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Username Post: '81 Caprice Diesel        (Topic#322842)
Very Senior Member
Posts: 1135

Age: 64
Loc: Urbana, Ohio, USA
Reg: 09-03-01
03-28-15 11:59 AM - Post#2534799    

Wow, I can't believe how long it's been since I have been on ChevyTalk. Too long actually. Anyways.....last year I bought a one owner '81 Caprice with a 5.7 engine,'s a 5.7 diesel. Has anyone swapped out a diesel for a gas engine, and if so, what all did you have to do? I've heard that I have to change the rearend, I've heard I can keep the current rearend. I've heard that I have to get a different transmission, I've heard I can keep the current transmission.

For living in the rustbelt of Ohio, the car is immaculate except the dash is cracked. It has power seats, power windows, and even has a factory 8-Track player I'm on the fence as to what to do. I was wanting to sell it, but as clean as it is, I'm leaning towards putting in a nice 350 engine. And if I go that route, the brakes, although they are power, does not have a booster. They run off of the power steering. I've also heard I can keep it that way, and others say I would have to add a booster. So it's like 50/50 as to what I can keep, and what I have to get rid of. I love the car though. It has 60/40 seats, and just floats down the road, no squeaks, no rattles. But I am not a diesel person, and right now, from the factory, it puts out something like 124 horses from under the hood. So if someone has swapped from a diesel to gas and has done it successfully, without sinking thousands and thousandths into it, PLEASE let me know what I have to swap (other than the engine) to help me make up my mind as to keeping it. It's always been garaged, and from when I bought it, it still has been in the garage. I'm looking to add on this year due to the fact that the last two years my '02 Dodge Ram has set out and the rust mites have seriously started in, and I do not like leaving a vehicle sit outside in crappy weather. So drop me a PM, or post on here as to what I need to do to make a successful swap over to gas.


No current toys in the garage
Member #6136


Dedicated Member
Posts: 6195
Age: 47
Loc: Elgin IL
Reg: 11-18-02
03-29-15 08:12 AM - Post#2534992    
    In response to Kevin45

Hey Kevin,

Can't say I can help you with your swap query, but congrats on getting the 1981 Caprice! Any pics, by chance?

1979 & 1989 Caprice Classics | pigValve, paceMaker, cowValve
"She became the envy of my dreams" __ Kenny Rogers __ 'Scarlet Fever'

Valued Contributor
Posts: 4085
Loc: Sweden
Reg: 08-23-07
03-29-15 01:25 PM - Post#2535123    
    In response to Kevin45

Can't answer everything, but some.

Keep the PS/PB! It's way better IMO. Had one in my 1980 C10 former diesel, that was the best, just excellent. Had another 6.2 diesel C20 (1981) that outperformed my other C20 gas trucks with regular booster.

Also means you have the freedom to put in a really wild cam in a future if so inclined.

Tranny is ok, but the converter stalls earlier than the gas ditto. With a low torque engine like a 305 or a OEM 350, you might want a looser converter, waiting for red lights in gear etc.

Rear axle - matter of taste, but there is no must, and IMO for a daily driver - no reason. Lower fuel consumption, higher top speed.

Put in a 383 with a OEM roller cam and vortec heads and the torque will be good with that converter (maybe) and that rear axle (definitelly).

Make use of the glow plug relay. It's an excellent connection point for accessoiries. mp;fea...

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Posts: 3827

Loc: Bedford, Texas, USA
Reg: 11-13-02
04-08-15 02:34 PM - Post#2537885    
    In response to Impala65SS

One thing that has not been mentioned is that I am sure that this car has the BOP pattern transmission. Many of the diesel cars/trucks had the TH350 or even TH400 behind them, however there were somewhat weak 200C, 250C and 200-4R transmissions used as well. A small block oldsmobile engine would be the easiest to swap in. 307, 350 or 403 olds. A 425/455 would also not be an overly difficult swap. Mondello olds once offered a conversion kit as well to convert the diesel back to a gasoline engine. With a offset ground 425 oldsmobile crank something in the neighborhood of a 465 cubic inch small block oldsmobile could be built.

1983 G20 Van, 350 TPI, Ported 906 Vortecs, Edelbrock 3817 Base, ASM oversize runners. Reed Custom Roller cam, 700r4, 12 bolt with 3.08 gears, Doug Thorley Tri-Y headers, true duals

Edited by 1983G20Van on 04-08-15 02:35 PM. Reason for edit: No reason given.

Valued Contributor
Posts: 2876
Age: 69
Loc: Stuart, Florida
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07-14-15 06:16 AM - Post#2561615    
    In response to Kevin45

Very interesting. It sounds like a nice car that you can easily make better. Please post your progress as you go along and good luck.


I'm originally from the ONCE great city of Flint, Michigan. The birthplace of General Motors, where A C Spark Plug was formed and headquartered, where the first Corvettes were hand built, and where my 1955 Chevy was made.

Valued Contributor
Posts: 3082
Loc: Cameron, Wi, USA
Reg: 11-09-01
07-24-15 07:03 PM - Post#2563857    
    In response to Maxbigblock

I had an 81 Bonneville with that pos diesel. The whole car was a disaster. Engine, trans, rearend were all weak and cost me a ton of money to replace and finally got rid of it. Run don't walk away plus I don't think its legal to do that if your state has inspections.

57 Bel Air 2dr Ht
327 700r4

Posts: 142
Loc: Krydor, Sask. Canada
Reg: 08-21-15
08-30-15 07:35 AM - Post#2572014    
    In response to 57tim

how did you make out with your 81 Caprice ? I run a few of these 5.7's. If I was you I would keep it stock if the engine is running fine. Learn how to treat a diesel and it is great. It is not a powerhouse so don't pull a trailer with it, but the fuel mileage beats any gas job.
If you want to swap to a gas then a 350 olds is about your best choice. Only mods would be the linkage to work the carb , wire up the distibutor to power it and the cable to the trans. Otherwise the exhaust manifolds, pulleys, hoses etc are all the same. No need to change the tranny or diff . The hydra boost brake / ps sysytem is very good so keep that too.

58 Impala Sport Coupe 348 tripower
58 Impala Convertible 348 tripower
58 Sedan Delivery
68 Impala 9 pass wagon original
49 Chev 5window ,diesel
82 Corvette

"5th Year" Silver Supporting Member
Posts: 550
Loc: Western NY
Reg: 06-15-02
08-26-17 07:57 AM - Post#2705654    
    In response to Kevin45

Looks like this is a very old thread now. I think the site needs to organize things a bit better when it comes to these "newer" cars. In this section of the forum I see Monza, Caprice, Malibu...

Anyway back to your 2 year old question. I have 2 of these diesel cars. Certainly keep the hydro boost brakes. The funniest thing is that's the latest add-on for guys with questionable vacuum cars to add. The rear end does not need to change. Very possibly the transmission has the universal bell housing so swapping in a chevy motor would be possible. The by far easiest thing to do though is simply use an Oldsmobile 5.7L. They are a direct replacement and every bracket and pulley will fit perfectly.

I also have a colleague at work with 2 original diesels which are still original diesels. He's a diesel mechanic and loves them. It sounds like the heads were a weak point and the injector pumps were easy to damage. I know I saw this late but if you pull your stuff out he would like to have some spare parts on the shelf and Ohio to Buffalo NY area is pretty close.

I drove one of mine home. A lot of them had "Goodwrench" motors in them because there were a lot of warranty cases. As I understood the Goodwrench replacement motors were hand built in a proto type shop and were an improvement. I think you can tell by the stickers on the valve covers. Mine ran great and fuel economy was excellent. It was not fast but really cool cruiser. So if you haven't already don't dump it; at least if you remove it let somebody else use the parts and pieces because for oddballs some things are just not available.


Edited by toro455 on 08-26-17 07:59 AM. Reason for edit: spelling


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