Olds Diesel Rods

Bib_Overalls · March 19, 2004, 08:29:38 PM

I was browsing through one of David Vizzard's SBC books, the one with 10 economical engine builds. Each engine has a profile and I noticed several references to Olds diesel rods. However, there was nothing in the text that talked to these rods. I thought I might find a reference in his book about building SBC bottom end but it is out of print. Can anyone tell me what rods are used (year/engine), what their length is, and what modifications are required. I am assuming these rods are stronger and may also be longer. I have a couple of blocks and cranks in the shop and thought I might build up a short block this winter. Starting to collect parts now and the idea of using stronger rods appeals to me.

jaybee · March 19, 2004, 11:28:53 PM

Can't speak about modifications, but I remember the engine. It was an Olds V8 modified to run on diesel. My Uncle had 1 in an 82 Caprice, think they were installed in full-sized GM cars and maybe pickups throughout the late 70s and early 80s. The fuel economy improvement wasn't that great, but at the time they were introduced diesel fuel was much less expensive than gasoline. New heads of course, but just about everything in the short block (including the block) was also beefed up to deal with the punishment of compression ignition. You may have trouble finding one, though. They weren't known for their long life and fell out of favor. It wasn't nearly as sturdy as a clean-sheet-of-paper diesel such as a Mercedes, but the bad rap (rattle?) wasn't entirely GMs fault. Diesels tend to get condensation and acids in the oil if used for frequent short trips, the way most of us drive. Uncle put quite a few miles on his, but he lived 12mi out of town where it always warmed up completely when driven.

Bib_Overalls · March 20, 2004, 12:57:45 AM

Quote from: "Crosley"I thought the diesel Olds motors used a sightly beefier version of the common 6 inch long Olds gas motor connecting rod

Did some net searching. Apparently the Olds rod has a length of 5.886" and it is beefier. Apparently they trimmed it a bit to put more meat in the diesel pistons. The journal size is 2.1, same as the SBC but their width is unknown. Don't know what pistons David used. Anything made for the 6" rod would be to far down in the hole. I'm going to persue this a bit.

Bruce Dorsi · March 20, 2004, 12:59:54 AM

Bib, I just checked a 2003 copy of the Sealed Power/Federal Mogul engine parts catalog.

They show Olds Diesel engines of 2 sizes:
....the 260 ci (4.3L) 3.5" bore for 1979 only, Vin code "P"

....the 350 ci (5.7L) 4.057" bore for 1978-1985, Vin code "N" for pass cars. ----This engine was also used in light-duty GMC trucks with Vin code "N" (1983-1984) or Vin code "Z" (1978-81)

Unfortunately, there is no listing of connecting rods available for these engines. So, I can not help with specs. ........They do have rods available for the gasoline engines though.

The diesel's rod bearings are used on several gas engines as well, but all seem to be specific to Oldsmobile engines only.

If needed, I may be able to come up with rod bearing specs, which may help with large-end dimensions.

There is also a listing for piston pin bushings for the small end of the rod. .....One size is listed as 1.196" rod eye bore for use in 1982-1984 engines. ......The other bushing is listed for 1978-1981 engines, but does not specify any dimensions.

There is no listing for diesel piston pins, so I can't provide specs on these.

There is no listing for diesel pistons either, so I can't tell if these used full-floating piston pins, or pins "pressed-in-piston." .....I think (CRS!) SBC's use pins "pressed-in-rod," unless you opt for aftermarket full-floating pins.
I'm sorry I couldn't be of more help!

enjenjo · March 20, 2004, 01:57:55 AM

FWIW, the 260 was a V6, and not a V8, and used the same internal parts as a V8 350 diesel. I have a 350 diesel out in the barn, it was a spare for a diesel Toronado I had. Never needed it, despite the bad rap 350 diesels got.

GPster · March 20, 2004, 06:52:00 AM

This might be a long shot, but back in the'80s sometime "POPULAR HOT RODDING" did a short series on converting a diesel Olds engine to gas. There may be some information that would be helpful to you there. It may have been at the time when Tex Smith was an owner/editor of that mag so he may have some of that stuff in his archives. In one of my dreams I thought they would make a "bullet proof" motor for a dirt-tracker that was geared so that it didn't have to run at 7,000 RPM all the time. That is just one of those things that I remember that usually has no value to anyone. Corvair turbocharged engines have better rods too. GPster

Phat · March 20, 2004, 01:00:13 PM

It was a trick we used many years ago in the SBC for circle track racing NASCAR said the rod had to have a GM part# on it and be stock.....LOL Its a longer rod and pulled good on the long straights. Tech guys never caught on to because the motor pumped fine (cubic inch) till somebody had to go and publish it in the mags. We were runing a pretty restricted motor as they made us run a stock 2 bl intake (which we would acid the crap out of) with the 4412 holley and stock exh manifold no porting and polishing(461x heads) only 1 inch in from the valve seat we were allowed for the 3-6 angle valve job. So NASCAR fixed the problem and allowed the sportman rod that had to be clearly marked and let us go to 6 inch(we found away to get a 6 3/8 rod in it but you would never run a 4 bl on it as it would bend the wrist pins they were so thin and the pistons only had 2 rings). The longer rod worked real good on those restricted motors as the piston dwell was much longer and you could get the cyl full. Now it would be a waste of time as those Olds rods would cost us about 500 bucks to get good to race. The lenghts were all over the place the weights were pretty bad also. But it did have a stock GM part # so we were good to go till the cat was out of the bag. The long rod motors ran like crap on the shorter tracks and we really had to play with cams to get the proper cyl fill. Wanna know about the 40 lb sbc crank with a GM# LOL or the 11 lb flywheel. We did a lot of R and D to get a couple of tenths.

Bruce Dorsi · March 20, 2004, 07:00:26 PM

Quote from: "enjenjo"FWIW, the 260 was a V6, and not a V8, and used the same internal parts as a V8 350 diesel.

Actually, the 260 ci diesel was a V8, had a 3.5" bore, and was only made in 1979.

The 262 ci diesel was a V6, had the 4.057" bore (same as V8 diesel), and was made in 1982-1985. ....I believe this is the engine you were thinking of.
:b-d:
Don't mind me, I'm just picking nits!

enjenjo · March 20, 2004, 07:16:39 PM

You are right, I didn't read everything carefully, or I would have seen that it was for 79 only.

Bib_Overalls · March 22, 2004, 02:09:10 AM

Seems the Olds 350 diesel blocks can be used to build a strong gas motor. With a big block crank and a 1/8" overbore they are like 425 CI. The diesel rods are not used in this combination. So I guess the Chevy guys found a way to make use of them. Chasing all of this down was an interesting diversion. If I come across a diesel and the price is right I may go for it.