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Vortec valve lift limit?! (update)

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Blazer_Boy, Dec 3, 2002.

  1. Blazer_Boy

    Blazer_Boy 1/2 ton status

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    I've always heard that Vortecs will only take .400 lift, or .420, wait, maybe .460, no no, .480. It seems every Smokey Yunik wanna be with his own website and these heads has their own figure. So I went to the source and asked the one who would know, the general himself (GM). Actually Pace Parts, but anyways, out of the box GM reccomends .475" and Pace says that you can get away with .480" I guess they should know because they also doing in house machining on these heads accept lifts in .500"+ range, I think they call them ZZ5 or something. I feel better about my .460 lift on my Vortecs.
     
  2. Diesel Dan

    Diesel Dan 1/2 ton status

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    Re: The last word on Vortec valve lift

    I know on the set I have the retainers touch the seals at ~.460" of valve lift. Running a .460" lift cam would not give enough running clearance and would ruin the seals before long. It cost me $50 to have 2 new vortec heads machined for larger diameter springs and old style seals.
     
  3. Blazer_Boy

    Blazer_Boy 1/2 ton status

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    Re: The last word on Vortec valve lift

    Well shoot, 7,000 miles on mine .447/.462 and no problems. The only things thats been done to them is a valve job and seals from the 69-80 engine kit. Got them off a warrantied from the dealer. It had a piston go bad after about 10,000 miles. What ratio rockers are you running? I'm still using the old cheapie 1.52 stock self aligning ones.
     
  4. Diesel Dan

    Diesel Dan 1/2 ton status

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    Re: The last word on Vortec valve lift

    I am not currently running the heads I have, paper weights in the garage. By going to the older style seals you may have gained additional clearance. Also I was measuring actual valve movement, so rocker ratio did not apply.

    I put a motor together for a buddies truck. It was a new crate motor, L31 vortec for '96-00 truck. Pulled the stock cam, removed heads. Installed the HOT CAM kit, .525", 1.6 roller rockers and had heads machined for supplied springs. Also drilled the heads for the coolant by-pass rather than plumb it from the water pump to the intake like a big block.

    I am thinking about using the vortec heads for my '91, along with a stock L31 roller cam. The heads I have might be the ones for the 3/4-1 ton, IIRC the exhaust valves might be sodium filled. So stainless valves are being considered.
     
  5. dyeager535

    dyeager535 1 ton status Premium Member

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    Re: The last word on Vortec valve lift

    Are yours the '906 casting? There was some (mis?)information in the January '03 Car Craft or maybe Hot Rod apparently saying that some of the HD truck Vortecs have restricted flow due to casting. I don't buy it (I've got 906's I think, mine have been paperweights so long I can't remember for sure lol)

    All I've heard about are the valve differences that you note, and flame hardened vs. pressed in exhaust seats.
     
  6. Diesel Dan

    Diesel Dan 1/2 ton status

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    Re: The last word on Vortec valve lift

    Yes, they are the '906s.
    When we bought the crate motor from Scoggin-Dickey I told them what we were doing and they recommended the 1/2ton version. They told me about the exhaust valves, makes sense some of the BBC used the sodium filled valves also.

    When the crate motor showed up I looked at the external head marks, on the end of the heads. They were different from the heads I have, so I assumed I have the HD heads.

    I was going to install the 1 piece stainless valves for less weight, better flow and peice of mind. Didn't want to chance dropping an exhaust valve.

    Not concerned about the flow of the castings. It is still way better than the stock TBI heads.
     
  7. dyeager535

    dyeager535 1 ton status Premium Member

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    Re: The last word on Vortec valve lift

    What head marks do yours have? Mine are the 3 triangles, or I guess you could call them peaks. Just kind of curious, like you said it probably doesn't matter, for the most performance Vortec's aren't the way to go anyway, but it would be nice to kind of sort out what the differences REALLY are.
     
  8. Blazer_Boy

    Blazer_Boy 1/2 ton status

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    Re: The last word on Vortec valve lift

    We've got three 906 sets laying around, including the ones on my 355. I'll look. I know its not little saw mark like I've seen on the newer ones.
     
  9. Blazer_Boy

    Blazer_Boy 1/2 ton status

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    Re: The last word on Vortec valve lift

    The marks on our 906's could basically be described as a big hooter facing upright /forums/images/graemlins/rotfl.gif. I popped the spring out of the stock 906. The heads came off of another warrantied motor from the dealer. The engine had a noise and the dealer did a rebuild. Guess what, the noise was still there. So they put in a new eninge and still the same old noise. It turned out to be the transmission. I don't know for sure how extensive the rebuild was. The valves looked pretty heavy on carbon, but the bores didn't have a lip. Probably just a bottom end rebuild, but be warned the valve seals may be something changed when the dealer did the rebuild.

    Anyways, I took a feeler gauge and stuck it between the bottom of the retainer and the top of the seal. I could jame .500" in there, but .480" fit very nicely with just a pinch of play. I just used a dial caliper to measure how thick the feeler gauge was because there's no way I'm counting everyone of the feelers.

    Moving right along here. My uncle had another set he wanted to use on his race car. He had a machine shop that I feel is shakey do the work. It was machined for 2.02/1.6 valves. There was no work done to unshroud the valves (not a huge deal on vortecs, but still). He also had double spring valve springs but on. The retainers also looked funky. They were really tall. They were also black instead of silver on the stock set we had. With those wierd retainers, it only cleared .432! /forums/images/graemlins/eek.gif. I sure saved his a$$ because he wanted to use .540" cam. All kinds of fun I guess. The retainers might be the reason why some heads clear and others smoosh the seals.
     
  10. Diesel Dan

    Diesel Dan 1/2 ton status

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    Re: The last word on Vortec valve lift

    Mine are like Blazer Boys, one big hooter pointing up!
    The ones on the crate motor had the 3 "saw teeth" style, IIRC.
     

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