'83 928S US - Non interference engine or not?
 

Hi, my timing belt snapped and was going to do belt, WP, and seals. Last time I checked on Pelican i was read that 928's up till '84 were non interference---meaning if the belt broke, the valves wouldn't clash with pistons causing damage. Is this absolutly correct?? Has anyone actually done a '83/4 timing belt replacement after the belt broke?

you need to post an engine code,
its under the top radiator hose about 2 inches forward of the clamp.
.should be M28/??

It should be non interference, but best to see what is actually in the car, and with a belt snap I would be doing some checking in addition to tb and wp.

Maybe a leak down test.

What made the belt snap?

If it were a EURO S engine then it would be bad news... US spec should be fine.

who knows
 

I've changed belts on US motor that weren't supposed to be but where. Even carbon build up can make it interference. since it's already broke, try to spin the cam around, if it makes it around your okay. btw where are you in NH, I'm in windham

I would not try turning the cams to see if they hit the pistons.
You may bend a valve that otherwise wasnt bent.

Otherwise the only way to validate the above suggestion would be to put the crank at TDC then turn the cams,
you would be checking to see if the valves would hit the #1 and #6 pistons.
Best bet put the crank at 45 degrees BTDC this would be indicated with the crank keyway in the 3 O clock position.
TDC = the keyway at 4 O clock position, all viewed when facing the crank.
Then put the cams to the line up marks then turn the crank to TDC

I have an 84 USA that Stan Shaw rescued from its previous owner.

The car had a broken timing belt.

Stan Shaw replaced it and the car runs very, very strong.

If heads were shaved and/or carbon build up, then it might have crashed valves, based on other folks comments. Why not just put a belt on and try it?

To the point of "Why not just put a belt on and try it? "

My white '84 was sold to me "needing a battery" when in fact the timing belt was broken. So, after a new belt, new WP, new idlers, and rebuilding the tensioner, etc. etc. the car runs great.

Mrmerlin, wouldn't turning the crank also risk damage to valves? I could be wrong but placing the crank at 45 only makes the 4 valve cars non contact, I don't think it works on the 2 valve ones. The ONLY thing he can really do with zero risk is take off the heads and start all over.

If its a USA car, 16V, all he needs to do is turn the crank clockwise to TDC, cams each clockwise to TDC marks, lock the flywheel and proceed with surgery. Better yet, like 32 V car practice, turn crank to 45 BTDC, cams to TDC, then crank remaining 45 deg to TDC, lock it down and go to work.

If its TB is already broken, the damage is already done, to Pete R's original point.


If bad noise is heard during rotation, then pull motor and heads. If it was a simple timing belt break due to age/bad tracking, etc, I doubt it will be a problem, though.

Its your car, what is the history on it? If it was neglected, TB broke while some high school kid was reving past 7000 rpm, then you have a different situation.

First post motor number so we can confirm its a USA 16V.

when the crank is at 45 BTDC then all of the pistons are down in the bores so no valve contact is possible this works for 16 or 32 V engines.
As has been noted before the OP should have posted the engine number in his car as this will be a guide to the possibility of valve clearance issues.
As Chris stated if the valves would hit and the belt is broken then the damage may already have been done. \
BUT in the off chance that the valve/s didnt hit then turning the cams to find isnt the best idea.

with a broken belt just put the crank at 45 BTDC it can be turned in the direction thats closest to 45BTDC
turn the cams to line up then turn the crank to TDC then put on the belt.
Some of the early Euro engines are not IntF while later ones are

I see what your saying Mrmerlin. The crank may be close to 45. But it may not be either. The pistons and valves could be touching now and any movement will bend the valve. It is by far easier to feel contact by turning the smaller lighter cam with a small wrench than by rotating the lower end. If he turns a cam and feels the slightest touch he can pull the cams off. No rotation at all is recommended but as opposed to pulling off both cam towers, the cam rotation is the lesser of 2 evils

Usually I rotate them with plugs in.

I guess its obvious, but best to pull the sparkplugs to gain sensitivity, then.

I rotated my motor over by hand, spark plugs removed, while looking down through cyl #5 intake port on head (valve open all the way) and watched the piston come up towards the valve - no contact. That was a US 84. I would think that trying to rotate the cam could be bad because it tends to jump with the spring tension on the valves. Rotating crank with no plugs installed requires light enough force on a ratchet that you will be able to feel if the pistons touch anything. Automatic trans cars may be different?

thnxs for responses.....car isn't at my house so can't lift the code off the engine, but...as i said the car is a US...auto trans.... 95K....I got car 3 years ago as a driver but car was neglected...took wait and see stance hence I didnt pump any money into extras i.e. paint, or rims ....had expections of doing extensive repairs but so far just required alternator....original aluminum ball joint failure could've killed me.. next to no chance it has a euro 310 hp, swapped ex post facto Stuttgart ..about same power "feel" as my '78 euro....vin is ,wpojbo922ds861158....timing belt shredded because of age....cracks prevalent on belt...car was travelling 25 MPH...I guess 2 of you have had experience of just changing belt with no damage done ;) so maybe i'll just have new belt put in...then do a leak down to confirm...yes?

hi pete....i'm in raymiond, nh...car is in derry near you...please private messagwithwith phone # i want to talk to you

No, these belts are incredibly strong, old belt was used as a lifting strap to pull a motor I bought once. Something else froze up and broke the belt, and the whole timing belt system, all the pulley's and all the tensioner parts need inspection and replacement if worn.

^^^^That is highly likely.

Make the investment in 500 or $600 in parts and get it running.