Can a 5.7 diesel convert to an Olds 350?
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5.0 and 5.7 Discussion, Can a 5.7 diesel convert to an Olds 350? in Cadillac Engine Technical Discussion; I hope I'm in the right area! I have a friend who has a 1978 Caddy Eldorado and he says ...
  1. #1
    nenevold is offline Cadillac Owners Member
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    Question 5.7 liter diesel swap

    I hope I'm in the right area! I have a friend who has a 1978 Caddy Eldorado and he says it has a 5.7 liter diesel. Did Caddy make a 5.7 diesel in 1978, and if so, will a 1970 Olds 350 Rocket fit without to many modifications?

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    ben72227 is offline Banned
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    Re: 5.7 liter diesel swap

    Yes, the Eldorado had a 5.7 diesel in the 1978 model. I'm pretty sure it was the first year the diesel was offered on the eldos too. And I'm not sure about a modification with that particular engine, but it could probably be done, as many of the diesels (unfortunately) were converted to gasoline engines.

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    nenevold is offline Cadillac Owners Member
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    Re: 5.7 liter diesel swap

    Thanks ben72227. You've answered half of my questions already! Thanks again

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    nenevold is offline Cadillac Owners Member
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    Question Can a 5.7 diesel convert to an Olds 350?

    I am looking at purchasing a 1978 Eldorado with a 5.7 liter diesel in it that isn't running. I have a 1970 Olds 350 Rocket engine that I would like to replace the diesel with. I have been told that an Olds 350 bolts right in to where a G.M. 5.7 diesel was previously installed. I am wondering if this is the case in this particular application and if the motor mounts in the Caddy and the tranny bell housing would bolt up to the Olds. Any ideas??

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    CoupeDevilleRob's Avatar
    CoupeDevilleRob is offline Cadillac Owners Enthusiast
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    Re: Can a 5.7 diesel convert to an Olds 350?

    They are going to move this to a different forum but....

    The GM 5.7 Diesel is an Olds 350. The diesels were converted from gas engines, which is why they sucked. Just use the accesory brackets from the Diesel on the gas engine and everything should be pretty direct.

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    roebigd is offline Cadillac Owners Member
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    Re: Can a 5.7 diesel convert to an Olds 350?

    It is a very easy and quick changeover since everything bolts right in , make sure the fuel tank is taken out and cleaned as the diesel fuel will ruin the float in the carburetor. I have done a lot of these in the eighties, email me if you have any questions
    Dennis

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    Re: Can a 5.7 diesel convert to an Olds 350?

    Quote Originally Posted by CoupeDevilleRob

    The GM 5.7 Diesel is an Olds 350. The diesels were converted from gas engines, which is why they sucked. Just use the accesory brackets from the Diesel on the gas engine and everything should be pretty direct.
    What he said. Hotrodders love the diesel blocks too.

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    Re: Can a 5.7 diesel convert to an Olds 350?

    Quote Originally Posted by CoupeDevilleRob
    They are going to move this to a different forum but....

    The GM 5.7 Diesel is an Olds 350. The diesels were converted from gas engines, which is why they sucked. Just use the accesory brackets from the Diesel on the gas engine and everything should be pretty direct.
    The diesels take a lot of stuff from the oldsmobile 350 gas engine, but it isnt a gasoline 350 block that makes up the diesel. The Rocket 350 will go right in, but you need to change the torque convertor or the engine will perform sluggishly. The torque convertors on diesels have a different stall to them so you will need to change that.

    Blaze

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    Re: Can a 5.7 diesel convert to an Olds 350?

    I did several conversions back in the day as well. The Olds "gas" engine IS a direct replacement for the 350 Diesel. I never used such an old donor engine but iy "should" be the same. Usually, the only mods needed are the P/S pulley and motor mount orientation as I recall. The diesel engine harness simply unplugs and leaves you with all you need for the gas engine. On the later years, you'd have to replace the T/V cable for the trans but since yours should have a vacuum controlled valve body (versus cable controlled), you should be fine. Make sure to not damage the oil pan and oil pump pick-up on the old engine, because you'll need them on the new one (FWD pans & pick-ups are different). As for the changing of the torque converter and flushing of the fuel tank, I never did either and had no ill effects from not doing them, but I would suggest that the converter change DOES make some sense. Also, if you have emmissions inspections where you're at, you'll need to install a catalytic converter.
    When you're done, leave the "Diesel" badges on it and you'll have a great sleeper!

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    Re: Can a 5.7 diesel convert to an Olds 350?

    Quote Originally Posted by Katshot
    I did several conversions back in the day as well. The Olds "gas" engine IS a direct replacement for the 350 Diesel. I never used such an old donor engine but iy "should" be the same. Usually, the only mods needed are the P/S pulley and motor mount orientation as I recall. The diesel engine harness simply unplugs and leaves you with all you need for the gas engine. On the later years, you'd have to replace the T/V cable for the trans but since yours should have a vacuum controlled valve body (versus cable controlled), you should be fine. Make sure to not damage the oil pan and oil pump pick-up on the old engine, because you'll need them on the new one (FWD pans & pick-ups are different). As for the changing of the torque converter and flushing of the fuel tank, I never did either and had no ill effects from not doing them, but I would suggest that the converter change DOES make some sense. Also, if you have emmissions inspections where you're at, you'll need to install a catalytic converter.
    When you're done, leave the "Diesel" badges on it and you'll have a great sleeper!
    I have some friends that put a gas 350 in there 98 regency and didnt change the torque convertor and they didnt noticed anything either now that I think about it. I may have it backwards. It mightbe when you put a gasoline designed transmission in a diesel. Yeah thats right. I had it backwards. The emissions regulations seem to get stricter as time passes. As Katshot said,if you have that in your state you might want to check even before you do it. In Illinois I had one that came factory with the diesel and then had a gas and they wouldnt pass it until I installed the computer controlled carburetor and the computer system. Factory changeovers they done had all that installed. When my grandparents bought the 81 Eldorado Diesel I have now they were offered the option of gas when the engine shot crap at 29,000 miles. They went with a diesel replacement though. So I would check on that emissions stuff first.

    Blaze

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    ben72227 is offline Banned
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    Re: Can a 5.7 diesel convert to an Olds 350?

    when the engine shot crap at 29,000 miles. They went with a diesel replacement though.
    Thats pretty much what happened to mine. Its on its 3rd engine (if i recall correctly from what grandpa told me), which i think is the last model (DX i think it was called) that they made for the '85 models when all of the kinks had finally been worked out. It runs fine to this day and its been in the car for 20+ years with about 30,000 - 40,000 miles on it. Anyway, the first year engine sucked and coupled with the fact that most people treated them like gasoline engines (they were, afterall, the first mainstream cars with diesels in them) they failed horribly.

    While you definately could replace the diesel, it would seem much wiser to keep it in (and get it running again if its shot), as they are becoming a collectors item (see www.olds-diesel.com) these days. And afterall, the eldos weren't really meant to go fast anyway, so... Did i mention they get great MPG for a car that huge?

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    Re: Can a 5.7 diesel convert to an Olds 350?

    They started the DX-Block in 1981. By 84-85 they pretty much figured out the headbolts were junk, so you usually dont have any problems with those years. Here is a great site for the diesel person. I most likely will be hosting the Oldsmobile Diesel Rally in my town this fall.

    http://members.tripod.com/~A350Diesel/menu.html

    http://members.tripod.com/~A350Diesel/newmain.html


    Blaze

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    Re: Can a 5.7 diesel convert to an Olds 350?

    On a related note (bringing a thread back from the dead) I've always wondered how bad it'd be to put a new Duramax into the Eldo as a replacement... I hate trying to rebuild this stupid fuel injector pump...

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    jspinale is offline Cadillac Owners Member
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    Re: 5.7 liter diesel swap

    Quote Originally Posted by nenevold
    I hope I'm in the right area! I have a friend who has a 1978 Caddy Eldorado and he says it has a 5.7 liter diesel. Did Caddy make a 5.7 diesel in 1978, and if so, will a 1970 Olds 350 Rocket fit without to many modifications?
    You will need to change the wiring harness from the firewall connection to the motor. JS

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    Re: Can a 5.7 diesel convert to an Olds 350?

    Quote Originally Posted by traumadog
    On a related note (bringing a thread back from the dead) I've always wondered how bad it'd be to put a new Duramax into the Eldo as a replacement... I hate trying to rebuild this stupid fuel injector pump...
    That would be cool. I know of some that have wondered about a 6.5 replacement.

    Blaze

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