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Thread: 71/72 Buick Riviera Cam Help

  1. #1
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    71/72 Buick Riviera Cam Help

    Hello everybody,

    My wife and I Bought a 1971 Buick Riviera from a chap in Nuneaton UK who imports cars from the US, He had 3 and broke 2 up to make a good one, however shelved the idea in 1992 and nothing was done until we cam along and bought it. It had an Oldsmobile 455 engine in it but it wasn't original nor in a working condition so the chap gave us a 1972 Riviera engine that we are rebuilding. Car wise the restoration is going well, have done all the chassis and suspension work and rebuilt the back brake's.

    Engine wise everything has been stripped, ground and skimmed and the block has been painted (original red) however I have a question and need help in determining what I need, I am debating as to use the Camshaft I have or replace it, but when I measure it, it just does not tally up to any other measurements I can find. below are the measurements of my Cam lobes, if there are any clever people out there could you please tell me if this is within tolerance for the year and what I can upgrade to easily if possible? thank you (just to be clear it is a 1972 Buick Riviera 455 engine)

    So the lift measurements I get are these...
    0.418
    0.356

    are these okay?
    Can I upgrade and if so what do I need as I am still to get valves, lifters and rods etc

    Thank you anyone for your help, its greatly appreciated.

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    I don't think you measured the cam correctly. The rocker Arm ratio (1.55) increases lift at the valve. So using your numbers, .418 X 1.55 = .648, and .356 X 1.55 = .552. I can tell you no stock cam would be that big. Stock rockers can handle a bit over .500 lift at the valve and that is it.

    The 1972 Buick V8's were rated at 8.5:1 static compression, and if you measured everything, it is more like 8.2:1. Static compression limits cam choices. The reason for this has to do with the compression stroke. When the piston starts to move up the bore on the compression stroke, the intake valve is still open. It closes as the piston moves up the bore. Since no actual compression can actually occur with an open valve, the actual running compression of the engine is less than the static compression. Different cams close the intake valve earlier or later. That is a big reason why you will see a static compression recommendation in an aftermarket's cam description. Bigger cams close the intake valve later, so they need more static compression. You can read more about this here in the article about Dynamic Compression Ratio.

    http://www.empirenet.com/pkelley2/DynamicCR.html

    I would stay with the stock cam. Here (below) is some more information on stock 455 cams.
    Attached Images Attached Images
    Larry

    1970 GS455 Stage1 Race weight 4025 lbs.
    TSP 470, 602 HP, 589 TQ
    MT headers, Gear Vendors Overdrive
    Best E.T. 11.54 Best MPH, 116.06
    1998 Riviera SC3800

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    Camshaft help continued

    Larry,

    Thank you for getting back to me, Those measurements I have supplied are including the 1.55X, so that is everything calculated, for example, if my math is correct.
    (1.44-1.17=0.27) 0.27X1.55=0.418
    (1.40-1.17=0.23) 0.23X1.55=0.356

    This is how I came to my lift conclusions.

    One thing I have discovered today to add more confusion to my situation, I have found on this website the casting numbers for the block, head and intake. According to those numbers it would seem I have a 71 block and 72 heads and intake. surely this wouldn't be out of factory so do you think this could be a problem and maybe a reason I can't find specs matching my camshaft online?

    Once again thank you so much for your time.

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    Depending on when the car was built, you could have 72 heads and intake, it's possible. I don't think you will find camshaft specs online for most if not all GM engines of that era. They didn't list them in the chassis or assembly manuals. That picture I posted is about as good as it gets. Dennis Manner was the lead engineer for the 400-430-455 engines.
    Larry

    1970 GS455 Stage1 Race weight 4025 lbs.
    TSP 470, 602 HP, 589 TQ
    MT headers, Gear Vendors Overdrive
    Best E.T. 11.54 Best MPH, 116.06
    1998 Riviera SC3800

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    You might want to have a look at some of the OE cam specs and numbers in the articles listed at the top of the page.


    WEBNOTE: When inserting an email in a posting, use the "smilie" @ so that web robots don't pick up your address and send you more junk mail!
    Members can be contacted by clicking on their "handle", but you are much better off to post to the thread!

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    Quote Originally Posted by RivieraHarrison835 View Post
    Larry,

    Thank you for getting back to me, Those measurements I have supplied are including the 1.55X, so that is everything calculated, for example, if my math is correct.
    (1.44-1.17=0.27) 0.27X1.55=0.418
    (1.40-1.17=0.23) 0.23X1.55=0.356

    This is how I came to my lift conclusions.

    One thing I have discovered today to add more confusion to my situation, I have found on this website the casting numbers for the block, head and intake. According to those numbers it would seem I have a 71 block and 72 heads and intake. surely this wouldn't be out of factory so do you think this could be a problem and maybe a reason I can't find specs matching my camshaft online?

    Once again thank you so much for your time.
    The rocker arm ratio went to 1.60:1 for the '71 and later 455 (per the shop manuals). Changing this multiplier should give better results. Numbers will get close to those in the chart.

    Too if you can take the measurements out to 3 decimal places, accuracy would be better since a subtraction is involved. Even better would be to use a dial indicator to measure the lobe lift directly without doing subtraction.

    If there is a question about identifying a block, use the 2-letter/3-digit engine production code which is stamped into the block.
    Last edited by TODD; 07-02-2018 at 03:55 AM.
    What has been, can be again. (Bob Wills, 1942)

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    Quote Originally Posted by TODD View Post

    If there is a question about identifying a block, use the 2-letter/3-digit engine production code which is stamped into the block.
    The letters and numbers are stamped into the deck surface between the 5 and 7 spark plugs. They should be visible if the block deck has never been machined to true it up.

    For 1971, the letters could be TR, TS, or TA. TS would be the 455 Stage1, TR would be the GS455 and big car engines except for the Riviera that got TA. Below is the stampings on a 1970 SP 350.
    Attached Images Attached Images
    Larry

    1970 GS455 Stage1 Race weight 4025 lbs.
    TSP 470, 602 HP, 589 TQ
    MT headers, Gear Vendors Overdrive
    Best E.T. 11.54 Best MPH, 116.06
    1998 Riviera SC3800

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