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advice on engine rebuild

This is a discussion on advice on engine rebuild within the GM Trucks forums, part of the Vehicle Specific category; 98 chevy truck 5.7 vortec we want to try to keep everything simple going to carb mostly going to be ...

  1. #1
    tk66k
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    advice on engine rebuild

    98 chevy truck 5.7 vortec we want to try to keep everything simple going to carb mostly going to be bracket racing i know i have to get an intake ..will any small block headers fit the vortec heads....i want to use small nos 100 shot any help would be great thanks tk

  2. #2
    Member Nitrous's Avatar
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    97 GMC with 02 LS6 engine

    Headers will fit but you will run into clearance issues mainly on the passenger side where the upper control arm and eccentrics hit. There aren't too many long tube headers out there but I kmnow Edelbrock made some a while back. Dougs headers makes a mid length that you can purchase through Summit. You can probably find some long tubes if you keep searching. I just got through fabbing a set but I have an LS6 in my truck so my headers wouldn't work for you but they are made on the same design for clearance on the passenger side. As far as the nitrous goes, no problem. The L31 will take 100 shot all day long with the stock bottom end. Just make sure to use some NGK TR6's and retard your timing 2 degrees for every 50 shot. You can buy an MSD digital 6 plus or similar box that will retard timing and control rev limiting.

    Good luck!

  3. #3
    tk66k
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    thanks for the info my first vortec rebuild and first use of nos i am planning on replacing rod bolts with arp's and useing forged pistons ...what do you think about rings ...gaps..gapless ???? cam 230dur 480 lift ???

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    Member Nitrous's Avatar
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    97 GMC with 02 LS6 engine

    Either rings will work fine but you can't go wrong with gapless. The lift is at max for stock L31 heads but it will work. Make sure you replace the valve springs. Carburated, the duration will be fine. If you were computer controlled 220 would be max with a stall for me.

  5. #5
    tk66k
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    carb all the way valve springs is a must going to get valve train in kit form ...what kind of power do you think i can achive with these stock heads cam from early post flat tops shaving heads to make sure they are flat hoping for 9:0 to 9:5 comp would like to have 350 hp at rear wheels ..truck will be lightened up alot of sheet metal will be removed is this real exceptions

  6. #6
    Member Nitrous's Avatar
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    97 GMC with 02 LS6 engine

    Before I put the LS6 in my truck I dynod 440 rwhp on nitrous (150) with the stock heads, comp cam, 1.6 roller rockers, shorty headers, 4.10 gears TB spacer, pulleys, 75mm MAF descreened and Custom tuning.

  7. #7
    tk66k
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    We Are Running 3:73 Gears At What Rpm Due You Bring On The Nos Are Just When You Hit Wotwe Have Some 9" Slicks I Think That The Size I Hope These Truck Heads Don't Hold Us Back To Much..is There Going To A Clearace Issue With Rocker Arms With 480 Or So Lift

  8. #8
    Member Nitrous's Avatar
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    97 GMC with 02 LS6 engine

    You start getting into coil bind around .480" I was running .522" lift on mine and finally broke a valve spring. That's when I put the LS6 in. I always spray WOT so the nitrous doesn't puddle up and cause a backfire or detonation. You can set up your kit to spray different RPMs at WOT though.

  9. #9
    tk66k
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    `first i would like to say thank you for all the helpful info....but i still have alot of ???? if i put fuel pressure regs on fuel line can i and will the stock in tank fuel pump work ?? i have read that n2o likes alot of duration i found a circle track cam with 234 dur and 450 lift but it doesn t say what centerline i would guess 108 -106 how would that affect the performace with n2o????? this is our set up so for scat bottom end i bought a edelbrock eps duel plane intake ..quick fuel 750 carb ... proform hei...vortec heads how does this sound any help advice our goal is 400hp we are going to run at least 100 shot and maybe even 150 if it will take it

  10. #10
    Member Nitrous's Avatar
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    97 GMC with 02 LS6 engine

    Here's a good article on a 400hp budget build.

    http://www.chevyhiperformance.com/te...ams/index.html

    Here's another on heads.

    http://www.chevyhiperformance.com/te...ift/index.html

    Here's some cam info to help you determine a cam.

    Lift Numbers are generally .390-.440" for a stock cam, .440"-460" for a "RV" cam, .460"-490" for a performance cam.

    Duration numbers should be looked at but the important duration number is the .050" lift as "advertised" duration can change from manufacture to manufacture. at .050 lift look for 200*-210* for a stock cam,210*-230 for an RV cam and 230*-240* for street/strip cams and anything larger is considered race.

    Lobe Seperation Angles determine where the power will be made. The wider the seperation the more efficient the cam, the smoother idle and better top end for a given amount of duration. A tighter lobe seperation angle will sacrifice drivability, idle quality, manifold vacuum, top end power for a trade off of a very narrow and peaky powerband. Essentially all the power can be compressed into a 1000rpm "window". Look for a 112-116 for a computer controlled or nitrous injected engine, 110-112 for a street strip or blown engine and as low as 102* for a short circle track application.

    Don't go with 106 - 108, I would go with a 112 - 116 LSA and additional 10 degrees or more exhaust duration than intake duration if possible.

  11. #11
    Nitrous Tuner LS2Tuner's Avatar
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    Well first off whatever cam company you chose you need to call them with all your info to get the correct one.
    Not many build heavy trucks so your off shelf grinds will NOT be your optimum choices. On the headers yeah any will work.
    A gap less ring will be a good choice and worth the extra money.
    GM has a intake we have used with good luck the part #12366573 or a RPM #7516.
    If it is going to be mostly a bracket car/truck I would put at least 11.5:1 compression.
    So you still haven't bought the heads yet?
    I don't care for the NGK's at all myself and I think the reach is different on the LS and Vortec heads if I remember correct. If your going to do a baby 100 shot you won't need to buy a box with a retard. Just set the initial @33-34 total depending on the heat mark on your plugs.
    I prefer the AutoLite race plug. The part # starts with AR.
    Don't be afraid of the bottle!!! Be afraid of your tune!!!

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