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Re: Fords new 7.3 liter engine is a pushrod engine? [Re: dave1251] #5180946 08/07/19 08:08 AM
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Pew Offline
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Originally Posted by dave1251
Originally Posted by Red91
I'm aware of the amount of time/mileage being put on di/turbo engines. Some are making it to high mileage, I'll give you that, but when they give trouble the cost is enough to make the customer jump ship for a new car. Some things get to a certain point of advancement where that's as good as they're going to get. By the beginning of this century we had made it. Port fuel injected engines with natural aspiration and distributorless ignition proved themselves to be long lived, relatively easy to work on, inexpensive to repair, and made more than enough power for the average consumer. Plus, fuel economy was basically the same as it is now.

Guys, I'm not hard to please. The Impala in my sig is about as basic of a car as you could get in 2005. By the time it rolled out of the factory, every bit of it's technology had been in use for twenty years in one form of another. It has port fuel injection and pushrods. It might make 170 hp but that's probably being quite liberal an estimate. I haven't driven or worked on anything newer with di/turbo/ohc and thought, "this is better". If anything, the honest truth is my thought was, "this thing shifts like it's retarded, it idles like it has a misfire, the power comes on at the most useless part of the Rev range, and overall they've managed to build a vehicle that does everything my 14 yr old car can do, but somehow worse." I'd love to see gm and Ford dump their ohc/di/turbo v6 engines for pi/na/pushrod engines like they were using 10-15 years ago. Sure, the Vulcan 3.0, 31/34/35/3900 v6s weren't powerhouses, but they worked and we're cheap to maintain. That's really all they average consumer needs. Sorry for the derailment, I'm just stating my opinion. Give me simple, reliable, and easy to work on over "advanced" any day.



I guess 1500RPM is too low for you. I guess you like making peak power at 4000.


For real. My 1L 3cyl engine makes peak torque at around 1300rpm.

Red91, I'm willing to bet your impala wouldn't pass safety and emission standards as a new car today either. I like simplicity too but if we kept to the thought of simplicity > technological advancements, we'd still be riding horse-drawn carriages.

Re: Fords new 7.3 liter engine is a pushrod engine? [Re: JHZR2] #5180953 08/07/19 08:21 AM
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Originally Posted by JHZR2
It seems like a stoichiometrically tuned DI would be a good case study for economics and power. The effect on cooling/combustion temperatures, etc would seem to have a benefit, especially under high duty cycles.

Honestly I’m surprised they didn’t push the hybrid DI/port to ensure cleanliness with the benefits of DI.

Interesting to read all the comments on timing chains. Wonder how many folks have actually lined up marks and measured wear in the chain and sprocket.



The wear I've seen from experience is nearly the same on non DI and DI engines further demonstration maintenance practices are key. Still it does not justify over maintenance which most members do.


make the inside of your engine oil cap white.
don't use.
Re: Fords new 7.3 liter engine is a pushrod engine? [Re: clinebarger] #5181120 08/07/19 11:48 AM
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Originally Posted by clinebarger

That's really the achilles heel of the 2V OHV arrangement.....Valve Control! About the only pattern failure I've seen with the 6.2L Ford is broken valve springs, And it's a 2V OHC arrangement. Ford is having trouble just controlling large/heavy valves & a Rocker Arm.....Now the 7.3L will have even larger valves & much more weight to control (Lifter, Pushrod, & Rocker Arm).


If valve float is an inherent weakness in an OHV engine, how is GM and Mopar mitigating it in the LSx and the Hemi(especially the Hellcat/Demon variants with forced induction)? I'm guessing stiffer, variable-coil valve springs with a beefier, bolted on rocker arm assembly, roller lifters and VVT?

Re: Fords new 7.3 liter engine is a pushrod engine? [Re: dave1251] #5181139 08/07/19 12:22 PM
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Red91 Offline
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I'm not following you. Are you referring to the max power range of pushrod v6 engines?


05 Chevy Impala
3.4 V6
Pit crew QS 10/30
Re: Fords new 7.3 liter engine is a pushrod engine? [Re: Red91] #5181148 08/07/19 12:34 PM
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nthach Offline
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Originally Posted by Red91
I'm not following you. Are you referring to the max power range of pushrod v6 engines?

https://mechanics.stackexchange.com...lve-float-and-how-does-it-impact-engines

Re: Fords new 7.3 liter engine is a pushrod engine? [Re: Pew] #5181150 08/07/19 12:35 PM
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Red91 Offline
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Yeah, I like that the car doesn't meet those standards. I can see out of it, it drives like all the 85-05 gm fwd sedans I've ever driven, and I can work on it, affordably at that. It gets decent fuel mileage, it makes decent power, it's comfortable and those are things that matter to me. It's personal preference. To each their own, but back to the point of the thread, I'm glad Ford is putting out this basic work truck engine with basic, "old" tech that has proven itself, and I hope the engine does do.


05 Chevy Impala
3.4 V6
Pit crew QS 10/30
Re: Fords new 7.3 liter engine is a pushrod engine? [Re: nthach] #5181153 08/07/19 12:38 PM
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Red91 Offline
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That link really isn't applying to my post.....


05 Chevy Impala
3.4 V6
Pit crew QS 10/30
Re: Fords new 7.3 liter engine is a pushrod engine? [Re: Red91] #5181175 08/07/19 01:05 PM
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Red91 Offline
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Nevermind Dave, I looked up the power figures and I see what you mean, but no, I have no issue with those engines making their power up high. Honestly, I could care less about the power, I care more for the reliability and ease of maintenance. I'll leave the low end torque to big inch, low stressed pushrod v8s.


05 Chevy Impala
3.4 V6
Pit crew QS 10/30
Re: Fords new 7.3 liter engine is a pushrod engine? [Re: nthach] #5181178 08/07/19 01:06 PM
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Red91 Offline
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Ok I looked at your post from a different perspective, and in my experience these engines never had an issue with valve float.


05 Chevy Impala
3.4 V6
Pit crew QS 10/30
Re: Fords new 7.3 liter engine is a pushrod engine? [Re: clinebarger] #5181328 08/07/19 05:01 PM
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Originally Posted by clinebarger
Originally Posted by nthach
Originally Posted by clinebarger
Originally Posted by andyd
If Ford didn't convert the 4.0 to OHC I'd be driving the newest old Ranger I can afford. Cam drive off the flywheel hub. On a Ford? Nevermind. .The DOHC V6s make me queasy with 6 feet of chain/belt riding on plastic guides. I'm sure Toyota builds a fine V 6 but the timing belt is scary.


The right chain "Cassette" is in the rear of the engine, The left "Cassette" is in the front, Both are driven off a "Jackshaft" that's driven off the front of the crankshaft buy a Primary timing chain.
They basically took a OHV 4.0L block & used the existing Camshaft bore for a Jackshaft.

I contend that a Timing Belt is the best way to run overhead camshafts, The reduction in harmonics alone are worth the scheduled replacement interval in most cases.
The old Timing Belt Toyota engines are tough as nails & you could generally get 200,000+ before the belt would actually fail.....Usually from dry rot/age.



Wasn't there an DOHC version of the GM 3400 that used a jackshaft to drive a separate timing belt? A friend has the 4.0L Cologne V6 in his Explorer. 144K on it, no death rattle. He uses SuperTech oil and filters and 3K OCIs, clean oil is vital for those engines.

The OEMs pawn timing chains as "maintenance free" but replacing them is a fact of life on most Mercedes, not so much the chain itself but the tension/guide rails breaking and causing total engine damage. I've seen the parts from a 1986 420SEL we had, the chain itself was beefy - it was a double-row IWIS chain but the guide rails aren't. Those older Mercedes V8s were interference engines, and the smaller US-spec 3.8L version from 1980-1985 used a cheaper single-row chain.

Toyota hybrids develop timing chain slap. I much prefer a belt. You might lose some skin and blood in the process of changing one out but if a critical system is also a regular maintenance item there's motivation to keep it running. The OEM and dealer belts I pulled off two Toyota engines in the family still looked great.


Yes....The LQ1. It was called a Intermediate Shaft as no timing components ran off the rear of the shaft.....Though it did run the Oil Pump drive at the rear.-

IWIS makes some of the best timing chains in the world, Have one in my L92! People tend to think that short cam-in-block timing chains don't wear....They most certainly do! And in the case of high RPM with High spring loads & aggressive lobe profiles.....They can break from Harmonics/Chain Whip.

That's really the achilles heel of the 2V OHV arrangement.....Valve Control! About the only pattern failure I've seen with the 6.2L Ford is broken valve springs, And it's a 2V OHC arrangement. Ford is having trouble just controlling large/heavy valves & a Rocker Arm.....Now the 7.3L will have even larger valves & much more weight to control (Lifter, Pushrod, & Rocker Arm).
Granted the hydraulic lash adjuster is built into the Rocker Arm on the 6.2L unlike other Modular engines that use a Roller Follower with the Lash Adjuster in the cylinder head (No added weight)


As much as I really like OHV pushrod engines for their simplicity......Ford abandoned it long ago. They could have easily stuck with the 6.2L architecture that IIRC has pretty large bore centers for the displacement (Room to grow)



{sigh} Overhead Cams. They produce great benefits in engine design in the form of stiffer valvetrains and freedom of port design, but there's no good way to drive them. Belts are cheap, but they are a maintenance item. Chains require extensive guide and tensioning systems, or they stretch, wear, jump time, and break. (My best friend at GM was release engineer on the timing chain system for the High-Feature V6. He stressed out and had to take a few weeks off to decompress. But the Gen 2 HF V6 has a much improved system.) I prefer gears, but they're expensive, and are an issue if somebody wants to mill the head or block decks.

GM and Chrysler have developed their pushrod V8's to be reliable up to 6000-ish rpm. So fortunately the LS and Hemi have been available for 15+ years for Ford to benchmark and learn from. From the cutaways I have seen on the 7.3, it looks like Ford has copied GM with ovate-wire beehive valve springs, and investment cast roller-fulcrum rocker arms. From what I've seen so far, the 7.3 looks like a big LS.

My suspicion for years has been that the extra friction caused by multiple overhead cams and four valves per cylinder erases whatever fuel economy benefit that the smaller displacement of OHC engines provides. And now everybody is jumping on the DI/high-compression/turbo/downsized displacement bandwagon, and are trying to make gasoline engines produce BMEP like diesel engines at 1500 rpm. So who needs the high-rpm capability of overhead cams? The name of the game in the auto industry now is to achieve 54 mpg CAFE by 2025. So fuel economy is king.


1985 Z51 Corvette track car
2002 Camaro Z28 LS1/6-speed
2001 Dodge Ram 2500 diesel
1972 GMC 1500 shortbed project truck
Re: Fords new 7.3 liter engine is a pushrod engine? [Re: dave1251] #5181341 08/07/19 05:09 PM
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Skippy722 Offline
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Originally Posted by dave1251
Originally Posted by Red91
I'm aware of the amount of time/mileage being put on di/turbo engines. Some are making it to high mileage, I'll give you that, but when they give trouble the cost is enough to make the customer jump ship for a new car. Some things get to a certain point of advancement where that's as good as they're going to get. By the beginning of this century we had made it. Port fuel injected engines with natural aspiration and distributorless ignition proved themselves to be long lived, relatively easy to work on, inexpensive to repair, and made more than enough power for the average consumer. Plus, fuel economy was basically the same as it is now.

Guys, I'm not hard to please. The Impala in my sig is about as basic of a car as you could get in 2005. By the time it rolled out of the factory, every bit of it's technology had been in use for twenty years in one form of another. It has port fuel injection and pushrods. It might make 170 hp but that's probably being quite liberal an estimate. I haven't driven or worked on anything newer with di/turbo/ohc and thought, "this is better". If anything, the honest truth is my thought was, "this thing shifts like it's retarded, it idles like it has a misfire, the power comes on at the most useless part of the Rev range, and overall they've managed to build a vehicle that does everything my 14 yr old car can do, but somehow worse." I'd love to see gm and Ford dump their ohc/di/turbo v6 engines for pi/na/pushrod engines like they were using 10-15 years ago. Sure, the Vulcan 3.0, 31/34/35/3900 v6s weren't powerhouses, but they worked and we're cheap to maintain. That's really all they average consumer needs. Sorry for the derailment, I'm just stating my opinion. Give me simple, reliable, and easy to work on over "advanced" any day.



I guess 1500RPM is too low for you. I guess you like making peak power at 4000.


I was going to say this exact thing. 90% of peak torque available from 1800rpm to 6,350rpm, my Chrysler spec ZF8 speed is absolutely perfect, idles so smooth you’ll forget it’s on... no forced induction or turbo needed. Push rod engines aren’t going to make a comeback for average consumer vehicles. Everything they do, DOHC with VVT does better.

Last edited by Skippy722; 08/07/19 05:10 PM.

2016 Chrysler 300S v6
2018 Dodge Grand Caravan GT

Slight Mopar obsession
Re: Fords new 7.3 liter engine is a pushrod engine? [Re: Skippy722] #5181377 08/07/19 05:48 PM
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Well, odd man out I may be, but I respectfully (and I mean respectfully) disagree with you guys on that. I'm going to hang on to pushrods for as long as I can, and you can have the di/turbo/ohc engines. Everybody has their preferences, and pushrod/pfi/na suits me. With that, I'm bowing out of this one because I've inadvertently detailed the topic. I really do hope this 7.3 works well.


05 Chevy Impala
3.4 V6
Pit crew QS 10/30
Re: Fords new 7.3 liter engine is a pushrod engine? [Re: Red91] #5181390 08/07/19 05:59 PM
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Originally Posted by Red91
Yeah, I like that the car doesn't meet those standards. I can see out of it, it drives like all the 85-05 gm fwd sedans I've ever driven, and I can work on it, affordably at that. It gets decent fuel mileage, it makes decent power, it's comfortable and those are things that matter to me. It's personal preference. To each their own, but back to the point of the thread, I'm glad Ford is putting out this basic work truck engine with basic, "old" tech that has proven itself, and I hope the engine does do.

Pushrod engines are newer than OHC. I don't know how this is continuously mixed up.


make the inside of your engine oil cap white.
don't use.
Re: Fords new 7.3 liter engine is a pushrod engine? [Re: dave1251] #5181403 08/07/19 06:10 PM
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Originally Posted by dave1251

Pushrod engines are newer than OHC. I don't know how this is continuously mixed up.


Some people think “more complex=newer technology”


2016 Chrysler 300S v6
2018 Dodge Grand Caravan GT

Slight Mopar obsession
Re: Fords new 7.3 liter engine is a pushrod engine? [Re: nthach] #5181605 08/07/19 10:59 PM
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Originally Posted by nthach
Originally Posted by clinebarger

That's really the achilles heel of the 2V OHV arrangement.....Valve Control! About the only pattern failure I've seen with the 6.2L Ford is broken valve springs, And it's a 2V OHC arrangement. Ford is having trouble just controlling large/heavy valves & a Rocker Arm.....Now the 7.3L will have even larger valves & much more weight to control (Lifter, Pushrod, & Rocker Arm).


If valve float is an inherent weakness in an OHV engine, how is GM and Mopar mitigating it in the LSx and the Hemi(especially the Hellcat/Demon variants with forced induction)? I'm guessing stiffer, variable-coil valve springs with a beefier, bolted on rocker arm assembly, roller lifters and VVT?


Not so much valve float.....Breaking valve springs is a phenomenon that is ALMOST exclusive to OHV engines. Though I recently seen a broken spring on a 3.6L Pentastar. And of coarse the many Ford 6.2L OHC engines I've seen with broken springs being an outlier.

LSx & Hemi's probably break springs more than any modern engine. The lowly 4.8L being the worst of the lot......Have to rev them to make power & it will only take so much duty cycle.

Beehive/Ovalet springs certainly help, Smaller diameter spring retainers reduce mass.
Hollow stem valves also help reduce mass, All the high performance engine your thinking of use hollow stem valves. Not a technology generally found on truck engines.

Roller lifters add mass & VVT doesn't change the cam profile just valve/cam timing. Not to be confused Variable Lift/Profile technology (Honda Vtec).


Broken springs may not be a wide spread topic/known issue.......Engines are replaced over it a lot of times. Where a simple vacuum gauge will diagnose it.


2001 Chevy Camaro L92/4L80E
2006 Chevy 2500HD LBZ/Allison 1000
2010 Toyota Corolla 2ZR-FE/U341E
2000 Toyota Avalon 1MZ-FE/A541E
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