Valve Adjustment Weirdness

Greetings all, I hope everyone is enjoying a great racing season. In preparation for my next race, I am performing the routine regimen of care and feeding which includes of course adjusting valves. Adjusting valves is nothing new to me and I have performed this procedure on various makes/models over my 46 years of existence on this fine planet of ours. However these VW’s are something else. As some of you know I’m still relatively new to FV. I maintain 2 Citation Vee’s that have engines from different engine builders. Admittedly, the motor in one car is pretty long in the tooth, while the other appears to have been refreshed (judging by the clean cylinder hone pattern) but then locked away for 11yrs or so but it still runs great.

The weirdness is this: When adjusting the valves, the lash changes as the crankshaft is turned. At first I simply wrote this off as wear on the valve tip (the valve rotating to a “new” spot causing the change in lash) however last night I realized that the lash is changing even before the valve is activated. For example if I set the lash with the piston at TDC on the compression stroke, the lash of both valves is greatly diminished (sometimes to 0) as I turn the the crank and the piston moves downward in the cylinder on the power stroke. Also I have noticed that if I check one valve at a time ie. one valve open, checking the other (being mindful of valve overlap), the lash of the un-opened valve becomes 2-3 thousandths greater than when the other valve is “unloaded” apparently due to some flex in the rocker shaft and/or rocker shaft studs.
It’s funny (not) ‘cause every time I tell myself I’m gonna adjust these valves “real quick” it turns into a 2 hour ordeal…

So first of all, before I go into total detective mode to answer the mystery as to why this is happening (although the rocker shaft phenomena seems pretty clear already), perhaps someone (or everyone) has encountered this already and can enlighten me as to what the heck is going on here? Camshaft bearing clearance, or 8mm head stud spring action are two of my early guesses..

Secondly, the adjustment method in described in Jim Schings book (one valve at time method, one valve open adjust the other) contradicts what is written in the VW factory manual which prescribes a single cylinder approach, adjusting each at TDC according to the firing order. So which method are you all using, and what lash setting are you using? Are you setting it it once and forgetting it, or do you spin the motor and try to dial it in somewhat?

Thanks,

Joe

I have always adjusted the valves in the firing order, 1234 backwards, because any variation beyond that position is irrelevant and beyond your control. Just in case you don't already know, when 1 is at "rock", 3 is tdc. Same for 2 and 4.

Joe,
I'm not sure what 'rock' is in the previous post.. but *I* use the indicators on my pulley. One is #1 TDC and the other is the next cylinder in the firing sequence - 180 degrees from each other. Rollin marks #1 with RED and the other side of the pulley with BLUE (generally).

I watch the valve movements from one side of the car, while rotating a rear tire to one or the other of the TDC markers to determine which cylinder is 'coming up'. Stop the crank at the mark and then check both valves (I find this the EASIEST and FASTEST way .. for me). I'll also mention that. if there is *ANY* side to side movement possible in the rocker arm... (there really HAS to BE SOME), then the actual lateral position of the rocker itself will affect the clearance measurement.. a LOT. ALSO.. the tips of the adjusters tend to become 'flattened' somewhat and an incredibly SMALL rotation of the adj screw can cause a MAJOR CHANGE in the measured clearance.

In the end, I find it doesn't really matter THAT much. +/- a thousandth or 2 is no big deal. You can drive yourself crazy trying to get them all to be perfect.. or you can just go racing with the rest of us :-).

I set mine to 0.004 cold - both intake and exhaust.. but I allow a bit more 'freedom' on the exhaust as to what I'll accept (on the bigger side). Remember that having a single valve adjusted with too much clearance is basically NOT NOTICEABLE on track.. but getting ONE valve just 0.001 too TIGHT will show up immediately.

In general, I don't find much change over time in my clearances. I can run through all of mine in about 5 minutes just using 'feel' to see if any are too TIGHT. The clearances are not likely to get bigger. They get tighter as the valve's 'beat in' to the seats. ... but, of course, always at least make a cursory check to catch a 'pulling head stud', or other 'shouldn't happen' item of concern.

I also make an effort to not (never?) mess with anything inside the valve covers before an 'important session'. The valve cover gaskets will LEAK easily. Generally, they get SUCKED IN .. leaving a BIG OIL HOLE to the outside air and a real mess to anyone behind you.. and often you have no option (if you notice it) but to come in before you run out of oil.

I GLUE the gaskets to the valve covers with RTV - clean and properly prep.. then apply RTV to gasket (both sides) and insert into valve cover. THEN apply light coat of grease to the edge of the head... so the gaskets stays with the COVER when you remove it. After the RTV has set (generally overnight), remove the cover and make SURE the gasket is STUCK in the cover and it comes free from the head easily. If all is OK, you should have no trouble until something 'happens' to cause the gasket or cover .. or attachment ... to fail. BUT ... I still try to NOT MESS WITH THEM before a session. That stuff should be done at HOME.. between races.
Steve, FV80

Mostly for new FV owners.....

If you have an unknown engine, the best thing would be to degree the cam off the pushrod to check for a worn cam. An engine builder would do this normally during a rebuild. As mentioned above, if the engine builder has corrected for TDC, then pop the dist cap off, and line a mark up and see what cylinder is firing. I like backwards 1,2,3,4 and I do one side at a time. I also roll the rear tire up on a few 2 x something to minimize oil loss when working on that side. My engine builder says .004 but I have heard .005 or .006 but no smaller than .004.

After an engine is broken in, I rarely find more than one or two valves out more than .001. I also carefully look over the rocker shaft - put a wrench on the shaft blocks, just to make sure nothing is loosening up. My racing engines have had the wave spacers removed and solid spacers installed (still using the clips) and I look for unusual signs of wear.

I do run leaded racing gas (figure what I pay is worth the potential rebuild costs) and I assume leaded AVgas should be good too. If you are running street gas - even the non-ethanol premium available in some markets - don't know how the valve seats like it. and of course floating the valves due to high RPM or bad springs could pound the valves into the seats.

Older engines used heavy springs to control float - the new ones are much lighter (and more expensive).

ChrisZ

Not sure what happened but I posted this yesterday and now it is gone. So lets try this again:

Valve Lifter Adjustments
Do the adjustment on a COOL engine:
1. Remove the number #1 & #2 side valve cover.
2. Turn the rear wheel forward until the #2 cylinder exhaust valve is just starting to open.
3. Adjust the #1 Exhaust valve rocker arm clearance to .004".
4. Adjust the #1 Intake valve rocker arm clearance to .004".
5. Adjust the #2 Intake valve clearance to .004".
6. Turn the rear wheel forward so that the #1 Intake is just starting to open.
7. Adjust the #2 Exhaust valve clearance to .004".
8. Clean the valve cover gasket and head mating surface and replace the valve cover.
9. Jack up the other side of the car, and remove the valve cover. Rotate the wheel forward so that the #4 Exhaust is fully open.
10. Adjust the #3 Intake and Exhaust valves to .004".
11. Adjust the #4 Intake to .004".
12. Move the rear wheel forward so that the #4 Intake is fully open.
13. Adjust the #4 Exhaust for .004".
14. Clean the valve cover gasket and head mating surface and replace the valve cover.

Hope this helps.
R/--
Harry
FV#77 CFR

Thanks for the replies guys, my first response to you all got lost in the server shuffle too. I will say that I tend to agree with Steven. Those valve covers are not coming off at the racetrack unless there’s a darn good reason! @Harry-I hope you all are having a great time down there in the CFR. Caroline and I wanted to come to Daytona. However, we could not fit it in our schedule this year. Hoping for next year! Joe

Hey Joe,

There is a good tech page on DriverzCup.com that includes instructions and a video along with some other good tidbits. I'd paste a link but I'm using someone else's computer and I can't copy/paste for some reason. Anyway, that's the method I use - I can't say its better than the other suggestions but it is pretty quick and easy.

Hope this helps and we get to see y'all at Roebling & Road Atlanta this fall!
Rich

https://driverzcup.com/tech/

If you look at the page initially it looks like a picture, but it is a video once you click on it. See you soon Joe!