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[maria]

As James said,

James hasn't posted on this thread - he is outside cleaning out the car    

Who is James & why has he not posted anything??[/quote]

Jamesv6cdx thats who he is and  the reason he not posted anything was he was out side cleaning his car pitchfork

[hotel21]

No offence intended, however things probably got a tad confused when accidental use of Maria/JamesV6CDX profiles.........  

May possibly avoid confusion if you double check when posting technical type responses??  

[JamesV6CDX]

Given that we share the sams PC at home, I must admit, when Maria leaves her account logged in, I will often sign onto the forum and reply to posts, before I realise I am logged in as her  

When it became apparent that I had answered something technical using her account, we just made light hearted fun of it - joking that she must have learned so much at the cambelt party that she was able to answer  -but the responses were really from me

I must admit I've not seriously followed this thread, but I'll have a more thorough read tomorrow, and if I need to address anything, I will

[hotel21]

Given that we share the sams PC at home, I must admit, when Maria leaves her account logged in, I will often sign onto the forum and reply to posts, before I realise I am logged in as her  

When it became apparent that I had answered something technical using her account, we just made light hearted fun of it - joking that she must have learned so much at the cambelt party that she was able to answer  -but the responses were really from me

I must admit I've not seriously followed this thread, but I'll have a more hthorough read tomorrow, and if I need to address anything, I will

Thanks.

As you appreciate, not every viewer of the community has spoken to you both in person and, by use of both profiles when posting, it gives confused messages.  Those who have met you both in person can seperate the two differing persona in the typed word but others will struggle.  Maria has thus become an instant expert!!    

[JamesV6CDX]

OHC engines are capable of much closer valve/piston clearances than the OHV/pushrod engines, hence incresing power output and efficiency.
 

Rubish I am afraid...

Remember - each to their own - and amicable debate is good

In answer to your post, if this is the case, why is there not an OHV engine in regular production, used in most euro shopping trolleys, that is capable of 45mpg and over 100bhp?

I personally feel that OHV is old hat.

As per Mark's post, it is down to personal preference. Now I have gained (some) experience, my preference is a belt which is relatively simple to change

[hotel21]

OHC engines are capable of much closer valve/piston clearances than the OHV/pushrod engines, hence incresing power output and efficiency.
 

Rubish I am afraid...

Remember - each to their own - and amicable debate is good

In answer to your post, if this is the case, why is there not an OHV engine in regular production, used in most euro shopping trolleys, that is capable of 45mpg and over 100bhp?

I personally feel that OHV is old hat.

As per Mark's post, it is down to personal preference. Now I have gained (some) experience, my preference is a belt which is relatively simple to change

Bring back Mr Fords original sidevalve.....  Everything was so much simpler then......  

[JamesV6CDX]

OHC engines are capable of much closer valve/piston clearances than the OHV/pushrod engines, hence incresing power output and efficiency.
 

Rubish I am afraid...

Remember - each to their own - and amicable debate is good

In answer to your post, if this is the case, why is there not an OHV engine in regular production, used in most euro shopping trolleys, that is capable of 45mpg and over 100bhp?

I personally feel that OHV is old hat.

As per Mark's post, it is down to personal preference. Now I have gained (some) experience, my preference is a belt which is relatively simple to change

Bring back Mr Fords original sidevalve.....  Everything was so much simpler then......  

Having said that, I am following a Mark1 Ford Escort Estate on ebay with genuine interest    

My grandad used to tell me of fun removing the collets on side valve engines... he rekoned it was a lot simpler when I showed him an OHC head from my Veccy Z18XE!

[Debs.]

Some Desmodromic I.C valve-train systems do away with belts, chains and valve springs; with those (and many more engineering and operational advantages) why aren`t they more popular?  :-?

Bevel-Desmo-Animation: http://www.bevel-enthusiasm.com/image/parts/bevelanime.mpg

[Andy B]

Some Desmodromic I.C valve-train systems do away with belts, chains and valve springs; with those (and many more engineering and operational advantages) why aren`t they more popular?  :-? ......

Have you never heard a Ducati? They sound like a bag of spanners.    

[Debs.]

Have you never heard a Ducati? They sound like a bag of spanners.    

[Marks DTM Calib]

OHC engines are capable of much closer valve/piston clearances than the OHV/pushrod engines, hence incresing power output and efficiency.
 

Rubish I am afraid... Take a look and the old bristol engine as used in the AC Ace before Carol Shelby molested it.

OHC engines main reason in racing is to reduce the reciprocating masses, there are no push rods or rockers to accelerate/decellerate on each cycle, as for the production engine this can't hurt, but the OHC design also significantly reduces the number of parts that need to be made and thus makes the engine cheaper to build. Hoever and SOHC design either has to have the valves all in a row (like the 8V engine) which is not so good for gas flow, ideally you want inlet and exhaust valves each side of the head, this can be done, but you can either add a set of rockers, as BMW and Triumph did (truimphs version being as woudl be expected a far more elegant solution!) or add a second cam.

Stewart

Not totaly correct either, its not a reciprocating mass you are reducing, it the valve train weight.

In addition, with SOHC there are simple ways of offsetting the valves and again the GM 4 pot is a good example with a hydraulic lifter at one end of a rocker, the valve at the other and the cam working on the upper surface....

[Kevin Wood]

The other important factor in reducing the valve train weight and using a 1:1 ratio of cam lift to valve lift is that the cam wears a lot better.

Because everything wears slower, and there are much fewer moving parts an OHC setup is almost maintenance free whereas a pushrod setup will always need adjustment - you have the tappets themselves, their interface with the pushrods, pushrod to rocker, rocker to shaft, rocker to valve stem. Wear in any of these will affect the clearances on a pushrod setup.

There are some advantages. It's much easier being able to keep the engine timed up when you're taking the head on and off, such as when checking clearances, for example. Then again, it's a pain when you need to tweak the cam timing. :-/

I'm not sure anyone has ever made a 100% reliable cam drive. Chain, belt and gears all have their faulure modes. Maybe we should go to using vertical driveshafts and bevel gears like the old aero engines had?

One day someone'll invent a cost effective actuator that will allow the ECU to directly control valve opening and closing events and we'll eliminate the cam completely, and have some real fun. How lairy would you like your cam today, sir?  8-)

Kevin

[Martin_1962]

OHC engines are capable of much closer valve/piston clearances than the OHV/pushrod engines, hence incresing power output and efficiency.
 

In answer to your post, if this is the case, why is there not an OHV engine in regular production, used in most euro shopping trolleys, that is capable of 45mpg and over 100bhp?

I personally feel that OHV is old hat.

That is not due to OHV vs OHC but to modern engine management systems, and the greater prevalence of 5 speed gear boxes, I could scrape 30mpg out of my Sunbeam on an A road run, and that was on twin carbs, and a four speed box, that would red line in top at around 120, yet it would pull talling gearing if it was available (some people ran 5 speed Ford boxes and got pretty good consumption). Best economy was 35mpg on the motorway at rep speeds and it was definately over 100bhp - it had 90bhp at the wheels.

Rolling road setup helped immensly

[Marks DTM Calib]

OHC engines are capable of much closer valve/piston clearances than the OHV/pushrod engines, hence incresing power output and efficiency.
 

In answer to your post, if this is the case, why is there not an OHV engine in regular production, used in most euro shopping trolleys, that is capable of 45mpg and over 100bhp?

I personally feel that OHV is old hat.

That is not due to OHV vs OHC but to modern engine management systems, and the greater prevalence of 5 speed gear boxes, I could scrape 30mpg out of my Sunbeam on an A road run, and that was on twin carbs, and a four speed box, that would red line in top at around 120, yet it would pull talling gearing if it was available (some people ran 5 speed Ford boxes and got pretty good consumption). Best economy was 35mpg on the motorway at rep speeds and it was definately over 100bhp - it had 90bhp at the wheels.

Rolling road setup helped immensly

If that was the case then the 1.3 endurance engine from Ford (built until 2005 with full sequential EFi and DIS spark) would be excellent but, its not, its a crock of ......

To many disadvantages with pushrods....period......and we havn't mentioned valve guide wear yet either....

[Martin_1962]

Some Desmodromic I.C valve-train systems do away with belts, chains and valve springs; with those (and many more engineering and operational advantages) why aren`t they more popular?  :-?

Bevel-Desmo-Animation: http://www.bevel-enthusiasm.com/image/parts/bevelanime.mpg

Cost & complexity - it took a young engineer called Massimo Bordi to develop a 4v version. He ended up getting a job at Ducati