Cadillac 368 vs. Olds 350

[Matt CLC#18621]

Thoughts Cadillac 368 vs. Olds 350 if one has a choice?

Regards,
matt 18621
i am 2nd

[TJ Hopland]

If you have the choice in the same car you must be talking about an 80 Eldo or Seville.    Engines on their own are pretty comparable maybe a slight edge to the olds for parts options and availability.   I may give an edge to the Olds because its very happy and a good design at 350.   The Cadillac was designed to be a 472 so its kinda big and heavy to be a 368.   I think it used the 472 stroke so that means a tiny bore which means tiny valves so its not likely a good breathing engine like most of those last ditch effort to downsize engines around 1980 were.   I think the Chev's were the worst,  lamwmowers had bigger valves.   

Where it gets tough is both have not very well understood and almost not supported EFI systems.   Without Bruce and 79 Eldo (forgot his name) the 76-80 system would be pretty much impossible to keep going.    The DEFI system on the 368 was the basis for the TBI system GM used till 95 on the trucks but 80 and 81 were the learning years where a lot changed so there are many one year one model parts that can be very difficult to find.   

[Matt CLC#18621]

Yes TJ, it's a Seville.
I'm guessing the 1981 Cadillac 368 with the computer disconnected is the same as the 1980 Cadillac 368?

Regards,
matt 18621
i am 2nd

[Eric DeVirgilis CLC# 8621]

Both are fairly rugged engines but the I believe the 350 FI had slightly more HP than the EFI 368 of 1980 which I think was 145 HP. The 4 bbl version 368 (RWD models) is 150 HP. Only California destined Eldorados/Sevilles got the 350FI in 1980. Since reliability is roughly equal, I'd prefer the engine with Cadillac heritage given the choice.

[Eric DeVirgilis CLC# 8621]

Yes TJ, it's a Seville.
I'm guessing the 1981 Cadillac 368 with the computer disconnected is the same as the 1980 Cadillac 368?

Mechanically there may be a number of mechanical similarities but the electronics governing these engines are very different. I've had both '80 368 FI & '81 V8-6-4 and they seem to start and perform a bit differently. HP was down to 140HP in the '81 6.0 liter.

[TJ Hopland]

I don't think there were enough differences between the 80 and 81 DEFI's to really make a difference.   RWD cars got a 4bbl in 80.     I think all had plastic valve covers which were apparently a problem when they were new and not brittle.  I think aftermarket covers from the 68-79's fit on the 80's.  Stock ones don't because the different rocker system clashes with the baffles in the stock covers.   The 81 has a unique cover due to 8-6-4 system so you are kinda stuck there unless you can find the parts to remove the solenoids and replace them with standard rocker pivots.   Someone once told me they may be Oldsmobile parts so maybe they are not hard to find.

Proper way to disable the 864 is disconnect the wire that sense 3rd gear in the transmission.  That way the system will never try to deactivate.    All other methods cause issues because it confuses the computer and things go downhill quick if the computer isn't happy.   Avoid any car where someone got creative to try and bypass the system,  there can be an endless amount of patches and hacks to try and make it still run.

["Cadillac Kid" Greg Surfas 15364]

Of course with just a little work the 368 can be replaced with a 425 or even a 472 using the 368 pan and exhaust manifolds
Greg Surfas

[79 Eldorado]

One interesting point is the new body for the Eldorado started in 1979 but the Seville new body, and move to FWD (for Seville), was one year later 1980-1985. I didn't realize it until recently but apparently the 1976-1979 RWD Seville was also carried over to 1980 for California. I assume all RWD Sevilles in 1980 were either California or where CA emissions were imposed.

The way I interpreted Matt's question to start, prior to clarification, was he must be talking about the Eldorado because I assumed he had zeroed-in on a body style. The Olds 350 and 368 were only offered in the same generation in the Eldorado. With the Seville the engine followed the generation change. So if it's a RWD Seville it's an Olds and if it's a bustle-back FWD it's a 368 (with this particular engine comparison).

That said the 350/5.7L Diesel was continued beyond 1980. Externally the diesel was an Oldsmobile meaning all of the accessories would easily swap. In fact before I bought my 1979 Eldorado I thought they were carburetor because one of my high school friends had an original '79 Diesel and the swap to Olds 350 was so perfect, without specific knowledge of what it should have, the install appeared factory original.

When I started looking for my Eldorado I limited my search to 1979 because it was the only year for the Olds gasoline engine. I also had 1979 Toronados for years and after 1979 GM started "pouring" tons of extra vacuum lines/ hoses/ wires all over the engine compartment. The 1979 design was a lot cleaner looking engine compartment in the 1979 Toronado. I mention that only because that was part of my mindset while looking for the Eldorado.

From what I've observed, since buying my '79 and joining this forum, is the 70's EFI was feared but seems to be better known now. Some of the fear was the concern regarding parts. As TJ mentioned Bruce Roe knows these systems basically upside-down and backwards. I am the "79 Eldo" T.J. was referring to and I was concerned about the parts being difficult to find. With help from this forum I was able to reverse engineer and improve the coolant/air temp sensors and the Fast-Idle-Valve heater "FIV". Bruce can fix any of the common failure modes in the ECU's. Most of the parts, other than sensors and FIV, outside the ECU seem pretty reliable but I always have my ears open on this site because I want to stay ahead of an issue. The good thing about the "70's" EFI systems is they were in production from late 1975 through 1980 so at least the technology had some years of stability. At a really general level the newer systems, moving to injectors in the TB, seemed like a step backwards. The TBI seemed to make the technology more affordable to generically release more generally across GM (maybe more of my impression than fact).

There are some experts on the newer systems but the ECM seems to be more of a "black-box". Bruce, to an extent, credits his ability to work on the "70's" ECU's to the vintage of electronics used. He's good enough that he would have likely "broken the code" to anything the fate of what he bought led him to.

How many years of the ECM technology were there which was used on the 368 starting in 1980? I think I've read the term DEFI is specific to only a couple of years. When it comes to aftermarket support the quantity of vehicle with parts interchange makes a huge difference. I spent about 2yrs working on the FIV and to get the cost to reasonable levels I purchased in quantities which made more sense to my heart than my head but at least there are several years sharing the same parts. I look at it as a hobby and the interest in the sensors basically funded the FIV.

Scott

[TJ Hopland]

I think Cadillac stuck with the term DEFI on the non transverse engine cars.  I can't remember if they dropped it with the transverse ones.  I don't think dropping the name really signified any specific change.   I don't remember the specifics but I know they changed some sensors the first couple years and I think just about all the connectors.  Stuff that worked good in the lab and on the test cars but didn't hold up so good in the real world. 

The diesels can be fun.  One that survived till today would have been a Wednesday car (look up the Johnny Cash song) so it was a 'good' one.  I have not really looked for parts recently but in the years I was playing with them they were getting harder to find but you are kinda in the same boat with some of the systems of any of the cars in question here so pick your poison sort of thing.   The diesel cars had extra insulation in em so they are extra quiet on the inside. 

[79 Eldorado]

T.J.
One of the guys I worked with for year, retired now, has 2 diesel Delta88's which he uses as daily drivers during the summer months. He's an expert at all things 5.7L diesel. The last time I spoke to him about the cars he wanted to have a spare injector pump on the shelf but he felt pretty comfortable other than that.

I have 2 cars born as diesels. Looking back part of me wishes I would have left at least one of them alone. Other than sound deadening another advantage I noticed is that,  if there was a full package available, the diesel cars got the full package. I cannot recall if anything was available on the Eldorado. I was a little disappointing Cadillac failed to include at least a temp gauge on my '79. I don't know if I ever posted a photo but I found a gauge from a mid to late 80's "A-Car" and I test fit it on the right side of my speedometer. In the end I decided against it but if someone had an original looking solution I would consider installing it.

You're probably correct on the DEFI term. I don't know the year specific terminology but I thought I recalled someone mentioning something like the system in even '80 was different than that of '81. My main point was that in picking your poison the least poisonous might be the technology which was common for more years. I know the 75-80 Seville/ Eldorado/ Deville (counting 75.5 Eldorado and 80' California cars) was essentially the same, but can that be said for technology which followed immediately after? I mean did a lot of the basic parts and control stay common for 4-6years? The aftermarket and service support is always dependent on the demand.

Scott
PS: I understood the reference to the Wed car

[Eric DeVirgilis CLC# 8621]

One interesting point is the new body for the Eldorado started in 1979 but the Seville new body, and move to FWD (for Seville), was one year later 1980-1985. I didn't realize it until recently but apparently the 1976-1979 RWD Seville was also carried over to 1980 for California. I assume all RWD Sevilles in 1980 were either California or where CA emissions were imposed.

Just to clarify, the 350 Olds FI was carried over to 1980 in Eldorado/Seville on CA cars but not the 1979 Seville body style itself. There was never a RWD Seville in 1980. First year Seville was introduced in spring of 1975 as 1976 model. Not a '75.

One other point - CA cars w 350 engine didn't have the MPG data display on the dash of the 368 DEFI cars. 

[TJ Hopland]

Lots of 80's cars got EFI so I wonder if DEFI was just Cadillac's term to make their system sound superior to all the other systems?   Only real difference other than they were first was they had the MPG readout and tied into the climate control for easier diagnostics.   And considering pretty much all the other makes went multiport sooner than GM did they needed something to make people thing they were getting something better?    I really like the TBI systems, very simple and reliable. 

[fishnjim]

A period of turbulence in the depowering of autos for emissions regs.   EPA v existing technology.   145 HP???  OMG!   That's in the range of a flattie straight eight, 40 years prior.
Frankly, I won't give two cents for any of these.   I like the body style "looks" but as this thread points out, you need to be "expert" on or know one to own them.
I think Cad was also expecting to drive customers to the dealer service, while GM was looking for cost reductions, with some of these contraptions.   They eventually got the bugs out, mostly by abandonment, but those with the bugs remained or died/scrapped.   Evolution of technology vs forcing too many constraints on a system.
The 5.7L diesel experiment was a complete flop from my memory.  There's always one or two that swear by anything, after the fact.   Turbo Diesel today is perfected and EPA is still messing it up.  They should've put turbos on gas motors long ago and we'd not be in the mess we're in, easy 30% reduction in fuel.   In terms of power/wt, torque, and reliability it's far superior to any gasoline engine. 

[bcroe]

3 original diesel cars here, after I converted them to an Olds small
block, they turned out to be great cruisers.  Big gas tanks, alternators,
batteries, no emissions testing.  The biggest issue was the axle ratio
was the same as a gas car, so the engine did not get into the power
range until near 40 mph in low.  This made them seem like slugs.  I
found that an electronically controlled switch pitch trans got the engine
into the power band far sooner, no trouble keeping up with city traffic,
will take AT LEAST a second off 0-60.  A few diesels came with 4
speeds which were a much better match. 

Olds rockers do not interchange with the 8/6/4 type, I tried. 

The 368 seemed to have valve and intake issues trying to meet 80
specs.  The 350 had no problem, offered in 50 states.  Yes the methods
used to measure hp were different and made these engines appear a
lot weaker than they were.  I swapped the 350s for the bolt in 403s. 
Field measurements with a VC2000 indicated it would deliver 260hp
with no modification beyond good duals.  A B car seen at 4100lb on
our farmers scale, did 0-60 in 7.49 sec, 91.2 mph quarter mile.  Not
a race car, but hard to beat that in any 4 door the General made in
those years. 

Turbos and diesels are a great marriage, but not ready soon enough. 
Bruce Roe

[79 Eldorado]

Just to clarify, the 350 Olds FI was carried over to 1980 in Eldorado/Seville on CA cars but not the 1979 Seville body style itself. There was never a RWD Seville in 1980.

Eric, I looked back at the thread which made me think that the RWD was carried over to 1980 in CA and I see that the context and photo in that thread lead me to believe I had been wrong for years (in thinking what you wrote was true). What had me believing the RWD was carried over was the OP from that thread mentioned the wood surround for the dash was a CA 1980 only color scheme and the dash, probably only to me, looked like the older RWD car. So my mistake and thank you.

First year Seville was introduced in spring of 1975 as 1976 model. Not a '75.

I wasn't thinking of Seville at all. I was thinking of what I've heard referred to as 1975.5 Eldorados. I've heard some people refer to them as 1975.5 or late 1975 models but I suspect they would have been considered by GM as an early introduction of the 1976 model. The normal SOP for GM cars typically being July of the prior calendar year; so July 1975 normal SOP for the 1976 MY.

My point was the number of years the technology covered. Even though 1976-1979 are considered the core years the 70's EFI started production prior to the normal cycle of 1976 MY cars and through to 1980 MY in CA; more than the 3 core years.

Scott

[bcroe]

Lots of 80's cars got EFI so I wonder if DEFI was just Cadillac's term to make their system sound superior to all the other systems?   Only real difference other than they were first was they had the MPG readout and tied into the climate control for easier diagnostics.   And considering pretty much all the other makes went multiport sooner than GM did they needed something to make people thing they were getting something better?    I really like the TBI systems, very simple and reliable.

I think Cad meant DEFI to distinguish the new for 80 digital ECM system, from their
earlier analog (not digital) ECU system.  Others used EFI to distinguish from a carb. 

I have seen the early system used on late 75 Eldo, through the 80 Eldo in Cal.  Not
sure how that lines up with a calendar.  Bruce Roe

[Eric DeVirgilis CLC# 8621]

Actually the first model year Fuel Injection became optional was in 1975 (500 engine). It was essentially the same system used in the 350 & later 425 until 1979. No FI option in 1980 RWD cars however but was  standard of course with gasoline V8 Eldorado & Seville.

While it is true that all-new models or existing models with major styling changes are often introduced much earlier in the calendar year than normally but I've never heard the mid-year (1975.5) thing being applied to a 1976 Eldorado since it was essentially unchanged from the 1975 model. 

[Eric DeVirgilis CLC# 8621]

I think Cad meant DEFI to distinguish the new for 80 digital ECM system, from their
earlier analog (not digital) ECU system.  Others used EFI to distinguish from a carb. 

That had always been my understanding as well.

[79 Eldorado]

Thoughts Cadillac 368 vs. Olds 350 if one has a choice?

I'm just guessing Matt was planning to look for or pull the trigger on a car and trying to decide on years to search... I mentioned when I first started looking I was only interested in a 1979 Eldorado. If I was looking now I wouldn't care as much what year but with the idea the HT4100 would be replaced at some point...and my impression/experience has been the TH325, through 1981, was a little better than the TH325-4L. In the end I would probably try to find the best example I could find....

Scott