I decided to not waste over $580 in buying new FI heads and will replace all the valves, and have the head itself tanked and valve jobbed at a machine shop. If the shop can determine if new valve guides are needed, and they can do FI heads with the odd 9mm larger stem on exhaust, I’ll approve that as well.
Getting the valve retainers off proved rather challenging, as there was quite a lot of caked up carbon on them and oil residue.
The springs are just coated in funk and this made getting the small valve retainers off somewhat troublesome on some valves. I did get them all out.
After first, on head 3/4 valve 1 intake, I encountered some bits of possibly broken plastic that made no sense. I found some of the same on the intake of valve 4.
I just thought it was dirt and grime that had solidified around the valve guide top and did not pay it any mind.
It wasn’t until head 1/2 that I discovered that the intake valves have a small round spacer on them. These parts were cracked and shattered on the the much hotter head 3/4.
Now I haven’t been into cylinders since I did the lapping and assembly of the new ones I purchased for the 2019 build.
I do not recall anything like that on those new heads. I have yet to figure out the purpose, but I assume it has something to do with the different between the 8mm intake steps and 9mm exhaust stems that are unique to the FI Beetle heads.
I am certainly hoping I can find replacements, as I cannot tell if these were plastic, or some kind of bakelite, or other high temp material. (Note: I have not started looking into these yet.)
So you can see the big difference in valve stems from the normal stock carb head valves and the FI valves.
The FI valves not only differ in valve size, they also differ in a given cylinder between the exhaust valve and the intake valve.
Non-FI Stock Type 1 Intake Valve: 35.5mm Intake Valve / 8mm stem
Non-FI Stock Type 1 Exhaust Valve: 32mm Intake Valve / 8mm stem
FI Stock Type 1 Intake Valve: 33mm / 8mm stem
FI Stock Type 1 Exhaust Valve: 30mm / 9mm stem
According to M. Vellat, one of the most knowledgeable VW Air-Cooled Beetle I’ve had the pleasure to interact with on Facebook, in talking about possibly using the basic stock replacement heads I have…
So long as one of the heads has a provision for the cylinderhead temperature sensor I wouldn’t lose any sleep over it. Type IIIs with D-Jetronic FI had 35.5×32 valves. Another difference is that the L-Jet heads have 9mm exhaust valve stems. a change made to reduce their odds of breaking. Late `74 carb’ed engines and Type IVs also use 9mm stems/guides for the same reason; you COULD track down some 9mm guides and put them into your heads, along with 9mm-stem 32mm exhaust valves, but IMO it wouldn’t be worth the trouble, the 8mm-stem valves aren’t that much more prone to breakage except under extreme conditions and should serve you well for at least 80K miles, if not 120K+.
Basically, it sounds like VW was fearful of the extra heat produced by the 75-79 engines and compensated for that in a more robust valve stem, though on a smaller sized valve. I really need to see if I can figure out why this all is, as I would think they would have just gone with a larger valve head (on both) and programmed the ECU to deal with it.
Now I know the analog ECU of the L-Jetronic doesn’t really have much in the way of similarities to modern FI, in fact, I’m constantly correcting myself by not calling it EFI. While the L-Jetronic system remained in production use on cars until 1989, perhaps it just was never implemented in this way by VW. I know it is extremely limited, being driven essentially by airflow sensor only for the adjustments made.