302 stock-ish engine rebuild

Discussion in 'Technical' started by CA189HJN, Dec 5, 2020.

  1. CA189HJN

    CA189HJN Robert Couse-Baker Supporting Member

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    In a month or two, I’m pulling the factory302 out of my ‘73 Maverick and taking it to a rebuilder. I kind-of have a plan, but I want input from the Maverick Comet community.

    My objective for the Maverick has been to improve street performance, safety and reliability while leaving the exterior original. So far, so good. I’ve rebuilt the front suspension, replaced the flat cam and lifters, installed disk brakes, Petronix III ignition and Street Demon carb, had a specialist rebuild the C4. It looks much like it did when I got it and now it runs pretty good: no clouds of smoke, no overheating, no dying at stop lights.

    But all is not well in the engine room: there’s oil on most of the plugs. The engine has a little over 70,000 miles, but that includes three decades of non-operation. It starts hard from cold and sounds like the fishing boat in Jaws until it warms up. If I were to wager a guess, the rings aren't sealing when cold (maybe a head-gasket leak?). Once warmed up, it runs fine around town, but extended freeway driving will load up the plugs. That means no road trips until after the rebuild.

    Keeping the car looking stock means compromises. I’ve decided to stay with the C4, the original 3.00:1 rear end, and stock-equivalent 205/65R15 tires (the change to 15-inch wheels was required to fit the aftermarket disk brakes). All of that limits how much power I can put to the ground. I love horsepower as much as the next guy, but I don’t want to waste any, especially at the expense of drivability and reliability.

    Current performance is entirely sufficient to keep up with modern traffic, which is all I want from a vintage car unless I win the Lotto. (If that happens, I’m going to park the Maverick, buy a 1966 GT40, install a supercharged Coyote crate engine, and drive it buck wild until I lose my licence).

    So, here’s my semi-stock rebuild plan. Top priority is durability. Second priority is street drivability (e.g. smooth idle, easy starts, low-end torque)

    1. A local engine builder will do the long-block
    2. Retain 28 oz balance, stock style timing-chain cover, 2 bbl cast-iron manifold, etc
    3. Magna-flux inspect block, rods and heads
    4. Bore and align crank and cam bores
    5. Mill manifolds, heads, block (if required)
    6. Spin-balance the rotating assembly
    7. Howards Cams 220225-08 roller-cam kit (a stock-style street grind)
    8. Will require custom pushrods and other finessing
    Once I reinstall the long block in the car, the real fun begins.
    1. Holley Sniper 2300 2 bbl EFI
    2. Holley EFI HyperSpark Ignition (allegedly plug and play with Sniper EFI)
    3. O2 sensor install (weld fitting, not clamp on)
    4. Drop fuel tank and install EFI pump (I don’t know yet which one)
    Any thoughts?

    engine room.JPG
     
  2. Krazy Comet

    Krazy Comet Tom Supporting Member

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    Probably the valve stem seals are all but non existent. I changed several sets on '60s/'70s engines with less than 75K. Allows vacuum, especially on decell to pull oil past valve guides, often oil consumption was quart in 300-400 miles.
     
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  3. greasemonkey

    greasemonkey Burnin corn

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    Don't waste your money on balancing and that intake manifold is going to hold it back pretty bad. And maybe pick up a set of iron gt40 heads. That would make a better setup in my opinion. Even if you keep the small injection system the heads and manifold would help a lot.
     
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  4. BBMS18

    BBMS18 Member

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    Correct me if I’m wrong. 73 302 would not have hardened valve seats, so I would agree that upgrading to newer heads would definitely be a better choice.
     
  5. 71gold

    71gold Frank Cooper Supporting Member

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    AOD transmission...:yup:
     
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  6. CA189HJN

    CA189HJN Robert Couse-Baker Supporting Member

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    I'm quite certain they're toast. The full valve job is a must. Thanks

    I appreciate the advice, and usually I'd be in total agreement about breathing, but this won't be a high-revving engine (Which also means it might not benefit from balancing, thanks). The exhaust is still going to run through the factory cast iron exhaust manifolds and the y-pipe single exhaust.

    True that, I'm sure some or all have recessed. The car has that "potato-potato-potato" sound at idle that I associate with old cars needing valve jobs.

    Yes, totally. Someday ...

    Thanks, Gentlemen
     
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  7. stumanchu

    stumanchu Stuart

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    If you have thermactor bumps in your exhaust ports, grind them off. If you can come out of the rebuild with 9.5:1 or close to it, power and economy will both increase. At least, if you want more compression, now is the time to figure that out and engineer the re-build to make it happen. Removing those bumps will help even a stock motor in my opinion.
     
  8. CA189HJN

    CA189HJN Robert Couse-Baker Supporting Member

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    I didn't even know about the smog bumps. Thanks! Since the heads have never been off, there should be plenty of room for head/cylinder head milling. I've been uncertain about compression ratios. Although the Sniper FI and ignition doesn't have a knock sensor, I think it will auto-adjust and make full use of the added compression.
     
  9. bmcdaniel

    bmcdaniel Senile Member

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    Heads, cam, intake, and exhaust is where you get efficient power from, regardless of what rpm range your planning on. The GT40 heads mentioned earlier are a good choice. You can use slightly larger than stock parts and have everything still look stock. It'll be more efficient and run cooler. As far as if balancing is needed, it depends on how much the new pistons weigh compared to the originals. If they're within a few grams you'll be ok for what your doing. Try to stay away from pistons that are "rebuilder specials" they sometimes have lower pin-to-crown height for lower compression.
     
  10. TeeEl

    TeeEl New Old Member

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    What's so important about "looking stock"?
    It's a Maverick, not a '64 GTO.
    And no one sees the gears. Align-boring is probably not necessary, and would bring the cam & crank closer together, requiring a custom length timing chain. Do a basic rebuild with minimal overbore, new rings, bearings, valvejob, good heads, cam, intake and exhaust. No sense in making it more complicated than it needs to be. You're not gonna hang with any of the modern stuff while having good fuel economy...
     
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  11. stumanchu

    stumanchu Stuart

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    I am going to toss this out there. What you are doing will be fairly expensive for modest gains. If you want to drive that car for 30 years in basically stock form, you have a good plan. If you only drive it 1000 miles a year, maybe new valve stem seals, or rebuilding just the heads, will make it run nice for a very long time at 1000 miles/year. just food for thought.
     
  12. CA189HJN

    CA189HJN Robert Couse-Baker Supporting Member

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    I think this is basically the direction I'm going. Since the heads have not been off yet, I don't know what surprises lurk within.

    It's hard to think of the world will be like in 2050, but I'm in this for the long haul. As reliability and fluid retention improves, I'm driving it a lot more. Our other car is a Miata, so the Maverick is getting used as the "big car" for shopping, hauling and picking up people at the airport. It's mostly short trips, but I expect 6,000 miles plus per year after (if) the normal world returns.
    Totally agree. But I really place a high value on reliability, smoothness and low-end throttle response.

    Looking stock is just my preference. We're fortunate in our community to have no brand police. Customizing a '64 Goat will get you thrown out of the Pricey Pontiac Purist group, but we have no such zealots. Good. Is there anyone on this forum doing concourse restoration of a Maverick or Comet? I don't think so, but it would be cool in it's own way. (my preference for a concourse Maverick would be a 1970 2-door, 200 CID I-6 and three on the tree, bone-stock in calypso coral over black. I've been looking, but clean ones are far rarer than trailer-queen '64 Goats). I just looked: there are 25 1964 Pontiac GTOs on Hemmings, and they all look boring to me.

    Good to know! Thank you.

    Thanks.
     
  13. BBMS18

    BBMS18 Member

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    I hate to give you the bad news......
    Nothing will ever be the same.:cry:
     
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  14. Ivan Colesnic

    Ivan Colesnic Member

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    Get a crate motor. For your goals I would not spend the money on all of that for almost stock hp. You will spend $1000 at the machine shop, 300 on cam, 300-400 on lifters, 120 on pushrods, probably 250 on pistons, 100 on headgaskets, 300 on an intake, 300 on a carb, double roller timing chain 100, and end up with 300 hp... at least get gt40 heads. I would skip magnafluxing, i would buy pistons with thinner than stock piston rings, I would not buy expensive bearings, i would zero deck the block, I would balance the whole thing.
     
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