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Thread: 265cu

  1. #1
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    265cu

    I have a technical question:
    can we improve the 265cu? and how?

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    Registered Member chevynut's Avatar
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    What do you mean by "improve"? Chevy already did that over the decades since it came out.
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    I mean: booster engine. because I don t want to change the engine. I want to keep the original

  4. #4
    Registered Member chevynut's Avatar
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    If you want to keep it original, it is what it is. You can make improvements to it with different heads, different cam....anything that will make it breathe better and pump more air will increase power. But keeping it original and making it perform better is going to be virtually impossible if it's in good shape now.
    56 Nomad, Ramjet 502, Viper 6-speed T56, C4 Corvette front and rear suspension


    Other vehicles:

    56 Chevy 2-door BelAir sedan
    56 Chevy 210 4-door sedan
    57 Chevy 210 4-door sedan
    1962 327/340HP Corvette
    1961 Willys CJ3B Jeep
    2001 Porsche Boxster S
    2003 Chevy Silverado 2500 HD Duramax
    2019 GMC Sierra Denali Duramax

  5. #5
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    Sure there is lots you can do to perk up the ole 265 and keep it very close to factory.Dont buy "it is what it is" for a second. Try ram horn manifolds to let it breath a little better. You can hide a 4 barrel carb under the air cleaner.Use an aircleaner that provides better air flow. You can get rid of the points and switch it to modern ignition system. Change the generator to an alternator. All that stuff is pretty cheap and easy and external. You could also tear it down and do plenty inside with cams and head work etc.

  6. #6
    Registered Member chevynut's Avatar
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    Dont buy "it is what it is" for a second.
    You don't read very well do you sleeper? I said if he wanted to keep it original, it is what it is.

    Here's what I said after that: "You can make improvements to it with different heads, different cam....anything that will make it breathe better and pump more air will increase power."

    That "anything" I mentioned includes many engine modifications that can be done to the "original" engine....but it won't be "original" anymore.

    Electronic ignition won't do much of anything for performance if the current ignition system is working right. All it does is eliminate maintenance. A 4 barrel carb would require a different intake manifold, and then it won't be "original" anymore, and performance gain without any other changes would be marginal, if any. Changing the generator to an alternator won't do squat for performance. IMO exhaust modifications won't help much unless restrictions on the intake side are dealt with. The piston is forcing the exhaust out, so it's easy to do. On a 265 I don't believe much can be gained by changing to another factory cast iron exhaust manifold by itself. It's a pretty small engine and doesn't need a lot of exhaust capacity.

    In fact, raising the compression ratio is one thing that will improve engine performance without any other changes. The efficiency of an engine is directly related to the compression ratio. Other than that, supercharging will give you the most improvement, if you want to go there.

    The question, Laf, is what do you mean by "original". Do you just want to keep the same block? Same heads? Same intake? Same exhaust? Same carb? Do just want it to look original externally? What kind of driving are you wanting to improve on? I don't think you're racing the car, so a lot of the changes that give you more top-end power won't help much for street driving.

    Another question is what gear ratio rearend and what transmission do you currently have? You can increase the performance of the car by lowering the gear ratio (increase it numerically) and it will "feel" more powerful because you will have more torque at the wheels. In fact, I suspect that this is what you're looking for. It will give you more seat of the pants feel of power than any engine modification you can do, for a low cost. The tradeoff is higher rpm on the highway.
    56 Nomad, Ramjet 502, Viper 6-speed T56, C4 Corvette front and rear suspension


    Other vehicles:

    56 Chevy 2-door BelAir sedan
    56 Chevy 210 4-door sedan
    57 Chevy 210 4-door sedan
    1962 327/340HP Corvette
    1961 Willys CJ3B Jeep
    2001 Porsche Boxster S
    2003 Chevy Silverado 2500 HD Duramax
    2019 GMC Sierra Denali Duramax

  7. #7
    Registered Member JT56's Avatar
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    I thought the 265 rods were considered a week point in those engines?

  8. #8
    Registered Member chevynut's Avatar
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    JT, "weak" is relative. If you're drag racing the car, it might matter. I'm thinking Laf is not happy with the street driving performance of his car. It probably doesn't take off well from stoplights, and doesn't accelerate well. That's how I suspect most guys drive an original car, not even street racing it. In that case, and if he doesn't do long highway trips (doubtful in Europe) then I think gearing should be looked at. He could even go to a stock 4:11 rear with a 3-speed overdrive that should perk it up. I have a full setup like that, but it would cost a fortune to ship.
    56 Nomad, Ramjet 502, Viper 6-speed T56, C4 Corvette front and rear suspension


    Other vehicles:

    56 Chevy 2-door BelAir sedan
    56 Chevy 210 4-door sedan
    57 Chevy 210 4-door sedan
    1962 327/340HP Corvette
    1961 Willys CJ3B Jeep
    2001 Porsche Boxster S
    2003 Chevy Silverado 2500 HD Duramax
    2019 GMC Sierra Denali Duramax

  9. #9
    Registered Member JT56's Avatar
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    I just remember hearing from my dad and his friends the rods were considered weak. Of course would be ok for normal driving.

  10. #10
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    If you were to drag race a modified 265, the rods might be a problem. Otherwise probably not.

    I do remember that the pistons were prone to cracking. Usually that wasn't a catastrophic problem - it didn't wipe out the block or anything serious. Just made a lot of noise and smoke.

    The stock gearing is pretty steep by today's standards, but it's instant torque at the wheels. Gas mileage will drop.

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