat tappet
Intake/exaust duration: 268/272
Intake valve lift with Factory rocker arm ratio: 0.450 inch
Exhaust valve lift with Factory rocker arm ratio: 0.455 inch

VALVE SPRINGS ( I have these) - speedmaster pce272.1007

- Dual valve spring
- outside diameter of outer spring- 1.45 in
-Coil bind height- 1.06 in
-Spring rate pounds / inch - 130 lb at 1.800 in
-Inside diameter of outer spring- 1.080 in
- inside diameter of inner spring- .834 in

CYLINDER HEADS - Speedmaster PCE281.2149

-Exhaust valve diameter - 1.60 in
-Intake valve diameter - 2.02 in

Assembly specifications from Speedmaster:
-max lift .600
-Coil bind 1.150
-Intake install: 135lbs @ 1.8
- Exhaust install 135lbs @ 1.8
-closed seat pressure 135 lbs
-open seat pressure 325 lbs


QUESTIONS:
1. Will this current configuration work ??
2. If not can I atleast use the springs I have ?
3. If so how can I calculate the spring pressure/spacers I will need ?


Thanks I'm advance for reading the post and taking time to help !

 

[Geoff 2]

[1] The cam is a mild performance cam & will work well for a mild increase in performance & HP. might have a slight lope in a 318, smooth idle in a 360.
[2] The springs you have will work nicely.
[3] The stated spring pressures are ok for what you want. You may need shims under the spring locators [ these go between spring & head ] to get the desired 1.8" installed height.

 

[sattydaddy]

Thank you Geoff 2. Just curious how did you come up with the desired spring height ?

 

[Geoff 2]

It is in the Speedmaster specs you posted: 1.8" @ 135 lb.

 

[RemCharger]

Strange they would recommend a dual roller spring on such a mild cam(almost stock).
A 340 spring would probably work, if it fits.
Measure and report back on the room

 

[Geoff 2]

I wouldn't call either of those springs hyd roller. The 2007 has the lowest rating, seat load & open pressure, of all the dual springs in the catalog.

 

[Wietse]

Comparing the specs of both kits, the flat tappet kit shows higher (145lbs @ 1.9") spring pressure then the roller version, (135 lbs @ 1.8").
So probably all you need is the right spacers they said is used for the flat tappet version.
I would recommend asking them what is exactly required to convert the heads you have on hand to the intended purpose you want to use them with.
Stick with the recommended spring pressures to avoid any problems with wiping the cam during break-in, also check with the manufacturer if there is a requirement to remove the inner springs during break-in to avoid damage.

 

[sattydaddy]

Strange they would recommend a dual roller spring on such a mild cam(almost stock).
A 340 spring would probably work, if it fits.
Measure and report back on the room

I called mopar and they recommended a 340 HP (RED SPRING) but I was trying to see if what I had would work to avoid having to buy new springs.

 

[Wietse]

Still have to get it to the correct installed height and have the correct pressure at closed and full lift.

 

[RemCharger]

Still have to get it to the correct installed height and have the correct pressure at closed and full lift.

And the spring has to fit the spring pocket and retainer.

 

[Wietse]

That's why i wonder, if the only difference between the FT and roller setup is the spring spacer (height) why not just get the right spacer and you are all done.
No need to go look for other springs, etc.

After speaking with the folks at Speedmaster I was told that the only difference is between these two loaded head assemblies were the spring height and the closed in open seat pressures with the flat tappet( 2146)having greater closed and open Seat pressure then the set of heads I was provided( 2149). I.E. they use the same exact valve springs between the 2 heads p/n pce272.1007 but a different spacer is used to achieve a different spring height and pressure.

Like OP said, Speedmaster already stated this that both heads use the same springs, just a different spacer was used.

 

[Geoff 2]

If SM say they are the same springs, then the numbers are not adding up. 145 @ 1.9" & 135 @ 1.8" ?.
This may just be a typo & if it is you want the lower spring tension [ 135 @ 1.9" ]. 145 is too much for flat tappet cam.

 

[Wietse]

I've seen the same in regards to the installed height vs spring load, since he mentioned there is a (different) spacer used it could be the installed height ( incl. spacer) is actually higher.
That's why i suggest OP to check with them and ask what he needs to get those heads usable for a FT cam, they know the requirement of spring load better than we do.

145 is too much for flat tappet cam.

Depends on the cam, mine is at #150 @ 1.880".