Do 2.0 timing marks differ from year to year?

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914Racer
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Do 2.0 timing marks differ from year to year?

Post by 914Racer » Wed Jul 31, 2002 11:40 am

I've been fighting overheating problems (head temps) and a lean mixture for some time now. I think I've found the culprit!! I've been lead to believe by the person I bought the car from that the etched mark on the fan of my '75 GC cased engine is the TDC mark for cylinder #1. So I used Pelican's handy template to mark the 27 BTDC mark and I timed to that.

Well after 2 dropped valve seats from overheating, I recently stuck a screwdriver in the sparkplug hole of cylinder one and physically felt for TDC. I then looked at the fan and didn't see the etched TDC mark. In fact it was about 4 fan blades away! My fan is installed properly and keyed correctly. I appears that the etched mark on my fan is or at least is closer to being the actual 27 degrees BTDC mark and there is no marking for TDC. So I was probably timed for about 54 degrees BTDC! Does this make sense? Can an engine run with that kind of advance? Has anyone heard of different timing marks for a 2.0 from year to year? Do I have the wrong fan? Sorry for the length.

Thanks,
Greg

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Dave_Darling
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Do 2.0 timing marks differ from year to year?

Post by Dave_Darling » Wed Jul 31, 2002 5:23 pm

The only difference in the fans, as far as I can tell, is the markings. It sounds like you did have the timing mark (27 BTDC) and thought it was the TDC mark. And 54 BTDC would cause lots of heat--and very hard starting... And a high idle that was difficult in the extreme to dial down.

--DD

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1974 VW-Porsche 914 2.0 (Type IV powered!)

Pelican Parts' 914 Tech Geek http://www.pelicanparts.com

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Bobby74
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Do 2.0 timing marks differ from year to year?

Post by Bobby74 » Thu Aug 01, 2002 4:35 pm

I've never seen a difference, but you may also have the dist drive cog in the wrong posistion. When the PO had the car he could've installed it a couple teeth off and that would throw all your marks off. Best bet is to look at where the notch is on the dist, and see if it lines up with the rotor at TDC. If the notch is off (way off not just 1/16") and the rotor is pointing at the #1 wire then chances are he did drop it in wrong (as in my car. but I'm to lazy to fish it out). Just compensate. Hopefully this narrows it down....
~Bobby

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Dave_Darling
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Do 2.0 timing marks differ from year to year?

Post by Dave_Darling » Fri Aug 02, 2002 10:53 am

The distributor driveshaft orientation has nothing to do with setting the correct timing. It may mean that your distributor has to be twisted around so that the vacuum cannister is inside the fan shroud, but that's about it.

The thing about spark timing is that the spark should occur when the timing mark on the fan is next to the notch in the fan housing. That's the ultimate reference--as long as the spark for #1 cylinder happens at 27 degrees BTDC on the #1 cylinder (at 3500 RPM), that's all you need. The timing light directly compares the spark time to the rotation of the crankshaft. So if you see the timing mark in the right spot at the right RPM, your timing is on.

As I said, that may only occur when the distributor is twisted further around than it can physically go, and if so then the driveshaft has to be re-installed. But that is the only problem with ignition timing when the driveshaft is in wrong.

Ray G. says there are other effects with the injection timing when the distributor driveshaft is off. I don't see how that occurs, but I do not have enough experience messing with the injection timing to have a solid opinion one way or another.

--DD

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1974 VW-Porsche 914 2.0 (Type IV powered!)

Pelican Parts' 914 Tech Geek http://www.pelicanparts.com

914Racer
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Joined: Fri Jun 07, 2002 2:01 am

Do 2.0 timing marks differ from year to year?

Post by 914Racer » Fri Aug 02, 2002 11:42 am

Dave,

I agree. If the cam timing is correct and the fan is keyed properly then the orientation of the driveshaft gear has no direct effect on the timing. The timing marks on the fan will be absolute. You'd just compensate by twisting the distributor to bring these marks into view which could cause some intereference with the fan housing like you said.

We did in fact confuse the notch as the TDC mark. Thing is, that my interpretation of the Pelican articles on timing and setting your valves seem to call this notch the TDC mark. Please take a look and tell me what you think. I'd hate to have other people led astray....or I could just be VERY stupid. The latter is most likely. The thing that tipped me off was the picture of YOUR fan at the bottom of the timing page.


http://www.pelicanparts.com/techarticle ... adjust.htm

On this page it is quoted:
When the impeller notch is aligned with the V-notch, and the rotor is pointing at the notch in the distributor housing, the car is at TDC for cylinder #1. (look at figure 8, that's the mark I used for TDC not 27 degrees before TDC).

http://www.pelicanparts.com/techarticle ... timing.htm

On this page it is quoted:
Or line it up with the notch in the impeller housing shown in Figure 4............Once you have it properly lined up, mark the impeller with some paint or some white-out. This is the mark that you will be setting the timing to.

Figure 4 clealy shows the notch being defined at TDC for cylinder 1. Then at the bottom of the page you define the notch as the 27 BTDC mark to which one should time. Let me know if I'm just nuts here or what.

Please let the record show I'm not trying to bash the absolutely excellent Pelican site or blame all my problems on them. Dave and Pelican are both excellent resources of both reasonably priced parts (Pelican) and invaluable knowledge (Dave). In fact I've bought quite a few parts from them and Dave has provided me with some excellent information on more than one occasion.

Thanks,
Greg

ray greenwood
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Do 2.0 timing marks differ from year to year?

Post by ray greenwood » Fri Aug 02, 2002 12:47 pm

Dave, the injection problem with relation to the drive gear is only a problem on D-jet. It has a not so perfect injection timing relationship with two cylinders even when set correctly. Its usually negligable. If the distributor timing is too far advanced or retarded, since the trigger points are slaved to the dist. body...it brings their injection point even farther out of wack ...on all four cylinders. At that point the injection timing will be even more of an idle and off the line problem than poor ignition timing.
The drive gear pinion itself being out of time....will only relate to injection timing if ...as you noted...your range of movement of the distributor is too restricted to actually bring the ignition timing back to where its marks need to be. If the drive is ninety degress out ...for instance ...to crank and valves...and you can bring the distributor around to 90 degrees off as well...all will be in time.
The real issue with the trigger points really comes in, when increases in timing changes as people tune the engine higher, cause you to adavance timing. The timing itself is moving farther into the "before" top dead center range of piston travel. the injection does not need to, but is slaved to the distributor. It can cause problems on some motors...especially with cam changes.
If you are 180 degrees out, and the ignition timing can be set up correctly ...its no problem. Two cylinders will still be out of sequence the same amount...just different cylinders. Being 90 degrees out actually causes a better running situation because...technically to be the same as stock at 90 degrees out...you would have to split one injector from each pair off, and swap it to the other pair. It depends upon wether it is in thr retard direction or the adavance...can't remember off the top of my head, but being out of sequence actually puts at least 3 of the cylinders closer to an opening point. Its just that the distributor will not fit in that way with the vacume can in either direction. Its when you get into being 15-20-45 degrees off that it really become apparent. Its far off everywhere from the injection opening points. If you slot the breaker plate screws to give about 10 degrees leeway, Once you set your timing up correctly... you can actuall yget smoother idle, more stable fuel pressure and a little better throttle response off the line by moving the breaker plate one way or the other. Sorry for the length. Ray

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Dave_Darling
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Do 2.0 timing marks differ from year to year?

Post by Dave_Darling » Fri Aug 02, 2002 2:47 pm

Greg, you are not wrong... It is confusing.

In part, it's confusing because different 914s put different markings on the fans. Most D-jet 914 fans got a "0" mark for TDC and a slash for 27 deg BTDC. (Timing mark at 3500 RPM.) Most L-jet 914 fans got one mark at 8 deg BTDC. (Timing mark at idle.) Some L-jet fans were marked at TDC as well; some not. Some replacement fans were only marked at TDC...

Finally, it has been pointed out to me that some fans apparently do not match others. They appear to be a half a fan-blade off.

I have no explanation for that.... Image

--DD

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1974 VW-Porsche 914 2.0 (Type IV powered!)

Pelican Parts' 914 Tech Geek http://www.pelicanparts.com

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