And they moved away from cast iron blocks and heads for ???
Another Dave's Auto Center
- Thread starter Donald
- Start date
Light weight, easy to manufacture, less energy to produce, etc.
Lighter weight = better fuel economy
More problems, easy distortion, pulled bolt threads, easy to ruin threads when assembly, warpage - leaks, lack of high load support, easy fretting, you know all that good stuff.
The moved from timing chains (how simple it was on my 1965 Mustang 289) to timing belts) that needed to be changed at $800 to $1000 a pop (let's not forget interference engines) and now back to timing chains. Maybe they will see the light and go back to cast iron blocks?
"now back to timing chains" Yeah because of the complaining about the belts. Problem is mile long timing chains, all mostly guided in plastic, and needing a tensioner to mess up. If you do the study, we see that timing belts needed to be changed at about 100k miles on some, and even now we see that many timing chains are due for replacement at about that same interval, because they wear at all those many hundred links causing enlongation or stretch, then the tensioner hits its max, the chain jumps the sprockets and sometimes not so good things happen.
Then the engineering and modern design stupidity continues, when they start driving some oil pumps with a belt submerged in the oil pan. As much that is paid for new vehicles all that stupidity should be changed to the best and most expensive long lasting way to accomplish the task. On a cheap inexpensive new vehicle then sure be stupid with your construction of it.
So then the question is what did the OHC provide? My 1965 289 Mustang had a simple timing chain and the cam was not OHC. It had pushrods. Did the OHC provide any benefit beyond eliminating pushrods? OHC and DOHC caused the timing chain path and length to go from simple to complex. For what benefit?
I'm with you. They can keep the OHC mess for racing engines, or old WW2 inline aircraft engines.
The big reason they went that way in the now times is easy to use the variable timing systems, for ex or in.
And back before variable cam timing, on little puddle jumpers like say the Geo Metro, it was a quick cheap way to go.
On cars like the old Lexus and maybe most Japanese engines were going that way, and of course their motor cycle engines had it for years. For high performance its a good deal less moving weights. Just not needed for a normal family car or truck.
Gosh seems all non US engines were OHC for years before it happened here?
OHC maximizes area for head design. Combustion chamber shape/size, valve size and orientation, intake and exhaust port size/shape all aren't influenced by the pushrod holes in the head casting, which are a significant portion of real estate in the head casting. It also eliminates restrictions based on valvetrain angles, not needing to worry about camshaft location in the block and limitations in rocker angle.
In a nutshell, in going OHC, many restrictions are eliminated and the head can be designed nearly completely independently of the block it's being bolted onto. There are benefits in initial design, future improvement/revision, engine architecture lifespan (2V, 3V, 4V Ford Modular, for example).
Conversely, pushrod/cam-in-block engines are relatively restricted and when significant revisions are required, the whole engine needs revised.
So do the advantages of an OHC outweigh the issues imposed by a long and complex timing chain path. The engine designers don't worry too much about maintenance issues at 100K miles.
Hopefully my 6.7 PSD does not have any of these issues.
So a recent short YT featured them pulling apart a 6.0 PSD that was not developing any oil pressure. The engine has been recently rebuilt at another shop. Dave discovered the shop that did the rebuild forgot to install any of the oil squirters.
His question to the YT audience (and now to BITOG members) is, is it ethical or reasonable for him to expose the shop that did the rebuild if they don't make it right for this customer?
His question to the YT audience (and now to BITOG members) is, is it ethical or reasonable for him to expose the shop that did the rebuild if they don't make it right for this customer?
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