Did SOHC's have any "rub strips" to dampen the timing chains?

[Qikbbstang]

Friend of mine built a Yates NASCAR motor for his street car. At first glance the timing cover looked like stock 351 FORD except for the lower passenger side bolt hole being larger to handle the dry sump pump's pivot. When you turned the housing over, the inside of the housing was majorly reworked to be essentially solid aluminum to support plastimeric "rub strips" against every bit of straight chain travel. The lengths of chain in a small block Ford are nothing compared to a SOHC -- just makes me think about the potential for crazy chain harmonics with all that chain.

[thatdarncat]

Yes there are rub strips for the long cam drive chain. Here is a Jay Brown photo from 2014 dragweek prep. One long rub strip across the top of the chain. Another bracket below that has a rub strip under the chain in the center and a rub strip inside the chain on the right side of the photo.

[Autoholic]

If you're really interested in the SOHC, download the 427 SOHC engine service manual pdf I created. Far faster and more efficient way for you to learn about the engine.

https://drive.google.com/open?id=0B3iyR3ENvnVsZ2xOcFZPanNGRTQ

[Qikbbstang]

Did that fellow (Bill Conley?) that video'd the SOHC valvetrain in action ever look at the timing chain's in action?

Wish I'd taken a picture of the NASCAR 351's timing cover's inside modifications to dampen/prevent chain harmonics. Smokey Yunick wrote an article stating that the cam could 'stop or even reverse' on chain harmonics (sounded completely insane I realize).  . One of the prime reasons for "belt drive" is to control harmonics.
   Check the lack of straight runs (sustained chain contact) of the chain in this Engine Buider's article.

 http://www.enginebuildermag.com/2011/11/cam-drives-and-timing-components/

[Autoholic]

Not that I know of. His spintron only focused on the valvetrain in one head mounted to a test stand. Jay has said that he's seen a sizable amount of chain stretch. Not that long ago I discussed the need for a gear drive. I've designed some of a possible gear drive but without a SOHC of my own, I won't make any serious progress anytime soon. If I really wanted to, I could dive into a crude CAD design, it's just a matter of doing it.

[WConley]

Hi BB -

I didn't use the stock chain drive on my spin test machine, but i am interested in chain harmonics.  (I did some work at Ford on the 4.6L SOHC / DOHC timing chain setup, which uses guides as well).

The problem with the 427 SOHC chain drive is that that the chain guides are flat.  Take a piece of string and pull it tight over a flat surface, like a table.  No matter how tight you make it, you can still pull up the middle of the string without much effort.  Now tighten the string across a curved surface and try to pull up the middle.  No can do!

That's why all modern engines use elliptical chain guides.  I've noodled a few designs for elliptical chain guides for the 427 SOHC.  It can be done fairly easily, but I wonder if folks would be interested?  I also have a design for an automatic pressurized oil tensioner for the chain.  Again I could build it, but would they come?

Good observation and interesting topic, BB.

- Bill

[Qikbbstang]

I'd added this to above thread but it drives home Bill's point about curved chain guides. When you think about it a whip sure makes a weapon out of flimsy pieces of leather and whipping a chain is downright frightening.



Wish I'd taken a picture of the NASCAR 351's timing cover's inside modifications to dampen/prevent chain harmonics. Smokey Yunick wrote an article stating that the camshaft could 'stop or even reverse' on chain harmonics (sounded completely insane I realize it sounds, but if you get down to millionth's of a second.....).  . One of the prime reasons for "belt drive" is to control harmonics.
   Check the lack of straight runs (sustained chain contact) of the chain in this Engine Buider's article.

 http://www.enginebuildermag.com/2011/11/cam-drives-and-timing-components/

[WConley]

From BB's linked article:



I think that's an Audi V8.  Only the Germans could make something that complicated.  There's probably a sensor behind that mess that needs to be changed every 30K miles....

Notice though that all of the chain guides are curved!  Even the short spans between the cam sprockets on the heads are elliptical (and have oil piston tensioners).  That's how important it is to keep chain oscillations damped down.

[whitea62.7t]

Easy on Audi's,  August Horch has a similar story to Henry Ford

[WConley]

I'm a Ford guy, but Henry was no saint.  He was decorated with the Grand Cross of the German Eagle, because Adolf Hitler admired him so much.



I don't think August Horch managed that, and he was a German 

[jayb]

  Only the Germans could make something that complicated.  There's probably a sensor behind that mess that needs to be changed every 30K miles....

LOL!  I know of at least one mechanic shop foreman who would whole-heartedly agree with that statement...

[Qikbbstang]

How dare you to say German's over-engineer equipment?..........................

 Impressive until you realize all it takes to replace it is a gang of prison trustees all chained together and a single sheriff's officer with a 12ga..  It doesn't look like it picks up litter... (oh wait German's don't litter). The trim completely around a pole manuver is priceless.

The maintenance procedures for that roadside-grass trimming contraption must resemble a commercial aircraft:

https://www.youtube.com/watch?v=82aIfpE43PE

[nhsohc]

I'd like to see how well those types of machines would work up here in NH.  First 100 yards, the blades would be junk.

[Autoholic]

If your aim is to have complete control over the cams on the SOHC, the best solution would be a gear drive. This would allow you to reverse direction on one of the cams, resulting in truly equal action from the left bank to the right bank. I don't think even the newer cams that compensate for the problem truly solve it, but then again I'm OCD and will look for something to justify OCD. You'd never have to worry about a chain breaking.

[TorinoBP88]

I can name a second mechanic to agree with that statement about German complication.  How about an X5 sun roof!  Then when it leaks it drains onto a $2500 computer.

After Owning old Mercedes, i can say on occasion i appreciate the thought they put into it, including things like force air cooled motor mounts, heated wiper bottles, hoses and sprayers,  but in the end, i no longer own one!


Back to FE's, im surprised the chain sliders are so small on the SOHC.