Correct O/T Mark on Timing Belt Install? - I think my PO did it wrong.

[Cloudbase]

I think the PO of my car installed the timing belt with the crank and camshaft pulley misaligned. He bought the car with a broken timing belt and rebuilt the head. When I pulled the timing belt covers this is how I found the pulley marks. I have not pulled the old timing belt yet.

Cam Pulley



Crank Pulley. I included 3 slightly different angles. It looks like he used the line on the actually pulse sensor teeth, not the O/T line.







Here's what it looks like behind the timing belt cover. There is a line on the pulley shaft and a notch that are also misaligned.



The Bentley manual and several DIY's show that the middle of the O/T mark should be used on the timing cover. Is this correct? I've put almost 50,000 miles on the car with it at present and it has always ran great.

[slammin.e28]

Oy gevalt!

Cam is correct. Crank is off, should be as you say, O|T on the mark, or the line with the V.

[ttrousdell]

^this

[Cloudbase]

Double handed

[downforce22]

yea the timing belt drive gear on the crank should be lined up in that notch. Maybe with the stock cam the valves just kissed the pistons and have been fine?

[Cloudbase]

It's always run great and pulls strong. Wonder???

[digger]

the engine will drive quite a bit different when you fix it

[Roland H]

If you do put it back on the "correct way" make sure you very carefully spin the engine and make sure the valves don't hit the pistons. While not likely, it is possible that there is a method to the PO's "stupidity."

Very strange stuff...

[Cloudbase]

Yeah, not a bad idea.

I'm going to re-adjust the valves too. The rotor and cap seem overly worn for only 50K miles. I don't see why that could have happened, but I'm going to replace those too.

[digger]

If you do put it back on the "correct way" make sure you very carefully spin the engine and make sure the valves don't hit the pistons. While not likely, it is possible that there is a method to the PO's "stupidity."

Very strange stuff...

sometimes people drive for a bit and then the valves smash the pistons so the engine might spin over but be so close that eventually it goes bang. ive seen it a few times in last coupe years from members on here

out of curiosity i would pull the valve cover and eye ball or measure how far the valves are off the seat at TDC now and after its corrected. on a stock cam at TDC (start of induction) both valves should be off the seat the same amount about 1mm or a bit more.

if the timing is that far retarded then the exhaust valve should be several mm of the seat at TDC and inlet valve closed

[mpowerful]

I have heard tell of people running one tooth up on cam essentially making the motor advanced one tooth. I think one tooth advanced or retarded is not going to cause a clearance issue. Its essentially same amount of adjustment youd get from an adjustable timing gear....any more than that though and it could be bang territory.

[slammin.e28]

If the exhaust was the one getting close, it has a bit more room to move before hitting the piston, smaller valve. Methinks if the intake was the one going down we'd have some SRS bent intake valves.

[jlevie]

Rotate the engine until the mark on the crank hub lines up with the V notch in the lower timing cover. Then remove the belt and adjust the cam until the marks line up. Install a new belt and then rotate the engine through two revolutions until the crank lines up and check the cam marks to be sure that the engine is in time.

[Cloudbase]

Got it all back together. With the marks aligned and the new belt on I rotated the engine 8 revolutions (two sets of 4) and check the marks each time. They always lined up. I also pulled the valve cover and plugs. With the marks lined up the #1 cylinder rocker arms looked level. I'm going to do a full valve adjustment tomorrow before I fire it up.

[Cloudbase]

Just want to update this thread. I've been on the road, so the E30 was laid up for a bit before I could get it all back together.

I installed the timing belt correctly, put everything back together, adjusted the valves, they were a little tight - like .009 maybe .008 on one or two. I didn't have the spring tool, so I used a go / no-go feeler gauge. Pretty cool, it's .009 on the front and .011 on the back. Makes it closer to .010. There is a little bit more valve tick, but that is to be expected.

I started it and bled the cooling system twice. It ran fine for both bleeds. I took it for a test drive, ran great. I notice no real difference in power, idle, or sound compared to before I changed the belt.

I also installed Koni Yellows (I thought I had Bilstein Sports with my H&R Sport Springs, but I think they were HD's because the ride is much better. Along with the shocks, I installed a completely overhauled cluster, two tone door pulls, and fixed both of my door handles. I have a set of Mazda RX-7 Calipers going on next week once I get the dam caliper springs. I also installed my intensive headlight cleaning system dual washer tank. Once the beast is running and stopping, I'll tackle the full install.

My distributor cap and rotor had quite a bit of oxidation (if that is the right word) and the plugs didn't look that great either. All of it had about 50K miles, but I'm thinking I'm going to replace the lot.

Also, if it gets cold enough for my cold start (non-start) issue to prevent, I'm going to trouble shoot my C191 connector more.