383 build questions
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383 build questions

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    Member ocelot's Avatar
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    Default 383 build questions

    I'm building a 383 for my jet boat, it's a fairly light hull 480#s. I have short block assembled, and picked up a set of vortec heads. They have been machined for guideplates and studs, but the spring pockets are still stock. I am running a hyd roller hot cam .525 lift. I plan on using LS springs 102# @ 1.8 closed , and 329# @ 1.265 open. Do these springs sound like they are good choice for my GMPP hyd roller lifters? Also will stock length valves be ok as well? Thanks

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    steelcomp was here
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    Quote Originally Posted by ocelot View Post
    I'm building a 383 for my jet boat, it's a fairly light hull 480#s. I have short block assembled, and picked up a set of vortec heads. They have been machined for guideplates and studs, but the spring pockets are still stock. I am running a hyd roller hot cam .525 lift. I plan on using LS springs 102# @ 1.8 closed , and 329# @ 1.265 open. Do these springs sound like they are good choice for my GMPP hyd roller lifters? Also will stock length valves be ok as well? Thanks
    Can you give more specs on the cam? You might be asking for trouble running those lifters on that cam. That seems like enough open pressure but I'd like to see more seat pressure. I'd install them @ 1.75, probably about 120#.
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    Camshaft, Hydraulic Roller Tappet, Duration at .050 in. 218/228, Lift .492/.492, Chevy, 5.7L, LT1, Each. using 1.6 rockers brings lift up to .525/.525. I have read to install springs @ 1.7???

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    steelcomp was here
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    Quote Originally Posted by ocelot View Post
    Camshaft, Hydraulic Roller Tappet, Duration at .050 in. 218/228, Lift .492/.492, Chevy, 5.7L, LT1, Each. using 1.6 rockers brings lift up to .525/.525. I have read to install springs @ 1.7???
    OK, you'll be good with those lifters.
    You can install them @ 1.7 but you need to check the actual (not advertized) coil bind. Put a retainer on them and squish them in a vise, then measure the spring only. You need no taller than 1.12 @ coil bind which might be a problem. For your minimum installed height, add your net lift +.050 to your actual coil bind.
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    gn7
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    Thsi is a Gen I or LT? with Gen I 23* heads? I think you would be better off with something like Isky's 235D spring or something similar. If you are going to use LS springs thats a broad term. Lots of LS configurations out there. You need springs from a LS 6



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    Seal to retainer interference on vortecs at about .460-.470 valve lift. The guide needs to be cut down for .525". Back in the early days, when vortecs became popular(98-99') it was a no no to put anything heavier than 110lbs or so. Hollow valves wont hang with the abuse was the reason given. I know a lot of people run more than this and were offered by parts houses as "performance cam ready" or "max lift .525" vortecs. I do know the factory Indmar 320HP 196/204 @.050 cam (also ram jet) will go to about 5200 rpm with 80lbs on the seat. I think 102 on the seat will go to 5500rpm every time with your cam.

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    gn7
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    Quote Originally Posted by MACHINEHEAD1 View Post
    Seal to retainer interference on vortecs at about .460-.470 valve lift. The guide needs to be cut down for .525". Back in the early days, when vortecs became popular(98-99') it was a no no to put anything heavier than 110lbs or so. Hollow valves wont hang with the abuse was the reason given. I know a lot of people run more than this and were offered by parts houses as "performance cam ready" or "max lift .525" vortecs. I do know the factory Indmar 320HP 196/204 @.050 cam (also ram jet) will go to about 5200 rpm with 80lbs on the seat. I think 102 on the seat will go to 5500rpm every time with your cam.
    Good point. I always considered .450 as the max safe. They may go more, but I never went there.
    I didn't know that vortecs had hollow valves. When you say 80 lbs on Idmar 320, is that a hyd roller?

    He may not need that much spring with this thing. That cam isn't that big for a 383. I think the thing only good to about 6000 in a 350, and I doubt thats where it makes max HP. It will definitely be less than that in a 383



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    Member ocelot's Avatar
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    Thanks for the info fellas.

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    Senior Member MACHINEHEAD1's Avatar
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    Yes hyd. roller. GN7, now you got me wondering if I got my info right about the valves. This came from a GMPP guy I used to know, 10+ years ago, brain may be fading a bit! He said dont mess with them at all. Dont try to port them or change springs or anything, you will screw them up. My 87 Suburban (3/4 ton) goes to 5200 and is done done at that RPM with the 194/204 hyd.roller cam. 216 hp at 4700 on dynojet with performer and headers with 800DP.

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    Senior Member VAMI's Avatar
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    Was that your only choice for heads?

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    Member ocelot's Avatar
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    No not my only option, every parts catalog has about 3 or 4 pages of sbc heads. jk. These were a good buy, and they are great heads other than the weight. For my power needs they will be a good choice.

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    Senior Member VAMI's Avatar
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    What do you hope to make hp?

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    What are your realistic hp goals and at what rpm?

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