Too Much Cam Lift?

Ricky B

Ricky B

Wiiide Open
Joined
Mar 20, 2005
Location
LKN - Tha Dirty Mo (Mooresville, NC)
Ok . . . just noticed something, am curious, quote from Chevy High Performance Magazine in an article discussing Vortec Heads:

http://www.chevyhiperformance.com/howto/97458/index.html


This leads us to valvesprings, which require the most attention in a performance application. Since this is an OEM iron head, GM designed the valve guide to also serve as the inside diameter (id) locating device for the valvesprings. The guide’s large diameter acts like a sleeve that keeps the single-wire valvespring located >> properly. The guide is also machined at the top to mount a positive-style, 0.560-inch-diameter valve-guide seal. All of this conspires to limit total valve lift to a safe figure between 0.420 and 0.430 inch. The limitation is the clearance between the bottom of the retainer and the top of the valve-guide seal.
Click to expand...


Now searches on the web produce different online sources ie: forums/etc boasting as much as .480 lift clearance on stock heads

Lets say, just by the odd chance . . . completely theoretical :lol: . . . that you have .488 lift on both sides of the cam

What symptoms would someone be able to recognize/look for as over cam lift problems to be?

Would perhaps your brand new engine progressively consuming more an more oil to the point its probably worse than a two stroke (Bout a quart every 5 gallons of Gas) yet still seeming to run just as powerful and without hiccup as when you first bolted it together, be a possible symptom? Or does that just still sound like rings?
 
Do a cylinder leakdown test first before guessing with $$$ parts. Remove rockers, pressurize cylinders, listen to see where the air is leaking from. Makes it obvious at that point.

Too much lift TYPICALLY will cause erratic performance,valve float, broken springs, accelerated guide/rocker/seal/lifter/cam wear.

Sound slike you need a cylinder leakdown test performed first.
 
I have run 480 lift cams with stock springs just have to check and be sure you dont have binding issues. but should always match springs and cam together. as for your problem I dont think its in your cam or springs also suggest cyl testing before any moneys spent.
 
if the valve guides or oil seals are worn the oil can get into the cylinder down the valve stem and that may not show on a leak down if the rings and valves are sealing good...
 
When does it smoke? all the time, heavy at startup?
 
The more I rev the more it smokes, the Z71 can roll coal above 2500 rpm, seriously, I should video it, its retarded :shaking:


Pretty sure its the rings, was more curious than anything else on the cam lift issue, regardless its not gonna get fixed any time soon the thing sits in the backyard mostly, but since I snapped the mainshaft in the Dodge I might have to drive it here and there a bit again.
 
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