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Message started by keithert on 02/12/08 at 06:03:53

Title: What's the effect of the cam issue?
Post by keithert on 02/12/08 at 06:03:53

If the cam chain issue occurs I assume the cams stop spinning and you are dead in the water. But will damage to the engine be done if this happens? Is the engine an interference design?

Title: Re: What's the effect of the cam issue?
Post by Kropatchek on 02/12/08 at 08:32:59

Depending on the position of the valves( open or closed) the piston can touch the valves. The valve(s) can bent or break and cause more damage inside the cylinder.

Title: Re: What's the effect of the cam issue?
Post by Lazy Old Rider on 02/12/08 at 11:21:27

Its been a while since I saw the reference, and dont know where I saw it, but the remark, not necessarily on this site, was that the tensioner breaks and falls into the Engine.

After seing other posts here I dont think that is the case, unless you oily handers can visualise broken bits falling down a valve hole or something.

I suspect that the Intertia of our big thumpers would mean that the piston has a number of chances of hitting one or more valves and is likely break a valve letting the bore be damaged as well.

A long time ago I had a BMW 750 car, twin Cylinder Bike engine being the motive power, and that dropped a valve (Just Broke) I had to rebuild the engine, bore was damaged.

Title: Re: What's the effect of the cam issue?
Post by verslagen1 on 02/12/08 at 12:02:52

535D514C505D4A4C380 wrote:

If the cam chain issue occurs I assume the valves stop spinning and you are dead in the water. But will damage to the engine be done if this happens? Is the engine an interference design?

Unless you're gonna go back to the flat head design, all engines are of an interference design. The valves open when the piston goes down and close when it goes up.

Title: Re: What's the effect of the cam issue?
Post by Savage_Greg on 02/12/08 at 12:09:37

I forget where, but I saw a photo of a piston that was damaged when it hit a valve. That happens because the valve timing is incorrect.

And somewhere a tensioner separated and the spring fell into the primary gears.

BTW - Valves don't "spin", and all 4 stroke reciprocating engines have an "interference design" if the valve timing becomes seriously incorrect :P

Title: Re: What's the effect of the cam issue?
Post by keithert on 02/12/08 at 12:25:29

1025323008616267570 wrote:

BTW - Valves don't "spin", and all 4 stroke reciprocating engines have an "interference design" if the valve timing becomes seriously incorrect :P

Sorry, I meant to say cams not valves. By interference I'm thinking of modern car engines where the clearance between piston and valve is so tight that if the timing is out of spec they can collide. In non-interferece engines the valve would have to be seriously incorrect to do this, like you said.

Title: Re: What's the effect of the cam issue?
Post by Rockin_John on 02/12/08 at 12:51:19

2B25293428253234400 wrote:

If the cam chain issue occurs I assume the valves stop spinning and you are dead in the water. But will damage to the engine be done if this happens? Is the engine an interference design?

Well of course if the cam chain lets go the cam stops spinning. But where the valves stops nobody knows. If you are lucky; the valve springs pull the cam around (if its free) until the rockers are on the low part of the cam lobes and the valves are all closed. If "unlucky" something freezes up the valve train/cam and some valve(s) are stuck at full open. Or worse yet something happens to make the spring clips let go; or the stem of the valve gets broken in it's guide. Then you have a nice big hunk of metal in there denting, bending, scratching every possible thing in the cylinder. On the cam chain side, I seem to recall at least one person's chain failure leading to a cracked crankcase; because the chain dropped and jammed up below it's crank sprocket. Does this sound right anyone, or am I remembering something wrong?

At any rate, it is best not to tempt fate when it comes to valve train timing and specs. My wife has a mid 90s Chrysler 4-cylinder car which had a reputation of having the timing belt let go at about 70k and destroying engines. We had the belt changed as a routine maintenance at about 60k just to be safe. I've also eluded the supposed imminent failure of the transmission in those vehicles at 65-70k by finding out that despite what the owners manual says: NEVER put Dexron in those Chrysler transmissions. Go to the Chrysler dealer and pay the $8 a gallon for their OEM type 4 or 5, and the transmission will last a l-o-n-g time, just as it should. An ounce of preventive maintenance is worth several busted knuckles and bloody fingers worth of wrenching later! ;)

Title: Re: What's the effect of the cam issue?
Post by Lazy Old Rider on 02/12/08 at 15:42:47

Interference Design?

I am way out of touch here but if you want to get rid of exhaust gas it must be on the "Up" stroke, so the Valve must be open.
Therefore if there is a performance advantage it must be inlet valves only that are interference or am I missing something?

Title: Re: What's the effect of the cam issue?
Post by viper on 02/12/08 at 17:50:06

Yes the exhaust valve starts to open just before BDC after the power stroke as the piston pass's BDC the ramp of the lobes profile opens the valve to its full open pos. while the piston is comening up as the piston nears TDC the lobe profile starts to allow the valve to start closing keeping it with enough clearance from piston as not to have contact. Many cams have profiles which will keep the exhaust valve open ever so slight past TDC of the exhaust stroke an allow the intake valve to start to open This allows air fule mix to pass out the exhaust .This is a scavaging to clear cylinder of exhaust gas's and start the intake stroke. Many do not realize there is a very low vacume at the exhaust port as the valve nears closing but this relies on the cam lobe profiles. This is one reason it is very importain to address valve adjustments with the correct engine temp and the correct clearance You must sure make sure you are at TDC at the end of the compression stroke.
It's late Iv'e said enough
Ridw on Ride safe
Viper

Title: Re: What's the effect of the cam issue?
Post by viper on 02/12/08 at 17:58:37

Sorry as you can see I can't see the key board or I have forgotten how to spell.
Ride on Ride safe
Viper

Yes again valve timeing cam lift and cam profile (the way the lobes are ground) Make power

Title: Re: What's the effect of the cam issue?
Post by Savage_Greg on 02/13/08 at 08:13:54

Maybe it wouldn't be an issue on a side valve engine...

But the Savage40 ain't one...and neither is my Malibu or Dodge for that matter.

Title: Re: What's the effect of the cam issue?
Post by keithert on 02/13/08 at 08:24:34

I think that most older overhead valve engine have enough clearance that unless the valves come out of their guides they cannot impact the pistons. I was hoping the Savage engine was an old enough design to be non-interference. Below is an excerpt from a wiki on timing belts that describes the difference between interference and non-interference. But in the case of the cam chain it sounds like the valves are not the main issue, but the issue is the chain dropping down into the engine and causing havoc.

Quote:

Depending on the design of the engine, the piston and valve paths may "interfere" with one another and incorrect timing in their movements may result in the piston and valves colliding. (Such designs are also called "interference head" or "interference engines", and include virtually all diesel engines. Conversely, non-interfering engines, such as the Mazda B engine, are called "free-wheeling" or "non-interference" engines.)

In interference designs, regular service is especially important as incorrect timing may result in the pistons and valves colliding and causing extensive engine damage and therefore costly repairs. The piston will likely bend the valves or if a piece of valve or piston is broken off within the cylinder, the broken piece may cause severe damage within the cylinder, often also affecting the crankshaft. Some manufacturers, such as Nissan, have switched back to timing chains for the majority of their engines because of the breakage problems associated with belts. However, in some newer engines, timing belts are designed to last the effective life of the engine. Other manufacturers, such as Toyota, use a mix: timing chains on their interference engines and timing belts on their non-interference engines.

Title: Re: What's the effect of the cam issue?
Post by Savage_Greg on 02/13/08 at 08:49:13

5759554854594E483C0 wrote:

Well, then based on Wiki, the simple answer is "no". If you loose the cam chain you will be F*&$&@...

Now, why do you ask?

Title: Re: What's the effect of the cam issue?
Post by verslagen1 on 02/13/08 at 09:06:00

How can all these engine mfgrs have "non-interference" designs when the savage doesn't, especially concidering it low compression ratio?

Every car that I've every owned has had the issue. Can anyone confirm this design feature?

Title: Re: What's the effect of the cam issue?
Post by keithert on 02/13/08 at 09:21:42

1C293E3C046D6E6B5B0 wrote:

[quote author=5759554854594E483C0 link=1202825033/0#11 date=1202919874]

Now, why do you ask?

Well, I originally asked because I am considering a Savage and want to know the risks involved with the cam issue. But it looks like the issue isn't so much the valves as the other damage it can cause. The bike I am getting only has 600 miles, so I will just start off using synthetic oil and check the tensioner every 5k miles.

Title: Re: What's the effect of the cam issue?
Post by Lazy Old Rider on 02/13/08 at 10:01:50

68776E7B6C1E0 wrote:

Thanks much clearer, probably gives higher compression, less stroke and more revs as I think about it

Title: Re: What's the effect of the cam issue?
Post by T Mack 1 on 02/13/08 at 10:43:07

Reminder to all, many pistons are hybrid. The engine/head combo are "interference" but the pistons face has grooves cut into them to create non-interference or valve clearence (see below).

The LS650 piston has a flat face. :'(

http://i21.ebayimg.com/02/i/000/d8/31/8bbe_12.JPG

Title: Re: What's the effect of the cam issue?
Post by smokin_blue on 02/14/08 at 03:19:21

342730312E2325272C73420 wrote:

V-man, I can confirm existance of the non-interferance engine. The discussion and quote earlier in the thread is correct. Many engines are "interferance engines" that is if the valves are open and the piston comes up (with out the valves moving) they go SMACK. Hello bent or broken valves. Engines such as the B-Series mazada which has the description of non-interferance head is correct. The valves can be wide open and the piston come up and not touch a valve. It has to do with how much head volume do you have and how you shape it/ use it. My '86 Mazda B2000 (the engine described by Keithert) does just that. Right after a very experienced high end mechanic and previous owner of my Mazda told me don't worry about the timing belt at 60K they go for 90k all the time.....mine stripped while starting it at a rest stop 120miles from home. After spining the engine many times until I diagonosed what had happend I called home and my dad and a buddy brought up a flat bed trailer and hauled me home. Per the manual (and quote by Kiethert) I paid $32 for an OEM timing belt, set the cam timing, installed and was good to go. If I had may sister's Nissan at the time it would have been a $600-$800 job. (as that one would have gone SMACK!)

Title: Re: What's the effect of the cam issue?
Post by azjay on 02/14/08 at 05:56:50

valve angles, total lift, combustion chamber shape, etc. determine interference or not. the ford 2.3l ohc is a non-interference design, as the is the 2.0l. if the valves are open at STOCK lift, the pistons will not contact them, while rotating the crank and not the cam. if you mill the head, change the cam for more lift, you change the rules. the savage IS an interference design, if the cam chain pops, internal parts will run into each other.

Title: Re: What's the effect of the cam issue?
Post by Rockin_John on 02/14/08 at 13:30:59

6C77676C740D0 wrote:

Not much of a Ford fan after about 1959... But I did have the opportunity to do a timing belt on a friend's Pinto with the 2.3L as a teen back in the 70s. I was pretty sure it was a "non-interference" design since the belt let go on the Pinto when the engine was revved up real tight. :D As I recall, it only took about an hour or less to change the belt on those.

I guess over a few decades that little 2.3L reached almost legendary status. I recall that they got 212HP out of it in the "Turbo T-Bird." And there were several spec racing classes in both autos and boats based on the little beast.

As I previously mentioned: the Chrysler 2.0L and 2.3L (made by Mitsubishi IIRC) of later years would go: Bang! Clank, clank, clank... if you let the belt give way on them. Very not-cool. :-/

Title: Re: What's the effect of the cam issue?
Post by azjay on 02/14/08 at 17:31:35

[quote author=6459555D5F58697C595E58360 link=1202825033/15#19 date=1203024659

I guess over a few decades that little 2.3L reached almost legendary status. I recall that they got 212HP out of it in the "Turbo T-Bird." And there were several spec racing classes in both autos and boats based on the little beast.
[/quote]

that is true, my dad raced in the 2.5l modified hydro class. (he and esslinger were on a fisrt name basis). running straight alcohol, he made 300+ hp, somewhere over 320 hp it starts to break cylinder walls :o

the little chryslers have a good following too.

Title: Re: What's the effect of the cam issue?
Post by verslagen1 on 02/14/08 at 18:12:30

Dam, learned something new. Thanks guys.