J heads and Lunati cam question

[Tadjou]

Question from me to Lunati tech support:

I have the 60403LK cam kit that I want to use with stock SB Mopar J heads with 2.02 intake vales and stock 1.5 rocker ratio. What springs do you
recommend for the 60403LK cam kit? Is it possible to run a single spring
with this cam and which single spring do you recommend?

Answer from Lunati tech support:

If you have enough installed height we have some single springs that would
work but Chryslers are sort of known for their short installed height
springs. That's why the one we show for it, part #73949, is a double. Part
#73949K1LUN is springs, retainers and locks. The main thing is you have to
have enough pressure to control the cam to whatever rpm you want to turn. I
would say 100lbs seat and about 300lbs. open. I would assume you want a
single so it will fit on the head with no issues but a double will last a
lot longer. We don't have any singles unless you can get the installed
height up to 1.800" or so. In that case you could run #73126.

Anybody know the the typical install height on a J head?

73126 - Lunati Valve Springs Details

Description Single w/ Damper
OD 1.500''
ID 1.086''
Seat Load,Height/Load 1.800''/103
Open Load, Height/Load 1.250''/303
Coil Bind 1.100''
Max Lift 0.640''
Rate 364
Retainer 638-75702

 

[BJR Racing]

They vary from 1.62 to 1.68 installed height depending on the year of heads and the valves used and the style of locks used, 2 groove or 4 groove.

 

[Tadjou]

They vary from 1.62 to 1.68 installed height depending on the year of heads and the valves used and the style of locks used, 2 groove or 4 groove.

So I should bite the bullet and have the heads machined for the dual springs.

Thank for the info.

 

[ramcharger]

We were having a discussion on this very thing here: http://www.forabodiesonly.com/mopar/showthread.php?t=54162

I'm using Crane single springs installed @ 1.590 and am presently experiencing valve float with the 60401 Lunati @ 5100 rpm. If i was to do it over, I would have used the duals. There is some debate as to whether what I'm experiencing is actually valve float or a secondary ignition problem such as rotor phasing.

 

[Tadjou]

Thanks for the heads up on the other thread.

 

[69superbee]

I had the same issue last year with a my lunati cam

638-00043LK
Adv. Duration: 292°/292°
Gross Lift: .480''/.480''
RPM Range: 2500-5500

I ordered a new set of lunati single springs. I hope this solves the problem or I will taking my other set of J heads to have them cut for double springs.

I used the same spring for the same comp cam and I had one exaust valve float at about 5600 to 5800.

I suspected that it is was a slightly sunk exaust valve but, I am changing the springs just in case.

Pete