Max lift on cam

Hey out there.  I've got a 69 olds 350. The heads are shaved .030 and have Mondello's adjustable valvetrain kit. The performer rpm camshaft lists .496/.520 lift, which I am thinking about buying. I have read several different articles, one from Mondello's technical manual, that stock valve guides can't handle any more than .500 without modification. The current cam I am using is .484/.512 and clearance doesn't seem to be an issue. Just wondering if anyone else has run into this. Any info would be greatly appreciated.  

I cant say I've ran into that problem cuz I am a machinist and I make things work so I dont have to second guess myself.  But I have had a stock olds head on a flow bench with the stock valves and retainers and flowed them up to .600" lift,  If I remember right the retainer hit the guide around .620" but that is also without the valve seal.  Do your heads have stock guides or replacement guides installed, do you have umbrella seals or posi locks. I would take out the valve spring and install a tiny checker spring and take a caliper and see how much lift you can have before the retainer hits the seal and subtract about .040" from that for clearance.  

I believe the guides are stock. The umbrella seals are in place and I have comp cams magnum roller tip rockers. Clear up to .620?  Sounds better than .500".  .040 would be sufficient clearance between the seal and retainer?  

i believe it was around .620 without the seal in place,  but like I said I would install a checker spring to check.  and yes .040 clearance between the seal and retainer will be enough,  are you using stock springs and retainers??  

Theretainers are stock but the springs are a replacement matched to the cam through Crane. Just a single spring with no crazy pressures.  

With replacement guides the clearances are less than .520 and will not clear the edelbrock rpm cam specs. guides need to be cut, according to Mondello, to .700 total height.  

I would go lower,  about .600,  I drill out the old guide, mill it down to .200 and pound in the new guide and mill the new guides to .400 on top of that (for .500 posi locks,  I use .502 diameter guides) for a total of .600,  if your gonna do all that talk to the machinist and make sure he knows what hes doing,  he might have his own method like milling down the old guide all the way, but i leave mine up to help keep the guide stable  

the heads are off.  I checked each guide height and was suprised to find that the average height is .700.  Kind of suprised that Mondello would print in his tech. manual that .700 was sufficient clearance for a tall cam.  They are now cut to .600 total height. Thanks for the advice Oldsfreak.  Maybe you should write a tech manual.  

The stock valve springs and rocker arms are limited to just under .500 lift at the valve. A set of high performance Z28 springs can handle the .520 lift and should be the same diameter. Just make sure the installed height of the springs are correct when installing them. As for the rocker arms you mentioned they can only handle .500 lift max. according to Mondello website. You need to switch a long slot rocker arm or better yet a set roller rocker arm for that high of lift. If you are using stock valve cover you may need to replace them with a tall style to get the clearance the valve train needs too.  

The springs are Crane replacements with approx 100 lbs od pressure seated. The rockers are Comp Cams Magnum roller tip with long slots for higher lift.  The springs, according to Crane, can handle valve lift up to .520. With a slightly shorter lift cam, valve cover clearance was not an issue. The roller tip kit that I purchased through Mondello is actually rated for .550 lift.  The standard adjustable rocker kit is rated for .500.  

thanks nmorse,  I know a lot of crap for my age and the gears in my head are always turning,
what kind of rockers is in your mondello kit,  do they look like comp cams,  or is the top surface polished,  PRW polishes theirs,  PRW rockers are very cheap but work very well,  their stainless full rollers on a SBC are handling a little over 400lb open pressure,  for under $200  cant go wrong

and the diameter on z28 springs are 1.25,  oldsmobile replacements are 1.437  

You are right. Chevrolet springs are wider than Olds. In the Mondello kit, the rockers are Comp Cams roller tip with the screw in studs, guide plates, and poly locks. The pushrods are the hardened, oil restricted, correct length.  I guess the factory pushrods create bad geometry with taller cams. I was a little disappointed to find the Comp Cams label in my box of Mondello valvetrain upgrade after he poo-pooed their rocker kit in his book. I do believe the whole kit was almost $400.  

haha,  Just remember that Joe isnt running that place anymore,  they want like $200 for those pushrods dont they?  just make sure that the rocker tip is centered on the valve,  mark the tip of the valve with some grease will work,  put on the rocker and rotate the engine a few times and make sure the push rod is the correct length,  you will see where the rocker rides by the marking in the grease