368 help needed
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500, 472, 425, 368 Discussion, 368 help needed in Cadillac Engine Technical Discussion; i have a 1984 fleetwood hearse with a 368. i think it has the v864 system as well. i was ...
  1. #1
    jcowart is offline Cadillac Owners Member
    Automobile(s): 84 fleetwood hearse
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    368 help needed

    i have a 1984 fleetwood hearse with a 368. i think it has the v864 system as well. i was trying to find out if there were any quick, relativly cheap performance upgrades i could do to try to squeeze as much horse power out of this motor as possible. was also wondering if any of the parts from a 472 or a 500 would interchange.

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  3. #2
    BRUCE ROE is offline Cadillac Owners Fanatic
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    Re: 368 help needed

    The 425/472/500 are the same family, pretty much a bolt in for a 368. Bruce Roe

  4. #3
    drmenard is offline Cadillac Owners Enthusiast
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    Re: 368 help needed

    I would find a 472 or 500 and bolt it in with only a few small mods ...some needed bolt on parts can be found on a 77-79 full size caddy.. If your looking for more power out of that 368, your just not going to get much... almost not worth it...

  5. #4
    deVille33 is offline Cadillac Owners Connoisseur
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    Re: 368 help needed

    Not knowing your thoughts on performance persuit, the first thing to do would be ensure that your engine is in good tune. Good plugs, proper tuning, everything under the distributor cap in good condition, All vacuum motors working and holding required vacuum. Check those vacuum hoses for cracks. Timing set properly? Is there any hissing in the interior? These engines have vacuum controls everywhere, and a loss in vacuum causes performance loss. Keep in mind that this engine was not engineered with performance in mind.
    If your considering an engine swap, keep the 425 in mind. It's lighter than the two bigger sisters, but still plenty torquey.

  6. #5
    KrisK is offline Cadillac Owners Member
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    Re: 368 help needed

    Can you bolt V-8-6-4 heads on a 425 block? Or more specifically can you use a 425 block in an 81 seville?

  7. #6
    deVille33 is offline Cadillac Owners Connoisseur
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    Re: 368 help needed

    You can, but the results wouldn't be enhancing this engine's performance. You'll create more problems for you to address.

  8. #7
    KrisK is offline Cadillac Owners Member
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    Re: 368 help needed

    Quote Originally Posted by deVille33 View Post
    You can, but the results wouldn't be enhancing this engine's performance. You'll create more problems for you to address.
    It seems strange that adding 50+ cubic inches would not enhance the performance. What kinds of problems would I encounter?

  9. #8
    drmenard is offline Cadillac Owners Enthusiast
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    Re: 368 help needed

    I think the heads would bolt on, but would not work..gaskets and water passages are not the same... But the outside mesurements are the same...So you can bolt in a 500, 472 or a 425... for your car if you did a swap you would need bigger exhaust... you could use 77-79 caddy 425 exhaust manifolds and Y pipe... they will bolt on with no mods.. with a couple little mods you could use that 425 Y pipe and 500 or 472 exhaust manifolds... most guys that do this swap use 425 pullies so they don't use a air pump, smog,....If you can find a good running stock motor it can be used ' but the best thing to do is change the timing chain and gears to one of the good $100 ones not the cheap $35 ones.. the stock ones had plastic on them and always breaks..

  10. #9
    KrisK is offline Cadillac Owners Member
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    Re: 368 help needed

    Quote Originally Posted by drmenard View Post
    I think the heads would bolt on, but would not work..gaskets and water passages are not the same... But the outside mesurements are the same...So you can bolt in a 500, 472 or a 425... for your car if you did a swap you would need bigger exhaust... you could use 77-79 caddy 425 exhaust manifolds and Y pipe... they will bolt on with no mods.. with a couple little mods you could use that 425 Y pipe and 500 or 472 exhaust manifolds... most guys that do this swap use 425 pullies so they don't use a air pump, smog,....If you can find a good running stock motor it can be used ' but the best thing to do is change the timing chain and gears to one of the good $100 ones not the cheap $35 ones.. the stock ones had plastic on them and always breaks..
    Thanks for the tips. It's a shame the 368 heads won't work on the 425 block, I would like to increase the displacement and really would like to keep the V-8-6-4 function.

  11. #10
    deVille33 is offline Cadillac Owners Connoisseur
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    Re: 368 help needed

    The 368 heads are resrictive relative to the stock 425 heads and offer more resistance to fuel mix flow. This would cause the suspended fuel to drop out and collect on the walls of the passage. Your mixture that reaches the cylinder would lean out and then go the other way with fuel droplet runoff. Cylinder port matching is a science in it's own. This and the fact that the manifold is an updraft design complicates your fuel delivery characteristics.

  12. #11
    KrisK is offline Cadillac Owners Member
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    Re: 368 help needed

    Quote Originally Posted by deVille33 View Post
    The 368 heads are resrictive relative to the stock 425 heads and offer more resistance to fuel mix flow. This would cause the suspended fuel to drop out and collect on the walls of the passage. Your mixture that reaches the cylinder would lean out and then go the other way with fuel droplet runoff. Cylinder port matching is a science in it's own. This and the fact that the manifold is an updraft design complicates your fuel delivery characteristics.
    Could the 368 heads be ported to offer less resistance to the situation you describe?

  13. #12
    deVille33 is offline Cadillac Owners Connoisseur
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    Re: 368 help needed

    I don't know if the castings would support this operation, as newer casting processes allow thinner casting walls.

  14. #13
    DouglasJRizzo is offline Cadillac Owners Enthusiast
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    Re: 368 help needed

    The 368 is an excellent engine and is directly related to the 425/472/500 engines. What works for the others will work for this engine as well. If memory serves correctly, the V-8-6-4 modular displacement system was not used on limousines and commercial chassis vehicles. Check your VIN - is there's a "Z" someplace, it's a commercial chassis car.

    Before swapping engines, you may want to try a mild cam upgrade from 500cid.com or similar supplier. The 368 camshaft is so mild that the engine runs out of breath at about 60 or 70 mph. During the 55 mph national nightmare, no one worried too much, but with the heavy custom body of the hearse, a little more torque would do wonders.

  15. #14
    DouglasJRizzo is offline Cadillac Owners Enthusiast
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    Re: 368 help needed

    Quote Originally Posted by deVille33 View Post
    The 368 heads are resrictive relative to the stock 425 heads and offer more resistance to fuel mix flow. This would cause the suspended fuel to drop out and collect on the walls of the passage. Your mixture that reaches the cylinder would lean out and then go the other way with fuel droplet runoff. Cylinder port matching is a science in it's own. This and the fact that the manifold is an updraft design complicates your fuel delivery characteristics.
    This would cause little problem today. Huge ports and high flow heads are not really needed on the street to make power. In fact, with today's low volatility fuels, you may actually LOSE power by doing that. The smaller ports will provide enough flow for the engine to breath right, IF other factors such as camshaft and fuel delivery are addressed. The 425 heads have smaller ports than the 472/500 engines and the 368 smaller still. These were originally looked down upon, but if you look at the port size of the heads on the Z06 and ZR1 Corvette, you'll find them to be not large at all. In fact, the smaller port 368 heads will give SUPERIOR flow VELOCITY on the street which makes throttle response and torque better and more pronounced. It's not the CFM you should be concerned with, its VELOCITY of the flow of mixture.

    The manifold could be swapped out easily enough. But you may find it to be just fine for street work as well.

    I would not hesitate at all to use the standard 368 heads with nothing more than a chamber clean up and maybe a 3 angle valve job - maybe. They'll flow just fine to make plenty of street fueled horsepower. I'd upgrade camshaft, injectors, and ignition and watch the monster come alive.

  16. #15
    KrisK is offline Cadillac Owners Member
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    Re: 368 help needed

    From what I've read the V 8-6-4 was used on the commercial chassis vehicles from 1981 until 1984. I will look into a camshaft upgrade but I would still rather have the extra displacement of the 425 with the cylinder deactivation capability of the V 8-6-4 system. If I can get the 368 heads to work on the 425 block and add a more aggresive camshaft I will be a happy camper.

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