Does anyone know if there is a cam lift 'limit' when useing these heads because of valve guide interference?

 

Yes, that is known.

Yes, there can be interference.

With stock components, about all the lift you can count on, is around .480", before the bottom of the retainers run into the valve guides.

 

ya know that's weird, I just got mine back from the machine shop, told them I had .535" lift on intake, and to make sure it'll be ok (since they were doing final assembly for me...), he used teflon valve seals, with umbrellas and non-offset retainers, and said he didn't have to do anything for that much lift....?

 

Probably because your retainers aren't stock.

 

that's true, but I thought non stock retainers would be the same dimensions, and would have the same interference, unless they used .050 offset locks or something (which he said he didn't need to use...)



anyway cob, .480" is a commonly used spec, however if you're getting the heads machined for positive valve seals, they can usually take the guide bosses down to account for more lift, if you're not getting machine work done, .050" offset locks are very cheap.

 

Aftermarket retainers are basically NEVER the same as stock ones.

 

Have the shop shorten all the guide boss tops by .200" when they cut for positive seals. Just got mine back and one valve only had .470" between the stock retainer and new installed .530" dia positive seal. Many times, especialy after grinding new valve seats for larger valves the seat ends up higher in the chamber which reduces the installed height and the guide(seal) to retainer bottom clearance.
Ya have to check it after the valve job and check each valve. they will not all be the same. Again, shortening the guide top by .200" usually does it.
For stock diameter springs on these heads, Comp cams #CCA-4753 spring shim kit (48 pieces) usually has enough shims to correct the spring installed heights for a pair of heads. It's $24.39US @ Summit. You can also use your old oil shields as shims. They are .030"

Here is an example: Mine look like this. Intake installed height 1.77"
so I'll use a .075" stack 1 .060" +1.015" to get a shimmed 1.695" installed height.

Exhaust is 1.84" to 1.81". without shims. So I'll use a .105" stack on the 1.81" ones and a .105" stack + a old oil shield (.030) on the 1.84" ones for a 1.705"
installed height.
using Comp 981 springs (110# @1.70") Coil bind= 1.13"

so with a .507" intake and .510" exhaust Camshaft (valve) lift I'll have .058" open spring coil clearance intake and .065" on the exhaust side. @ max valve lift.