Replacing 5.7 Olds Diesel With 6.2 N/A?

[Duncan Sterling]

A buddy of mine has a 1980 Pontiac Bonneville with an Olds 5.7 diesel.

Ran great for a long while, delivering up to 27 MPG on the highway, and 125 HP (according to his GTECH). But then it started having head gasket problems after a few head bolts cracked and let the heads warp (towing a boat once or twice probably didn't help things with this non tow rated motor).

He's all ready to go through the motor and put it back in the car, but I'm wondering how hard it would be to drop a 6.2 J motor in to replace the 5.7.

I'm guessing he'd need to redo the engine mounts (olds to chevy), the exhaust would have to be custom, and he'd need an adapter to match up the motor with the (olds) TH350 trans in the car now.

The 5.7 already has a 4 row radiator, so I'm guessing that might still be OK.

What else might he need to make a swap work?

TIA,

--Duncan

[john8662]

I'm not a 5.7 anything advocate but I'd just put the 5.7 diesel back in where it came.

There have seen some members in the past that have done this swap, and it's possible.

Best case scenario:

Replace 5.7/TH350 with a 6.2 paired with the appropriate TH700, it will end up being the same length as the existing TH350 was (so crossmember and driveline will still work, yes driveline uses same spline).

I think the main problem is going to be getting the appropriate clearance on the sides of the engine (exhaust, etc.) and knowing that the clearance is going to decrease because the 6.2 oil pan will be hangin' down lower than the 5.7 pan did.

I've talked to quite a few GM diesel people, who actually liked the 5.7 diesel, and I'm starting to see that they were not all that bad, and when you look at the problems the 6.2 has. The BIGGEST problem with the 5.7 diesel was it had the high compression ratio just like the 6.2 does, but with less head bolts to hold it all together. Just like we do on our 6.2's for pulling (Think Arveetek) we get shaved pistons to drop the compression ratio. I think this would be the BEST route for any 5.7 build, and would probably almost solve the head gasket blowing issues of the 5.7L Diesel.

-edited to fix fast typo's

[ 07-02-2005, 07:40 PM: Message edited by: john8662 ]

[arveetek]

I agree with John. I'd stick with the 5.7L myself. I had a 5.7L before my 6.2L, and I liked it pretty well, until it blew head gaskets twice in 2 years. If I knew then what I know now, I would have fixed it right, and it would probably still be running, delivering superior fuel economy.

Visit www.olds-diesel.com (http://www.olds-diesel.com) for more information.

Casey

[20050420|7|006071|000022|69.19.2.78]

You can also put copper o rings in the head`s ;)

[mhagie]

If one is to retain the 5.7 it would be wise to scrounge around for some updated parts, the 80 wasn't a very good combo.
The newer you go on the 5.7 the better it gets
the engine by 85 was as good as a 6.2 for reliability.
You will need at least an 82 to get the D block with roller lifter cam and all the goodies.
I would do a search for a 84-85 engine,a Mr Goodwrench might still be available?
If you insist on changing to a 6.2 be patient as 78 Chev will see this post and he has done this swap and if memory serves me he said it wasn't a hard job at all.
I put 230K on a 82, it was rebuilt at 130K, had it decked,balanced,and all that good stuff,Fel-Pro gaskets and it ran like a champ.
Merle

[catmandoo]

Merle has good points,i myself still have one,it's an 83 "88" ,mid year 80 they went to the roller cams,i believe they also went to steel cranks at that time,for some odd reason it seems that the ones with the early style steel return lines from the inj's run better,we had a 78 that had an updated goodwrench short block put in and that thing could smoke the tires something fierce.if the engine was totally junk i would probably go for the 6.2,but if it's just the headgaskets,i'd keep her going,just use NEW headbolts,and they use about 6 different ones.so take the old ones with you to the gm dealer,i've gotten them from napa before and within 2 years popped a head off one.also look at the little tag on the front of the pump if it has an e on it (if my memory is correct,it's been about 12 years since i had one off)it has the nickle pump this is the good one to have.

[5.7L oldsdiesel]

Engines from 1978-1980 offered a flat tappet camshaft.Also known as the D block.Trust me,a D block is a good one,and not bad as alot of people say.If driven with sense and the fuel pedal is'nt on the floor 24/7,the D block will live.I have two engines in operation.Both are D blocks and both have been worked hard day and night.Over 300,000K on each of them.One has pencil injection(builds speed like a train)and the remaining engine i have offers poppet injection.More economical,but slightly less power.In 1981,a roller cam was introduced,along with roller lifters.This was done to extend oil change intervals.All oldsmobile diesel engines from 78-85 use a cast nodular crankshaft,and not steel.The reason why later engines run smoother is because of offset wrist pin bores,and if you buy replacement pistons,you'll find that they are offset slightly.The only advantage a DX block has over the D block is the roller camshaft offered in 1981 and the offset wrist pin bores introduced in 1982.During manufacturing in 1978-1980,some crankshafts were poorly cast due to porosity problems or some sort of metalurgy problems.This is what i've read in several magazines.The E tag that is placed on the injection pump means the pump has a steel governor installed and not the older pellathane flex ring,but the steel version does give trouble as well.

[catmandoo]

sounds like you got yourself a nice setup in your truck there,just the other day i saw an old 80 stepside pickup that still had the 5.7 in it,but man was it rusty,

[5.7L oldsdiesel]

Thank you for the compliment on the truck i own.Yes,its a pretty nice vehicle.Very dependable and its never let me down in the 6 yrs i've owned it.I installed the olds 350 diesel in the year 2000 and its worked great ever since.I had it painted last year.It's a two tone color(red/silver) and looks pretty good i must say.

[Dan Wilson]

I replaced the 5.7 in 2 cars now with the 6.2.
1. 82 fleetwood cad 4 door with 6.2 J motor.
2. 81 ganprix 2door with 6.2 C motor from a van.
Try it you will like it.
Dan