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Thread: Mazda 929 VC engine head

  1. #1
    Junior Member
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    Apr 2010
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    Brisbane, Australia
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    26

    Mazda 929 VC engine head

    Hey guys,
    Another query about the ol' VC motor. I am doing the head gasket at the moment and a thought crossed my mind. The gasket i got fits the MA, NA, VB and VC engines, so I wondered how easy (and what advantages it would provide, if any?). one thing I thought I would need is a new exhaust manifold, as the VC one is square and the MA is round (I think).
    Cheers guys!

  2. #2
    Senior Member
    Join Date
    Jan 2008
    Location
    Villeneuve, Qld, Australia
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    508
    Hey Rainman!

    Yes mate the gasket does most of the bigger 'A' series Mazda engines. Yes you're right too about the MA going to round port exhausts.

    After playing around with Mazda piston engines for over 20 years now, I'd probably recommend just using the whole MA engine. There isn't a lot of gain putting the MA head on, as you increase the compression ratio and probably blow out the headgasket again! The MA stroke is different and the piston isn't flush with the top of the cylinder block, but in your VC it is. The VC engine does run a bit nicer though.

    If you do go up to the MA, look for a motor out of the series two 626 rwd or later 929. the flow rates were the best out of all the engines of the time. The best way to tell if find an engine already out of the car, is to look on the front of the cylinder head, just under the distributor moulding. There should be a four digit number cast into the head - 8057 is the good number.

    Another quick trap on the VC, they is usually two inlet manifold gaskets in your VRS gasket kit, pay particular attention if you replace it as the VC was the only one out of all of them that uses a balance port between the manifold tubes. When looking at the manifold, they are located between the very outer tubes(cyl 1 and 4) and go to cyl 2 and 3. One gasket lines up nicely and the standard that does NA,MA etc exposes those ports and it engine won't run and you'll pull your hair out trying to find the fault! Seen many a VC engine pulled apart again looking for something else!!

  3. #3
    Junior Member
    Join Date
    Apr 2010
    Location
    Brisbane, Australia
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    Thanks b1500boy,
    thats interesting about the balance port... I noticed it when i was putting it all back together, but didn't pay much attention as the gasket that was on there covered them with paper but left a gap behind... what are they supposed to do?

    I take it the idea is to leave them open to breath or is it to block them off? ATM they are open, as i used gasket glue (It didn't cross my mind to order the VRS set, i just got the head gasket and thought i'd glue everything else.)

    Maybe i'll go back and make sure they aren't/or are filled in and get the right gasket... hmmm...

    I wondered why I was getting some strange noises from the engine too, and now I know. The camshaft chain gear was put on the wrong way by the last gear so it was rubbing against the screws in the back of the rocker gear! an easy mistake to make i suppose but it was burred quite badly...

    There's a '79 MA engine and gearbox on ebay, maybe i'll splurge a bit...

    Thanks for the help!

  4. #4
    Senior Member
    Join Date
    Jan 2008
    Location
    Villeneuve, Qld, Australia
    Posts
    508
    From what I can make out, the VC got the balance ports on the manifold because of idle quality being poor due to the fuel quality and stroke difference to the MA.

    Both engines had quite a large CFM airflow through the heads, the MA with its larger stroke idled a lot better. Yeap, that gasket does cover them, the more standard inlet manifold gasket that does the MA, NA etc exposes them to atmosphere and major lean out/no idle or running!

    Yeap, that a fairly common thing I see to the cam gear on back to front or loose, makes some very odd noises indeed.

    If you do upgrade, the best plan is to get both engine and box. The MA runs a different flywheel and clutch - a dished flywheel type set up.

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