1972 valves - Non-intrusive?

WesH · 03-27-2013, 05:08 AM

Are the valves in a 72 engine non-intrusive? in other words, if the cam chain breaks and the motor still runs, are the valves getting pounded by the pistons? Please tell me no....grin

tharbert · tharbert's Garage

No - intrusive...just like any other MY.

pete3799 · pete3799's Garage

Broken cam chain = expensive.

theiceman · 03-27-2013, 05:52 AM

i think the phrase you are looking for is " interference engine" and yes it is .. if your tensioners are making a noise you might get away with it .. but if the chain broke its tear down time .. and parts for that engine ? .. wow..

motogman · 03-27-2013, 05:21 PM

Quote:

Originally Posted by theiceman

... and parts for that engine ? .. wow..

??? Why are parts for a 72 that much different - I assume you mean pricewise? What make a 72 "special"?

boba · 03-27-2013, 05:34 PM

Quote:

Originally Posted by motogman

??? Why are parts for a 72 that much different - I assume you mean pricewise? What make a 72 "special"?

Any year will be costly.

pwd72s · 03-27-2013, 05:38 PM

Quote:

Originally Posted by motogman

??? Why are parts for a 72 that much different - I assume you mean pricewise? What make a 72 "special"?

Nothing...all 2.4 engines were the same. They were made during the '72='73 model year. By "the same" I mean internally, model to model..T, E, or S. The internals were different for each...and mid year '73. the 911T switched from MFI to CIS injection.

The '72 is "special" with it's forward mounted oil tank with the filler on the right rear quarter...the only year to have that feature. Also, the '72 "S" came standard with a front mounted radiator oil cooler...that became an option in '73.

WesH · 03-28-2013, 07:05 AM

I plan on removing the sheet metal this weekend, pull the cover and see what I have going on. Is there any chance the valves and pistons are not beat up? I'm hoping the pin came loose but if the valves are slapped around, I'll pull engine and build it fresh.... Thoughts? The car will crank and idle to my amazement.....

kodioneill · kodioneill's Garage

Are you sure it's not a loose rocker? Pull the valve covers and have a look.

WesH · 03-28-2013, 09:10 AM

Yea, Cam is not turning at all on the passenger side.

snbush67 · snbush67's Garage

Do you mean that the cam is not turning with the engine running, or is it stuck?

Do you have the chain covers off?

Can you turn the cam with a wrench by hand? Pull the plugs and try.

I doubt that there is no damage but anything is possible, if it turns freely and all the rockers are not cracked or broken, no strange noises then you might be OK.

If so then the next step is a compression test that should tell you if your rings and valves are ok.

boba · 03-28-2013, 10:40 AM

Since you say it will start and idle, it is most likely running on just 3 since the right bank cam is not turning.
You may have minimal damage, but until you look at the heads, pistons and valves you will not know the extent. The risk is that you may be able to get it running again without opening it up only to have a valve head break off due to slight damage from light contact.
Knowledge is peace of mind.

69911e · 03-28-2013, 11:31 AM

Yes, there is a chance no internal damage. I had the chain slip, break 3 rocker arms, and do no internal damage. Just fixed the chain & replaced the rocker arms. You could try a leak down to determine damage.

WesH · 03-28-2013, 12:13 PM

Pulled the valve covers and that where I discovered the cam is not turning at all. Rockers appear to be intact but will do a deep dive on them to verify. Did not try to manually turn. I will pull the cam chain covers this weekend to see what going on. Pending resolution, I'll fix, run compression and leak down tests while keeping fingers crossed. Then decision time....... My thanks for all the positive feedback.

WesH · 03-29-2013, 05:04 PM

Update: Pulled Cam cover. Pics to follow. Good news is: Chain is intact. Bolt was loose and only one round to take it off. Washer behind bolt was warped. Found metal in bottom, pic to follow. Not sure where it came from. Rotated engine and used mirror to check all teeth. Seem to be fine. My first thought was teeth from sprockets. Pic posted of the dowel that seems to be sheared off. I need the experts to weigh in here. Cam is free and turning manually.
Also, pic of the cam tensioner, Is this the updated one?
Thinking, if the metal parts are from the pin, I can re-time, run compression and leak down checks and just maybe be ok. I'll post the pics in high def so maybe someone can zoom in to see that the metal pieces are from. (Pin or sprockets) My thanks, Wes

WesH · 03-29-2013, 05:11 PM

Pic of cam sprocket.

James Brown · James Brown's Garage

see if you can get a picture of the cam end of the chain. oh, ok thanks. might be the sprocket on the cam that sheared off

howard freeman · howard freeman's Garage

Those look like pieces of sprocket. Check the sprocket on the cam & tensioner wheel & look for missing teeth. If they are all there, then the intermediate shaft sprockets are broken. That will entail a complete teardown. I have been working on these cars since 1977 & have never seen a 911 engine jump time & do no damage. Never.
Howard

James Brown · James Brown's Garage

16 or so teeth on that inner cam sprocket so many more parts floating around the engine. You know what that means, sorry

snbush67 · snbush67's Garage

If there are no oil lines to the tensioners then they are the old pressure fed kind. The one in the pic looks collapsed but it is really hard to tell from that angle.

Your best bet is a complete tear down and rebuild, anything else is a gamble.

Financially it might be wise to just find a healthy lower mileage or rebuilt engine 3.0-3.6.

Or you might be able to get some decent mileage from a your 1.2 liter.