Max Valve Lift in V8

[Phil257]

Hi Guys,

Getting close to having my engine running. Its a 3.5 late 70's (not Stiff Block) with single valve springs. I'm running a Crow Cam 37776
Specs are
Valve Timing
IN. 25/65
EX.74/26
Advertised Duration

270
280
0.050" Duration
204
214
L/C
112
Max Lift
IN .420"
EX .442"
Rev Range
1800
4800
Dual pattern cam for maximum driveability in
street modified engine.

I'm a bit concerned about the .442" lift causing coil bind with standard springs.
Is anyone out there running this cam or similar lift with no valve train modifications

Any helps appreciated,

Cheers,

Phil

[PhilipA]

All I can do is refer you to "How to Power tune Rover V8 Engines" Chapter 6 Camshafts and Valve Springs page82
heading "1976 -1993 Cylinder Heads"

"The single valve springs of all engines fitted with such (1976-2004) will need to be changed to prevent coil binding if more than .430ins/10.9 MM of valve lift is to be used."
The book quotes Piper VSSV8 which has one less coil so is OK.
Regards Philip A

[Phil257]

Thanks Philip,

I've been looking into it a bit further, and have been told that while coil bind might be okay, the standard valves will likely break due to harmonic oscillations at higher lifts and should be replaced. Looks like a new set of springs is in order before I fire it up.

Cheers,

Phil

[djam1]

I once had a high lift cam put in a 3.5 foolishly I didnt change valve springs and it broke a valve spring within 2000km
Be careful its annoying to have to remove all the broken bits

[Phil257]

I've got my new valve springs now. Supposedly good for .6" lift and fitted with a damper spring. Hopefully get them fitted up this weekend. At least this way if I dont like my cam I can easily change and not have to worry about lift (not that I'll ever get anywhere near .5" let alone .6").

[33chinacars]

Hi Phil Should have got a set of valve springs from Crow to match your cam. Watch out you dont have to much valve seat presure or you will end up with valve seat recession. Not an overly wild cam so shouldn't need to strong a spring but consult Crow for exact specs