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Hello I have a 78 coupe deville, that I was thinking about swaping out my 425 for a 350 chevy. Has anyone done this swap and how do the motor mounts and exhaust manifolds fit?

thanks Joe
 

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the 425 is a slug. It's torguey but mine is getting old and it is easier to build a 350 to whatever kind of power that you want.
 

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I think it is Cad company that sells a ready made little brother 425 trade in, 433ci that makes like 400HP & 500TQ for reasonable. (As far as crate engines go) AC, cruise, fuel lines, carb linkage, motor mounts, tranny, exhaust hookups etc etc all hook right up change to a sbc and you change all this stuff also.

Plus you would need all your altenator, power steering, fan etc for sbc and make the shroud work and the list goes on. For what? To have a lesser motor that won't live as long, make as much power or torque but was cheaper to buy. Yes you can buy the chevy crate cheaper but at what cost? I am not anti chevy or ill aware of the chevy virtues. But did you know a 425 or especially a 472 or 500 can ROCK as a hi po street motor?
 

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Thanks for the info. Do either of these companys make an intake for the 425? I have found a 75 500 in a calais for 200$. This is a low compression motor only slightly more powerful than my 425. My question is, what year heads would I have to put on this motor to raise the compression to around 10.5:1? This motor is complete and sounds like a good deal.
 

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The only smaller combustion chamber head for the 500 is a 76cc head. It was used from '68-'73. The problem with swapping heads is, you'll end up with compression MUCH higher than 10.5:1. I think I remember someone saying that late pistons with early heads will net compression in the 12 or 13:1 range.
You can, however use the 425 heads on the 500. I believe the chamber size is 96cc's. The problem with the 425 heads is that they don't flow very well and are only good for low RPM applications on a 472/500.
You CAN get 10:1 compression with early heads but you have to change the pistons to do it.
 

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Thanks for the info, the yard I found the 500 at has a 73 472, but that sounds like a little too much compression for a daily driver! Thanks for the help. What are you putting your 500 in?
 

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The 73 472 was an excellent motor. I would consider putting in a new timing chain, fresh oil pump, MTS-10 cam or equivalent and an Edlebrock intake and go. Oh yea have distributer curve kit put in and send the 472 Q-jet to The Carb shop for a cheap (relative to buying new) stage II rebuild set up for your car/combo. Frankly you and your buddies will flat crap how well and strong it will run. Compared to a sbc in that car you will say WHAT WAS I THINKING! Oh yea you will say hey I didn't know. Life is good with a big Cad under the hood :)
 
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