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84 fleetwood hearse
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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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95 FWB 81SDV 96 FWB 94 Fleetwood
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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...
 

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1977 Coupe (blue), 1977 Coupe (yellow), 1977 Coupe (green)
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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.
 

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1996 Fleetwood Brougham; 1993 Pinninfarina Allante
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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?
 

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

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1996 Fleetwood Brougham; 1993 Pinninfarina Allante
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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?
 

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95 FWB 81SDV 96 FWB 94 Fleetwood
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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..
 

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1996 Fleetwood Brougham; 1993 Pinninfarina Allante
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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.
 

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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.
 

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1996 Fleetwood Brougham; 1993 Pinninfarina Allante
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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?
 

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

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1975 hearse, 1976 hearse
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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.
 

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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.
 

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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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14 CTS-V Wagon, 09 ESV, 84&86 Fleetwood Hearse
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from what i know the 4/6/8 motor was only used in 81 in all caddys that had the 368 power plant in 82 the commercial chassis (hearse got the carbed 368 while limos got the 4/6/8 368 until 85. I have an 84 superior hearse with the carbed 368. a dead give away is the valve covers have a tall deck in the center that would indicate a 4/6/8 motor. also a mechanical fuel pump on the drivers side just under the powersteering pump would indicate the carbed 368. Just wanted to mention those since you said your car is a hearse and as far as i know all 84s should have the carbed motor, but then again hearses are optioned very unique and anything could be possible.
 
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