Vortec Head Modification/Upgrade

Bt Doctur

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Tony, just remember that total lift is the cam lobe lift AND the rocker arm ratio for total lift.
 

FreeBeeTony

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Tony, just remember that total lift is the cam lobe lift AND the rocker arm ratio for total lift.

Understood, so when I increased the height of the back of the rocker arm by 0.35, the valve should have opened 0.525 (0.35*1.5); correct?
Or am I missing something?
 

achris

More fish than mountain goat
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What's the lobe lift? Lift the back of the rocker by that amount. As the rocker is 1.5:1, the valve lift will be lobe lift * 1.5....

Chris......
 

FreeBeeTony

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Lobe lift from CompCam: 0.335.........so I used 0.35 in my test as in post #20.
 

FreeBeeTony

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An observation, see pics below.
The valve stem on the exhaust valves protrude through the retainers more than the intake.
The rollers on the rockers just about make contact w/ the valve stem. Can I use different locks/keepers on the intake valves to make the retainers a bit lower?
 

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Bt Doctur

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You will need to remove the valves and check their stem height first., from all my years in motors they should all be the same height. If the valves are exactly the same then the problem could be a seat installed too deep in the head.
 

FreeBeeTony

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I think it has more to do w/ the location of the keeper on the valve stem. Even if the valve was installed too deep or not deep enough it wouldn't change the amount the valve stem is sticking out past the retainer.
I am going to contact CompCams and ask their opinion. I had a similar problem when I had my heads redone by the machinist last time but it was much worse.
I have a feeling the dimension between the end of the valve stem and the location of the retainer-slot is different between the intake and the exhaust valves.
Will report back after I contact CompCams.

UPDATE:

Just found this !!!

Another difference between Vortec valves and the earlier non self aligning head valves is the tip length. Earlier valves are 0.250" on both intake and exhaust valves. Self aligning head intake valves have a 0.260" groove-to-tip length, exhaust valves use a 0.289" groove-to-tip length. That said, the typical SBC valve tip length of 0.250" will work just fine with self aligning rockers. Like with ANY rocker arm/valvetrain combination, the
valve train geometry
needs to be verified.
 
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FreeBeeTony

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MORE!!! [h=3]Locks[/h]
Warning
Note: On Vortec and other heads using self aligning rocker arms, using a +0.050" lock can cause interference between the rocker tip and the locks/retainer. Rocker contacting the locks/retainer has been encountered using a combination of c/n 906 Vortec heads, Comp Pro Magnum rockers p/n 1317, Comp retainer p/n 787, Comp spring p/n 26918, and the +0.050" locks.

The engine builder must mock up the assembly and check the clearance closely. In the case there's insufficient clearance, there are a few options:
  • Use non self aligning rocker arms. Requires guide plates be installed.
  • Use longer valves
  • Use a different spring/retainer combo that uses a standard lock
  • If just the locks are hitting the rocker, using a shorter (lash cap compatible) lock like the Edelbrock p/n 9615 may help. This 7 degree lock is 0.050" lower than a regular lock.
  • Warning
    Use extreme caution if making the spring seat any deeper.
I contacted CompCams and their response was that they have not heard of the problem as I described.

I am going to continue to research and may elect to use different locks on the intake valves.
 

aimlow

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Have the heads or block been milled? Pushrods may need to be custom fitted for length?
 

aimlow

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lash caps are generally a band-aid for another problem.
 

CamaroMan

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what you can do is use a soft spring and put the head on.. smear something on the valve tip and see what "wear pattern" the rocker tip is making on the surface of the valve end.. it should rub centered and spaced equally/ as centered as possible. If the rocker roller wheel gets too close at the end of the valve tip at you might have trouble.. The valve length will determine this.. Also hopefully you didnt cut too much away - you need to have correct install height for correct spring pressure - If you cut away too much you can space at the bottom of the spring if u need to..
 

aimlow

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Pushrod length will also affect the pattern. Plus, you don;t want the rocker arm to hit the edge of the retainer.
 

FreeBeeTony

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I ordered locks w/ installed height of -0.050.
See pics below.The 1st set of pics are w/ the regular locks on both intake and exhaust.
The 2nd set of pics are w/ the -0.050 locks on the intake valves.
Notice how much better (IMHO) the rocker tip contacts the intake valve.
This was my last cut on the test heads I have..........
Now it's time for the real thing.........just have to get the heads off the engine in the boat!
Hope to get the heads off and do the work over the XMAS break,
Happy Holidays to all my iBOATS friends!!
 

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aimlow

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Are the pushrods the correct length? Lotta thread on the studs sticking out.
 

FreeBeeTony

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Heads aren't even on the engine yet..........rockers are just sitting on the studs for a check.......
 

FreeBeeTony

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Was just going by how the rockers were sitting on the stems.....
See below for more Vortec info:

The Vortec head features a very large boss at the base of the valve guide that measures 0.850-inch in diameter and is used to locate the 1.250-inch outside diameter (O.D.) valve spring. The head uses 0.560-inch I.D. seals mounted directly on the top of the guide. This guide boss is also very tall. This height restricts the room between the top of the seal and the bottom of the valve spring retainer at max valve lift. There are two simple approaches to modifying the head to accept a performance valve spring that will create the room necessary to allow greater valve lift.

This is my next move:

The second solution is less expensive but requires more effort and to purchase a machine tool to modify the valve guide boss to add clearance. COMP sells a slick little tool that will machine the guide down to a 0.530-inch O.D. seal size while also lowering the boss height. The boss height of our heads measured 0.730-inch from the spring seat. It is this height that minimizes the seal-to-retainer clearance. With the tool set up in our ½-inch drill motor, it took a few minutes to machine all 16 guide bosses, being careful to lower the guide height only enough to create 0.550-inch retainer-to-seal clearance.
 
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