While pricing a new cam - the DC engine book says I need these springs.

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Syleng1

Syleng1

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Good Morning Mopar world- and it is a glorious day today.

So I've got a real brain storm idea about adjustable rockers on my relatively mild 71'340 in the Demon with my 4-speed and currently 3.23 gears 8-3/4- ready to change pumkins. But it has snow balled into a major set of changes- the wife thinks I am nuts... all to go faster on the track with this street car.

I was going to go with a MP cam 284 .528/.528 Mechanical P4120653 for the 273 adjustable rockers.
Now when I go back in the archives in to my DC Engine book for this profile I'm showing a valve spring of DCC-3614542 for this cam.

I cannot seem to find this spring new anymore - okay no issues but can not find any specs on this spring to match it up to a diffrent spring.
Anyone have a clue on what the specs were for this spring. All I can find is it is Chrome Silicon and it is good up to .650" of lift but no heights or diameters and no spring pressures.
Next selection is DCC-3412068 its a bit heavier but available.

I thought about going with a diffrent brand camshaft where I can buy a full complete kit (cam, lifters, springs, ect.) but I have always been a fan of the Mopar Performance parts. I personally have had really good luck with them.
Thank you,
Joe
A) Background on this engine is less than 20k on lower end (steel crank and 2 notch factory pistons - stock bore)and just about 3k on the heads (2.02' / 1.60" J heads completely redone only pulled for hardened valve seats but had them go right thru the heads- guides, valves and seals- port matched to intake and manifolds)
B) LD-340 intake
C) Current camshaft is a 272 .455" lift cam Hydraulic with pressed stock rockers. -
D) removing the 340 exhaust manifolds and installing Doug's 1-5/8" long tubes
E) currently 3.23 -1 8-3/4" with 25" tall tire- installing a 3.91 gear with 26.0 - 7" slick
F)Thermoquad
G)Electronic ignition- Chrysler
H) P/S but manual disk brakes BBP
I) 833 4-speed with low 1st gear ratio
 
Well, that sounds like a nice combo.
Do note that MP is no longer keeping up with there parts. What ever is left over is all there is.

P3614542; 1.67 - 1.70 installed height / Dual/damper
Spring O.D./ 1.45 O.D.
Wire Diameter .185
Cam lift range .500-.610
Closed pressure @ 1.67 / 110lbs.
Open pressure @ 1.27 / 295lbs.

Least posted before I could get the next specs in so just scroll down to the next post for specs.
 
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Find out the specs for that spring and then go to an aftermarket manufacturer and get one to match (or in that ballpark)...

Also: Word of caution, we installed the 273 rockers on a 340 and I had to grind some clearance where the rocker hit the spring a little bit... Mock it up and check your set-up... Not a show stopper, but it's good to grind a little to get clearance to the spring...

A quick hit on a bench grinder will do it...
 
P3412068 is different in these specs:

1.46 O.D.
.191 wire diameter
.520 - .620 cam lift range
135 lbs. closed
325 lbs. open

It should be easy to match up another manufacturers spring to the MP spring spec's. Look at Crane and Comp Cams or call if you don't find the on line specs.
 
Why not use a different manufacturer of cam with similar or same specs where they have matched springs available?
 
Because he likes & has good luck with the Purple cams as said above. That is his choice. What's the problem?
 
I think Comp 995 springs should work, nothing wrong with MP cams, they do work.

Dual Valve Springs
  • I.D. of Outer Dia.: 1.073"
  • I.D. of Inner Dia.: .697"
  • Seat load: 115lbs @1.700''
  • Open load: 336lbs @1.150''
  • Coil bind: 1.020''
  • Rate: 402lbs/in
  • With damper
  • 16/pkg
 
What is the outside diameter it f that spring?
 
Use the Comp 987-16 and RIDE.
 
wonder if .528 is too big for stock head flow which stalls around .485 ?
what rpm do you want to shift or where do you want it to peak?
...comp 995-16 should be enough.
 
after lash and loss at the rocker arm, if rocker ratio is less than 1.5, and lifter angle, it will be close to .485
 
The ones I have measured were right in the 1.4xx range, even with a true 1.5 rocker and lashed at .026 on the intake and 0.28 exhaust that MP recommends, and lifter angel loss of .010-.020 your in the .480 range.
 
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ir3333 said:
wonder if .528 is too big for stock head flow which stalls around .485 ?
what rpm do you want to shift or where do you want it to peak?
...comp 995-16 should be enough.
Click to expand...


I can make any head stall at about any lift I want. Never chose lift based on stall point.
 
krazykuda said:
Find out the specs for that spring and then go to an aftermarket manufacturer and get one to match (or in that ballpark)...

Also: Word of caution, we installed the 273 rockers on a 340 and I had to grind some clearance where the rocker hit the spring a little bit... Mock it up and check your set-up... Not a show stopper, but it's good to grind a little to get clearance to the spring...

A quick hit on a bench grinder will do it...
Click to expand...



This sounds like a time when a B3 shim kit would fit the bill.

Unless you have a spring diameter of 1.687, and even then it still shouldn't need to have clearance ground into it.

If the geometry is correct, the rocker and the spring almost never ever hit. They can't.
 
Joe, I ran the 484/284 hyd. cam with stock rockers arms and Comp springs/steel retainers in a very close set-up to yours. It would run lo 13's at 108. Bob
 
ir3333 said:
if the valve is wide open and passes all the air the port can flow then
will opening the valve further accomplish anything?
Click to expand...


I will tell you that you can't predict exactly what the port does under load. Like I said, I take a pretty damn good head and make it back up on the bench. All heads do it.

I'll take more time with the valve out of the way then to have the valve not open as far. You can use lift averaging.

As I've posted before, I'm not a low lift flow guy. The piston is in the way, and there is no need to have both valves off the seat, flowing like a banshee. Then you have to reduce overlap at the cam.

There is more to it than just saying don't open the valve any further than where flow stalls. I'd should say more but it costs big money to learn this stuff. I don't mind helping, but some of it I just don't want to disclose.

I will say this....flowing at 28 inches is pretty much a waste of time, except for comparison. To develop a port, there is more to it than 28 inches.
 
gtsdude said:
I think Comp 995 springs should work, nothing wrong with MP cams, they do work.

Dual Valve Springs
  • I.D. of Outer Dia.: 1.073"
  • I.D. of Inner Dia.: .697"
  • Seat load: 115lbs @1.700''
  • Open load: 336lbs @1.150''
  • Coil bind: 1.020''
  • Rate: 402lbs/in
  • With damper
  • 16/pkg
Click to expand...
These work, I've used them with that .528 solid, but the real drop in spring is the mp#847 spring.
 
rumblefish360 said:
Well, that sounds like a nice combo.
Do note that MP is no longer keeping up with there parts. What ever is left over is all there is.

P3614542; 1.67 - 1.70 installed height / Dual/damper
Spring O.D./ 1.45 O.D.
Wire Diameter .185
Cam lift range .500-.610
Closed pressure @ 1.67 / 110lbs.
Open pressure @ 1.27 / 295lbs.

Least posted before I could get the next specs in so just scroll down to the next post for specs.
Click to expand...
Rumblefish360 - Thank you- that was the info i needed to make the informed decision.
 
rumblefish360 said:
Because he likes & has good luck with the Purple cams as said above. That is his choice. What's the problem?
Click to expand...
Rumblefish360- Thank you for the "back up." Although I appreciate the suggestions- I like what I like. :)
 
ir3333 said:
if the valve is wide open and passes all the air the port can flow then
will opening the valve further accomplish anything?
Click to expand...
IR3333- in a way you are correct. You can only flow what it will flow. BUT the time it takes to close the valve and open it is not diffrent and allows for more air to move. Slightly I grant you but it is diffrent. Years ago we would install 5/16" chevrolet valves in the heads.... not much from the Chrysler 3/8" stems but it did flow a bit better.
 
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