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Thread: The mythical 4500 RPM limit for the GM HEI Module - David Vizard's work

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    Default The mythical 4500 RPM limit for the GM HEI Module - David Vizard's work

    I've always wondered where the 4500 RPM limit "rumor" about GM's HEI module came from and finally found the source, in a book David Vizard authored called "How to Build Max-Performance Chevy Small-Blocks on a Budget". The relevant pages are actually available on the internet - How to Build Max-Performance Chevy Small-Blocks on a Budget - David Vizard - Google Books

    I was a little disappointed after reading all of the the various things that Vizard has written. In the end it seems like he's using the old technique of selling aftermarket products by pointing out "flaws" in existing product. I think that he started by selling MSD product, then went to DUI distributors. He even plugged Pertronix in one article. In some of his latest stuff he's lowered the "weakness" limit to 3300 RPM.

    Ignition Systems Cheat Sheet for the Chevy Small Block

    Small-Block Engine Build - Popular Hot Rodding Magazine Page 3

    Looks like he's "currently" selling Blue Pheonix Plasma stuff - Blue Phoenix Plasma Ignition Dyno Test by David Vizard - YouTube

    He's selling oil additives here - Oil Extreme

    Just filling in some gaps before I lose all of the links. If you read some of his original writing, it reads like good science but is short on actual measurements. The weak spark limit seems to be a supposition based on "module voltage output". He never actually measured if there was a misfire, just said that there should be.

    For the record...
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    1976 280Z, with some minor modifications

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    Boat Anchor Repairman Captain Obvious's Avatar
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    Yeah, that sure starts to sound like marketing propaganda aimed at increasing your own sales by torpedoing someone else's product.

    I used to take my GM to 6000 RPM every once in a while and it never gave me any trouble doing that.

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    Found another Vizard article where he shows actual dyno results with a module change (stock coil though, apparently). Above 5000 RPM (V8 engine, = 6,667 L6 RPM), he shows a dramatic change. But he's still promoting MSD and Performance Distributor products. Just odd that there's not more out there on this.

    Chart #9:

    Twelve Engine Output Tips - Dandy Dyno Dozen - Stock Car Racing Magazine All Pages
    1976 280Z, with some minor modifications

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    Registered User EuroDat's Avatar
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    My 280Z has been going strong since I made the HEI mod. Certainly better that the old tiu. It revs to 6000rpm not problems even under full throttle. I don't go about 6000rpm so its good enough for my stock L28.
    chas
    Chas
    5/77 280Z HLS30 403100 with some modifications
    Original colour: 305 Light Blue. The PO changed it to Red

  5. #5
    Crumudgeon
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    Someone noticed Vizard is a product whore? Imagine that; A magazine writer skewing an article to sell more products or even, heaven forbid, just reprinting a manufacturer's press release as editorial content. Whoda thunk it?

    All these magazine writers are product whores. They are not writing articles to help you out, they write articles to make them and their magazines money.
    LeonV likes this.

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