Who Thinks OHCs are a good idea for V engines?

[andyd]

OH boy ! a 3 foot timing chain relying on plastic rub strips and an oil pressure driven tensioner. What could go wrong? Oh, and if you are Ford, drive one bank from the back of the engine ? That flat head air plane motor looks better and better to me. Especially after a look at the front end of a V-6 stuffed into a Jeep.

 

[kschachn]

Originally Posted By: andyd
OH boy ! a 3 foot timing chain relying on plastic rub strips and an oil pressure driven tensioner. What could go wrong? Oh, and if you are Ford, drive one bank from the back of the engine ? That flat head air plane motor looks better and better to me. Especially after a look at the front end of a V-6 stuffed into a Jeep.

Makes a timing belt look pretty good doesn't it?

 

[OneEyeJack]

That "D-Motor" flathead airplane motor appears to work well despite it's old fashioned layout. I've been looking for more details about the inside of the engine but have drawn a blank.

 

[Lyman]

The chains on my Jeep 4.7 are a nightmare. Though after 168,000 miles they are quiet as can be. I bet the tensioners are maxed out.

 

[KrisZ]

Design screw up are design screw ups (read: bad compromises) regardless of technology used. Just because some engines have badly implement timing chain or belt system, it doesn't make the whole concept bad.

 

[Yah-Tah-Hey]

I'm still in love with the Ford flathead V8. Ran good, easy to maintain and very reliable. Times change.

 

[OneEyeJack]

The Corvette people think simple and compact work well.

 

[IndyIan]

Originally Posted By: OneEyeJack
The Corvette people think simple and compact work well.

I think so too, as the LS motors seem to have almost no downsides at all, except needing a bit more displacement to match peak hp numbers of OHC engines.
I suspect an OHC engine is slightly easier to get good efficiency out of as well, otherwise somebody would use an 4 cyl OHV motor in a regular car. Not many care these days what is really under the hood of a regular car, 2 or 4 valves per cylinder or VVT or even turbo or not.

 

[BrocLuno]

I care... It's about air flow efficiency. Motors are air pumps and they can be made to work very efficiently if fed right. OHC is usually about 3 or 4 valves per cylinder. A two valve layout can easily be done with push rods.

But, it's also about parts count and operating RPM. If you are going to spin a motor, maybe OHC is a better choice as there is less complexity and inertia issues to deal with.

Long chains have been used in many ICE's for a long time. As long as they are beefy enough and well oiled (?), they can last well over 100,000 miles. It's the ones that are not well oiled that get into trouble sooner ...

 

[Fsharp]

Originally Posted By: IndyIan

I suspect an OHC engine is slightly easier to get good efficiency out of as well, otherwise somebody would use an 4 cyl OHV motor in a regular car.


I've often wondered why GM doesn't do this. They could use the same head design as their LT engines. There 5.3 makes 355 horsepower so a 2.65 liter 4 made from half of it would be about 178hp. They could even make a 210hp 3.1L, although it would need some balance shafts for sure!

 

[nthach]

Originally Posted By: Blkstanger
The chains on my Jeep 4.7 are a nightmare. Though after 168,000 miles they are quiet as can be. I bet the tensioners are maxed out.

If you think that's bad, look at the Ford 4.0L SOHC Cologne V6s in the Explorer/Ranger - 3 separate chains, the engine needs to be pulled to access the right hand chain assemblies. I've read the Audi V8s are a nightmare as well.

Mercedes V8s were bad as well for chains - not exactly a easy job either since the chain needs to be "rolled" in while keeping the cams and crank in time.

 

[Tomioka]

If you think that's something wait until you see the chain setup on a GM 3.6L or Audi V8.

 

[mahansm]

Rolling the chain in wasn't all that bad. Remove plugs, release tensioner, remove one valve cover, and that's all the disassembly required.
Grind off a couple pin ends, clip the new chain on the old one, and start cranking. Crimp the pins and reassemble.

Now, trying to diagnose being way down on top end power later... much fun. After looking at fuel pressure/flow, exhaust, timing, and various other things
it turned out that the left bank was one tooth off. oops...

 

[OneEyeJack]

If there's such a thing as a measurement for power density the Chevy push rod V8's would look pretty good. Simple is good and most driving is done at much lower power outputs. The Corvette people have got it right. All you have to do is put up with the shame of having a very powerful car that does not have overhead cams and is cheaper to fix if something inside goes wrong.

 

[SwampSurvivor]

Originally Posted By: kschachn
Originally Posted By: andyd
OH boy ! a 3 foot timing chain relying on plastic rub strips and an oil pressure driven tensioner. What could go wrong? Oh, and if you are Ford, drive one bank from the back of the engine ? That flat head air plane motor looks better and better to me. Especially after a look at the front end of a V-6 stuffed into a Jeep.

Makes a timing belt look pretty good doesn't it?


Neither is appealing to me, to be honest.

I don't want to have to pay a shop $1000 every 100K miles to change the timing belt.

 

[Jarlaxle]

Seen many Fords wind up 250,000+ miles (or more) on untouched factory timing chains.

 

[tig1]

Have owned Fords for the last 16 years with OHC chains have not had any issues at all.

 

[SteveSRT8]

Simplicity always wins for me. Long term driving experience showed me that less complex has fewer parts and is far less likely to fail, all other things being equal. Power density is very equal these days with forced induction. All of my sons drag racing buds use large single/dual turbos on LS based engines. Win a lot. There are other very hot makes there too but you can create a very quick car very cheaply with LS engines.

Look around on the net you'll find some extremely potent pushrod mills...

 

[Silverado12]

Originally Posted By: SteveSRT8
Simplicity always wins for me. Long term driving experience showed me that less complex has fewer parts and is far less likely to fail, all other things being equal. Power density is very equal these days with forced induction. All of my sons drag racing buds use large single/dual turbos on LS based engines. Win a lot. There are other very hot makes there too but you can create a very quick car very cheaply with LS engines.

Look around on the net you'll find some extremely potent pushrod mills...


Not only that but a lot of the LS guys do it with a junkyard engine. I will say that the 1998 Mustang I had was super quiet with almost 170,000 miles. Timing chain seemed ok.

 

[HerrStig]

Shops around here do an I 4 Camry belt, water pump and cam seals for 350 bucks, not 1000.