yes, on an elementary level that's all you need to know.

 

When a smaller engine displacement proves to do the same job and return better fuel economy than its larger competition, pretty sure that qualifies for more efficient.

When both Chrysler and GM gave up their larger displacement gasoline engines in the HD lineup they admitted it was because of the having to put forth a significant investment to keep them competitive with the 6.8L 3V. Chrysler and GM also completely dropped a gasoline engine offering for the 4500 and up chassis leaving only the diesel. They knew they couldn't compete, and again look through automotive publishing's from 2003-2008 and you'll see they flat out admitted it. They both left Ford's V10 to be the only gasoline offering out of the "big three" in Class 4, 5, 6, and even 7 trucks. Ram finally came back with the 6.4L Hemi in the 4500 and 5500, after watching Ford F450 and F550 6.8L selling very well.

The technology just wasnt present at the time to keep the pushrod competitive with the OHC. The OHC modular engines served their purpose for the time being and now the new 7.3L pushrod is fitted with superb variable camshaft timing surpassing Chrysler and GMs pushrod engines. Im not saying the OHC design is the end all be all design for an internal combustion engine. You have to recognize the technology for the time period it was leading.

 

Actually, GM dropped their 8.1L V-8 because of low sales in the 2500 and 3500 series trucks, where the take rate was somewhere around 3%. At the time, GM was also looking to get out of the medium duty truck market (at least temporarily), so there was no justification for a unique engine program with that low volume. The GM 8.1L was developed into the Powertrain Solutions 8.8L Gasoline/CNG/LNG engine which is currenty available in Freightliner medium duty trucks and International school buses.

Thr Ram V-10 was dropped simply because the 5.7L Hemi made more power than the old LA based 8.0L.

Ford wanted to replace both the 3 valve 5.4L and 6.8L with the 'Boss' 6.2L in 2011. Unfortunately the 6.2L had problems with heat rejection in high GVW vehicles, which kept it out of the 450 and larger trucks.

 

I was unaware of the 8.8L being based off the 8.1L. Did the 8.8L pick up where the 8.1L left off, or was there a gap? I have not seen the 8.8L outside of gensets but it appears to be a more recent offering in trucks.

Chrysler not offering a gasoline engine option in their 4500 and 5500 models was a hot topic in 2003/2004. When GM dropped the 8.1L in 2008/2009 it was also big news along with what you mentioned about exiting the medium duty market.

I read quite a bit about both the duramax and 8.1L being overall underwhelming compared to the Powerstroke and 6.8L 3V at the time. There were many publications about GM not wanting to invest the money seeing as Ford of course was leading sales by a large margin with more powerful and efficient powerplants, and Chrysler was doing rather poorly with 4500/5500 sales since 2003 because of the lack of a gasoline option. The 5.7L Hemi did fill the gap in the 2500/3500 but was quite underwhelming in that platform even with impressive power numbers.

I had heard a few times about the 6.2L not meeting the heat soak conditions of the medium duty testing, but never actually read something published by Ford or a legitimate source quoting Ford on the topic. It does make sense though, but it makes you wonder since the BOSS platform was being engineered as early as 2005 why they didnt pursue an alternative to or at least revise the Triton V10? Instead, they kept the same unchanged 3V 6.8L (2005-2019) up to the release of the 7.3L in 2020.

 

The last year for the 8.1L in GM trucks was 2008, not sure when the PSI 8.8L first showed up in a vehicle.

Outside of the first gen. LB7 Duramax, I would say all the way through 2011 (when the 6.7L came out) he Duramax was a better bet than a 6.0L or 6.4L Powerstroke. I work for a large fleet and those Powerstrokes really were that bad. Usually about 35,000 miles between some expensive catastropic failure, and absolutely no fun to work on. Broken engines make no horsepower or torque. Remember those engines cost Ford sales leadership in class 4 and 5 truck sales, Ram has been #1 ever since.

I thought the 8.1's ran well, certainly had more power than the 2 valve 6.8L V-10.

I heard the 6.2L heat rejection story from a retired Ford engineer, but never read it anywhere. I tend to believe it to be true because Ford really wanted to replace the V-10. Not that there was anything in particular wrong with them, but because the engines were very expensive to produce. High quantity of expensive parts like valves, cam followers, camshafts, balance shaft, ect.. Luckily the 6.8L never had VVT with the lousy cam phasers the 3 valve 5.4L had. We replaced a LOT of 3 valve 5.4's.

The Mods were designed from the start for front wheel drive cars, which dictated minimal engine length and resulted in small cylinder bores, very tight bore spacing, and thin main/rod bearings. Ford president at the time Jac Nasser decreed that V-8's were essentially dead and a road to nowhere, so Ford would have only 1 V-8 engine family and that would be the Mod.. Bye-bye Windsor and Lima (over the protest of the truck group, I was told). The 5.4L with it's borderline ridiculous undersquare bore/stroke was as large as that engine family could be with 8 cylinders. The V-10 was born out on necessity to replace the Lima with something Mod based. And 6.8L was the largest Ford could go as the V-10 shared bore and stroke with the 5.4L. The 3 valve heads came about because the small cylinder bore shrouded the intake valves so much. All and all a big compromise.

The 6,2L was a 'clean sheet'. Ample bore spacing, plenty of room for a good 2 valve head, VVT reengineered. One minor problem was it couldn't replace the V-10 in something like an F-550, but since the 3 valve V-10 worked O.K. Ford kept it around despite the high cost. Brian Wolfe mentioned some thought was given to a tall deck 'Boss' but increasing the deck height made the engine so wide it wouldn't fit in a Super Duty, so out of that the 7.3L gas was born.

 

Just remember what gas prices and the economy were like in 2008. We had a map in our warehouse at work that said how much $$$$ in diesel it cost an owner/operator in Michigan to various cities in the US in 1998 and then at the time in 2008. It was 3x more...
Here we are with gas at or over $5/gallon in parts of the country. I spent $1000 in gas in 2 days. Sure do miss early 2020 prices right about now.

 

Never mind, not worth my time debating with juveniles.

 

Why, because someone used this emoji?

I enjoyed reading this thread and never knew the 8.1L was turned into an 8.8L for commercial use.

 

A 4.6L DOHC is 28" long x 29.125" tall x 30" wide
A 8.8l is 31.85" long x 30.13" tall x 27.45" wide. 26,465in³ (4.6L) vs 26,342in³ (8.8L)
The 8.8L is 3.85" longer, 1" taller and 2.55" narrower.
280CI vs 535CI and the dimensions are pretty close. I would say the displacement/HP rating is better on the 4.6DOHC but dimensionally it takes up a ton of space compared to a 535CI pushrod engine.
The 8.8 also come is Turbocharged and intercooled applications.

 

The size and cost of an OHC engine was definitely a deciding factor in going back to a pushrod. The OHC served its purpose of meeting EPA emissions and fuel economy standards. Just about every auto manufacturer switched their 4cyl and 6cyl pushrod engines to OHC engines as early as the 80s so they could keep up with emissions and fuel economy.

Ive read up quite a bit on the 8.8L since it was mentioned here. Looks to be a relatively new vehicle offering. 2019 was the oldest model truck I could find with one. Looks like International had a hand in the development which isnt too promising. Lots of problematic engines produced under their Navistar name.

 

Problematic diesels maybe but how many pushrod gas engines designed to run on LNG or propane has anyone produced let alone a turbocharged engine? If this was a diesel from them I'd be worried but GM designed most of it 40+ years ago. Its also a roller motor with a forged crank and high flow heads.

 

Ive seen a few 8.8L in gensets as far back as 2015. Never serviced or seen the long term on those sets though. They were natural gas. The Ford 6.8L 2v was a popular natural gas genset engine. Ive seen too many of those over the years.

The numbers on the international school bus page for the 8.8L are really impressive. If I were still running class 6 trucks in my fleet I would give the 8.8L a try. It has the 7.3L beat by a long shot on torque.

 

You seem to think that the main driver of the OHC engines is "efficiency" with no actual realization that a 4.8L or 5.3L GM does just as good or better than a 4.6L or 5.4L Ford as far as fuel usage is concerned....with far fewer problematic parts (pushrods don't fail that often). "Efficiency" from a cost-to-operate standpoint WILL NOT favor a stupid design using multiple chains, tensioners, failure-prone variable timing camshaft sprockets, and the likely possibility of multiple-hour sparkplug changes that require special extraction tools for broken plugs or insanely precise torque values to keep threads from pulling/stripping or plugs from blowing out.

Add to that argument that I put a 7.3L Powerstroke directly in place of a 4.6L in a Crown Vic and the thing takes up the same amount of length and width real estate under the hood. It's taller (because of the alternator and ac compressor placement) and weighs more but the heater box and brake booster clearance is the same for both. No more downshifting on 6% grades from that 190 HP turd that has to have its guts wrung out to make power either. 215 horsepower at a usable RPM sure is nice.


Why does it seem to surprise everyone that a larger displacement engine (8.1L vs. 7.3L or 6.8L) makes more usable power? I was with GM when the 8.1L came out and they'd pass everything (especially similar model year Duramaxes) but a gas station. Keep oil in them and they were fantastic tow rigs as long as it was a longbox or had an aftermarket, larger capacity tank in a shortbox.

 

The reason, and this is a "fact" that automakers started replacing pushrod engines with the OHC design as early as the 80s was due to emissions and fuel economy regulations. The OHC design offers a much better platform to maximize overall efficiency out of an engine. Yes, GM stuck with pushrod and the 4.8L or 5.3L you speak of get significantly less fuel mileage than the 4.6L or 5.4L at the time they were both competitive. When the 5.0L OHC came out it again was a more efficient engine than GMs 4.8L or 5.3L. Gm eventually went direct injection on the 5.3L to bring its efficiency up. Ive had plenty of 5.3L Ecotec engines in the shop that have needed heads removed and ports/valves cleaned because of the direct injection, yet I have not serviced camshaft phasers on a 5.0L. You want to talk about costly unnecessary parts and repairs I can talk all day about gasoline direct injection and high pressure fuel systems. Then there is the GM 8.1L and 6.0L that also get significantly less economy than the Ford 6.8L and 6.2L they compete with. What did GM do with its new 6.6L gasoline engine? Direct injection again with a high pressure fuel system that's sure to require costly repairs.

I get it, you dont like an OHC engine but your opinion not based on fact doesn't help anyone. The 5.4L 3V had problems, there is also a very long list of Ford OHC engines that were very reliable and problem free starting in the late 80s up to our current time.

 

Yeah, I haven't been a professional auto tech for over 24 years........

Wait, I have.

OHC can s*** it. Nothing says reliability like FEET of timing chain rubbing against plastic guides or even better yet...a STUPID BELT.
The last good OHC was the 2.3L Lima (definitely NOT the GM Quad 4) because it was a non-interference design with easy belt changes....

I am so glad my 91 Oldsmobile has the PUSHROD 2.5L Iron Duke and not that fecal abortion OHC option it could have had...it wouldn't be at 300K and still running like a top.

I'd say. It tops every "worst engine" list out there.