Timing and/or TDC marks on the 1800 engine

Chris Hobbs · Post by **Chris Hobbs** » Thu Sep 04, 2003 8:50 pm

It appears to me that between the Muir, Haynes, and Clymer manuals for Type 4 maintenance, there is no consistent information for locating both TDC (for valve setting) and 7.5 BTDC (for timing) marks on my 1800 engine. The fan pulley has only ONE RED MARK on it, and various instructions (plus the sticker that VW put on the fan housing) seem to alternately use that same mark both for the TDC valve adjustment as well as the 7.5 BTDC timing mark. I figure one red mark can't be both--can it?

My solution to date has been to consider the red mark as TDC, and use it for both valve adjustment and timing--even though this doesn't make sense. What do other forum members do in this case?

vwbill · Post by **vwbill** » Thu Sep 04, 2003 9:09 pm

Hey Chris, I used to have a 1800 but cant remember the difference.
Hope Ray can help! so are you looking at the front of the cooling fan cover or in the timing hole on the top of the motor? Did you do the TDC check via the number one piston via the plug hole? Then you get a idea of the TDC. Sorry I'm not much help I wish I had the 1800 but I have the 1700EA motor in my 412 2d sedan. I'm stuck in rebuild hecksville right now. Good luck Chris! Wahoo, Bill

raygreenwood · Post by **raygreenwood** » Fri Sep 05, 2003 6:11 pm

There is a decent amount about this ,here and there in the archives. The 1800's for the most part did not have a "0". They had a mark for maximum advance for strobe timing. This is because...other than for the more advanced tuning...with different than factory parts sometimes..that we do now, the idle timing is not relevant...and static timing should not be done anyway. I actualy like to run just a bit more than stock timing at idle. In those years, the timing was picked up and checked by the "machine" at the dealer through the two nodes on the flywheel andthe crank pickup on the right hand side of the bell housing. It was read through the umbilical from the diagnostic socket.

Either swap in a 1.7 fan....bolts right up... or crank this thing around to "0" using a dial indicator on the piston....and make a mark. Ray

Chris Hobbs · Post by **Chris Hobbs** » Fri Sep 05, 2003 11:09 pm

So, this tells me that I should treat the red mark on the fan pulley as the 7.5 BTDC setting for timing at idle. And then find some way to measure out a new TDC mark of my own for setting the valves. So all the manuals are wrong, I really don't have a mark there already for TDC. Crap! My valves are slightly out of adjustment then.

I assume your suggestion about the 1700 fan pulley means that they came with two marks--perhaps red AND black?

alsehendo · Post by **alsehendo** » Sat Sep 06, 2003 12:21 am

Find TDC by sticking something down the spark plug hole--make shure roter is pointing at #1--then mark TDC on Fan. Then relate your marks to factory ones. At least you will have a starting point.

raygreenwood · Post by **raygreenwood** » Sat Sep 06, 2003 7:16 pm

NO! Generally the red mark on 1800 is 27* BTDC. There is no idle timing mark on most of the 1800's. As I noted, The factory did not set the timing by idle. It was irrelevant to them, as they power timed the engine to make sure you were not overadvanceing. That was 27 BTDC at 3500 rpm. You must find TDC on #1. Then mark the fan yourself. Ray

Chris Hobbs · Post by **Chris Hobbs** » Sat Sep 06, 2003 8:27 pm

I understand the 27 BTDC number--I have seen it on Muir's ignition timing chart for 1700 engines. Also, both Muir and Clymer say to time at 3500 rpm. Fair enough. However, the fan housing itself has a factory sticker that says 7.5 BTDC and shows a picture of a strobe gun aiming at the timing notch on the fan pulley. What else to aim at but the red mark lined up in the notch?

The fan housing sticker also tracks with the Haynes manual (1974 edition), which says to time 7.5 BTDC at idle. If you can't trust a VW factory sticker, what can you trust?

I guess I'm starting to answer my own question--the red mark is 7.5 BTDC, and there isn't any TDC valve adjust mark. I'll just have to measure and make one myself.

By the way (for the previous poster), you can't use the old pencil-in-the-spark-plug-hole trick to find TDC on a Type 4 engine. The plugs are in the wrong orientation and you just end up crunching the pencil. Ask me how I know.

Thanks, guys!

raygreenwood · Post by **raygreenwood** » Sun Sep 07, 2003 9:53 pm

Yep there are a lot of consistancy issues with the timing...this may help. Removethe fan....Looking at the fan head on...ther are four welded on square nuts. There are bolts going through these. They sandwhich the fan together. That means that there are four equal "pillars" with four equal quadrants between them. Each quadrant has 10 fan blades in it.
The BOSS for the crank locating pin on the back...points"nearly directly to one of these quadrant pillars...that one of the sandwich bolts goes through. Mark that boss so you know where it is from the front. Now...the group of ten blades to the right of that "pillar" that the pin is lined up with...contains "0". Put your left index finger on the "pillar" that the locating pin points to. Hold onto the fan...and count over 6.5 fan blades to the right. That is "0". 27 before is dead on the 10th blade in that quadrant. To be precise...the "0" mark goes 1/32" before blade 6.5.
That would make it 6 and 4/10's blades from where your left index finger is resting on the bolt pillar. When you mark the "0"...go ahead and get a very good straight edge and an accurate measureing tape....and find the spot on the fan 180* out from the "0" mark. Mark it too. The "0" will be for adjusting valves on 1, 3...the 180 mark will be for 2 and 4. ray

alsehendo · Post by **alsehendo** » Sun Sep 14, 2003 3:07 am

Well at some point the piston has to stop going up and start going down. Using 2 by 4 to do this, (pencil) is pretty hard. An extremely small diameter very pointed stick works better. Were then piston grabs the toothpick ended like stick will be close to TDC--besides all I said to do was use this spot to determine were the factory marks were. 1 or 2 degrees in a stock engine isn?t going to mean much anyway also and according to a factory trained VW T4 aircooled bus and car manic who now has his own shop in Wisconsin the best way to set these up is for max advance and ignore TDC ad BTD compeetly.

alsehendo · Post by **alsehendo** » Sun Sep 14, 2003 3:59 am

I ment ignore TDC and 7.5 BTDC set to what advance value you want--max advanve, check type4rum for some sugestions. Mine seems to make the most power at 33.

If you want to be a profectionest check out how people do lifter geometry with a modified solid and or depth gages. Actual the cam is were the real timming should be taken from anyway, not the fan/crank.

alsehendo · Post by **alsehendo** » Sun Sep 14, 2003 4:57 am

Here is your solution if you just want your valve lashs set.
Setting lifters without even knowing timing is posible in VW engine.

When valve on one cylinder is at max lift?fully open.
The corresponding valve in the opposite cylinder is fully closed.
Example #1 exhaust is fully open #3 exhaust is fully closed

1) Loosen all the adjustment screws
2) Rotate crank until rocker #1 exhaust rocker is at bottom of its travel-opening valve
3) Set clearances of #3 exhaust to what you want it is fully open-its setting on cam heal
4) Set them all them same way with the opposite valve at max lift/fully open

raygreenwood · Post by **raygreenwood** » Sun Sep 14, 2003 12:51 pm

Alsehendo...that formula will be totally different with different cams and profiles...but its close. You can also use...
Intake just beginning to close (like 3*)..adjust exhaust
Exhaust just starting to open...adjust intake

It depends upon how radical the flanks of the lobe are, approaching the basecircle. It can get you in trouble on some cams. For the most accurate..use a dial indicator to find out where the base circle begins andadjust within that. Ray

alsehendo · Post by **alsehendo** » Sun Sep 14, 2003 4:46 pm

It is just very easy to use a mirror on one side and adjust the other without looking up top.

I do tend to use backyard mechanics, which I realize often are not the best, however the fact that I seem to be able to get away with unsophisticated methods is why I have been driving these aircooled vehicles for years in the first place including T4 vans. My 76 Van went 160K before I sold it for 1K more than I paid for it, and the Vanagon seems to run like a clock, and get great gas mileage without the help of sophisticated tuning techniques.

At least until the late 80's the tradition continued, working on Golf vs a Subaru is like night and day. To bad this VW tradition has faded in resent times. The new Beetle owner has no idea why we purchased them in the 60's and 70's. When asking people why did you purchase your new Bettle the typical responce is there cute. People don't even change their own oil any more

Most of my friends, couples, fork out 500 + month and pay huge insurance premiums + pay periodically for expensive repair bills. To me this is insane.

The 412 was no different, if parts were available the average backyard mechanic would have no problem fixing it themselves. FI makes it a little harder, however L-Jet is also pretty simple. My suggestion is to get two completely functioning FIs working and swap parts if needbe after basic troubleshooting techniques are done.

Note: I do sympathize with all the people that have to drive a tank (SUV) in order to feel safe. There are some bad drivers out there! Our little cars can get pushed around on the road and we don't have 200hp to escape.

vwbill · Post by **vwbill** » Sun Sep 14, 2003 8:54 pm

So when should the valves be set, when the piston first reaches the top of the stroke or at the mid point of the stroke before the down stroke?
If you use a dial gauge do you set the valve when the push rod first reaches the top or just before the down side? I guess what I'm asking is do you want the cam to be at the top of the lobe center or the beginning of the cam lobe curve? I always set them by setting the piston at the mid point of the travel of the piston on the fire stroke. Thanks! Wahoo Bill

raygreenwood · Post by **raygreenwood** » Sun Sep 14, 2003 10:50 pm

VWbill...thats a good question. Heres an odd answer. We have a tendency to believe that when we are at TDC like the factory tells us...hat we are at the lowest pont on the cam lobe. Thats not quite true. Try this experiment:

Set up a valve/cylinder at TDC. Instead of setting at .006"....set it at "0" lash. Don't worry..we are not going to drive it this way. Now....continue to turn the negine over slowly.....Aha! guess what! slack isappearing between the valve adjusting screw and valve tip!!!! You will find between .008 and .012" of extra slack in the rotation. So the factory valve adjustment point is not the lowest part of the cam.

Though i do have to believe that VW knows this. I have found that even with the engine and CHT about as hot as they can get with normal running....if I check the valve clearance hot at TDC....I get about .003-.004". The reason for valve lash is so there is some slack somewhere in the 360 degrees of rotation. If you adjust the valves hot so there is only about .0015-.002" of slack at TDC....especially with Djet...you get noticibly better HP, throttle response, less valve noise..and less valve adjuster screw wear.

By the way...this also corresponds to adjusting the valves to .006"...not at TDC...but halfway in between the ACTUAL lowest base circle point on the cam...and the factory recommended TDC setting. Make sense? I simply remarked my fan in two locations.

Alsehendo: I agree and disagree with what you posted. For years I drove 411's and 412's with seat of the pants backyard mechanical tuning. Yes..they drove and lasted fine. But when I finally started getting a little more accurate on things like ...valve adjstment points, advance unit stop points and idle timing....I found that I was able to adjust the MPS much more accurately . They run MUCH MUCH better than stock...and cooler. Not saying you are doing anything wrong....but the D-jet...especially....responds much better to closer adjustemnt. It already has cam timing issues with its injection points. It affects vacume and fuel pressure stability. That affects the ability to more accurately tune. you would be surprised at what degree of tune the stock engine is actually capable of. Its worth about 5hp over stock. Its worth more...if your state of tune actually keeps you about 5hp under the stock rating...which is most common. Most people push it off to the slowness of the auto trans. The auto trans is NOT slow...not with a 3.79:1 or 3.91:1 final drive. Its usually losing power. I would never have found the tuning issues if I had not had a 4 speed model. I KNEW the gears in the 4 speed were not slow....so I worked on the tuning. Ray

Shoptalkforums.com

Timing and/or TDC marks on the 1800 engine

Timing and/or TDC marks on the 1800 engine

timing question

Valve timing?