383 SBC Build advice
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  1. #1
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    383 SBC Build advice

    I'm soon to start building a 383 with a target of 500bhp/500 ft/lbs, and from a fair bit of research I have come across several combinations that should do the trick.

    I've got my donor block which is from a '90 GMC Vandura which from last night's investigations is a 2 bolt, non roller block... at least it has a 1 piece seal going for it.

    Having bought the donor car, broken it, retained the V5 and trans for BIVA reasons (two major components from the donor and all that malarkee for age related plate and pre '93 emissions etc) I'm pretty committed to using this block, especially as it was low mileage, virginal an ran perfectly before I removed it.

    So... a few questions if I may.....?

    From my research it seams that the threshold for needing 4 bolt mains is circa 500 bhp to be safe, so I guess I'll need to get it machined for splayed 4 bolt caps??

    Who in the UK is experienced and good quality for this type of machining work?

    Also, my research also suggests that from about 450 bhp upwards, roller cams tend to be used, which is a problem, as I don't have a roller enabled block.

    It seems as if a roller cam is good for about 20bhp gain on a like for like spec motor. Is there any way of equipping a non roller block with a roller cam, or any other suggestions of how I can make up the loss of power from having to use a flat tappet cam without just going for a crazy cam profile which will ruin flexibility?


    My intended spec 'was' before I discovered it wasn't a roller block was...

    383
    ARF 195 heads
    10.5 CR
    Comp Cams Xtreme Energy (12-433-
    Forged Eagle Rods
    Forged Eagle Crank
    KB pistons
    Edlebrock Perf RPM manifold
    Edlebrock Thunder series 850 Carb
    MSD etc, etc.


    Thoughts, comments and guidance appreciate. Ta.

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  3. #2
    Exceeded sell by date Plumpcars's Avatar
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    You can buy retro fit roller cams/lifters to fit the early blocks but they work out quite pricey. Your spec will depend upon weight of vehicle, gearing, converter, intended use etc.

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    I didn't realise you can retro fit a roller into a non roller block? Any links to these parts as a sample? Does a '90 block fit into the early catagory?? I always saw pre '86 (2 piece seal) as an early block?

    The motor will potentially have a dual role.... initially, and primarily, it will be mated to a Porsche G50 manual transmission in a mid engined conversion weighing approx 1100 kgs.

    With reference to weight and gearing.... I assume this is to calculate the best combination of torque converter stall versus cam range? If so, on a manual transmission car, this becomes less important...? Or have I got that wrong?

    Intended use will be occasional weekend blast + RWYB drag days. Does need a small element of streetability though.

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    COMP Cams: Camshafts

    COMP Cams® - Camshaft Breakdown


    I thought the change to hydraulic roller came in the late eighties so surprised that your engine doesn't have one? Is it different because it's a van?
    I only mentioned car spec as obviously you want the package to remain tractable. Having a light car and manual will make life easier for you.

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    This-

    Where the Chevy Rollers Are
    The original small-block Chevy remained basically unchanged from 1955 through 1985. But in 1986 Chevy finally addressed that leaky two-piece rear main seal by making it one piece, and later added hydraulic roller cams to the 305- and 350ci passenger-car engines that retained the same 0.842-inch lifter diameter. The factory conversion to hydraulic roller cam added slightly taller lifter bosses and three small cast-in perches that mount a stamped-steel spider, along with a two-bolt cam retainer plate located at the nose of the camshaft to limit fore-aft movement in the block. While all passenger-car small-blocks from 1987 on were roller-cammed, light-duty trucks used this same iron block but stuck with a flat-tappet camshaft. This means the block comes with the casting provisions for adapting a factory hydraulic roller camshaft. At the most, you may have to drill and tap a couple of holes. We've even seen four-bolt main hydraulic roller cam blocks.

    The hydraulic roller-cammed motors also come with a stepped drive face on the cam, which requires a different cam sprocket with a smaller bolt circle. This is the basic difference between a factory-style hydraulic roller cam and the standard early small-block Chevy flat-cam mount. So the idea is to use a later-model, one-piece rear main seal block with the factory hydraulic roller cam configuration. That way you can reuse the factory hydraulic roller lifters and tie-bar arrangement along with the factory-style cam timing gear. It keeps the price down to almost nothing and frees up more money to spend on a good aftermarket hydraulic roller camshaft. This is an especially good idea when stepping up to a budget cast 383-style crank, rod, and piston package


    Roller Warning
    One area where you must be careful with production-based small-block Chevy hydraulic roller lifters is with high-lift camshafts. According to Crane's Director of Valvetrain Research and Development, Mark Campbell, valve lifts of more than 0.530 inch at the valve with a 1.5:1 rocker can allow the lifter to fall deep enough into the lifter bore (because of the lobe's small base circle) that the steel retainer can lose its grip on the lifter body. This allows the lifter to spin in the bore and destroy the camshaft. In checking a few cam catalogs, it is possible to order a hydraulic roller camshaft with enough lobe lift (in excess of 0.354 inch) to create this situation, so just be careful. This is why Crane created a long-travel hydraulic roller lifter that will allow you to run a high-lift hydraulic roller cam with the stock lifter configuration. These eliminate the problem but are also much more expensive than OE replacement lifters. Another solution would be to run a 1.6:1 rocker ratio with a reduced lobe lift cam to accomplish more valve lift.

    Read more: http://www.carcraft.com/techarticles...#ixzz1ahEx2JCm
    Read more: Chevy Small Block - Car Craft Magazine

    Read more: Chevy Small Block - Car Craft Magazine

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    Thanks for the reply..... Not all post '87 blocks had the casting provision for roller cams, including mine....

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    From reading the Chevy High performance article, the retro fit kit solves the problem. I trust that a post '87> non roller block can accept the pre'87 retro fit kit?

    If so, we're laughing all the way to the 11's....

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    I see no reason why not.

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    Splendid. Just the 1 piece rear seal difference then...?

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